10-Q

PART I—FINANCIAL INFORMATION

Item 1. Financial Statements.

SPERO THERAPEUTICS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(In thousands, except share and per share data)

(Unaudited)


	September 30,			December 31,
	2025			2024
Assets
Current assets:
Cash and cash equivalents	$	48,616		$	52,889
Collaboration receivable, current - related party		868			49,391
Other receivables		1,591			3,085
Prepaid expenses and other current assets		1,248			1,911
Total current assets		52,323			107,276
Operating lease right of use assets		1,694			3,114
Other assets		153			153
Total assets	$	54,170		$	110,543

Liabilities and Stockholders' Equity
Current liabilities:
Accounts payable		1,395			7,306
Accrued expenses and other current liabilities		7,809			17,724
Operating lease liabilities		1,899			1,746
Income taxes payable		163			174
Deferred revenue, current		—			368
Deferred revenue, current - related party		2,383			21,756
Total current liabilities		13,649			49,074
Non-current operating lease liabilities		1,452			2,551
Deferred revenue, non-current		12,575			12,219
Deferred revenue, non-current - related party		—			576
Total liabilities		27,676			64,420
Commitments and contingencies (Note 9)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized, no shares issued and outstanding as of September 30, 2025 and December 31, 2024		—			—
Common stock, $0.001 par value; 120,000,000 shares authorized as of September 30, 2025 and December 31, 2024; 56,311,795 shares issued and outstanding as of September 30, 2025 and 54,593,527 shares issued and outstanding as of December 31, 2024		56			55
Additional paid-in capital		509,024			505,706
Accumulated deficit		(482,586	)		(459,638	)
Total stockholders' equity		26,494			46,123
Total liabilities and stockholders' equity	$	54,170		$	110,543

The accompanying notes are an integral part of these condensed consolidated financial statements.

SPERO THERAPEUTICS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS

(In thousands, except share and per share data)

(Unaudited)


	Three Months Ended September 30,						Nine Months Ended September 30,
	2025			2024			2025			2024
Revenues:
Grant revenue	$	2,394		$	5,650		$	5,544		$	14,893
Collaboration revenue - related party		3,048			7,754			19,949			17,721
Collaboration revenue		—			65			12			319
Total revenues		5,442			13,469			25,505			32,933

Operating expenses:
Research and development		8,597			26,864			32,875			67,921
General and administrative		4,174			5,198			16,876			16,648
Impairment charges		587			—			587			—
Restructuring		—			—			258			—
Total operating expenses		13,358			32,062			50,596			84,569
Loss from operations		(7,916	)		(18,593	)		(25,091	)		(51,636	)
Other income (expense):
Interest income		532			1,182			2,136			3,707
Other income (expense), net		2			(26	)		7			(39	)
Total other income, net		534			1,156			2,143			3,668
Net loss before income taxes		(7,382	)		(17,437	)		(22,948	)		(47,968	)
Income tax benefit		—			290			—			290
Net loss and comprehensive loss	$	(7,382	)	$	(17,147	)	$	(22,948	)	$	(47,678	)

Net loss per share attributable to common stockholders, basic and diluted	$	(0.13	)	$	(0.32	)	$	(0.41	)	$	(0.89	)

Weighted average shares of common stock outstanding, basic and diluted:		56,280,844			54,124,862			55,866,392			53,869,824

The accompanying notes are an integral part of these condensed consolidated financial statements.

SPERO THERAPEUTICS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(In thousands)

(Unaudited)


	Nine Months Ended September 30,
	2025			2024
Cash flows from operating activities:
Net loss	$	(22,948	)	$	(47,678	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		—			2
Non-cash lease cost		834			775
Impairment charges		587			—
Stock-based compensation		3,318			6,290
Changes in operating assets and liabilities:
Collaboration receivable, current and non-current - related party		48,523			45,156
Other receivables		1,494			(1,151	)
Prepaid expenses and other current assets		663			2,123
Other assets		—			282
Accounts payable		(5,911	)		4,712
Accrued expenses and other current liabilities		(9,915	)		8,771
Deferred revenue, current and non-current		(12	)		(319	)
Deferred revenue - related party, current and non-current		(19,949	)		(17,721	)
Other long-term liabilities		—			(74	)
Operating lease liability		(946	)		(921	)
Income taxes		(11	)		(290	)
Net cash used in operating activities		(4,273	)		(43	)
Net decrease in cash and cash equivalents:		(4,273	)		(43	)
Cash, cash equivalents and restricted cash at beginning of period		52,889			76,333
Cash, cash equivalents and restricted cash at end of period	$	48,616		$	76,290

The accompanying notes are an integral part of these condensed consolidated financial statements.

SPERO THERAPEUTICS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY

(In thousands, except share amounts)

(Unaudited)


					Additional
	Common Stock				Paid-in		Accumulated			Stockholders'
	Shares		Par Value		Capital		Deficit			Equity
Balances at June 30, 2025		56,187,308	$	56	$	507,976	$	(475,204	)	$	32,828
Issuance of common stock upon the vesting of restricted stock units		124,487		—		—		—			—
Stock-based compensation expense		—		—		1,048		—			1,048
Net loss		—		—		—		(7,382	)		(7,382	)
Balances at September 30, 2025		56,311,795	$	56	$	509,024	$	(482,586	)	$	26,494

					Additional					Spero Therapeutics, Inc.
	Common Stock				Paid-in		Accumulated			Stockholders'
	Shares		Par Value		Capital		Deficit			Equity
Balances at December 31, 2024		54,593,527	$	55	$	505,706	$	(459,638	)	$	46,123
Issuance of common stock upon the vesting of restricted stock units		1,718,268		1		—		—			1
Stock-based compensation expense		—		—		3,318		—			3,318
Net loss		—		—		—		(22,948	)		(22,948	)
Balances at September 30, 2025		56,311,795	$	56	$	509,024	$	(482,586	)	$	26,494


					Additional
	Common Stock				Paid-in		Accumulated			Stockholders'
	Shares		Par Value		Capital		Deficit			Equity
Balances at June 30, 2024		54,009,139	$	54	$	502,049	$	(421,603	)	$	80,500
Issuance of common stock upon the vesting of restricted stock units		305,276		—		—		—			—
Stock-based compensation expense		—		—		2,154		—			2,154
Net loss		—		—		—		(17,147	)		(17,147	)
Balances at September 30, 2024		54,314,415	$	54	$	504,203	$	(438,750	)	$	65,507

					Additional
	Common Stock				Paid-in		Accumulated			Stockholders'
	Shares		Par Value		Capital		Deficit			Equity
Balances at December 31, 2023		52,999,680	$	53	$	497,913	$	(391,072	)	$	106,894
Issuance of common stock upon the vesting of restricted stock units		1,314,735		1		—		—			1
Stock-based compensation expense		—		—		6,290		—			6,290
Net loss		—		—		—		(47,678	)		(47,678	)
Balances at September 30, 2024		54,314,415	$	54	$	504,203	$	(438,750	)	$	65,507

The accompanying notes are an integral part of these condensed consolidated financial statements.

SPERO THERAPEUTICS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

Nature of the Business and Basis of Presentation

The Company is a clinical-stage biopharmaceutical company focused on identifying and developing novel treatments for rare diseases and diseases caused by multi-drug resistant (“MDR”) bacterial infections with high unmet need.

The Company’s clinical-stage product candidate, tebipenem HBr, has completed a Phase 3 trial to treat adult patients with complicated urinary tract infections (“cUTIs”), including pyelonephritis, caused by certain microorganisms. In May 2025, the Company and GSK announced that the pivotal Phase 3 PIVOT-PO trial evaluating tebipenem HBr met its primary endpoint and was stopped early for efficacy. Results from the Phase 3 PIVOT-PO trial were featured in a late breaking oral presentation on October 20, 2025, at IDWeek in Atlanta, GA. GSK plans to submit the data from the trial as part of an FDA filing during the fourth quarter of 2025.

In March 2025, following a reprioritization of its programs, the Company announced that it was no longer pursuing a Phase 2 clinical trial for SPR206, and the Company has ceased further development of the program. Additionally, in November 2025, the Company announced that it ceased development of SPR720, a product candidate for first-line treatment of nontuberculous mycobacterial (“NTM”) pulmonary disease (“NTM-PD”). Following the termination of its earlier stage programs, the Company remains focused on completing its obligations under the GSK License Agreement and other corporate activities.

The Company is subject to risks and uncertainties common to companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, protection of proprietary technology, compliance with government regulations, risks of failure or unsatisfactory results of nonclinical studies and clinical trials, the need to obtain marketing approval for its product candidates, the need to successfully commercialize and gain market acceptance of its product candidates, the ability to in-license or acquire other products or new technologies and the ability to secure additional capital to fund operations. The Company’s product candidates will require additional preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

The accompanying consolidated financial statements of the Company have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) and include the accounts of the Company and its consolidated subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

To date, the Company has funded its operations with payments received under license and collaboration agreements and funding from government contracts, and from the proceeds of multiple common stock offerings. The Company has incurred recurring cash outflows from operating activities and losses in most periods since its inception, including net losses of $7.4 million and $17.1 million for the three months ended September 30, 2025 and 2024, respectively, and $22.9 million and $47.7 million for the nine months ended September 30, 2025 and 2024, respectively. In addition, as of September 30, 2025, the Company had an accumulated deficit of $482.6 million. The Company expects to continue to generate operating losses for the foreseeable future.

In accordance with Accounting Standards Update (“ASU”) 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that these consolidated financial statements are issued. As of the issuance date of these quarterly consolidated financial statements, based on its current operating plans, the Company expects the decrease in clinical expense as a result of the completion of the PIVOT-PO Phase 3 trial for tebipenem HBr and the decision to cease development of SPR720, and existing cash and cash equivalents will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of these quarterly consolidated financial statements. The Company currently expects that it will require additional funding to fund the development of its product candidate(s) through regulatory approval and to support its continued operations. The Company may seek additional funding through public or private financings, debt financing, collaboration agreements, government grants or other sources. If the Company's access to capital is restricted or associated borrowing costs increase as a result of developments in financial markets, the Company's operations and financial condition could be adversely impacted. There is no assurance that the Company will be successful in obtaining sufficient funding on acceptable terms, if at all, and it could be forced to delay, reduce or eliminate some or all of its research and development programs, or product portfolio expansion efforts, which could materially affect its business prospects or its ability to continue operations.

Interim Financial Information

The consolidated balance sheet at December 31, 2024 was derived from audited financial statements, but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of September 30, 2025, and for the three and nine months ended September 30, 2025, have been prepared by the Company pursuant to the rules and regulations of the SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2024, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024, on file with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s financial position as of September 30, 2025, and results of operations for the three and nine months ended September 30, 2025 and 2024, and cash flows for the nine months ended September 30, 2025 and 2024 have been made. The results of operations for the three and nine months ended September 30, 2025 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2025.

Summary of Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, revenue recognition, the accrual for clinical trial costs and other research and development expenses and the valuation of stock-based awards. There may be changes to those estimates in future periods. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances, facts and experience. Actual results may differ from those estimates or assumptions.

Segment Information

The Company manages its operations as a single segment for the purpose of assessing performance and making operating decisions. The Company’s singular focus is on identifying and developing novel treatments for rare diseases and diseases caused by MDR bacterial infections with high unmet need. Substantially all of the Company’s tangible assets are held in the United States.

Concentrations of Credit Risk and of Significant Suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains most of its cash and cash equivalents in two accredited financial institutions. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs. As of September 30, 2025 and December 31, 2024, the Company had no off-balance sheet risks, including but not limited, to foreign exchange contracts, option contracts, or other hedging arrangements.

Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents. Cash and cash equivalents include cash held in banks and money market instruments.

Leases

At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than one year are recognized on its consolidated balance sheets as right-of-use assets and short-term and long-term lease liabilities, as applicable. The Company has elected not to recognize leases on its consolidated balance sheets with terms of one year or less. As of September 30, 2025, the Company had no short-term leases with terms of one year or less. Options to renew a lease are not included in the Company’s initial lease term assessment unless there is reasonable certainty that the Company will renew. The Company monitors its plans to renew its material leases on a quarterly basis.

Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. Certain adjustments to the right-of-use asset may be required for items such as incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, and in a similar economic environment. Since the Company does not have any debt and has not been rated by any major credit rating agency, the Company’s IBR was estimated by developing a synthetic credit rating for the Company.

During the third quarter of 2025, the Company identified indicators resulting in the need for an impairment analysis. The analysis resulted in the identification of multiple lease components, while historically the Company had elected to account for the lease and non-lease components together as a single lease component (see Note 4).

Other Assets

Other assets consist of deposits.

Impairment of Long-Lived Assets

Long-lived assets consist of operating lease right-of-use assets. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows.

Fair Value Measurements

Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

•

Level 1—Quoted prices in active markets for identical assets or liabilities.

•

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

•

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s cash equivalents are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities.

Revenue Recognition – Collaboration Revenue

The Company has entered into licensing agreements that are evaluated under Accounting Standards Codification (“ASC”), Topic 606 (“Topic 606”), Revenue from Contracts with Customers, through which the Company licenses certain of its product candidates’ rights to a third party. Terms of these arrangements include various payment types, typically including one or more of the following: upfront license fees; development, regulatory and commercial milestone payments; payments for manufacturing supply services; and/or royalties on net sales of licensed products.

Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract with a customer; (ii) identify the performance obligations under the agreement; (iii) determine the transaction

price, including constraint on variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) determine how the revenue will be recognized for each performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration to which it is entitled in exchange for the goods or services it transfers to a customer.

Once a contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations. The exercise of a material right may be accounted for as a contract modification or as a continuation of the contract for accounting purposes.

The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract). In assessing whether a promised good or service is distinct in the evaluation of a collaboration arrangement subject to Topic 606, the Company considers factors such as the research, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, the Company is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct.

The transaction price is then determined and allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. The SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. In certain circumstances, the Company may apply the residual method to determine the SSP of a good or service if the standalone selling price is considered highly variable or uncertain. The Company validates the SSP for performance obligations by evaluating whether changes in the key assumptions used to determine the SSP will have a significant effect on the allocation of arrangement consideration between multiple performance obligations.

If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment.

If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received.

In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less. When an arrangement contains payment terms that are extended beyond one year, a significant financing component may exist. The Company assessed its revenue-generating arrangements in order to determine whether a significant financing component exists and concluded that a significant financing component exists in certain arrangements. The significant financing component is calculated as the difference between the stated value and present value of the milestones payable and is recognized as interest income over the extended payment period. Judgment is used in determining: (i) whether the financing component in a license agreement is significant and, if so, (ii) the discount rate used in calculating the significant financing component.

For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied.

The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied at a point in time or over time, and if over time this is based on the use of an output or input method.

In determining the accounting treatment for these arrangements, the Company develops assumptions to determine the stand-alone selling price for each performance obligation in the contract. The Company develops the estimated standalone selling price for the license using a discounted cash flow model. To develop this model, the Company applies significant judgment in the determination of the significant assumptions relating to forecasted future revenues, development timelines, the discount rate, and probabilities of technical and regulatory success. The Company develops the estimated standalone selling price for the research and development services using a discounted cash flow model. The assumptions to develop the estimated standalone selling price for the related research and development services include estimates of costs to be incurred to fulfill its obligations associated with the performance of the research and development services, plus a reasonable margin.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including personnel salaries, stock-based compensation and benefits, allocated facilities costs, depreciation, manufacturing expenses, costs related to the Company’s government contract and grant arrangements, and external costs of outside vendors engaged to conduct preclinical development activities, clinical trials as well as the cost of licensing technology. Upfront payments and milestone payments made for the licensing of technology are expensed as research and development in the period in which they are incurred. Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed.

External Research and Development Costs and Accruals

The Company has entered into various research and development contracts with clinical research organizations and other companies both inside and outside of the United States. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company recognizes external research and development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers. This process involves reviewing open contracts and purchase orders, communicating with applicable personnel to identify services that have been performed on the Company’s behalf, and estimating the level of service performed and the associated cost incurred for the service when the Company has not yet been invoiced or otherwise notified of actual costs. There may be instances in which payments made to these vendors exceed the level of service provided and will result in a prepayment of the expense. The Company records accruals for estimated ongoing research and clinical trial costs based on the services received and efforts expended pursuant to multiple contracts with these vendors. When evaluating the adequacy of the accrued liabilities, the Company analyzes the progress of the studies or trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Restructuring

The Company made estimates and judgments regarding the amount and timing of its restructuring expense and liability, including one-time termination benefits and other exit costs accounted for upon the announcement of the restructuring in October 2024 (see Note 8).

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Stock-Based Compensation

The Company issues stock-based awards to employees and directors in the form of stock options and restricted stock units. The Company measures and recognizes compensation expense for its stock-based awards granted to its employees and directors based on the estimated grant date fair value in accordance with ASC Topic 718, Compensation—Stock Compensation, and determines the fair

value of restricted stock units based on the fair value of its common stock. The Company measures all stock-based options granted to employees and directors based on the fair value on the date of grant using the Black-Scholes option-pricing model. Compensation expense of those awards is recognized over the requisite service period, which is generally the vesting period of the respective award. The Company records the expense for awards with service-based conditions using the straight-line method over the requisite service period, net of any actual forfeitures. The Company has also granted certain awards subject to performance-based vesting eligibility and a subsequent partial time-based vesting schedule. The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

Comprehensive Income (Loss)

Comprehensive income (loss) includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. For the three and nine months ended September 30, 2025 and 2024, there were no components of other comprehensive income (loss), and therefore comprehensive loss is the same as net loss.

Net Income (Loss) per Share

When the Company issues shares that meet the definition of participating securities, the Company follows the two-class method when computing net income (loss) per share. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. Net income (loss) per share attributable to common stockholders is calculated based on net income (loss) attributable to the Company.

Basic net income (loss) per share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) attributable to common stockholders is computed by adjusting net income (loss) attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period, including potential dilutive shares assuming the dilutive effect of common stock equivalents.

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement.

On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was signed into law. Under the OBBBA provisions, effective with tax years beginning on or after January 1, 2025, taxpayers can expense qualified domestic research and development expenditures, including all direct, indirect, overhead and software development costs. Taxpayers are still required to capitalize and amortize these costs over fifteen years if conducted outside the United States. The Company is evaluating OBBBA to determine its impact on the Company's consolidated financial statements.

Recently Issued and Adopted Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise noted, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its consolidated financial statements and disclosures.

In September 2025, the FASB issued ASU 2025-07, Derivatives Scope Refinements and Scope Clarification for Share-Based Noncash Consideration from a Customer in a Revenue Contract. The new guidance will reduce the number of contracts (or embedded features within instruments) that are accounted for as derivatives under ASC 815, Derivatives and Hedging. The ASU adds a new scope exception to the derivatives guidance for underlying based on the operations or activities specific to one of the parties to the contract. The ASU also clarifies that share-based noncash consideration received from a customer as consideration for the transfer of goods or services in a revenue contract is subject to the revenue guidance and not the financial instruments guidance unless and until the company’s right to receive or retain the share-based noncash consideration is “unconditional,” as defined in the ASU. The Company is evaluating ASU 2025-07 to determine its impact on the Company's consolidated financial statements.

In July 2025, the FASB issued ASU 2025-05, Measurement of Credit Losses for Accounts Receivable and Contract Assets. The ASU relates to estimating credit losses under CECL for current accounts receivable and current contract assets arising from revenue transactions accounted for under ASC 606, Revenue from Contracts with Customers, including those acquired in a transaction accounted for under ASC 805, Business Combinations. The ASU does not apply to other types of accounts receivable and loans. For all entities, the ASU provides a practical expedient to assume that current conditions as of the balance sheet date will persist through the reasonable and supportable forecast period for eligible assets. Entities will still be required to adjust historical data used in the estimation to reflect current conditions. In addition, entities other than public business entities can also make an accounting policy election to consider subsequent collections of balances received after the balance sheet date through a date selected by the entity. This policy election is available only if the entity elects the practical expedient. The date selected must be when or before financial statements are available to be issued. Under this accounting policy election, no credit loss would be recorded on balances that have been collected through subsequent receipts. Remaining uncollected amounts would be evaluated for credit losses using the practical expedient. The Company is evaluating ASU 2025-05 to determine its impact on the Company's consolidated financial statements.

In November 2024, the FASB issued ASU 2024-03, “Disaggregation of Income Statement Expenses”, to provide disaggregated disclosures of specific expense categories underlying all relevant income statement expense line items on an annual and interim basis. The disclosure requirements will be applied on a prospective basis, with the option to apply them retrospectively. The effective date for the standard is for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The Company is evaluating ASU 2024-03 to determine its impact on the Company's consolidated financial statements.

In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures. This ASU is related to the disclosure of rate reconciliation and income taxes paid. This guidance became effective for annual periods beginning after December 15, 2024. This standard is not expected to have a material impact on the Company's consolidated financial statements, but it requires increased disclosures within the notes to the consolidated financial statements.

Fair Value Measurements and Marketable Securities

The following tables present information about the Company’s assets that are measured at fair value on a recurring basis (in thousands):


	Fair Value Measurements at September 30, 2025 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	—	$	48,101	$	—	$	48,101
Total cash equivalents		—		48,101		—		48,101


	Fair Value Measurements at December 31, 2024 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	—	$	52,258	$	—	$	52,258
Total cash equivalents		—		52,258		—		52,258

Excluded from the tables above is cash of $0.5 million and $0.6 million as of September 30, 2025 and December 31, 2024, respectively. During the nine months ended September 30, 2025, there were no transfers between Level 1, Level 2 and Level 3 categories.

Long-lived Assets and Right-of-use Asset Impairment

During the third quarter of 2025, the Company evaluated its real estate lease in light of the sublease agreements entered into in September 2025. This change in the use of the Cambridge, Massachusetts office space led management to test the recoverability of the carrying amount of the asset group related to the sublease. Accordingly, the Company reviewed certain of its right-of-use assets and other lease related assets under the sublease asset group for impairment in accordance with ASC 360 “Property, Plant, and Equipment”.

As of September 30, 2025, the carrying amount of the asset group exceeded the Company’s anticipated undiscounted value of the sublease income over the sublease term. As a result of the evaluation, the Company recorded an impairment charge of $0.6 million associated with the right-of-use asset in the third quarter of 2025. The asset group was written down to its fair value calculated using a discounted cash flow method (income approach). The fair value of the asset group was determined by utilizing projected cash flows from the sublease, discounted by a risk-adjusted discount rates of 11.4% that reflects the level of risk associated with receiving future cash flows. The inputs utilized in the analyses were classified as Level 3 inputs within the fair value hierarchy as defined in ASC 820, “Fair Value Measurement”. Refer to Note 9, Commitments and Contingencies, for further information about the sublease. The remaining carrying value of the operating lease right-of-use asset of $1.7 million will be amortized on a straight-line basis over the remaining lease term.

Accrued Expenses and Other Current Liabilities

The following table presents the Company’s accrued expenses and other current liabilities as of September 30, 2025 and December 31, 2024 (in thousands):


	September 30, 2025		December 31, 2024
Accrued payroll and related expenses	$	5,643	$	5,456
Accrued external research and development expenses		1,483		9,493
Accrued professional fees		601		2,199
Accrued restructuring expenses		—		456
Accrued other		82		120
Total accrued expenses and other current liabilities	$	7,809	$	17,724

Common Stock

“At-the-Market” Offering

On March 11, 2021, the Company entered into a Controlled Equity Offering Sales Agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (“Cantor”) and filed a universal shelf registration statement on Form S-3, which became effective on March 29, 2021 (the “2021 Form S-3”), and pursuant to which the Company registered for sale up to $300.0 million of any combination of its common stock, preferred stock, debt securities, warrants, rights and/or units from time to time and at prices and on terms that the Company could determine, including up to $75.0 million of its common stock available for issuance pursuant to the “at-the-market” offering program under the Sales Agreement.

The 2021 Form S-3 expired on March 29, 2024. The Company filed a new universal shelf registration statement on Form S-3 with the SEC on March 15, 2024, which became effective on March 22, 2024 (the “2024 Form S-3”), and pursuant to which the Company registered for sale up to $300.0 million of any combination of its common stock, preferred stock, debt securities, warrants, rights and/or units from time to time and at prices and on terms that the Company may determine, including up to $75.0 million of its common stock available for issuance pursuant to the Sales Agreement.

Under the Sales Agreement, Cantor may sell shares of the Company’s common stock by any method permitted by law deemed to be an “at-the-market” offering as defined in Rule 415 of the Securities Act of 1933, as amended (the “Securities Act”), subject to the terms of the Sales Agreement.

During the three and nine months ended September 30, 2025 and 2024, the Company did not sell any shares of its common stock under the Sales Agreement.

Stock-Based Compensation

The Company maintains two equity compensation plans, the 2017 Stock Incentive Plan, as amended (the “2017 Plan”), and the 2019 Inducement Equity Incentive Plan, as amended (the “2019 Inducement Plan”, and together with the 2017 Plan, the “Equity Plans”), which provide for the grant of stock-based awards to its directors, officers, consultants and other employees. The Equity Plans

provide for the grant of non-qualified and incentive stock options, as well as restricted stock units (“RSUs”), restricted stock and other stock-based awards.

On June 12, 2025, the stockholders of the Company approved an amendment to the 2017 Plan to increase the number of shares of the Company's common stock authorized for issuance under the 2017 Plan by 3,000,000 shares.

As of September 30, 2025, an aggregate of 21,345,127 shares of common stock have been authorized and reserved for issuance under the Equity Plans and an aggregate of 8,881,274 shares of common stock were available for future issuance under the Equity Plans.

Stock Options

No options were granted for the nine-month period ended September 30, 2025. The weighted-average grant date fair value of options, estimated as of the grant date using the Black-Scholes option pricing model, was $1.12 per option for those options granted during the nine months ended September 30, 2024.

The following table summarizes stock option activity under the Equity Plans (excluding RSUs) during the nine months ended September 30, 2025:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2024		2,814,850		$	10.71		4.45	$	—
Forfeited or cancelled		(414,417	)		14.96
Outstanding as of September 30, 2025		2,400,433		$	9.98		3.87	$	20,880
Outstanding as of September 30, 2025 - vested and expected to vest		2,400,433		$	9.98		3.87	$	20,880
Exercisable at September 30, 2025		2,370,248		$	9.96		3.84	$	20,522

As of September 30, 2025, there was approximately $0.2 million of total unrecognized compensation expense related to stock options, which is expected to be recognized over a weighted-average period of less than a year.

Restricted Stock Units

The following table summarizes RSU activity under the Equity Plans during the nine months ended September 30, 2025:


	Number of RSU Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2024		6,038,732		$	1.97
Granted		3,952,047			0.88
Vested and released		(1,718,268	)		2.36
Forfeited or cancelled		(2,822,875	)		1.48
Outstanding as of September 30, 2025		5,449,636		$	1.31

As of September 30, 2025, there was approximately $5.2 million of total unrecognized compensation expense related to RSUs, which is expected to be recognized over a weighted-average period of approximately 2.57 years.

The fair value of the RSUs is determined on the date of grant based on the market price of the Company’s common stock on that date. Each RSU represents the right to receive one share of the Company’s common stock upon vesting. The majority of the Company's RSUs vest in four equal annual installments, subject to the individual’s continued service to the Company through the

applicable vesting date, and are subject to the terms and conditions of the Company’s form of RSU agreement under the 2017 Plan and 2019 Inducement Plan, as applicable.

Stock-Based Compensation Expense

The Company recorded stock-based compensation expense related to incentive stock options, nonqualified stock options, stock grants, and stock-based awards in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2025		2024		2025		2024
Research and development expenses	$	397	$	703	$	1,321	$	2,123
General and administrative expenses		651		1,451		1,997		4,167
Total	$	1,048	$	2,154	$	3,318	$	6,290

Restructuring

On October 29, 2024, the Company implemented a strategic restructuring initiative and corresponding reduction in workforce. The Company restructured its operations to reduce costs and reallocate resources in support of the development of tebipenem HBr and other corporate activities. As of September 30, 2025, the Company recognized $1.1 million in expense related to the October 29, 2024 restructuring and does not expect to incur any further charges related to this restructuring.

The following tables summarize the restructuring related charges by line item within the Company’s consolidated statements of operations where they were recorded during the three and nine months ended September 30, 2025 (in thousands):


	Three Months Ended September 30, 2025						Nine Months Ended September 30, 2025
	Research and Development		General and Administrative		Total		Research and Development		General and Administrative		Total
Restructuring and other employee costs	$	—	$	—	$	—	$	190	$	68	$	258
Total restructuring charges	$	—	$	—	$	—	$	190	$	68	$	258

The restructuring charge was included in accrued expenses and other current liabilities in the Company’s consolidated balance sheets as of September 30, 2025. Activity for the period is summarized as follows (in thousands):


	As of September 30, 2025
Balance as of December 31, 2024	$	456
Charge to expense		258
Payments made		(714	)
Balance as of September 30, 2025	$	—

Retention Awards

Non-Executive Retention Awards

In connection with the 2024 restructuring, on October 29, 2024, the Board of Directors approved retention awards for non-executive employees of the Company. Subject to remaining actively employed and in good standing with the Company, aggregate retention awards of $4.4 million were approved to be paid as a cash bonus, with one half payable upon the achievement of each of two clinical execution milestones related to facilitating the clinical progress of the PIVOT-PO trial for tebipenem HBr.

The awards contained certain clawback provisions in the event an employee voluntarily terminates his or her employment prior to the achievement of the second clinical execution milestone.

Expenses related to these retention awards were recognized over the employee service period from October 29, 2024 through the third quarter of 2025.

In May 2025, retention awards of $2.2 million were paid to non-executive employees due to the achievement of the first clinical execution milestone. In October 2025, retention awards of $2.2 million were paid to non-executive employees due to the achievement of the second clinical execution milestone.

Executive Retention Awards

On November 8, 2024, the Compensation Committee of the Board of Directors approved a retention program for the Company’s executive team, which included the then-current Chief Executive Officer, Chief Financial Officer, Chief Operating Officer and Chief Human Resources Officer. The purpose of the program was to help ensure that the Company retained members of its executive team who were considered critical to the development of tebipenem HBr in its PIVOT-PO, global Phase 3 clinical trial of tebipenem HBr in patients with cUTI. The retention program provided these members of the executive team with the opportunity to earn a cash bonus in an amount equaling 75% of the aggregate of their then-current base salary plus target annual bonus upon achievement of certain performance milestones related to facilitating the progress of PIVOT-PO and certain goals related to the Company’s stock price appreciation or financial stewardship. Specifically, the retention bonus was payable in three equal installments based on each of three milestones, with the first and second installments payable upon the achievement of two separate clinical execution milestones. The remaining installment was payable upon the achievement of the stockholder value added milestone, related to stock price appreciation or financial stewardship milestone by no later than the fourth quarter of 2026.

The program contains certain clawback provisions in the event an executive voluntarily terminates his or her employment prior to the achievement of the second clinical execution milestone. The program also provides for full payment in the event of certain change in control transactions.

Expenses related to the achievement of each of the two clinical milestones were recognized over the employee service period from October 29, 2024 through the third quarter of 2025. Expenses related to the achievement of the Company's stock price appreciation or financial stewardship milestone were fully recognized during the quarter ended June 30, 2025.

The total retention payments aggregate to $1.2 million, adjusted for terminations, of which (i) $0.4 million was paid to executives in May 2025 upon achievement of the first clinical milestone, (ii) $0.4 million was paid to executives in October 2025 upon achievement of the second clinical milestone, and (iii) $0.4 million was paid to executives in November 2025 upon achievement of the stockholder value added milestone.

Commitments and Contingencies

As a public biotechnology company, the Company operates in a regulated environment, and from time to time, is party to various legal proceedings and receives regulatory inquiries arising in the ordinary course of business. The costs and outcome of litigation, regulatory, investigatory or other proceedings cannot be predicted with certainty, and some lawsuits, claims, actions or proceedings may be disposed of unfavorably to the Company and could have a material adverse effect on the Company’s results of operations or financial condition. In addition, intellectual property disputes often have a risk of injunctive relief which, if imposed against the Company, could materially and adversely affect its financial condition or results of operations. If a matter is both probable to result in a material liability and the amount of loss can be reasonably estimated, the Company accrues the estimated loss. Disclosure is provided when a loss is considered probable, but the loss is not reasonably estimable and when a material loss is reasonably possible but not probable. If such a loss is not probable or cannot be reasonably estimated, a liability is not recorded. As of September 30, 2025 and December 31, 2024, no material accruals have been recorded for potential contingencies related to these matters.

License Agreements

The Company has entered into license agreements with various parties under which it is obligated to make contingent and non-contingent payments (see Note 11).

Operating Leases

The Company has entered into an operating lease agreement with respect to its corporate headquarters located at 675 Massachusetts Avenue, Cambridge, Massachusetts. In September 2025, the Company entered into sublease agreements for a portion of its lease through the remainder of its lease term. The Company recorded sublease income as a reduction of lease expense, in an amount of less than $0.1 million for the three and nine months ended September 30, 2025.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its Board of Directors and its officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or executive officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The process surrounding the Investigation and the Wells Notice (both as defined below) has resulted in

legal expenses and certain liabilities for the Company and the named individuals, and each of the named individuals, as directors and/or officers of the Company at the time of the initiation of the Investigation and Wells Notice, are entitled to indemnification for certain costs associated with the Investigation and the Wells Notice. The Company maintains a general liability insurance policy that covers certain expenses and liabilities of our directors and officers arising out of claims based on acts or omissions in their capacities as directors or officers (the “D&O Insurance”), however, the total expenses and liabilities in connection with the Investigation and the Wells Notice and the amount that will be covered by such D&O Insurance is unknown at this time. The Company is not aware of any claims under indemnification arrangements that will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of September 30, 2025 or December 31, 2024.

Legal Proceedings

Securities Class Action Lawsuits and Derivative Actions

Two putative class action lawsuits were filed against the Company and certain of its current and former officers in the United States District Court for the Eastern District of New York, one captioned Richard S. Germond v. Spero Therapeutics, Inc., Ankit Mahadevia, and Satyavrat Shukla, Case No. 1:22-cv-03125, filed on May 26, 2022, and the other captioned Kashif Memon v. Spero Therapeutics, Inc., Ankit Mahadevia, and Satyavrat Shukla Case No. 1:22-cv-04154, filed on July 15, 2022. The parties moved to consolidate the two complaints on July 22, 2022, which were ordered consolidated on August 5, 2022 (“Consolidated Putative Class Action”). The parties filed an Amended Complaint on December 5, 2022, purported to be brought on behalf of stockholders who purchased the Company's common stock from September 8, 2020 through May 2, 2022. The Amended Complaint generally alleges that the Company and certain of its current and former officers violated Sections 10(b) and/or 20(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and Rule 10b-5 promulgated thereunder by making allegedly false and/or misleading statements concerning the New Drug Application (“NDA”) for tebipenem HBr in an effort to lead investors to believe that the drug would receive approval from the FDA. Plaintiffs seek unspecified damages, interest, attorneys’ fees, and other costs. The Company filed a fully-briefed Motion to Dismiss on June 21, 2023. By Order entered on September 30, 2024, the Motion to Dismiss was granted, dismissing the Amended Complaint in its entirety. The Court ordered the case to be closed by Memorandum and Order entered on October 28, 2024.

A stockholder derivative action was filed against the Company, as nominal defendant, and certain of the Company's current and former officers in the United States District Court for the District of Delaware, captioned Marti v. Mahadevia, et al., Case. No. 1:23-cv-01133-RGA (the “First Derivative Complaint”), on October 11, 2023. The plaintiffs both purport to be current stockholders, and the allegations are primarily the same as those made in the Consolidated Putative Class Action. The First Derivative Complaint was transferred to the Eastern District of New York on November 13, 2023. A second stockholder derivative action was filed against the Company, as nominal defendant, and certain of its current and former officers in the Supreme Court of the State of New York, Kings County, captioned Heil v. Mahadevia, et al., Case. No. 505153/2024 (the “Second Derivative Complaint”), on February 21, 2024. The Second Derivative Complaint makes primarily the same allegations as the First Derivative Complaint, and the Consolidated Putative Class Action. The plaintiffs in both derivative suits agreed to a stay pending decision on the class action, subject to court approval. By Order entered on September 30, 2024, the motion to stay the First Derivative Complaint was denied as moot due to the dismissal of the Consolidated Putative Class Action. On March 20, 2025, the Second Derivative Complaint was voluntarily dismissed by the plaintiff. On March 31, 2025, the First Derivative Complaint was voluntarily dismissed by the plaintiff.

Additional lawsuits against the Company and certain of its officers or directors may be filed in the future. If additional similar complaints are filed, absent new or different allegations that are material, the Company will not necessarily announce such additional filings.

SEC Investigation and Wells Notice

On January 9, 2025, the Company responded to a “Wells Notice” from the staff of the Boston Regional Office (the “Staff”) of the SEC regarding its preliminary determination to recommend a civil enforcement action or administrative proceeding against the Company, its former Chief Executive Officer and Chairman of the Board of Directors, Ankit Mahadevia, M.D., and its former Chief Financial Officer, President and Chief Executive Officer, Satyavrat “Sath” Shukla, relating to certain public disclosures by the Company from March 31, 2022 leading up to the Company’s announcement on May 3, 2022 that it had determined to cease commercialization of tebipenem HBr based on feedback from the FDA, and whether the Company’s disclosures may have violated the federal securities laws (the “Investigation”).

Specifically, the contemplated civil enforcement action, if approved by the SEC Commissioners, could include allegations that the Company violated Section 17(a) of the Securities Act and Sections 10(b) and 13(a) of the Exchange Act and Rules 10b-5, 12b-20, and 13a-1 thereunder; and could allege against Dr. Mahadevia and Mr. Shukla violations of Section 17(a) of the Securities Act and Section 10(b) of the Exchange Act and Rules 10b-5 and 13a-14 thereunder. The Company continues to cooperate with the SEC, has engaged in further dialogue with the Staff and maintains that the Company’s disclosures were appropriate.

A Wells Notice is neither a formal charge of wrongdoing nor a final determination that the recipient has violated any law, but is a preliminary determination by the Staff to recommend to the SEC Commissioners that a civil enforcement action or administrative proceeding be brought against the recipients. It provides the recipients the opportunity to address in a non-public forum the issues raised by the Staff before a recommendation is made to the SEC regarding an enforcement action. If the SEC were to authorize an action against the Company and/or any of the identified individuals, it may seek an injunction or cease-and-desist order against future violations of provisions of the federal securities laws, the imposition of civil monetary penalties, disgorgement or other equitable relief.

10.

Government Contracts

BARDA

In July 2018, the Company was awarded a contract from Biomedical Advanced Research and Development Authority (“BARDA”) of up to $44.2 million to develop tebipenem HBr for the treatment of cUTI caused by antibiotic resistant Gram-negative bacteria and for assessment against biodefense pathogens. The original award committed initial funding of $15.7 million over a three-year base period from July 1, 2018 to June 30, 2021 for cUTI development activities.

Through a number of contract modifications and the exercise of additional contract options by BARDA, the committed funding was $65.6 million as of September 30, 2025, and the period of performance is through October 31, 2026.

The Company recognized $2.4 million and $5.6 million of revenue under the BARDA agreement during the three months ended September 30, 2025 and 2024, respectively, and $5.5 million and $14.6 million of revenue under the BARDA agreement during the nine months ended September 30, 2025 and 2024, respectively.

As of September 30, 2025, of the $65.6 million of committed funding, the Company has cumulatively recognized $63.5 million of grant revenue under the BARDA agreement.

Biodefense Study Option

As of September 30, 2025, uncommitted funding of $12.7 million is outstanding under the award. This uncommitted funding is exercisable by BARDA, subject to the availability of funding as well as progress and results from biodefense studies, if initiated, as part of an inter-agency collaboration between BARDA and the Defense Threat Reduction Agency.

NIAID

In May 2021, the Company was awarded a five-year contract from the U.S. National Institute of Allergy and Infectious Diseases (“NIAID”) under the Agency’s Omnibus Broad Agency Announcement No. HHS-NIH-NIAID-BAA2020-1 award mechanism to support further development of SPR206. Funding was to be used to offset certain expenses related to manufacturing, clinical, non-clinical and regulatory activities. The Company was to receive up to $27.0 million over a base period and six option periods, including an additional contract modification of $3.4 million executed in August 2024 for SPR206 Phase 2 start up activities under Option 1 of the NIAID agreement. As of September 30, 2025, $10.5 million of funding had been committed under this award and the Company has cumulatively recognized $5.3 million of grant revenue under the NIAID agreement.

In March 2025, following a reprioritization of its programs, the Company announced that it ceased development of SPR206. On April 4, 2025, NIAID communicated that it had terminated the contract for convenience effective immediately.

The Company did not recognize any revenue under the NIAID agreement during the three months ended September 30, 2025, and recognized $0.1 million of revenue under the NIAID agreement during the three months ended September 30, 2024. The Company recognized less than $0.1 million and $0.3 million of revenue under the NIAID agreement during the nine months ended September 30, 2025 and 2024, respectively.

11.

License, Collaboration and Service Agreements

The Company has certain obligations under license agreements with third parties that include annual maintenance fees and payments that are contingent upon achieving various development, regulatory and commercial milestones. Pursuant to these license agreements, the Company is required to make milestone payments if certain development, regulatory and commercial milestones are achieved, and may have certain additional research funding obligations. Also, pursuant to the terms of each of these license agreements, when and if commercial sales of a product commence, the Company will pay royalties to its licensors on net sales of the respective products.

Tebipenem HBr Agreements

GSK License Agreement

On November 7, 2022, the Company closed the transactions contemplated by the GSK License Agreement, which was entered into on September 21, 2022. Pursuant to the terms of the GSK License Agreement, the Company granted GSK an exclusive royalty-bearing license, with the right to grant sublicenses, under the Company’s intellectual property and regulatory documents and a sublicense under certain intellectual property of Meiji Seika Pharma Co. Ltd. (“Meiji”) and Meiji’s regulatory documents to develop, manufacture and commercialize tebipenem pivoxil and tebipenem HBr and products that contain tebipenem pivoxil and tebipenem HBr (the “GSK Licensed Products”) in all territories, except certain Asian countries previously licensed to Meiji (Japan, Bangladesh, Brunei, Cambodia, China, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, South Korea, Taiwan, Thailand and Vietnam (the “Meiji Territory”)) (the “GSK Territory”). If the Company’s license with Meiji is terminated, or if Meiji forfeits or loses its rights to develop, manufacture and commercialize tebipenem HBr and products that contain tebipenem HBr in any countries in the Meiji Territory, then GSK will have an exclusive first right to negotiate with the Company to add any such countries to the GSK Territory.

Under the terms of the GSK License Agreement, in November 2022, the Company received an upfront payment of $66.0 million for GSK to secure rights to tebipenem pivoxil and tebipenem HBr.

In July 2023, the Company received written agreement from the FDA, under a special protocol assessment (“SPA”), on the design and size of PIVOT-PO, a pivotal Phase 3 clinical trial of tebipenem HBr in patients with cUTI, including acute pyelonephritis. Under the terms of the GSK License Agreement, the Company received a $30.0 million development milestone payment during the third quarter of 2023.

In December 2023, the Company commenced enrollment in PIVOT-PO with its first patient, first visit. Under the terms of the GSK License Agreement, the Company is entitled to receive a $95.0 million development milestone that is payable in four equal semiannual installments. The Company received the first installment payment of $23.8 million for such development milestone in the first quarter of 2024, the second installment payment of $23.8 million in the third quarter of 2024, the third installment payment in the first quarter of 2025 and the Company received the final development milestone payment of $23.8 million in the third quarter of 2025.

In May 2025, the Company announced that the PIVOT-PO Phase 3 trial met its primary endpoint and was stopped early for efficacy after a review of data from a pre-specified interim analysis of data from 1,690 patients enrolled in the trial. GSK plans to submit the data from the trial as part of an FDA filing during the fourth quarter of 2025.

Remaining potential payments under the GSK License Agreement, which include milestones and royalties based on future regulatory events, commercial launch, and achievement of pre-specified sales thresholds, are as follows (in millions):


Contingent Event	Milestone Payment
Tebipenem NDA Submission by GSK	$	25.0
Total potential commercial milestones based on first commercial sales	$	101.0	*
First commercial sale of a product in the United States		—		$	51.0
Second anniversary of first commercial sale of a product in the United States		—		$	25.0
First commercial sale of a product in two European countries		—		$	25.0
Total potential sales milestone payments	$	225.0
Net annual sales greater than $200.0		—		$	25.0
Net annual sales greater than $300.0		—		$	25.0
Net annual sales greater than $400.0		—		$	25.0
Net annual sales greater than $500.0		—		$	50.0
Net annual sales greater than $750.0		—		$	50.0
Net annual sales greater than $1,000.0		—		$	50.0

*Under the terms of the GSK License Agreement, the maximum potential milestone amount was revised from $150.0 million after PIVOT-PO was stopped early for efficacy following completion of a pre-specified interim analysis of data from 1,690 patients enrolled in the trial, thereby reducing the overall cost of the trial to the Company; the maximum potential milestone payment of $150.0 million was contingent upon the trial continuing to full enrollment, with 2,637 patients enrolled in the trial.

In addition to the milestones described above, GSK is obligated to pay royalties to the Company on annual net sales of GSK Licensed Products in the GSK Territory. Such royalties are 1% for annual sales up to $750.0 million each year and range from high single-digit percentages on annual net sales above $750.0 million each year to low double-digit percentages on annual net sales above $1,000.0 million each year.

Amendments to the GSK License Agreement

In July 2023, the Company entered into Amendment 1 to the GSK License Agreement, which updated the timeframe for technology transfer in the GSK License Agreement.

In December 2023, the Company entered into Amendment 2 to the GSK License Agreement, which added a country to the locations for PIVOT-PO trial enrollment. Under the terms of Amendment 2, the Company may receive up to an additional $4.3 million in milestone payments based on activities in such country. The Company received the first milestone payment under Amendment 2 of $1.2 million in August 2024 and received the second milestone payment of $1.3 million in October 2024. The third milestone was achieved in December 2024 and the milestone payment of $0.7 million was received in February 2025. Given the PIVOT-PO trial evaluating tebipenem HBr has been stopped early for efficacy, the fourth milestone of $1.1 million will not be achieved.

In March 2024, the Company entered into Amendment 3 to the GSK License Agreement, which assigns its rights to Product Trademarks (as defined in Amendment 3 to the GSK License Agreement) to GSK.

In October 2024, the Company entered into Amendment 4 to the GSK License Agreement, under which the Company is expected to receive an additional $0.8 million upon completion of activities related to an additional Phase 1 clinical study. The Company received $0.4 million of the milestone payment in January 2025 and anticipates receipt of the remaining milestone payment in the fourth quarter of 2025.

Royalties are subject to reduction in the event of third-party licenses, entry of a generic product or expiration of patent and regulatory exclusivity prior to the tenth anniversary of the first commercial sale of a GSK Licensed Product in a particular country.

The Company is responsible for the execution and costs of the follow-up Phase 3 clinical trial of tebipenem HBr. GSK will be responsible for the execution and costs of any additional further development, including additional Phase 3 regulatory filing and commercialization activities for tebipenem HBr in the GSK Territory. The Company is also responsible for providing and paying for the clinical supply of tebipenem HBr while GSK will be responsible for the costs of the commercial supply of tebipenem HBr. A joint development committee has been established between GSK and the Company to coordinate and review development activities for tebipenem HBr in the United States.

Unless earlier terminated due to certain material breaches of the GSK License Agreement or by GSK for convenience, or otherwise, the GSK License Agreement will expire on a jurisdiction-by-jurisdiction and GSK Licensed Product-by-GSK Licensed Product basis on the latest to occur of (i) loss of patent exclusivity, (ii) loss of regulatory exclusivity or (iii) ten years following the date of the first commercial sale of such licensed product in such country (the “GSK Royalty Term”). During the GSK Royalty Term, the Company has agreed not to develop, manufacture or commercialize any oral carbapenem for any indication or any oral antibiotic for cUTI; this restriction does not apply to any third party which acquires control of the Company after the date of the GSK License Agreement if certain conditions are met.

The Company has the right to terminate the GSK License Agreement upon a material breach by, or bankruptcy of, GSK. GSK has the right to terminate the GSK License Agreement at any time upon a specified number of days’ notice or upon a material breach by, or bankruptcy of, the Company. In addition, in the event that GSK has the right to terminate the GSK License Agreement due to a material breach by the Company, GSK may elect not to terminate the GSK License Agreement and in lieu thereof may assume the responsibility and expense of development of tebipenem HBr in the United States, in which event GSK’s obligation to make further development payments to the Company (including unpaid installments of any earned milestone payments) would cease, and/or to reduce all subsequent commercial and sales milestone payments and royalty payments otherwise due by GSK to the Company under the GSK License Agreement by 50%. In the case of a Change of Control (as defined in the GSK License Agreement) of the Company, GSK similarly may, in lieu of terminating the GSK License Agreement, assume responsibility and expense of development of tebipenem HBr in the United States and no development milestones would be payable to the Company, as described above.

The GSK License Agreement contains representations and warranties, other covenants, indemnification provisions and other terms and conditions customary for transactions of the type contemplated by the GSK License Agreement. In support of certain of its rights to indemnification, GSK also has certain rights to suspend payments otherwise owed to the Company, as well as the right to offset payments otherwise owed to the Company against certain indemnifiable claims.

Accounting Analysis and Revenue Recognition

The Company determined that GSK is a customer and that the GSK License Agreement is within the scope of Topic 606 as licensing intellectual property and performing ongoing research and development services are ordinary activities that are ongoing and central to the Company’s operations. Accordingly, in determining the appropriate amount of revenue to be recognized, the Company performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised

goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measured the transaction price, including the constraint on variable consideration; (iv) allocated the transaction price to the identified performance obligations in proportion to their SSP; and (v) recognized revenue when each performance obligation was deemed to be satisfied.

Based on that evaluation, the Company identified two performance obligations, related to the license and to research and development services.

The Company developed the estimated SSP for the license using a discounted cash flow model. In developing this estimate, the Company applied significant judgment in the determination of the significant assumptions relating to forecasted future cash flows, the discount rate, and the probability of success. The SSP for the research and development services was estimated based on the Company’s estimate of costs to be incurred to fulfill its obligations associated with the performance of the research and development services, plus a reasonable margin.

At contract inception, the total transaction price was $64.7 million, which included the initial payment of $66.0 million in the fourth quarter of 2022 and the discount of $1.3 million related to the stock purchase agreement (“GSK SPA”) with Glaxo Group Limited, an affiliate of GSK. At contract inception, $45.7 million of the initial $64.7 million was allocated to the license transfer performance obligation, which was fully satisfied and recognized as revenue upon delivery of the license. The remaining $19.0 million was allocated to the research and development services obligation and is being recognized over time as services are delivered, which was originally estimated to be over a three-year period.

The Company recognized revenue for the license performance obligation at a point in time, that is upon transfer of the license to GSK. Control of the license was transferred on September 21, 2022 (the “GSK Effective Date”) and GSK could begin to use and benefit from the license at the GSK Effective Date.

The $30.0 million milestone payment received by the Company under the GSK License Agreement, was accounted for as variable consideration under Topic 606 and was added to the transaction price in the third quarter of 2023. Of this $30.0 million milestone, $21.2 million was recognized upon achievement of the milestone and the remaining $8.8 million was allocated to the research and development services performance obligation and will be recognized over time as the services are delivered, on a cumulative catch-up basis.

The Company is entitled to receive the $95.0 million milestone payment in four equal semiannual installments under the GSK License Agreement. This milestone payment was accounted for as variable consideration under Topic 606 and was added to the transaction price in the fourth quarter of 2023. The Company determined that a significant financing component of $2.5 million exists related to extended payments terms granted to GSK. The Company presents the effects of the financing component separately from collaboration revenue – related party as a component of interest income in its consolidated statement of operations. Of the $95.0 million milestone payment, $64.7 million was recognized upon achievement of the milestone in the fourth quarter of 2023, and the remaining amount after the $2.5 million significant financing component was allocated to the research and development services performance obligation and will be recognized over time as the services are delivered.

The milestone installment payments are classified as collaboration receivable – related party on the Company’s consolidated balance sheet as of September 30, 2025. The Company received the first milestone installment payment of $23.8 million in the first quarter of 2024, the second milestone payment of $23.8 million in the third quarter of 2024, and the third milestone payment of $23.8 million in the first quarter of 2025. The Company received the final development milestone payment of $23.8 million in the third quarter of 2025.

The potential future development milestone payments from the GSK License Agreement will be accounted for as variable consideration under Topic 606. Given the uncertain nature of these payments, the Company determined they were fully constrained as of September 30, 2025 and not included in the transaction price. The Company can also earn sales-based royalties.

Pursuant to Amendment 2 to the GSK License Agreement, the Company allocated $3.2 million of the total potential additional milestone payments of $4.3 million to the research and development services obligation, as those development milestones were considered probable of achievement. These potential milestones were accounted for as variable consideration under Topic 606 and were added to the transaction price in the fourth quarter of 2023 and will be recognized over time as services are delivered. Due to the pivotal Phase 3 PIVOT-PO trial evaluating tebipenem HBr meeting its primary endpoint and stopping early for efficacy, the remaining $1.1 million milestone will not be achieved.

Pursuant to Amendment 4 to the GSK License Agreement, the Company allocated $0.8 million of the total potential additional milestone payments to the research and development services obligation, as those development milestones were considered probable of achievement. These potential milestones were accounted for as variable consideration under Topic 606 and were added to the transaction price in the fourth quarter of 2024 and will be recognized over time as services are delivered.

In relation to the May 2025 announcement that the pivotal Phase 3 PIVOT-PO trial evaluating tebipenem HBr met its primary endpoint and has stopped early for efficacy, the Company updated the estimated costs to complete its performance obligations under the GSK License Agreement and updated the timeline for completion of performance obligations resulting in the recognition of additional revenue as a cumulative catch-up in the second quarter of 2025. In total and inclusive of the above, the Company recognized $3.0 million and $7.8 million during the three months ended September 30, 2025 and 2024, respectively, and $19.9 million and $17.7 million during the nine months ended September 30, 2025 and 2024, respectively, related to the performance obligations, which were recorded as collaboration revenue – related party on its consolidated statement of operations.

The remaining transaction price balance of approximately $2.4 million from the GSK License Agreement allocated to the research and development services performance obligation has been recorded as deferred revenue - related party in the condensed consolidated balance sheets. As of September 30, 2025, the research and development services related to the performance obligations are expected to be recognized as costs are incurred over the remaining project development timeframe.

Meiji License Agreement

In June 2017, the Company entered into agreements with Meiji, whereby Meiji granted to the Company a license under certain patents, know-how and regulatory documentation to research, develop, manufacture and sell products containing the carbapenem chemical compound having the generic name, tebipenem pivoxil in the licensed territory. In exchange for the license, the Company paid Meiji an upfront, one-time, nonrefundable, non-creditable fee of $0.6 million, which was recognized as research and development expense. In October 2017, the Company paid a $1.0 million milestone payment to Meiji upon the enrollment of the first patient in the Company’s Phase 1 clinical trial of tebipenem HBr. The payment was recorded as research and development expense in the statement of operations and comprehensive loss for the year ended December 31, 2017. The Company paid Meiji approximately $1.6 million during the fourth quarter of 2018 related to fixed assets which will be used in manufacturing related activities at Meiji. This equipment has been capitalized as property and equipment in the consolidated balance sheets as of December 31, 2024. In October 2021, the Company paid a $1.0 million milestone payment to Meiji upon submission of an NDA to the FDA for tebipenem HBr. The Company was obligated to pay Meiji a low double-digit percentage of any sublicense fees received by the Company up to a maximum amount of $7.5 million, which the Company fully paid by the fourth quarter of 2023. The Company recorded these amounts as research and development expenses in the Company’s consolidated statement of operations.

The Company is obligated to make future milestone payments of $1.0 million upon receipt of NDA approval from the FDA for tebipenem HBr, and to pay royalties, on a product-by-product and country-by-country basis, of 1% of net sales of products licensed under the agreement.

The agreement continues in effect until the expiration of all payment obligations thereunder (including royalty payments and licensee revenue) on a product-by-product and country-by-country basis, unless earlier terminated by the parties. Pursuant to the terms of the agreement, in addition to each party’s right to terminate the agreement upon the other party’s material breach (if not cured within a specified period after receipt of notice) or insolvency, the Company also has unilateral termination rights (i) in the event that the Company abandons the development and commercialization of tebipenem HBr for efficacy, safety, legal or business reasons, and (ii) under certain circumstances arising out of the head license with a global pharmaceutical company.

SPR720 Agreements

Vertex Assignment and License Agreement

In May 2016, the Company entered into an agreement with Vertex Pharmaceuticals Incorporated (“Vertex”) whereby Vertex granted the Company certain know-how and a sublicense to research, develop, manufacture and sell products for a proprietary compound, as well as a transfer of materials. In exchange for the know-how, sublicense and materials, the Company paid Vertex an upfront, one-time, nonrefundable, non-creditable fee of $0.5 million, which was recognized as research and development expense. As part of the agreement, the Company is obligated to make future milestone payments of up to $80.2 million upon the achievement of specified clinical, regulatory and commercial milestones and to pay Vertex tiered royalties, on a product-by-product and country-by-country basis, of a mid-single-digit to low double-digit percentage based on net sales of products licensed under the agreement. During the three and nine months ended September 30, 2025 and 2024, the Company did not record any research and development expense under this agreement, and the next milestone under this agreement is not accrued because it is not probable.

The agreement continues in effect until the expiration of all payment obligations thereunder, with royalty payment obligations continuing on a product-by-product and country-by-country basis until the later of ten years after the first commercial sale of such product in such country or the date of expiration in such country of the last to expire applicable patent. Further, Vertex has the right to terminate the agreement if provided with notification from the Company of intent to cease all development or if no material development or commercialization efforts occur for one year. In November 2025, the Company announced that it ceased development of SPR720, a product candidate for first-line treatment of NTM-PD.

SPR206 Agreements

Cantab License Agreement

In June 2016, the Company entered into a stock purchase agreement (the “Cantab Agreement”) with Pro Bono Bio PLC, a corporation organized under the laws of England, and its affiliates, including PBB Distributions Limited (“PBB”), Cantab Anti-Infectives Ltd. and New Pharma License Holdings Limited. Under the Cantab Agreement, the Company is obligated to make future milestone payments of up to $5.8 million upon the achievement of specified clinical and regulatory milestones and a payment of £5.0 million ($6.7 million as of September 30, 2025) upon the achievement of a specified commercial milestone. In addition, the Company agreed to pay to PBB royalties, on a product-by-product and country-by-country basis, of a low single-digit percentage based on net sales of products licensed under the agreement. During both the three and nine months ended September 30, 2025 and 2024, the Company did not record any research and development expense related to the achievement of regulatory milestones for SPR206, as no milestones were met or are probable of being met as of the balance sheet date.

The Cantab Agreement continues indefinitely, with royalty payment obligations thereunder continuing on a product-by-product and country-by-country basis until the later of ten years after the first commercial sale of such product in such country or the expiration in such country of the last to expire valid claim of any of the applicable patents. In March 2025, the Company notified the parties of the Cantab agreement of its decision to cease development of SPR206.

Everest Medicines License Agreement

On January 4, 2019, the Company, through its wholly owned subsidiary New Pharma License Holdings Limited (“NPLH”), entered into a license agreement (the “Original Everest License Agreement”), with Everest Medicines II Limited (“Everest”). Under the terms of the Original Everest License Agreement, the Company granted Everest an exclusive license to develop, manufacture and commercialize SPR206 or products that contain SPR206 (the “Everest Licensed Products”), in Greater China (which includes People’s Republic of China, including Hainan Island, the Hong Kong Special Administrative Region of the People’s Republic of China, and the Macau Special Administrative Region of the People’s Republic of China), Taiwan, the Republic of Korea (South Korea), the Republic of Singapore, Malaysian Federation, Kingdom of Thailand, the Republic of Indonesia, Socialist Republic of Vietnam and the Republic of the Philippines (the “Everest Territory”). The Company retained development, manufacturing and commercialization rights with respect to SPR206 and Everest Licensed Products in the rest of the world and also retained the right to develop or manufacture SPR206 and Everest Licensed Products in the Everest Territory for use outside the Territory. In addition to the license grant with respect to SPR206, the Company, through its wholly owned subsidiary, Spero Potentiator, Inc., a Delaware corporation, granted Everest a 12-month exclusive option to negotiate with it for an exclusive license to develop, manufacture and commercialize SPR741 in the Everest Territory.

Under the terms of the Original Everest License Agreement, the Company received an upfront payment of $3.0 million that was recognized in the first quarter of 2019, comprised of a $2.0 million payment to license SPR206 and $1.0 million for the exclusive option to negotiate a license to develop SPR741. The Company also received a milestone payment of $2.0 million in the fourth quarter of 2020 upon completion and delivery of the results of a clinical study.

On January 15, 2021, the Company entered into an amended and restated license agreement (“the Amended Everest License Agreement”) with Everest and Spero Potentiator, Inc., which amended and restated in its entirety the Original Everest License Agreement. The Amended Everest License Agreement modified the dates and values of certain milestone events related to development and commercialization of SPR206 to allow Everest to make more significant investments in the development of SPR206 beyond what was contemplated at the time of the Original Everest License Agreement. The Original Everest License Agreement provided that the Company could receive up to $59.5 million upon achievement of certain milestones. The Amended Everest License Agreement provides that the Company may receive up to $38.0 million upon achievement of certain milestones, of which $2.0 million has been received to date. In addition, under the Amended Everest License Agreement, the Company assigned patents in the Everest Territory to Everest, rather than licensing such patents to Everest, and the option related to SPR741 and the related provisions have been removed. Under the terms of the Amended Everest License Agreement, the Company is also entitled to receive high single-digit to low double-digit royalties on net sales, if any, of Everest Licensed Products in the Everest Territory following regulatory approval of SPR206. Everest has the right to sublicense to affiliates and third parties in the Everest Territory.

Everest is responsible for all costs related to developing, obtaining regulatory approval of and commercializing SPR206 and Everest Licensed Products in the Everest Territory, and is obligated to use commercially reasonable efforts to develop, manufacture and commercialize Everest Licensed Products, including to achieve certain specified diligence milestones within agreed-upon periods. A joint development committee has been established between the Company and Everest to coordinate and review the development, manufacturing and commercialization plans with respect to Everest Licensed Products in the Everest Territory.

Unless earlier terminated due to certain material breaches of the contract, or otherwise, the Amended Everest License Agreement will expire on a jurisdiction-by-jurisdiction and Everest Licensed Product-by-Everest-Licensed Product basis upon the latest to occur of expiration of the last valid claim under a licensed patent in such jurisdiction, the expiration of regulatory exclusivity in such jurisdiction or ten years after the first commercial sale of such Everest Licensed Product in such jurisdiction. The Amended Everest License Agreement may be terminated in its entirety by Everest upon 90 or 180 days’ prior written notice, depending on the stage of development of the initial Everest Licensed Product.

As of the date of the filing of this Quarterly Report on Form 10-Q, all performance obligations under the contract by the Company were fully satisfied.

As of September 30, 2025, remaining future milestone payments of $34.0 million from Everest are fully constrained, and will be recognized when and if achievement of those milestones becomes probable.

The Company did not recognize revenue under this agreement during both the three and nine months ended September 30, 2025 and 2024. The Company notified Everest of its decision to cease development of SPR206 in March 2025.

Pfizer License and Share Purchase Agreements

On June 30, 2021, the Company and Pfizer Inc. (“Pfizer”) entered into the Pfizer License Agreement and the Pfizer Purchase Agreement. Under the terms of the Pfizer License Agreement, the Company granted Pfizer an exclusive royalty-bearing license to develop, manufacture and commercialize SPR206 or products that contain SPR206 (the “Pfizer Licensed Products”) globally with some territorial exceptions (the “Pfizer Territory”). The Pfizer Territory excludes the United States and the Everest Territory.

In connection with the Pfizer Purchase Agreement, Pfizer purchased 2,362,348 shares of the Company’s common stock at a price of $16.93 per share for a total investment of $40.0 million. The Company received no other upfront payments but is eligible to receive up to $80.0 million in development and sales milestones, and may also receive high single-digit to low double-digit royalties on net sales of SPR206 in the Pfizer Territory. Achievement of these payments cannot be guaranteed. The Company and Pfizer agree that upon Pfizer’s request, the parties will negotiate in good faith regarding procuring a clinical or commercial supply of the compound.

Under the Pfizer Purchase Agreement, the fair market value of the 2,362,348 shares of the Company’s common stock issued to Pfizer was determined to be $27.5 million, which was valued using an option pricing valuation model as the shares are subject to certain holding period restrictions. The Company accounted for the associated premium of $12.5 million as a freestanding equity-linked instrument under ASC Topic 815. The premium was allocated as consideration for the Pfizer License Agreement and evaluated under Topic 606. The premium was determined not to be constrained and was included in the calculation of the total transaction price related to the Pfizer License Agreement as of June 30, 2021.

The Company is responsible for all costs related to developing and obtaining regulatory approval of SPR206 and Pfizer Licensed Products in the Pfizer Territory, with a focus on the European market, and is obligated to use commercially reasonable efforts, including to achieve certain specified diligence milestones within agreed-upon periods. A joint development committee was established between the Company and Pfizer to coordinate and review the development, manufacturing and commercialization plans with respect to Pfizer Licensed Products in the Pfizer Territory. Pfizer is responsible for commercializing SPR206 and the Pfizer Licensed Products in the Pfizer Territory.

Unless earlier terminated due to certain material breaches of the contract or at Pfizer’s convenience, or otherwise, the Pfizer License Agreement will expire on a jurisdiction-by-jurisdiction and licensed product-by-licensed product basis after ten years from the effective date. The Pfizer License Agreement will automatically renew for an additional ten-year term unless terminated. The Company notified Pfizer of its decision to cease development of SPR206 in March 2025.

Accounting Analysis and Revenue Recognition

The Company determined that Pfizer is a customer and that the Pfizer License Agreement is within the scope of Topic 606 as licensing intellectual property and performing ongoing research and development services are ordinary activities that are ongoing and central to the Company’s operations. Accordingly, in determining the appropriate amount of revenue to be recognized, the Company performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measured the transaction price, including the constraint on variable consideration; (iv) allocated the transaction price to the identified performance obligations in proportion to their SSP; and (v) recognized revenue when each performance obligation was deemed to be satisfied.

Based on that evaluation, the Company identified two performance obligations, license and know-how transfer and research and development services related to upcoming milestones. The Company determined that the supply agreement is a customer option and not a material right, as the pricing to Pfizer is not at a significant discount. Furthermore, Pfizer has the right to use third parties to manufacture the compound, or to manufacture the compound itself.

At contract inception, $1.4 million of the then transaction price of $12.5 million was allocated to the license and know-how transfer performance obligations, which was fully satisfied and recognized as revenue upon delivery of the license. The additional $11.1 million was allocated to the research and development services obligation and is being recognized over time as services are delivered.

In the third quarter of 2022, upon the completion of a milestone related to regulatory engagement for SPR206, Pfizer communicated its approval that the milestone was achieved, and the Company received $5.0 million under the Pfizer License Agreement, which the Company accounted for as variable consideration under Topic 606 and was added to the transaction price in the third quarter of 2022. Of this $5.0 million milestone, $0.9 million was recognized during the third quarter of 2022 and the remaining $4.1 million was allocated to the research and development services performance obligation and is recognized over time as the services are delivered.

The potential license maintenance fees and development milestone payments from the Pfizer License Agreement will be accounted for as variable consideration under Topic 606. Given the uncertain nature of these payments, the Company determined they were fully constrained as of September 30, 2025 and not included in the transaction price. The Company can also earn sales-based royalties.

The Company recognizes revenue for the license performance obligation at a point in time, that is upon transfer of the license to Pfizer. Control of the license was transferred on the Effective Date and Pfizer could begin to use and benefit from the license at the Effective Date.

In total, and inclusive of the above, the Company did not recognize any revenue from the contract during the three months ended September 30, 2025, and recognized $0.1 million of revenue from the contract during the three months ended September 30, 2024. The Company recognized less than $0.1 million and $0.3 million of revenue from the contract during the nine months ended September 30, 2025 and 2024, respectively.

The remaining transaction price balance of approximately $12.6 million from the Pfizer Purchase Agreement allocated to the research and development services performance obligation has been recorded as deferred revenue in the condensed consolidated balance sheets. In March 2025, following a reprioritization of its programs, the Company announced that it ceased development of SPR206.

12.

Segment Information

The Company manages its operations as a single operating segment for the purpose of assessing performance and making operating decisions, resulting in a single reportable segment. The Company’s singular focus is on identifying and developing novel treatments for rare diseases and diseases caused by MDR bacterial infections with high unmet needs. The Company earns revenue from collaboration agreements with third parties and grant revenue in connection with various government awards. The Company has determined that its Chief Operating Decision Maker (“CODM”) is its Chief Executive Officer. The CODM reviews the Company’s financial information on a consolidated basis for the purpose of allocating resources and assessing financial performance. The measure of segment assets is reported on the balance sheet as total consolidated assets. All of the Company’s tangible assets are held in the United States.

The accounting policies for the operating segment are consistent with the Company’s policies for the consolidated financial statements. The key measure of segment profit or loss that the CODM uses to allocate resources and assess performance is the Company’s consolidated profit or loss, as reported on the consolidated statements of operations and comprehensive loss. This is reviewed against budgeted expectations to assess segment performance and allocate resources. The Company's reportable segment net

revenues, significant segment expenses and consolidated loss for the three and nine months ended September 30, 2025 and 2024, consisted of the following:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2025			2024			2025			2024
Revenues:
Grant revenue	$	2,394		$	5,650		$	5,544		$	14,893
Collaboration revenue - related party		3,048			7,754			19,949			17,721
Collaboration revenue		—			65			12			319
Total revenues		5,442			13,469			25,505			32,933

Less:
Tebipenem HBr		4,959			18,020			20,321			39,937
SPR720		178			3,879			975			13,087
SPR206		—			157			49			503
Research and development personnel related (including stock-based compensation)		2,244			3,836			8,192			10,768
Facility related and other, research and development		1,216			972			3,338			3,626
General and administrative personnel related (including stock-based compensation)		2,352			3,273			9,838			9,781
Professional and consultant fees		1,185			1,374			5,433			5,183
Facility related and other, general and administrative		637			551			1,605			1,684
Other segment items*		585			26			838			39
Interest income		(532	)		(1,182	)		(2,136	)		(3,707	)
Income tax benefit		—			(290	)		—			(290	)
Consolidated loss	$	(7,382	)	$	(17,147	)	$	(22,948	)	$	(47,678	)

*Other segment items include impairment charges (see Note 4), restructuring charges (see Note 8), and other income, net.

13.

Net Loss per Share

Basic and diluted net loss per share attributable to common stockholders of the Company was calculated as follows (in thousands, except share and per share amounts):


	Three Months Ended September 30,						Nine Months Ended September 30,
	2025			2024			2025			2024
Numerator:
Net loss attributable to common stockholders	$	(7,382	)	$	(17,147	)	$	(22,948	)	$	(47,678	)

Denominator:
Weighted average shares of common stock outstanding, basic and diluted		56,280,844			54,124,862			55,866,392			53,869,824

Net loss per share attributable to common stockholders, basic and diluted	$	(0.13	)	$	(0.32	)	$	(0.41	)	$	(0.89	)

The Company excluded potentially dilutive securities from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders of the Company is the same. The Company excluded the following potential shares of common stock, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2025		2024		2025		2024
Options to purchase common stock		2,400,433		2,856,663		2,400,433		2,856,663
Unvested RSUs and PSUs		5,449,636		7,490,341		5,449,636		7,490,341
		7,850,069		10,347,004		7,850,069		10,347,004

14. Subsequent Events

The Company has evaluated, for potential recognition and disclosure, events that occurred prior to the date at which the consolidated financial statements were available to be issued. There were no material subsequent events.

Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations.

You should read the following discussion and analysis of our financial condition and results of operations together with the unaudited financial information and the notes thereto appearing elsewhere in this Quarterly Report on Form 10-Q, and the audited financial information and the notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2024. Some of the information contained in this discussion and analysis or set forth elsewhere in this Quarterly Report on Form 10-Q, including information with respect to our plans and strategy for our business, includes forward-looking statements that involve risks and uncertainties. As a result of many factors, including those factors set forth in the “Risk Factors” in Part II, Item 1A of this Quarterly Report on Form 10-Q, our actual results could differ materially from the results described in, or implied by, the forward-looking statements contained in the following discussion and analysis.

Overview

We are a clinical-stage biopharmaceutical company focused on identifying and developing novel treatments for rare diseases and diseases caused by MDR bacterial infections with high unmet need.

Our clinical-stage product candidate, tebipenem HBr, has completed a Phase 3 trial with the potential to be the first broad-spectrum oral carbapenem to treat adult patients with cUTIs, including pyelonephritis, caused by certain microorganisms. In May 2025, we and GSK announced that the pivotal Phase 3 PIVOT-PO trial evaluating tebipenem HBr met its primary endpoint and was stopped early for efficacy. Results from the Phase 3 PIVOT-PO trial were featured in a late breaking oral presentation on October 20, 2025, at IDWeek in Atlanta, GA. GSK plans to submit the data from the trial as part of an FDA filing during the fourth quarter of 2025.

In March 2025, following a reprioritization of our programs, we announced that we were no longer pursuing a Phase 2 clinical trial for SPR206 and we have now ceased further development of the program. Additionally, in November 2025, we announced that we ceased development of SPR720, a product candidate for first-line treatment of NTM-PD. Following the termination of our earlier stage programs, we remain focused on completing our obligations under the GSK License Agreement and other corporate activities.

We have experienced mostly net losses and significant cash outflows from cash used in operating activities since our inception. Our ability to generate product revenue sufficient to achieve profitability will depend heavily on the successful development and eventual commercialization of tebipenem HBr, or any product candidate we may develop in the future. As of September 30, 2025, we had an accumulated deficit of $482.6 million, and cash and cash equivalents of $48.6 million. We expect to continue to incur significant expenses and operating losses for at least the next year. Based on our cash and cash equivalents as of September 30, 2025 and the decrease in clinical expense as a result of the completion of the PIVOT-PO Phase 3 trial for tebipenem HBr and the decision to cease development of SPR720, we believe that our cash runway will be sufficient to fund our operating expenses and required capital expenditures into 2028. During this period, we plan to prioritize finalizing the Phase 3 clinical trial activities for tebipenem HBr under our GSK License Agreement. Beyond this point, or in the event we change our current operating plan, we will need additional funding to support our continuing operations and explore our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, government funding arrangements, collaborations, strategic alliances and marketing, distribution or licensing arrangements. If we are not able to secure adequate additional funding, we will have to make further reductions in spending. In that event, we may have to delay, scale back, or eliminate some or all of our planned development activities. The actions necessary to reduce spending under this plan at a level that mitigates the factors described above are not considered probable, as defined in the accounting standards and therefore, the full extent to which management may extend our funds through these actions may not be considered in management’s assessment of our ability to continue as a going concern.

We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for our product candidates. If we obtain regulatory approval for any of our future product candidates and do not enter into a commercialization partnership, we expect to incur significant expenses related to developing our internal commercialization capability to support product sales, marketing and distribution. Further, we expect to incur additional costs associated with our continued operation as a public company.

Because of the numerous risks and uncertainties associated with pharmaceutical product development, we are unable to accurately predict the timing or amount of increased expenses or when or if we will be able to achieve or maintain profitability. Even if we are able to generate product sales, we may not become profitable. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to continue our operations at planned levels and be forced to reduce or terminate our operations.

Recent Developments

Tebipenem HBr

In May 2025, we and GSK announced that the pivotal Phase 3 PIVOT-PO trial evaluating tebipenem HBr, an investigational oral treatment for cUTIs, including pyelonephritis, met its primary endpoint and has stopped early for efficacy. The decision followed a recommendation from an Independent Data Monitoring Committee (“IDMC”) that completed a pre-specified interim analysis of data from 1,690 patients enrolled in the trial.

The trial met the primary endpoint of non-inferiority of tebipenem HBr compared to intravenous imipenem-cilastatin in hospitalized adult patients with cUTI, including pyelonephritis, on overall response (composite of clinical cure plus microbiological eradication) at the test-of-cure visit. The IDMC review did not identify any new safety concerns beyond what has been reported in other studies with tebipenem, with diarrhea and headache as the two most reported adverse events. Results from the Phase 3 PIVOT-PO trial were featured in a late breaking oral presentation on October 20, 2025, at IDWeek in Atlanta, GA. GSK plans to submit the data from the trial as part of an FDA filing during the fourth quarter of 2025.


Contingent Event	Milestone Payment
Tebipenem NDA Submission by GSK	$	25.0
Total potential commercial milestones based on first commercial sales	$	101.0	*
First commercial sale of a product in the United States		—		$	51.0
Second anniversary of first commercial sale of a product in the United States		—		$	25.0
First commercial sale of a product in two European countries		—		$	25.0
Total potential sales milestone payments	$	225.0
Net annual sales greater than $200.0		—		$	25.0
Net annual sales greater than $300.0		—		$	25.0
Net annual sales greater than $400.0		—		$	25.0
Net annual sales greater than $500.0		—		$	50.0
Net annual sales greater than $750.0		—		$	50.0
Net annual sales greater than $1,000.0		—		$	50.0

*Under the terms of the GSK License Agreement, the maximum potential milestone amount was revised from $150.0 million after PIVOT-PO was stopped early for efficacy following completion of a pre-specified interim analysis of data from 1,690 patients enrolled in the trial, thereby reducing the overall cost of the trial to us; the maximum potential milestone payment of $150.0 million was contingent upon the trial continuing to full enrollment, with 2,637 patients enrolled in the trial.

In addition to the milestones described above, GSK is obligated to pay royalties to us on annual net sales of GSK Licensed Products in the GSK Territory. Such royalties are 1% for annual sales up to $750.0 million each year and range from high single-digit percentages on annual net sales above $750.0 million each year to low double-digit percentages on annual net sales above $1,000.0 million each year.

SPR206

In March 2025, following a reprioritization of our programs, we announced that we were no longer pursuing a Phase 2 clinical trial for SPR206 and had ceased further development of the program. On April 4, 2025, the National Institute of Allergy and Infectious Diseases (“NIAID”) informed us that it was canceling the five-year contract, awarded in May 2021, under the Agency’s Omnibus Broad Agency Announcement No. HHS-NIH-NIAID-BAA2020-1 award mechanism to support further development of SPR206, effective immediately, for its convenience.

SPR720

In November 2025, we announced that we have ceased development of SPR720.

Components of Our Results of Operations

Sales Revenue

To date, we have not generated any revenue from product sales. If our development efforts for our current and future product candidates are successful and result in regulatory approval, we may generate revenue in the future from product sales. We cannot predict if, when, or to what extent we will generate revenue from the commercialization and sale of our product candidates. We may never succeed in obtaining regulatory approval for any of our product candidates.

Grant Revenue

We expect a portion of our revenue for the next few years will continue to be derived from payments under our active government awards and any awards that we may receive in the future.

Collaboration Revenue

Collaboration revenue relates to our agreements with Pfizer and GSK.

Operating Expenses

Research and Development Expenses

Research and development expenses consist primarily of costs incurred for our research activities, including the development of our product candidates, and are comprised of:

•

employee-related expenses, including salaries, related benefits, travel and stock-based compensation expense for employees engaged in research and development functions;

•

expenses incurred in connection with the preclinical and clinical development of our product candidates, including under agreements with contract research organizations (“CROs”);

•

costs incurred in connection with our government awards;

•

the cost of consultants and contract manufacturing organizations (“CMOs”) that manufacture drug products for use in our preclinical studies and clinical trials;

•

facilities, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, insurance and supplies; and

•

payments made under third-party licensing agreements.

We expense research and development costs as incurred. Nonrefundable advance payments we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed.

Our direct research and development expenses are tracked on a program-by-program basis and consist primarily of external costs, such as fees paid to consultants, contractors, CMOs and CROs in connection with our preclinical and clinical development activities. License fees and other costs incurred after a product candidate has been designated and that are directly related to the product candidate are included in direct research and development expenses for that program. License fees and other costs incurred prior to designating a product candidate are included in early-stage research programs. We do not allocate employee costs, costs associated with our preclinical programs or facility expenses, including depreciation or other indirect costs, to specific product development programs because these costs are deployed across multiple product development programs and, as such, are not separately classified.

Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later-stage clinical trials.

At this time, we cannot reasonably estimate or know the nature, timing and costs of the efforts that will be necessary to complete the preclinical and clinical development of any of our product candidates. The successful development and commercialization of our product candidates is highly uncertain. This is due to the numerous risks and uncertainties, including the following:

•

successful completion of clinical trials with safety, tolerability and efficacy profiles that are satisfactory to the FDA or any comparable foreign regulatory authority, including on account of the disruptive impacts of any global health, economic or political crises;

•

receipt of marketing approvals from applicable regulatory authorities;

•

establishment of arrangements with third-party manufacturers to obtain manufacturing supply;

•

obtainment and maintenance of patent, trade secret protection and regulatory exclusivity, both in the United States and internationally, including our ability to maintain our license agreement with Meiji with respect to tebipenem HBr;

•

protection of our rights in our intellectual property portfolio;

•

launch of commercial sales of our product candidates, if approved, whether alone or in collaboration with others;

•

acceptance of our product candidates, if approved, by patients, the medical community and third-party payors;

•

competition with other therapies; and

•

a continued acceptable safety profile of our product candidates, if approved.

A change in the outcome of any of these variables with respect to the development of any of our product candidates would significantly change the costs and timing associated with the development of that product candidate. We may never succeed in obtaining regulatory approval for any of our product candidates.

General and Administrative Expenses

General and administrative expenses consist primarily of salaries and related costs, including stock-based compensation, for personnel in executive, finance and administrative functions. General and administrative expenses also include direct and allocated facility-related costs as well as professional fees for legal, patent, consulting, investor and public relations, accounting and audit services. We also anticipate that we will continue to incur accounting, audit, legal, regulatory, compliance, infrastructure and director and officer insurance costs, as well as investor and public relations expenses associated with our continued operation as a public company.

Impairment Charges

During the third quarter of 2025, we evaluated our real estate lease in light of our new sublease agreements. As a result of the evaluation, we recorded an impairment charge of $0.6 million associated with the right-of-use asset in the third quarter of 2025.

Restructuring

In October 2024, we implemented a strategic restructuring initiative and corresponding reduction in workforce. We restructured our operations to reduce costs and reallocate resources in support of the development of tebipenem HBr and other corporate activities. As of September 30, 2025, we had recognized $1.1 million in expense related to the October 2024 restructuring and do not expect to incur any further charges related to this restructuring.

Other Income (Expense)

Interest Income (Expense)

Interest income (expense) during the three and nine months ended September 30, 2025 and 2024 consists of interest income related to the significant financing component related to the GSK License Agreement and interest earned on our cash equivalents, which are primarily invested in money market accounts, as well as interest earned on our investments in marketable securities.

Other Income (Expense), Net

Other income (expense), net, consists of insignificant amounts of miscellaneous income, as well as realized and unrealized gains and losses from foreign currency-denominated cash balances and vendor payables.

Critical Accounting Policies and Significant Judgments and Estimates

Our consolidated financial statements are prepared in accordance with GAAP. The preparation of our consolidated financial statements and related disclosures requires us to make estimates, assumptions and judgments that affect the reported amount of assets, liabilities, revenue, costs and expenses, and related disclosures. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.

Our critical accounting policies are those most critical to the judgments and estimates used in the preparation of our financial statements. We have made no changes to our existing critical accounting policies described in our Annual Report on Form 10-K for the year ended December 31, 2024.

Results of Operations

Comparison of the Three Months Ended September 30, 2025 and 2024

The following tables summarize our results of operations for the three months ended September 30, 2025 and 2024 (in thousands):


	Three Months Ended September 30,
	2025			2024			$ Change
Revenues:
Grant revenue	$	2,394		$	5,650		$	(3,256	)
Collaboration revenue - related party		3,048			7,754			(4,706	)
Collaboration revenue		—			65			(65	)
Total revenues		5,442			13,469			(8,027	)

Operating expenses:
Research and development		8,597			26,864			(18,267	)
General and administrative		4,174			5,198			(1,024	)
Impairment charges		587			—			587
Total operating expenses		13,358			32,062			(18,704	)
Loss from operations		(7,916	)		(18,593	)		10,677
Other income (expense):
Interest income		532			1,182			(650	)
Other income (expense), net		2			(26	)		28
Total other income (expense), net		534			1,156			(622	)
Net loss before income taxes		(7,382	)		(17,437	)		10,055
Income tax benefit		—			290			(290	)
Net loss	$	(7,382	)	$	(17,147	)	$	9,765

Grant Revenue


	Three Months Ended September 30,
	2025		2024		$ Change
BARDA Contract (Tebipenem HBr)	$	2,394	$	5,567	$	(3,173	)
NIAID Contract (SPR206)		—		83		(83	)
Total grant revenue	$	2,394	$	5,650	$	(3,256	)

Grant revenue recognized during the three months ended September 30, 2025 and 2024 consisted of the reimbursement of qualifying expenses incurred in connection with our various government awards. The decrease in grant revenue during the three months ended September 30, 2025 was primarily due to a decrease of $3.2 million under our BARDA contract for tebipenem HBr, and a decrease of $0.1 million under our NIAID agreement relating to SPR206.

Collaboration Revenue


	Three Months Ended September 30,
	2025		2024		$ Change
GSK (Tebipenem HBr)	$	3,048	$	7,754	$	(4,706	)
Pfizer (SPR206)		—		65		(65	)
Total collaboration revenue	$	3,048	$	7,819	$	(4,771	)

During the three months ended September 30, 2025, we recognized $3.0 million in collaboration revenue related to our agreement with GSK and no revenue related to our agreement with Pfizer. During the three months ended September 30, 2024, we recognized $7.8 million in collaboration revenue related to our agreement with GSK and $0.1 million in collaboration revenue related to our agreement with Pfizer. The decrease in revenue under the GSK License Agreement was directly related to the adjusted service period due to the pivotal Phase 3 PIVOT-PO trial stopping early for efficacy in the first half of 2025 following the pre-specified interim analysis.

Research and Development Expenses


	Three Months Ended September 30,
	2025		2024		$ Change
Direct research and development expenses by program:
Tebipenem HBr	$	4,959	$	18,020	$	(13,061	)
SPR720		178		3,879		(3,701	)
SPR206		—		157		(157	)
Unallocated expenses:
Personnel related (including stock-based compensation)		2,244		3,836		(1,592	)
Facility related and other		1,216		972		244
Total research and development expenses	$	8,597	$	26,864	$	(18,267	)

Direct costs related to our tebipenem HBr program decreased by $13.1 million during the three months ended September 30, 2025, compared to the three months ended September 30, 2024, due to a decrease in clinical activities related to our pivotal Phase 3 PIVOT-PO trial, which met its primary endpoint and was stopped early for efficacy during the first half of 2025.

Direct costs related to our SPR720 program decreased by $3.7 million during the three months ended September 30, 2025, as compared to the three months ended September 30, 2024, due to decreased clinical activity during the period related to our Phase 2a clinical trial of SPR720. Subsequently, in November 2025, we announced that we ceased development of SPR720.

Direct costs related to our SPR206 program decreased by $0.2 million during the three months ended September 30, 2025, primarily due to decreased preclinical activity. In March 2025, following a reprioritization of our programs, we announced that we ceased development of SPR206.

The decrease in personnel-related costs of $1.6 million was primarily a result of reduced headcount costs as a result of the restructuring in the fourth quarter of 2024. Personnel-related costs for the three months ended September 30, 2025 and 2024 included stock-based compensation expense of $0.4 million and $0.7 million, respectively.

Facility-related and other costs primarily reflect costs related to supporting our research and development staff.

General and Administrative Expenses


	Three Months Ended September 30,
	2025		2024		$ Change
Personnel related (including stock-based compensation)	$	2,352	$	3,273	$	(921	)
Professional and consultant fees		1,185		1,374		(189	)
Facility related and other		637		551		86
Total general and administrative expenses	$	4,174	$	5,198	$	(1,024	)

The decrease in personnel-related costs of $0.9 million was primarily a result of reduced headcount costs as a result of the restructuring in the fourth quarter of 2024. Personnel-related costs for the three months ended September 30, 2025 and 2024 included stock-based compensation expense of $0.7 million and $1.5 million, respectively.

The decrease in professional and consultant fees of $0.2 million was primarily due to a decrease in legal and consulting expenses incurred in the three months ended September 30, 2025.

Facility-related and other costs primarily reflect costs related to supporting our general and administrative staff.

Impairment Charges

Impairment charges related to our right of use asset were $0.6 million for the three months ended September 30, 2025, compared to no charges for the three months ended September 30, 2024.

Other Income (Expense), Net

Other income (expense), net was $0.5 million for the three months ended September 30, 2025, compared to $1.2 million for the three months ended September 30, 2024. Total other income for the three months ended September 30, 2025, included $0.5 million of interest income, of which $0.2 million related to the significant financing component recognized under the GSK License Agreement, offset by immaterial fluctuations in unrealized foreign currency. Total other income for the three months ended September 30, 2024, included $1.2 million of interest income, of which $0.4 million related to the significant financing component recognized under the GSK License Agreement, offset by immaterial fluctuations in unrealized foreign currency.

Comparison of the Nine Months Ended September 30, 2025 and 2024

The following tables summarize our results of operations for the nine months ended September 30, 2025 and 2024 (in thousands):


	Nine Months Ended September 30,
	2025			2024			$ Change
Revenues:
Grant revenue	$	5,544		$	14,893		$	(9,349	)
Collaboration revenue - related party		19,949			17,721			2,228
Collaboration revenue		12			319			(307	)
Total revenues		25,505			32,933			(7,428	)

Operating expenses:
Research and development		32,875			67,921			(35,046	)
General and administrative		16,876			16,648			228
Impairment charges		587			—			587
Restructuring		258			—			258
Total operating expenses		50,596			84,569			(33,973	)
Loss from operations		(25,091	)		(51,636	)		26,545
Other income (expense):
Interest income		2,136			3,707			(1,571	)
Other income (expense), net		7			(39	)		46
Total other income, net		2,143			3,668			(1,525	)
Net loss before income taxes		(22,948	)		(47,968	)		25,020
Income tax benefit		—			290			(290	)
Net loss	$	(22,948	)	$	(47,678	)	$	24,730

Grant Revenue


	Nine Months Ended September 30,
	2025		2024		$ Change
BARDA Contract (Tebipenem HBr)	$	5,515	$	14,577	$	(9,062	)
NIAID Contract (SPR206)		29		316		(287	)
Total grant revenue	$	5,544	$	14,893	$	(9,349	)

Grant revenue recognized during the nine months ended September 30, 2025 and 2024 consisted of the reimbursement of qualifying expenses incurred in connection with our various government awards. The decrease in grant revenue during the nine months ended September 30, 2025 was primarily due to a decrease of $9.1 million under our BARDA contract for tebipenem HBr, and a decrease of $0.3 million under our NIAID agreement relating to SPR206.

Collaboration Revenue


	Nine Months Ended September 30,
	2025		2024		$ Change
GSK (Tebipenem HBr)	$	19,949	$	17,721	$	2,228
Pfizer (SPR206)		12		319		(307	)
Total collaboration revenue	$	19,961	$	18,040	$	1,921

During the nine months ended September 30, 2025, we recognized $19.9 million in collaboration revenue related to our agreement with GSK and less than $0.1 million in collaboration revenue related to our agreement with Pfizer. During the nine months ended September 30, 2024, we recognized $17.7 million in collaboration revenue related to our agreement with GSK and $0.3 million in collaboration revenue related to our agreement with Pfizer. The increase in revenue under the GSK License Agreement was directly related to the adjusted service period due to the pivotal Phase 3 PIVOT-PO trial stopping early for efficacy in the first half of 2025 following the pre-specified interim analysis.

Research and Development Expenses


	Nine Months Ended September 30,
	2025		2024		$ Change
Direct research and development expenses by program:
Tebipenem HBr	$	20,321	$	39,937	$	(19,616	)
SPR720		975		13,087		(12,112	)
SPR206		49		503		(454	)
Unallocated expenses:
Personnel related (including stock-based compensation)		8,192		10,768		(2,576	)
Facility related and other		3,338		3,626		(288	)
Total research and development expenses	$	32,875	$	67,921	$	(35,046	)

Direct costs related to our tebipenem HBr program decreased by $19.6 million during the nine months ended September 30, 2025, compared to the nine months ended September 30, 2024, due to a decrease in clinical activities related to our pivotal Phase 3 PIVOT-PO trial which met its primary endpoint and was stopped early for efficacy during the first half of 2025.

Direct costs related to our SPR720 program decreased by $12.1 million during the nine months ended September 30, 2025, as compared to the nine months ended September 30, 2024, due to decreased clinical activity during the period related to our Phase 2a clinical trial of SPR720. Subsequently, in November 2025, we announced that we ceased development of SPR720.

Direct costs related to our SPR206 program decreased by $0.5 million during the nine months ended September 30, 2025, primarily due to decreased preclinical activity. In March 2025, following a reprioritization of our programs, we announced that we ceased development of SPR206.

The decrease in personnel-related costs of $2.6 million was primarily a result of reduced headcount costs as a result of the restructuring in the fourth quarter of 2024. Personnel-related costs for the nine months ended September 30, 2025 and 2024 included stock-based compensation expense of $1.3 million and $2.1 million, respectively.

Facility-related and other costs primarily reflect costs related to supporting our research and development staff.

General and Administrative Expenses


	Nine Months Ended September 30,
	2025		2024		$ Change
Personnel related (including stock-based compensation)	$	9,838	$	9,781	$	57
Professional and consultant fees		5,433		5,183		250
Facility related and other		1,605		1,684		(79	)
Total general and administrative expenses	$	16,876	$	16,648	$	228

The increase in personnel-related costs of $0.1 million was primarily a result of retention bonus and executive severance expense in our general and administrative functions during the period offsetting reduced headcount costs as a result of the restructuring in the fourth quarter of 2024. Personnel-related costs for the nine months ended September 30, 2025 and 2024 included stock-based compensation expense of $2.0 million and $4.2 million, respectively.

The increase in professional and consultant fees of $0.3 million was primarily due to an increase in legal and consulting expenses incurred in the nine months ended September 30, 2025.

Facility-related and other costs primarily reflect costs related to supporting our general and administrative staff.

Impairment Charges

Impairment charges related to our right of use asset were $0.6 million for the nine months ended September 30, 2025, compared to no charges for the nine months ended September 30, 2024.

Other Income (Expense), Net

Total other income (expense), net was $2.1 million for the nine months ended September 30, 2025, compared to $3.7 million for the nine months ended September 30, 2024. Total other income for the nine months ended September 30, 2025, included $2.1 million of interest income, of which $0.9 million related to the significant financing component recognized under the GSK License Agreement, offset by immaterial fluctuations in unrealized foreign currency. Total other income for the nine months ended September 30, 2024, included $3.7 million of interest income, of which $1.2 million related to the significant financing component recognized under the GSK License Agreement, offset by immaterial fluctuations in unrealized foreign currency.

Liquidity and Capital Resources

Since our inception, we have incurred significant operating losses. We have recognized revenue to date from funding arrangements with the U.S. Department of Defense, NIAID, CARB-X and BARDA, the GSK License Agreement and our license agreements with Everest and Pfizer. We have not yet commercialized any product candidates and we may not generate revenue from sales of any product candidate. To date, we have funded our operations with payments received under license and collaboration agreements and funding from government contracts, and from the proceeds of multiple common stock offerings. As of September 30, 2025, we had cash and cash equivalents of $48.6 million.

We filed the 2024 Form S-3 on March 15, 2024, which became effective on March 22, 2024, and pursuant to which we registered for sale up to $300.0 million of any combination of our common stock, preferred stock, debt securities, warrants, rights and/or units from time to time and at prices and on terms that we may determine, including up to $75.0 million of our common stock available for issuance pursuant to the Sales Agreement with Cantor. Under the Sales Agreement, Cantor may sell shares of our common stock by any method permitted by law deemed to be an “at-the-market” offering as defined in Rule 415 of the Securities Act, subject to the terms of the Sales Agreement.

During the three and nine months ended September 30, 2025, we did not sell any shares of our common stock under the Sales Agreement.

Cash Flows

The following table summarizes our sources and uses of cash for the nine months ended September 30, 2025 and 2024 (in thousands):


	Nine Months Ended September 30,
	2025			2024
Cash used in operating activities	$	(4,273	)	$	(43	)
Net decrease in cash and cash equivalents	$	(4,273	)	$	(43	)

Operating Activities

Net cash used in operating activities for the nine months ended September 30, 2025, was $4.3 million, primarily resulting from our net loss of $22.9 million, adjusted for an increase to non-cash items of $4.7 million (primarily stock-based compensation). Net cash provided by changes in our operating assets and liabilities was $13.9 million and consisted primarily of a $48.5 million decrease in the collaboration receivable-related party, due to the receipt of the third and fourth installment payments from GSK (see Note 11), a $20.0 million decrease in deferred revenue, a $9.9 million decrease in accrued expenses, a $5.9 million decrease in accounts payable, a $0.7 million increase in prepaid expenses and other assets, a $1.5 million net increase in other receivables, and a $0.9 million decrease in operating lease liability and other liabilities.

Net cash used in operating activities for the nine months ended September 30, 2024, was less than $0.1 million, primarily resulting from our net loss of $47.7 million, adjusted for an increase to non-cash items of $7.1 million (primarily stock-based compensation). Net cash provided by changes in our operating assets and liabilities was $40.6 million and consisted primarily of a

$45.2 million decrease in our related party collaboration receivable, due to the receipt of the first and second installment payments from GSK (see Note 11), a $18.0 million decrease in deferred revenue, a $1.2 million net increase in receivables, a $4.7 million increase in accounts payable, a $2.4 million increase in prepaid expenses and other assets, an increase of $8.8 million in accrued expenses, and a $1.3 million decrease in operating lease liability and other liabilities.

Changes in accounts payable, accrued expenses and other current liabilities and prepaid expenses and other current assets in all periods were generally due to the advancement of our programs and the timing of vendor invoicing and payments. Changes in deferred revenue are primarily related to the GSK License Agreement and our license agreement with Pfizer. Changes in collaboration receivable related to the GSK License Agreement.

Investing Activities

We did not undertake any investing activities during the nine months ended September 30, 2025 or 2024.

Financing Activities

We did not undertake any financing activities during the nine months ended September 30, 2025 or 2024.

Funding Requirements

Our future use of operating cash and capital requirements, and the timing and amount thereof, will depend largely on:

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the timing and costs of any ongoing and planned clinical trials;

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the initiation, progress, timing, costs and results of preclinical studies and clinical trials of our product candidates and potential new product candidates;

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the amount of funding that we receive under government contracts that we have applied for or may apply for in the future;

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the number and characteristics of product candidates that we pursue;

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the outcome, timing and costs of seeking regulatory approvals;

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the costs of commercialization activities for our product candidates if we receive marketing approval, including the costs and timing of establishing product sales, marketing, distribution and manufacturing capabilities;

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the terms and timing of any future collaborations, licensing or other arrangements that we may establish;

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the amount and timing of any payments we may be required to make, or that we may receive, in connection with the licensing, filing, prosecution, defense and enforcement of any patents or other intellectual property rights, including milestone and royalty payments and patent prosecution fees that we are obligated to pay pursuant to our license agreements;

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the costs of preparing, filing and prosecuting patent applications, maintaining and protecting our intellectual property rights and defending against any intellectual property related claims;

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the costs of operating as a public company;

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the extent to which we in-license or acquire other products and technologies; and

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costs associated with litigation and any government investigation.

As of September 30, 2025, we had cash and cash equivalents of $48.6 million. In accordance with ASU 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), we are required to evaluate whether there are conditions and events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern from the issuance date of our financial statements. Based on such cash and cash equivalents as of September 30, 2025 and the decrease in clinical expense as a result of the completion of the PIVOT-PO Phase 3 trial for tebipenem HBr and the decision to cease development of SPR720, we believe that our cash runway will enable us to fund our operating expenses and required capital expenditure requirements for at least 12 months from the issuance of the financial statements included in this report and into 2028.

This timeline is subject to uncertainty as to the timing of future expenditures. We have developed plans to mitigate this risk, which primarily consist of raising additional capital through some combination of equity or debt financings, potential new collaborations and/or reducing cash expenditures. If we are not able to secure adequate additional funding, we plan to make reductions in spending. In that event, we may have to delay, scale back, or eliminate some or all of our planned clinical trials, and research stage programs. The actions necessary to reduce spending under this plan at a level that mitigates the factors described above are not

considered probable, as defined in the accounting standards and therefore, the full extent to which management may extend our funds through these actions may not be considered in management’s assessment of our ability to continue as a going concern.

We have based these estimates on assumptions that may prove to be wrong, and we could utilize our available capital resources sooner than we expect. Because of the numerous risks and uncertainties associated with research, development and commercialization of pharmaceutical product candidates, we are unable to estimate the exact amount of our working capital requirements. Our future funding requirements will depend on and could increase significantly as a result of many factors, including those listed above.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our operations through a combination of equity offerings, debt financings, government funding, collaborations, strategic alliances and marketing, distribution or licensing arrangements. To the extent that we raise additional capital through the sale of equity or convertible debt securities, our stockholders’ ownership interests will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our common stockholders. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making acquisitions or capital expenditures or declaring dividends. If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. If our access to capital is restricted or associated borrowing costs increase as a result of developments in financial markets, our operations and financial condition could be adversely impacted. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed, we may be required to delay, limit, reduce or terminate our research, product development or future commercialization efforts or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

Contractual Obligations and Commitments

During the three and nine months ended September 30, 2025, there have been no material changes to our contractual obligations and commitments from those described under the heading “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Contractual Obligations and Commitments” in our Annual Report on Form 10-K for the year ended December 31, 2024.

Off-Balance Sheet Arrangements

We did not have during the periods presented, and we do not currently have, any off-balance sheet arrangements, as defined in the rules and regulations of the SEC.

Recently Issued and Adopted Accounting Pronouncements

A description of recently issued accounting pronouncements that may potentially impact our financial position and results of operations is disclosed in Note 2 to our consolidated financial statements appearing elsewhere in this Quarterly Report on Form 10-Q.

Item 3. Quantitative and Qualitative Disclosures About Market Risk.

As of September 30, 2025, we had cash and cash equivalents of $48.6 million, consisting of cash and money market accounts. The primary objectives of our investment activities are to preserve principal, provide liquidity and maximize income without significantly increasing risk. Our primary exposure to market risk is interest income sensitivity, which is affected by changes in the general level of U.S. Treasury interest rates. We did not have any assets classified as marketable securities as of September 30, 2025. As we incur research expenses in foreign countries, we face exposure to movements in foreign currency exchange rates, primarily the Euro, British Pound and Australian dollar against the U.S. dollar. Historically, foreign currency fluctuations have not had a material impact on our consolidated financial statements.

Please note, that we are a smaller reporting company as defined by Rule 12b-2 of the Exchange Act and are not required to provide the information under this item. Therefore, the above disclosure is discretionary.

Item 4. Controls and Procedures.

Evaluation of Disclosure Controls and Procedures

We maintain “disclosure controls and procedures,” as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act, that are designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is recorded, processed, summarized and reported, within the time periods specified in the SEC’s rules and forms. Disclosure controls and procedures include, without limitation, controls and procedures designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is accumulated and communicated to the company’s management, including its principal executive and principal financial officers, as appropriate to allow timely decisions regarding required disclosure. Management recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives and management necessarily applies its judgment in evaluating the cost-benefit relationship of possible controls and procedures.

Our management, with the participation of our Chief Executive Officer and Chief Financial Officer (our principal executive officer and principal financial officer), evaluated the effectiveness of our disclosure controls and procedures as of September 30, 2025. Based on the evaluation of our disclosure controls and procedures as of September 30, 2025, our Chief Executive Officer and Chief Financial Officer concluded that, as of such date, our disclosure controls and procedures were effective at the reasonable assurance level.

Changes in Internal Control over Financial Reporting

No change in our internal control over financial reporting (as defined in Rules 13a-15(d) and 15d-15(d) under the Exchange Act) occurred during the three months ended September 30, 2025 that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

PART II—OTHER INFORMATION

Item 1. Legal Proceedings.

Securities Class Action Lawsuits and Derivative Actions

Two putative class action lawsuits were filed against the Company and certain of its current and former officers in the United States District Court for the Eastern District of New York, one captioned Richard S. Germond v. Spero Therapeutics, Inc., Ankit Mahadevia, and Satyavrat Shukla, Case No. 1:22-cv-03125, filed on May 26, 2022, and the other captioned Kashif Memon v. Spero Therapeutics, Inc., Ankit Mahadevia, and Satyavrat Shukla Case No. 1:22-cv-04154, filed on July 15, 2022. The parties moved to consolidate the two complaints on July 22, 2022, which were ordered consolidated on August 5, 2022 (“Consolidated Putative Class Action”). The parties filed an Amended Complaint on December 5, 2022, purported to be brought on behalf of stockholders who purchased our common stock from September 8, 2020 through May 2, 2022. The Amended Complaint generally alleges that the Company and certain of its current and former officers violated Sections 10(b) and/or 20(a) of the Exchange Act and Rule 10b-5 promulgated thereunder by making allegedly false and/or misleading statements concerning the NDA for tebipenem HBr in an effort to lead investors to believe that the drug would receive approval from the FDA. Plaintiffs seek unspecified damages, interest, attorneys’ fees, and other costs. The Company filed a fully-briefed Motion to Dismiss on June 21, 2023. By Order entered on September 30, 2024, the Motion to Dismiss was granted, dismissing the Amended Complaint in its entirety. The Court ordered the case to be closed by Memorandum and Order entered on October 28, 2024.

SEC Investigation and Wells Notice

On January 9, 2025, the Company responded to a “Wells Notice” from the Staff of the SEC regarding its preliminary determination to recommend a civil enforcement action or administrative proceeding against the Company, its former Chief Executive Officer and Chairman of the Board of Directors, Ankit Mahadevia, M.D., and its former Chief Financial Officer and President and Chief Executive Officer, Satyavrat “Sath” Shukla, relating to certain public disclosures by the Company from March 31, 2022 leading up to the Company’s announcement on May 3, 2022 that it had determined to cease commercialization of tebipenem HBr based on feedback from the FDA, and whether the Company’s disclosures may have violated the federal securities laws.

Item 1A. Risk Factors.

Careful consideration should be given to the following risk factors, in addition to the other information set forth in this Quarterly Report on Form 10-Q, including the section of this Quarterly Report on Form 10-Q titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and related notes, and in other documents that we file with the SEC, in evaluating our company and our business. If any of the events described in the following risk factors and the risks described elsewhere in this Quarterly Report on Form 10-Q actually occur, our business, financial condition, results of operations and future growth prospects could be materially and adversely affected, and the trading price of our securities could decline. Our actual results could differ materially from those contained in the forward-looking statements we have made in this Quarterly Report on Form 10-Q and those we may make from time to time. The risks and uncertainties described below are not the only ones we face. Additional risks not presently known to us or other factors not perceived by us to present significant risks to our business at this time also may impair our business operations.

Risks Related to Product Development and Commercialization

As of November 2025, we have ceased development of our SPR720 oral program and have shifted our focus and resources to advancing the clinical development of our tebipenem HBr program, as well as other corporate activities. Consequently, our business and prospects are substantially dependent on our tebipenem program and our collaboration with GSK. If we fail to execute successfully on this re-prioritized strategic focus, or our collaboration with GSK fails to advance the clinical development of the tebipenem HBr program, our business and prospects may be materially adversely affected.

As of November 2025, we have ceased development of our SPR720 oral program and have shifted our focus and resources to advancing the clinical development of our tebipenem HBr program, as well as other corporate activities. Additionally, in March 2025, we announced that we ceased development of SPR206. We believe this re-prioritized strategic focus is the best way to optimize our financial and other resources to advance our goal of identifying and developing novel treatments for rare diseases and diseases caused by MDR bacterial infections with high unmet need. However, there is no assurance that we will successfully execute this strategy. As described below, there are risks inherent in the clinical development process, especially for earlier-stage programs. If we are unable to execute successfully on this re-prioritized strategic focus, our business and prospects may be materially adversely affected.

As a result, we are currently substantially dependent on our tebipenem program and our collaboration with GSK. As described under Note 11 to our consolidated financial statements, GSK has the right to terminate the GSK License Agreement (1) at any time upon a specified number of days’ notice, (2) upon a material breach by us or (3) upon a bankruptcy of Spero. Alternatively, in the case of a material breach by Spero, GSK may, in lieu of terminating the GSK License Agreement, elect to reduce any commercial milestone payments to Spero by 50%. In addition, in such circumstance, GSK may assume the responsibility and expense of development of tebipenem HBr in the United States, in which case no development milestone payments would be payable to Spero (including unpaid installments of any earned milestone payments). In the case of a Change of Control (as defined in the GSK License Agreement) of Spero, GSK similarly may, in lieu of terminating the GSK License Agreement, assume responsibility and expense of development of tebipenem HBr in the United States and no development milestones would be payable to Spero, as described above. Any termination of the GSK License Agreement or any failure to earn, or reduction in, milestone payments may materially adversely affect our business and prospects.

Our ability to realize the value of tebipenem HBr depends on obtaining FDA approval. Even if such approval is obtained, the timeline of, and any requirements imposed as part of, such approval may impact the attractiveness of eventual commercialization of tebipenem HBr through our partnership with GSK.

We currently have no products approved for sale and have invested a significant portion of our efforts and financial resources in the development of tebipenem HBr as a product candidate for the treatment of bacterial infections causing cUTI. Our ability to realize the value of tebipenem HBr depends on the potential FDA approval, and the expected timeline and other requirements that would affect the attractiveness of eventual commercialization of tebipenem HBr through our partnership with GSK. Further, as part of any approval, the FDA could impose labeling requirements restricting the use of tebipenem HBr, which could reduce its commercial prospects, unless such requirements are subsequently modified to reduce such restrictions. If any of these outcomes occur, our business could be materially harmed.

If our clinical trials fail to produce favorable results, we may incur additional costs or experience delays in completing, or ultimately be unable to complete, the development and commercialization of any of our product candidates.

We may not commercialize, market, promote or sell any product candidate in the United States without obtaining marketing approval from the FDA or in other countries without obtaining approvals from comparable foreign regulatory authorities, such as the European Medicines Agency (“EMA”), and we may never receive such approvals. We must complete extensive preclinical development and clinical trials to demonstrate the safety and efficacy of our product candidates in humans before we will be able to obtain these approvals. Clinical testing is expensive, difficult to design and implement, can take many years to complete and is inherently uncertain as to outcome.

The clinical development of any of our product candidates is susceptible to the risk of failure inherent at any stage of drug development, including failure to demonstrate efficacy in a trial or across a broad population of patients, the occurrence of severe adverse events, failure to comply with protocols or applicable regulatory requirements, and determination by the FDA or any comparable foreign regulatory authority that a drug product is not approvable. A number of companies in the pharmaceutical industry, including biotechnology companies, have suffered significant setbacks in clinical trials, even after promising results in earlier nonclinical studies or clinical trials. The results of preclinical and other nonclinical studies and/or early clinical trials of our product candidates may not be predictive of the results of later-stage clinical trials. Notwithstanding any promising results in early nonclinical studies or clinical trials, we cannot be certain that we will not face similar setbacks.

In addition, preclinical and clinical data are often susceptible to varying interpretations and analyses. Many companies that believed their product candidates performed satisfactorily in preclinical studies and clinical trials have nonetheless failed to obtain marketing approval for the product candidates. Even if we believe that the results of our clinical trials warrant marketing approval, the FDA or comparable foreign regulatory authorities may disagree and may not grant marketing approval of our product candidates.

In some instances, there can be significant variability in safety and/or efficacy results between different trials of the same product candidate due to numerous factors, including changes in trial procedures set forth in protocols, differences in the size and type of the patient populations, adherence to the dosing regimen and other trial protocols and the rate of dropout among clinical trial participants, among others. It is possible that even if one or more of our product candidates has a beneficial effect, that effect will not be detected during clinical evaluation as a result of one of the factors listed or otherwise. Conversely, as a result of the same factors, our clinical trials may indicate an apparent positive effect of a product candidate that is greater than the actual positive effect, if any. Similarly, in our clinical trials, we may fail to detect toxicity of or intolerability of our product candidates or may determine that our product candidates are toxic or not well tolerated when that is not in fact the case. In the case of our clinical trials, results may differ on the basis of the type of bacteria with which patients are infected. We cannot make assurances that any clinical trials that we may conduct will demonstrate consistent or adequate efficacy and safety to obtain regulatory approval to market our product candidates.

We may encounter unforeseen events prior to, during, or as a result of, clinical trials that could delay or prevent us from obtaining regulatory approval for any of our product candidates, including:

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the FDA or other comparable foreign regulatory authorities may disagree as to the design or implementation of our clinical trials;

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we may be delayed in or fail to reach agreement on acceptable terms with prospective CROs and clinical trial sites, the terms of which can be subject to extensive negotiation and may vary significantly among different CROs and trial sites;

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clinical trials of our product candidates may produce unfavorable or inconclusive results;

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we may decide, or regulators may cause us, to conduct additional clinical trials or abandon product development programs;

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the number of patients required for clinical trials of our product candidates may be larger than we anticipate, enrollment in these clinical trials may be slower than we anticipate, participants may drop out of these clinical trials at a higher rate than we anticipate or we may fail to recruit suitable patients to participate in clinical trials;

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our third-party contractors, including those manufacturing our product candidates or conducting clinical trials on our behalf, may fail to comply with regulatory requirements or meet their contractual obligations to us in a timely manner, or at all;

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the FDA or institutional review boards may not authorize us or our investigators to commence a clinical trial or conduct a clinical trial at a prospective trial site;

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regulators or institutional review boards may require that we or our investigators suspend or terminate clinical trials of our product candidates for various reasons, including noncompliance with regulatory requirements or a finding that the participants are being exposed to unacceptable health risks, undesirable side effects or other unexpected characteristics of the product candidate;

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the FDA or comparable foreign regulatory authorities may fail to approve the manufacturing processes or facilities of third-party manufacturers with which we enter into agreements for clinical and commercial supplies;

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the supply or quality of our product candidates or other materials necessary to conduct clinical trials of our product candidates may be insufficient or inadequate; and

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the approval policies or regulations of the FDA or comparable foreign regulatory authorities may significantly change in a manner rendering our clinical data insufficient for approval.

We could also encounter delays if a clinical trial is suspended or terminated by us, by the institutional review boards (“IRBs”) responsible for overseeing such trials, by the Data Safety Monitoring Board (“DSMB”) if any, for such trial or by the FDA or other regulatory authorities. Such authorities may suspend or terminate a clinical trial due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a drug or changes in governmental regulations or administrative actions.

If we are required to conduct additional clinical trials or other testing of any of our product candidates beyond the trials and testing that we contemplate, if we are unable to successfully complete clinical trials or other testing of our product candidates, if the results of these trials or tests are unfavorable or are only modestly favorable or if there are safety concerns associated with any of our product candidates, we may:

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incur additional unplanned costs;

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be delayed in obtaining marketing approval for our product candidates;

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not obtain marketing approval at all;

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obtain approval for indications or patient populations that are not as broad as intended or desired;

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obtain approval with labeling that includes significant use or distribution restrictions or significant safety warnings, including boxed warnings;

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be subject to additional post-marketing testing or other requirements; or

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be required to remove the product from the market after obtaining marketing approval.

Our failure to successfully initiate and complete clinical trials of our product candidates and to demonstrate the efficacy and safety necessary to obtain regulatory approval to market any of our product candidates would significantly harm our business. Our product candidate development costs will also increase if we experience delays in testing or marketing approvals and we may be required to obtain additional funds to complete clinical trials. We cannot make assurances that our clinical trials will begin as planned or be completed on schedule, if at all, or that we will not need to restructure our trials after they have begun. Significant clinical trial delays also could shorten any periods during which we may have the exclusive right to commercialize our product candidates or allow our competitors to bring products to market before we do and impair our ability to successfully commercialize our product candidates, which may harm our business and results of operations. In addition, many of the factors that cause, or lead to, delays of clinical trials may ultimately lead to the denial of regulatory approval of any of our product candidates.

If we experience delays or difficulties in the enrollment of patients in clinical trials, clinical development activities could be delayed or otherwise adversely affected.

The timely completion of clinical trials in accordance with their protocols depends, among other things, on our ability to enroll a sufficient number of patients who remain in the study until its conclusion. The initiation, continuation and completion of our clinical trials relies on our ability to locate and enroll a sufficient number of eligible patients to participate in clinical trials as required by the FDA or comparable foreign regulatory authorities, such as the EMA. Patient enrollment is a significant factor in the timing of clinical trials, and is affected by many factors, including:

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the size and nature of the target patient population;

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the severity of the disease under investigation;

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the proximity of patients to clinical sites;

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the patient eligibility criteria for participation in the clinical trial;

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the design of the clinical trial;

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the availability of clinically evaluable patients;

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our ability to recruit clinical trial investigators with appropriate competencies and experience;

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competing clinical trials and clinicians’ and patients’ perceptions as to the potential advantages and risks of the product candidate being studied in relation to other available therapies, including any new drugs that may be approved for the indications that we are investigating;

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our ability to obtain and maintain patient consents; and

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the risk that participants enrolled in clinical trials will drop out of the trials before completion.

Our inability to enroll a sufficient number of patients for our clinical trials would result in significant delays or might require us to abandon one or more clinical trials altogether. Enrollment delays in our clinical trials may result in increased development costs for any of our product candidates, slow down or halt our product candidate development and approval process and jeopardize our ability to seek and obtain the marketing approval required to commence product sales and generate revenue, which would cause the value of our company to decline and limit our ability to obtain additional financing if needed.

Congress also amended the Federal Food, Drug, and Cosmetic Act (“FDCA”) to require sponsors of a Phase 3 clinical trial, or other “pivotal study” of a new drug to support marketing authorization, to design and submit a diversity action plan (“DAP”) for such clinical trial. The action plan must describe appropriate diversity goals for enrollment, as well as a rationale for the goals and a description of how the sponsor will meet them. In the future, we will be required to submit a DAP to the FDA by the time we submit a Phase 3 clinical trial, or pivotal study, protocol to the agency for review, unless we are able to obtain a waiver for some or all of the requirements for a DAP. It is unknown at this time how the DAP may affect the planning and timing of any future Phase 3 clinical trial for our product candidates. However, initiation of such trials may be delayed if the FDA objects to our proposed DAPs for any future Phase 3 clinical trial for our product candidates, and we may experience difficulties recruiting a diverse population of patients in attempting to fulfill the requirements of any approved DAP.

In June 2024, as mandated by the FDCA, the FDA issued draft guidance outlining the general requirements for DAPs. Unlike most guidance documents issued by the FDA, the DAP guidance when finalized will have the force of law because Food and Drug Omnibus Reform Act of 2022 (“FDORA”) specifically dictates that the form and manner for submission of DAPs are specified in FDA guidance. On January 27, 2025, in response to an executive order issued by President Trump on January 21, 2025 on Diversity, Equity and Inclusion programs, the FDA removed the draft DAP guidance from its website. That action, along with similar actions by the Trump Administration to remove many other healthcare webpages, is currently the subject of ongoing litigation. On July 3, 2025, the U.S. District Court for the District of Columbia ruled that the administration’s actions to remove these webpages, including the draft DAP guidance, is unlawful under the Administrative Procedure Act. The court ordered the restoration of many of these webpages. In late July 2025, the FDA restored the draft DAP guidance to its website with a statement that “information on this page may be modified and/or removed in the future subject to the terms of the court’s order and implemented consistent with applicable law.” Accordingly, in light of these ongoing actions, there is considerable uncertainty surrounding the draft DAP guidance and how the FDA will consider DAPs in connection with its review of marketing applications.

Analyses of preliminary or interim data from our clinical studies that we announce or publish from time to time may change as more patient data become available and are subject to audit and verification procedures that could result in material changes in the final data.

We currently have no products approved for sale and we cannot guarantee that we will ever have marketable products. Clinical failure can occur at any stage of clinical development. Clinical trials may produce negative or inconclusive results, and we or any future collaborators may decide, or regulators may require us, to conduct additional clinical trials or preclinical studies. We will be required to demonstrate through well-controlled clinical trials that our product candidates are safe and effective for use in a diverse population before we can seek marketing approvals for their commercial sale. Success in preclinical studies and early-stage clinical trials does not mean that future larger registration clinical trials will be successful. This is because product candidates in later-stage clinical trials may fail to demonstrate sufficient safety and efficacy to the satisfaction of the FDA and comparable foreign regulatory authorities despite having progressed through preclinical studies and early-stage clinical trials.

Analyses of preliminary or interim data from our clinical studies are not necessarily predictive of analyses of final data. Analyses of preliminary and interim data are subject to the risk that one or more of the clinical outcomes may materially change, as more patient data become available and we issue our final clinical study report. Preliminary or interim data also remain subject to audit and verification procedures that may result in the final data being materially different from the preliminary data we previously published. As a result, analyses of interim and preliminary data should be viewed with caution until the analyses of final data are available. Adverse differences between preliminary or interim data and final data could affect our planned clinical path for any of our product candidates we advance into clinical trials, including potentially increasing cost and/or causing delay in such development.

In some instances, there can be significant variability in safety and efficacy results between different clinical trials of the same product candidate due to numerous factors, including changes in trial protocols, differences in size and type of the patient populations, differences in and adherence to the dosing regimen and other trial protocols and the rate of dropout among clinical trial participants. We therefore do not know whether any clinical trials we may conduct will demonstrate consistent or adequate efficacy and safety sufficient to obtain marketing approval to market our product candidates.

Serious adverse events or undesirable side effects or other unexpected properties of any of our product candidates may be identified during development or after approval that could delay, prevent or cause the withdrawal of regulatory approval, limit the commercial potential, or result in significant negative consequences following marketing approval.

Serious adverse events or undesirable side effects caused by, or other unexpected properties of, our product candidates could cause us, an IRB, or regulatory authorities to interrupt, delay or halt our clinical trials and could result in a more restrictive label, the imposition of distribution or use restrictions or the delay or denial of regulatory approval by the FDA or comparable foreign regulatory authorities. If any of our other product candidates are associated with serious or unexpected adverse events or undesirable side effects, the FDA, the IRBs responsible for overseeing our studies, or a DSMB, could suspend or terminate our clinical trials or the FDA or comparable foreign regulatory authorities could order us to cease clinical trials or deny approval of our product candidates for any or all targeted indications. Treatment-related side effects could also affect patient recruitment or the ability of enrolled patients to complete the trial or result in potential product liability claims. Any of these occurrences may harm our business, financial condition and prospects significantly.

If unexpected adverse events occur in any of our ongoing or planned clinical trials, we may need to abandon development of our product candidates, or limit development to lower doses or to certain uses or subpopulations in which the undesirable side effects or other unfavorable characteristics are less prevalent, less severe or more acceptable from a risk-benefit perspective. Many compounds that initially showed promise in clinical or earlier stage testing are later found to cause undesirable or unexpected side effects that prevented further development of the compound.

Undesirable side effects or other unexpected adverse events or properties of any of our other product candidates could arise or become known either during clinical development or, if approved, after the approved product has been marketed. If such an event occurs during development, our trials could be suspended or terminated and the FDA or comparable foreign regulatory authorities could order us to cease further development of, or could deny approval of our product candidates. If such an event occurs after such product candidates are approved, a number of potentially significant negative consequences may result, including:

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regulatory authorities may withdraw or limit their approval of such product;

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we may decide to or be required to recall a product or change the way such product is administered to patients;

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regulatory authorities may require additional warnings on the label, such as a “black box” warning or a contraindication, or impose use restrictions;

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regulatory authorities may require one or more post-market studies to monitor the safety and efficacy of the product;

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we may be required to implement a risk evaluation and mitigation strategy (“REMS”), which may include the creation of a medication guide outlining the risks of such side effects for distribution to patients or restrictions on distribution or other elements;

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we could be sued and held liable for harm caused to patients exposed to or taking our product candidates;

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our product may become less competitive; and

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our reputation may suffer.

We believe that any of these events could prevent us from achieving or maintaining market acceptance of the affected product candidate, if approved, or could substantially increase commercialization costs and expenses, which could delay or prevent us from generating revenue from the sale of our products and harm our business and results of operations.

Even if a product candidate does obtain regulatory approval, it may never achieve the market acceptance by physicians, patients, hospitals, third-party payors and others in the medical community that is necessary for commercial success and the market opportunity may be smaller than we estimate.

Even if we obtain FDA or other regulatory approvals and are able to launch any of our product candidates commercially, the approved product candidate may nonetheless fail to gain sufficient market acceptance among physicians, patients, hospitals (including pharmacy directors) and third-party payors and, ultimately, may not be commercially successful. For example, physicians are often reluctant to switch their patients from existing therapies even when new and potentially more effective or convenient treatments enter the market. Further, patients often acclimate to the therapy that they are currently taking and do not want to switch unless their physicians recommend switching products or they are required to switch therapies due to lack of coverage and reimbursement for existing therapies. If an approved product candidate does not achieve an adequate level of acceptance, we may not generate significant product revenues or any profits from operations. The degree of market acceptance of any product candidate for which we receive approval depends on a number of factors, including:

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the efficacy and safety of the product candidate as demonstrated in clinical trials;

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relative convenience and ease of administration;

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the clinical indications for which the product candidate is approved;

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the potential and perceived advantages and disadvantages of the product candidates, including cost and clinical benefit relative to alternative treatments;

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the willingness of physicians to prescribe the product and of the target patient population to try new therapies;

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the willingness of hospital pharmacy directors to purchase the product for their formularies;

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acceptance by physicians, patients, operators of hospitals and treatment facilities and parties responsible for coverage and reimbursement of the product;

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the availability of coverage and adequate reimbursement by third-party payors and government authorities;

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the effectiveness of our sales and marketing efforts;

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the strength of marketing and distribution support;

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limitations or warnings, including distribution or use restrictions, contained in the product’s approved labeling or an approved REMS;

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whether the product is designated under physician treatment guidelines as a first-line therapy or as a second- or third-line therapy for particular infections;

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the approval of other new products for the same indications;

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the timing of market introduction of the approved product as well as competitive products;

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adverse publicity about the product or favorable publicity about competitive products;

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the emergence of bacterial resistance to the product; and

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the rate at which resistance to other drugs in the target infections grows.

Any failure of any of our product candidates that obtains regulatory approval to achieve market acceptance or commercial success would adversely affect our business prospects.

We may expend our limited resources to pursue a particular product candidate or indication and fail to capitalize on product candidates or indications that may be more profitable or for which there is a greater likelihood of success.

Because we have limited financial and managerial resources, we intend to focus on developing product candidates for specific indications that we identify as most likely to succeed, in terms of both their potential for marketing approval and commercialization. As a result, we may forego or delay pursuit of opportunities with other product candidates or for other indications that may prove to have greater commercial potential. For example, as of November 2025, we have ceased development of our SPR720 oral program and have shifted our focus and resources to advancing the clinical development of our tebipenem HBr program, as well as other corporate activities. Additionally, in March 2025, we announced that we have ceased development of SPR206.

Our resource allocation decisions may cause us to fail to capitalize on viable commercial products or profitable market opportunities. Our spending on current and future research and development programs and product candidates for specific indications may not yield any commercially viable product candidates. If we do not accurately evaluate the commercial potential or target market for a particular product candidate, we may relinquish valuable rights to that product candidate through collaboration, licensing or other royalty arrangements in cases in which it would have been more advantageous for us to retain sole development and commercialization rights to the product candidate.

If we or our collaborators are unable to establish sales, marketing and distribution capabilities or enter into sales, marketing and distribution agreements with third parties, we may not be successful in commercializing any of our product candidates if such product candidates are approved.

To achieve commercial success for any approved product, we must either develop a sales and marketing organization or outsource those functions to third parties. The development of sales, marketing and distribution capabilities will require substantial resources, will be time-consuming and could delay any product launch. If the commercial launch of a product candidate for which we recruit a sales force and establish marketing and distribution capabilities is delayed or does not occur for any reason, we would have prematurely or unnecessarily incurred these commercialization costs. This may be costly, and our investment would be lost if we cannot retain or reposition our sales and marketing personnel. In addition, we may not be able to hire a sales force in the United States

that is sufficient in size or has adequate expertise in the medical markets that we intend to target. If we or our collaborators are unable to establish a sales force and marketing and distribution capabilities, our operating results may be adversely affected.

Factors that may inhibit our efforts to commercialize our products on our own include:

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our inability to recruit and retain adequate numbers of effective sales and marketing personnel;

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the inability of sales personnel to obtain access to or persuade adequate numbers of physicians to prescribe any future products;

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the lack of complementary products to be offered by sales personnel, which may put us at a competitive disadvantage relative to companies with more extensive product lines; and

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unforeseen costs and expenses associated with creating an independent sales and marketing organization.

We intend to use collaborators to assist with the commercialization of any of our current and future product candidates, including the GSK License Agreement for the development and commercialization of tebipenem HBr. As a result of entering into arrangements with third parties to perform sales, marketing and distribution services, our product revenues or the profitability of these product revenues to us would likely be lower than if we were to directly market and sell products in those markets. Furthermore, we may be unsuccessful in entering into the necessary arrangements with third parties or may be unable to do so on terms that are favorable to us. In addition, we likely would have little control over such third parties, and any of them might fail to devote the necessary resources and attention to sell and market our products effectively.

If we or our collaborators do not establish sales and marketing capabilities successfully, either on our own or in collaboration with third parties, we will not be successful in commercializing our product candidates.

We face substantial competition from other pharmaceutical and biotechnology companies and our operating results may suffer if we fail to compete effectively.

The development and commercialization of new drug products is highly competitive. We face competition from major pharmaceutical companies, specialty pharmaceutical companies and biotechnology companies worldwide with respect to our product candidates that we may seek to develop and commercialize in the future. There are a number of large pharmaceutical and biotechnology companies that currently market and sell products or are pursuing the development of product candidates for the treatment of resistant infections. Potential competitors also include academic institutions, government agencies and other public and private research organizations. Our competitors may succeed in developing, acquiring or licensing technologies and drug products that are more effective or less costly than the product candidates that we are currently developing or that we may develop, which could render our product candidates obsolete and noncompetitive.

There are a variety of available oral therapies marketed for the treatment of cUTIs that we would expect would compete with tebipenem HBr, if approved, such as Levaquin, Cipro and Bactrim. Many of the available therapies are well established and widely accepted by physicians, patients and third-party payors. Insurers and other third-party payors may also encourage the use of generic products, for example in the fluoroquinolone class. However, the susceptibility of urinary tract pathogens to the existing treatment alternatives is waning. If tebipenem HBr is approved, the pricing may be at a significant premium over other competitive products. This may make it difficult for tebipenem HBr to compete with these products.

There are several IV-administered products marketed for the treatment of infections resistant to first-line therapy for Gram-negative infections, including Avycaz (ceftazidime-avibactam) from Allergan plc and Pfizer, Zerbaxa (ceftolozane-tazobactam) from Merck & Co., imipenem/cilastatin and Recarbrio (relebactam) from Merck & Co., Zemdri (plazomicin) from Cipla Therapeutics, Inc., Fetroja (cefiderocol) from Shionogi & Co. Ltd., and Vabomere (meropenem-vaborbactam) from CorMedix Inc., and Exblifep (cefepime/enmetazobactam) from Allecra Therapeutics.

Many of our competitors have significantly greater financial resources and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approvals and marketing approved products than we do. Mergers and acquisitions in the pharmaceutical and biotechnology industries may result in even more resources being concentrated among a smaller number of our competitors. Smaller and other early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. These third parties compete with us in recruiting and retaining qualified scientific and management personnel, establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs.

Even if we or our partners are able to commercialize any of our product candidates, the product may become subject to unfavorable pricing regulations, or third-party payor coverage and reimbursement policies that could harm our business.

Marketing approvals, pricing, coverage and reimbursement for new drug products vary widely from country to country. Some countries require approval of the sale price of a drug before it can be marketed. In many countries, the pricing review period begins after marketing or product licensing approval is granted. In some foreign markets, prescription pharmaceutical pricing remains subject to continuing governmental control even after initial approval is granted. As a result, we might obtain marketing approval for a product in a particular country, but then be subject to price regulations that delay our commercial launch of the product, possibly for lengthy time periods, which may negatively affect the revenues that we are able to generate from the sale of the product in that country. Adverse pricing limitations may hinder our ability to recoup our investment in one or more product candidates, even if our product candidates obtain marketing approval.

We currently expect that some of our product candidates, if approved, will be administered in a hospital inpatient setting. In the United States, governmental and other third-party payors generally reimburse hospitals a single bundled payment established on a prospective basis intended to cover all items and services provided to the patient during a single hospitalization. Hospitals bill third-party payors for all or a portion of the fees associated with the patient’s hospitalization and bill patients for any deductibles or co-payments. Because there is typically no separate reimbursement for drugs administered in a hospital inpatient setting, some of our target customers may be unwilling to adopt our product candidates in light of the additional associated cost. If we are forced to lower the price we charge for our product candidates, if approved, our gross margins may decrease, which would adversely affect our ability to invest in and grow our business.

To the extent any of our product candidates we develop are used in an outpatient setting, the commercial success of our product candidates will depend substantially, both domestically and abroad, on the extent to which coverage and reimbursement for these products and related treatments are available from government health programs and third-party payors. If coverage is not available, or reimbursement is limited, we may not be able to successfully commercialize our product candidates. Even if coverage is provided, the approved reimbursement amount may not be high enough to allow us to establish or maintain pricing sufficient to realize a sufficient return on our investments. Government authorities and third-party payors, such as health insurers and managed care organizations, publish formularies that identify the medications they will cover and the related payment levels. The healthcare industry is focused on cost containment, both in the United States and elsewhere. Government authorities and third-party payors have attempted to control costs by limiting coverage and the amount of reimbursement for particular medications, which could affect our ability to sell our product candidates profitably.

Increasingly, third-party payors are requiring higher levels of evidence of the benefits and clinical outcomes of new technologies and are challenging the prices charged. We cannot be sure that coverage will be available for any product candidate that we commercialize and, if available, that the reimbursement rates will be adequate. Further, the net reimbursement for outpatient drug products may be subject to additional reductions if there are changes to laws that presently restrict imports of drugs from countries where they may be sold at lower prices than in the United States. An inability to promptly obtain coverage and adequate payment rates from both government-funded and private payors for any approved products used on an outpatient basis that we develop could have a material adverse effect on our operating results, our ability to raise capital needed to commercialize products and our overall financial condition.

We cannot predict whether bacteria may develop resistance to our product candidates, if approved, which could affect their revenue potential.

Certain of our product candidates are designed to treat bacterial infections, including drug-resistant infections. The bacteria responsible for these infections evolve quickly and readily transfer their resistance mechanisms within and between species. We cannot predict whether or when bacterial resistance to any of such product candidates may develop.

For example, as a carbapenem, tebipenem HBr is not active against organisms expressing a resistance mechanism mediated by enzymes known as carbapenemases. Although occurrence of this resistance mechanism is currently rare, we cannot predict whether carbapenemase-mediated resistance will become widespread in regions where tebipenem HBr may be marketed if it is approved. The growth of drug-resistant infections in community settings or in countries with poor public health infrastructures, or the potential use of any of our product candidates outside of controlled hospital settings, could contribute to the rise of resistance. If resistance to any of our product candidates becomes prevalent, our ability to generate revenue from such product candidates could suffer.

If we are not successful in developing and commercializing additional product candidates, our ability to expand our business and achieve our strategic objectives would be impaired.

Although a substantial amount of our efforts are currently focused on our potential approval of our product candidate, tebipenem HBr, a key element of our strategy is to develop and commercialize a portfolio of therapeutics to treat drug resistant bacterial infections. We are exploring, and intend to explore in the future, strategic partnerships for the development of new product candidates.

Research programs to identify product candidates, whether pursued internally or through strategic partnerships, require substantial technical, financial and human resources, whether or not any product candidates are ultimately identified. Our research programs may initially show promise in identifying potential product candidates, yet fail to yield product candidates for clinical development for many reasons, including the following:

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the research methodology used may not be successful in identifying potential product candidates;

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we may be unable to successfully modify candidate compounds to be active in Gram-negative bacteria or defeat bacterial resistance mechanisms or identify viable product candidates in our screening campaigns;

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competitors may develop alternatives that render our product candidates obsolete;

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product candidates that we develop may nevertheless be covered by third parties’ patents or other exclusive rights;

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a product candidate may, on further study, be shown to have harmful side effects or other characteristics that indicate it is unlikely to be effective or otherwise does not meet applicable regulatory criteria;

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a product candidate may not be capable of being produced in commercial quantities at an acceptable cost, or at all;

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a product candidate may not be accepted as safe and effective by patients, the medical community or third-party payors; and

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the development of bacterial resistance to potential product candidates may render them ineffective against target infections.

If we are unsuccessful in identifying and developing additional product candidates, our potential for growth may be impaired.

Product liability lawsuits against us could divert our resources, cause us to incur substantial liabilities and limit commercialization of any products that we may develop.

We face an inherent risk of product liability claims as a result of the clinical testing of our product candidates despite obtaining appropriate informed consents from our clinical trial participants. We will face an even greater risk if we obtain marketing approval for and commercially sell any of our product candidates. For example, we may be sued if any product that we develop allegedly causes injury or is found to be otherwise unsuitable during clinical testing, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the product, negligence, strict liability or a breach of warranties. Claims could also be asserted under state consumer protection acts. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our product candidates. Regardless of the merits or eventual outcome, liability claims may result in:

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reduced resources for our management to pursue our business strategy;

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decreased demand for our product candidates or products that we may develop;

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injury to our reputation and significant negative media attention;

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withdrawal of clinical trial participants;

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initiation of investigations by regulators;

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product recalls, withdrawals or labeling, marketing or promotional restrictions;

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significant costs to defend resulting litigation;

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substantial monetary awards to trial participants or patients;

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loss of revenue; and

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the inability to commercialize any products that we may develop.

Although we maintain general liability insurance and clinical trial liability insurance, this insurance may not fully cover potential liabilities that we may incur. The cost of any product liability litigation or other proceeding, even if resolved in our favor, could be substantial. We will need to increase our insurance coverage if and when we receive marketing approval for and begin selling any of our product candidates. In addition, insurance coverage is becoming increasingly expensive. If we are unable to obtain or maintain sufficient insurance coverage at an acceptable cost or to otherwise protect against potential product liability claims, it could prevent or inhibit the development and commercial production and sale of our product candidates, which could adversely affect our business, financial condition, results of operations and prospects.

If we fail to comply with environmental, health and safety laws and regulations, we could become subject to fines or penalties or incur costs that could have a material adverse effect on our business.

We are subject to numerous environmental, health and safety laws and regulations, including those governing laboratory procedures and the handling, use, storage, treatment and disposal of hazardous materials and wastes. From time to time and in the future, our operations may involve the use of hazardous and flammable materials, including chemicals and biological materials, and may also produce hazardous waste products. Even if we contract with third parties for the disposal of these materials and wastes, we cannot completely eliminate the risk of contamination or injury resulting from these materials. In the event of contamination or injury resulting from our use of hazardous materials, we could be held liable for any resulting damages, and any liability could exceed our resources. We also could incur significant costs associated with civil or criminal fines and penalties for failure to comply with such laws and regulations.

We maintain workers’ compensation insurance to cover us for costs and expenses that we may incur due to injuries to our employees resulting from the use of hazardous materials, but this insurance may not provide adequate coverage against potential liabilities. Moreover, we do not currently maintain insurance for environmental liability or toxic tort claims that may be asserted against us.

In addition, we may incur substantial costs in order to comply with current or future environmental, health and safety laws and regulations. Current or future environmental laws and regulations may impair our research, development or production efforts, which could adversely affect our business, financial condition, results of operations or prospects. In addition, failure to comply with these laws and regulations may result in substantial fines, penalties or other sanctions.

Our internal computer systems, or those of our contract research organizations or other contractors or consultants, may fail or suffer cybersecurity incidents, which could result in a material disruption of our product development programs, and could subject us to liability.

We utilize information technology systems and networks to process, transmit and store electronic information in connection with our business activities. As the use of digital technologies has increased, cyber incidents, including deliberate attacks and attempts to gain unauthorized access to computer systems and networks, have increased in frequency and sophistication. In particular, ransomware attacks, including those from organized criminal threat actors, nation-states and nation-state supported actors, are becoming increasingly prevalent and severe and can lead to significant interruptions, delays, or outages in our operations, loss of data, including sensitive customer information, loss of income, significant extra expenses to restore data or systems, reputational loss and the diversion of funds. To alleviate the negative impact of a ransomware attack, it may be preferable to make payments to the threat actor(s), but we may be unwilling or unable to do so, including, for example, if applicable laws or regulations prohibit such payments. Finally, developments in artificial intelligence and machine learning provide threat actors with the capability to use more sophisticated means to attack our systems and may exacerbate cybersecurity risk. These threats pose a risk to the security of our systems and networks and the confidentiality, availability and integrity of our data. There can be no assurance that we will be successful in preventing cyber-attacks or successfully mitigating their effects.

Despite the implementation of security measures, our internal computer systems and those of our contract research organizations and other contractors and consultants are vulnerable to damage or disruption from hacking, computer viruses, malware, including ransomware, software bugs, unauthorized access, natural disasters, terrorism, war, and telecommunication, equipment and electrical failures. We have measures in place that are designed to prevent, and if necessary, to detect and respond to such cybersecurity incidents and breaches of privacy and security mandates. Our measures to prevent, respond to, and minimize such risks may be unsuccessful. While we have not, to our knowledge, experienced any significant system failure, accident or material cybersecurity incident to date, if such an event were to occur and cause interruptions in our operations or the operations of those third parties with which we contract, it could result in a material disruption of our programs and our business operations, as well as our financial condition. For example, the loss of clinical trial data from completed or ongoing clinical trials for any of our product candidates could result in delays in our development and regulatory approval efforts and significantly increase our costs to recover or reproduce the data. Such a loss could also expose us to regulatory enforcement, civil liability and reputational damage. To the extent that any disruption or cybersecurity incident results in a loss of or damage to our data or applications, or inappropriate disclosure or theft of confidential or proprietary information, in addition to incurring liability, the further development of our product candidates could be delayed or our competitive position could be compromised. Additionally, such disruptions or cybersecurity incidents could result in enforcement actions by U.S. or foreign regulatory authorities, regulatory penalties, and other legal liabilities such as but not limited to private litigation, the incurrence of significant remediation costs, disruptions to our development programs, business operations and collaborations, diversion of management efforts and damage to our reputation, all of which could harm our business and operations.

Our actual or perceived failure to comply with data protection laws and regulations could lead to government enforcement actions, private litigation and/or adverse publicity and could negatively affect our business.

We are subject to domestic and international data protection laws and regulations that address privacy and data security and may affect our collection, use, storage, and transfer of personal information. The legislative and regulatory landscape for data protection continues to evolve, and in recent years there has been an increasing focus on privacy and data security issues with the potential to affect our business. In the United States, numerous federal and state laws and regulations, including state data breach notification laws, state health information privacy laws and federal and state consumer protection laws govern the collection, use, disclosure and protection of health-related and other personal information. Failure to comply with data protection laws and regulations, where applicable, could result in government enforcement actions, which could include civil or criminal penalties, private litigation and/or adverse publicity and could negatively affect our operating results and business. For example, California has enacted the California Consumer Privacy Act (“CCPA”), which went into effect in January of 2020. The CCPA gives California residents expanded rights to access and require deletion of their personal information, opt out of certain personal information sharing, and receive detailed information about how their personal information is used. The CCPA provides for civil penalties for violations, as well as a private right of action for data breaches that may increase data breach litigation. Although the CCPA includes exemptions for certain clinical trials data, and the federal Health Insurance Portability and Accountability Act of 1996 (“HIPAA”) protected health information, the law may increase our compliance costs and potential liability with respect to other personal information we collect about California residents. Additionally in 2020, California voters passed the California Privacy Rights Act (“CPRA”), which went into full effect on January 1, 2023. The CPRA significantly amends the CCPA, potentially resulting in further uncertainty, additional costs and expenses in an effort to comply and additional potential for harm and liability for failure to comply. Among other things, the CPRA established a new regulatory authority, the California Privacy Protection Agency, which is tasked with enacting new regulations under the CPRA and will have expanded enforcement authority. In addition to California, more U.S. states are enacting similar legislation, increasing compliance complexity and increasing risks of failures to comply. In 2023, comprehensive privacy laws in Virginia, Colorado, Connecticut, and Utah all took effect, and laws in Montana, Oregon, and Texas took effect in 2024. Laws in a number of other U.S. states took effect, or are set to take effect, in 2025, and beyond, and additional U.S. states have proposals under consideration, all of which are likely to increase our regulatory compliance costs and risks, exposure to regulatory enforcement action and other liabilities.

In addition, other federal and state laws establish additional requirements for protecting the privacy and security of health information that is not protected by HIPAA. For instance, Washington state recently passed the “My Health My Data” Act, which came into force in 2024 and regulates “consumer health data,” which is defined as “personal information that is linked or reasonably linkable to a consumer and that identifies a consumer’s past, present, or future physical or mental health.” The “My Health My Data” Act provides exemptions for personal data used or shared in connection with certain research activities, including data subject to 45 C.F.R. Parts 46, 50 and 56. Notably, the “My Health My Data” Act contains a private right of action. In addition, Nevada recently enacted a consumer health data privacy bill, SB 370, which also took effect in 2024, and regulates “consumer health data.” SB 370 shares many similarities with Washington’s “My Health My Data” Act, and Connecticut recently amended its comprehensive privacy law to include heighted regulation of “consumer health data.” Additional states may adopt health-specific privacy laws that could impact our business activities and our collection and handling of health-related data.

Numerous other countries have, or are developing, laws governing the collection, use and transmission of personal information as well. For example, the European Parliament and the Council of the European Union adopted a comprehensive general data privacy framework called the General Data Protection Regulation (“GDPR”), which took effect in May 2018 and governs the collection and use of personal data in the European Union, including by companies outside of the European Union. The GDPR, which is wide-ranging in scope, imposes several requirements relating to the consent of the individuals to whom the personal data relates, the information provided to the individuals, the security and confidentiality of the personal data, data breach notification and the use of third-party processors in connection with the processing of the personal data. The GDPR also imposes strict rules on the transfer of personal data out of the European Union to the United States, enhances enforcement authority and imposes large penalties for noncompliance, including the potential for fines of up to €20 million or 4% of the annual global revenues of the infringer, whichever is greater.

The GDPR also confers a private right of action on data subjects and consumer associations to lodge complaints with supervisory authorities, seek judicial remedies, and obtain compensation for damages resulting from violations of the GDPR. Compliance with the GDPR has been and will continue to be a rigorous and time-intensive process that has increased and will continue to increase our cost of doing business or require us to change our business practices, and despite those efforts, there is a risk that we or our collaborators may be subject to fines and penalties, litigation and reputational harm in connection with any European activities, which could adversely affect our business, prospects, financial condition and results of operations.

Applicable data privacy and data protection laws may conflict with each other, and by complying with the laws or regulations of one jurisdiction, we may find that we are violating the laws or regulations of another jurisdiction. Despite our efforts, we may not have fully complied in the past and may not in the future. That could require us to incur significant expenses, which could significantly

affect our business. Failure to comply with data protection laws may expose us to risk of enforcement actions taken by data protection authorities or other regulatory agencies, private rights of action in some jurisdictions, and potential significant penalties if we are found to be non-compliant. Furthermore, the number of government investigations related to data security incidents and privacy violations continue to increase and government investigations typically require significant resources and generate negative publicity, which could harm our business and reputation.

We or third parties upon whom we depend may be adversely affected by natural disasters and/or health epidemics, and our business, financial condition and results of operations could be adversely affected.

Natural disasters could severely disrupt our operations and have a material adverse effect on our business operations. If a natural disaster, health epidemic or other events beyond our control occurred that prevented us from using all or a significant portion of our office, that damaged critical infrastructure, such as the manufacturing facilities of our third-party contract manufacturers, or that otherwise disrupted operations, it may be difficult for us to continue our business for a substantial period of time.

Risks Related to Our Financial Position and Need for Additional Capital

We have not generated any revenue from the sale of our products, have a history of losses and expect to incur substantial future losses. If we are unable to obtain additional capital, we may not be able to continue our operations on the scope or scale as currently conducted, and that could have a material adverse effect on our business, results of operations and financial condition.

We have not generated any revenue from the sale of our products and have incurred losses in most years since our inception in 2013. Our net loss was $7.4 million and $22.9 million during the three and nine months ended September 30, 2025, respectively. We have yet to have a product candidate approved for sale and we may never have a product candidate approved for commercialization.

In accordance with ASU 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), we have evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern within one year after the date that these consolidated financial statements are issued. Based on our cash and cash equivalents as of September 30, 2025 and the decrease in clinical expense as a result of the completion of the PIVOT-PO Phase 3 trial for tebipenem HBr and the decision to cease development of SPR720, we believe that our cash runway will be sufficient to fund our operating expenses and required capital expenditures into 2028. During this period, we plan to prioritize finalizing the Phase 3 clinical trial activities for tebipenem HBr under our GSK License Agreement. Beyond this point, or in the event we change our current operating plan, we will need additional funding, which we expect will primarily consist of raising additional capital through some combination of equity or debt financings, potential new collaborations or additional grant funding. If we are not able to secure adequate additional funding, we plan to make further reductions in spending. In that event, we may have to delay, scale back, or eliminate some or all of our planned development activities. The actions necessary to reduce spending under this plan at a level that mitigates the factors described above is not considered probable, as defined in the accounting standards and therefore, the full extent to which management may extend our funds through these actions may not be considered in management’s assessment of our ability to continue as a going concern.

We expect to continue to incur significant expenses and operating losses for the foreseeable future. If we are unable to achieve commercialization, revenue from product sales, and, ultimately, profitability, the market value of our common stock will likely decline.

We expect to continue to incur significant expenses and operating losses for the foreseeable future as we continue to advance our product candidates through preclinical and clinical development and marketing approval for such candidates whose clinical trials are successful. Our expenses will also increase substantially if and as we:

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conduct additional clinical trials and studies of our product candidates;

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continue to discover and develop additional product candidates;

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establish manufacturing and supply chain capacity sufficient to provide commercial quantities of any product candidates for which we may obtain marketing approval;

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maintain, expand and protect our intellectual property portfolio;

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hire additional clinical, scientific and commercial personnel;

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add operational, financial and management information systems and personnel, including personnel to support our product development and planned future commercialization efforts, face competing technological and market developments; and

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acquire or in-license other product candidates and technologies.

We currently have no products approved for sale and have historically invested a significant portion of our efforts and financial resources in the development of our product candidates, including tebipenem HBr, SPR206, and SPR720. Although we decided to cease further development of SPR206 and SPR720, our business remains heavily dependent on the successful development, regulatory approval, and, if approved, commercialization of tebipenem HBr and any future product candidates. We cannot be certain that any product candidate will receive regulatory approval or will be successfully commercialized even if it receives regulatory approval.

If our product candidates fail to demonstrate safety and efficacy in clinical trials, do not gain regulatory approval, or do not achieve market acceptance following regulatory approval and commercialization, we may never become profitable. Even if we achieve profitability in the future, we may not be able to sustain profitability in subsequent periods. Our prior losses, combined with expected future losses, have had and will continue to have an adverse effect on our stockholders’ equity and working capital. If we are unable to achieve and sustain profitability, the market value of our common stock will likely decline.

Because of the numerous risks and uncertainties associated with developing biopharmaceutical products, we are unable to predict the extent of any future losses or when, if ever, we will become profitable. Our expenses would increase if we are required by the FDA, or any comparable foreign regulatory authority to perform studies in addition to those currently expected, or if there are any delays in completing our clinical trials or the development of any of our product candidates.

If we are unable to raise capital when needed, or do not receive payments under our government awards or from our commercial partnership agreements, it could limit our ability to support our operations and explore our growth strategy.

Developing pharmaceutical products, including conducting preclinical studies and clinical trials, is a time-consuming, expensive and uncertain process that takes years to complete. Our expenses are likely to increase if we commence and advance additional studies for any future product candidates. If we obtain marketing approval for any product candidate, we expect to incur significant expenses related to development, product sales, marketing, distribution and manufacturing. Some of these expenses may be incurred in advance of marketing approval and could be substantial. Accordingly, we will be required to obtain further funding through public or private equity offerings, debt financings, collaborations, licensing arrangements, government funding or other sources. Adequate additional financing may not be available to us on acceptable terms, or at all. Our failure to raise capital as and when needed would have a negative effect on our financial condition and our ability to pursue our business strategy.

Based on our cash and cash equivalents as of September 30, 2025, and the decrease in clinical expense as a result of the completion of the PIVOT-PO Phase 3 trial for tebipenem HBr and the decision to cease development of SPR720, we believe that our cash runway will be sufficient to fund our operating expenses and capital expenditures into 2028. During this period, we plan to prioritize finalizing the Phase 3 clinical trial activities for tebipenem HBr under our GSK License Agreement. Beyond this point, or in the event we change our current operating plan, we will need additional funding to support our continuing operations and explore our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, government funding arrangements, collaborations, strategic alliances and marketing, distribution or licensing arrangements. If we are not able to secure adequate additional funding, we plan to make further reductions in spending. In that event, we may have to delay, scale back, or eliminate some or all of our planned development activities, including:

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the timing and terms of the potential FDA approval of tebipenem HBr;

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the timing, costs and results of our ongoing, planned and potential clinical trials for our product candidates;

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the amount of funding that we receive under our government awards;

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the number and characteristics of product candidates that we pursue;

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the outcome, timing and costs of seeking regulatory approvals;

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the terms and timing of any future collaborations, licensing or other arrangements that we may establish;

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the costs of preparing, filing and prosecuting patent applications, maintaining and protecting our intellectual property rights and defending against any intellectual property related claims;

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the costs of our continued operation as a public company; and

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the extent to which we in-license or acquire other products and technologies.

Raising additional capital may cause dilution to our stockholders, restrict our operations or require us to relinquish rights to our technologies or product candidates.

Unless and until we can generate a substantial amount of revenue from our product candidates, we expect to finance our future cash needs through public or private equity offerings, debt financings, collaborations, licensing arrangements and government funding arrangements. In addition, we may seek additional capital due to favorable market conditions or strategic considerations, even if we believe that we have sufficient funds for our current or future operating plans.

We filed the 2024 Form S-3 on March 15, 2024, which became effective on March 22, 2024 and pursuant to which we registered for sale up to $300.0 million of any combination of our common stock, preferred stock, debt securities, warrants, rights and/or units from time to time and at prices and on terms that we may determine, including up to $75.0 million of our common stock available for issuance pursuant to the Sales Agreement with Cantor. Under the Sales Agreement, Cantor may sell shares of our common stock by any method permitted by law deemed to be an “at-the-market” offering as defined in Rule 415 of the Securities Act, subject to the terms of the Sales Agreement.

We may seek to raise additional capital at any time. To the extent that we raise additional capital through the sale of common stock, convertible securities or other equity securities, the ownership interest of our then existing stockholders may be materially diluted, and the terms of these securities could include liquidation or other preferences and anti-dilution protections that could adversely affect the rights of our stockholders. In addition, debt financing, if available, would result in increased fixed payment obligations and may involve agreements that include restrictive covenants that limit our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends, which could adversely affect our ability to conduct our business. In addition, securing additional financing would require a substantial amount of time and attention from our management and may divert a disproportionate amount of their attention away from day-to-day activities, which may adversely affect our management’s ability to oversee the development of our product candidates.

If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams or product candidates or grant licenses on terms that may not be favorable to us.

We have a limited operating history and no history of commercializing pharmaceutical products, which may make it difficult to evaluate the prospects for our future viability.

Our operations to date have been limited to financing and staffing our company, and performing research and development activities to advance our product candidates. We have not yet demonstrated an ability to successfully obtain marketing approval, manufacture a commercial scale product, or arrange for a third party to do so on our behalf, or conduct sales and marketing activities necessary for successful product commercialization. Consequently, predictions about our future success or viability may not be as accurate as they could be if we had a longer operating history or a history of successfully developing and commercializing pharmaceutical products.

We expect our financial condition and operating results to continue to fluctuate significantly from quarter to quarter and year to year due to a variety of factors, many of which are beyond our control. Accordingly, stockholders should not rely upon the results of any quarterly or annual periods as indications of future operating performance

Our ability to use our net operating loss carryforwards may be limited.

As of December 31, 2024, we had U.S. federal, state and foreign net operating loss carryforwards (“NOLs”) of $165.2 million, $120.6 million and $4.6 million, respectively. $152.0 million of the federal NOLs can be carried forward indefinitely and $13.2 million of the federal NOLs begin to expire in 2034. The state NOLs begin to expire in 2034 and will expire at various dates through 2044. The foreign NOLs do not expire. Utilization of these NOLs depends on many factors, including our future income, which cannot be assured. Our NOLs, other than the NOLs that can be carried forward indefinitely, could expire unused and be unavailable to offset our future income tax liabilities. Any carryforwards that will expire prior to utilization were removed from deferred tax assets, with a corresponding reduction of the valuation allowance. In addition, under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended (the "Code") and corresponding provisions of state law, if a corporation undergoes an “ownership change,” which is generally defined as a greater than 50% change, by value, in its equity ownership by 5% stockholders over a three-year period, the corporation’s ability to use its pre-change NOLs and other pre-change tax attributes to offset its post-change income may be limited. We recently completed a Section 382 study and concluded that we underwent several ownership changes as defined by the Code, the last of which occurred during the year ended December 31, 2018. Future ownership changes, some of which may be beyond our control, may limit our ability to utilize our tax attributes.

Under current U.S. federal tax legislation, NOLs arising in tax years beginning after December 31, 2017 may be used to offset only 80% of taxable income (although such NOLs may be carried forward indefinitely).

Risks Related to Our Dependence on Third Parties

We may not achieve the milestones triggering payments to us in our existing, or any future, license and collaboration agreements with third parties.

We have and may continue to seek third-party collaborators for development and commercialization of certain of our product candidates. Currently we are party to license and collaboration agreements with third parties as described in Note 11 to our consolidated financial statements appearing elsewhere in this Quarterly Report on Form 10-Q. Our likely collaborators for any other marketing, distribution, development, licensing or broader collaboration arrangements we may pursue include large and mid-size pharmaceutical companies, regional and national pharmaceutical companies and biotechnology companies.

We may derive revenue from research and development fees, license fees, milestone payments and royalties under any collaborative arrangement into which we enter. Our ability to generate revenue from these arrangements will depend on our collaborators’ abilities to successfully perform the functions assigned to them in these arrangements. In addition, our collaborators may have the right to abandon research or development projects and terminate applicable agreements, including funding obligations, prior to or upon the expiration of the agreed upon terms. As a result, we can expect to relinquish some or all of the control over the future success of a product candidate that we license to a third party.

We face significant competition in seeking and obtaining appropriate collaborators. Collaborations involving our product candidates may pose a number of risks, including the following:

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collaborators have significant discretion in determining the efforts and resources that they will apply to these collaborations;

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collaborators may not perform their obligations as expected;

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collaborators may not pursue development and commercialization of our product candidates or may elect not to continue or renew development or commercialization programs based on clinical trial results, changes in the collaborators’ strategic focus or available funding or external factors, such as an acquisition, that divert resources or create competing priorities;

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collaborators may not be able to develop, manufacture, market and sell our product candidates and use our intellectual property without infringing or misappropriating the intellectual property and other proprietary rights of third parties;

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collaborators may delay clinical trials, provide insufficient funding for a clinical trial program, stop a clinical trial or abandon a product candidate, repeat or conduct new clinical trials or require a new formulation of a product candidate for clinical testing;

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product candidates discovered in collaboration with us may be viewed by our collaborators as competitive with their own product candidates or products, which may cause collaborators to cease to devote resources to the commercialization of our product candidates;

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a collaborator with marketing and distribution rights to one or more products may not commit sufficient resources to the marketing and distribution of such product or products;

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disagreements with collaborators, including disagreements over proprietary rights, contract interpretation or the preferred course of development, might cause delays or termination of the research, development or commercialization of product candidates, might lead to additional responsibilities for us with respect to product candidates, or might result in litigation or arbitration, any of which would be time-consuming and expensive;

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collaborators may not properly maintain or defend our intellectual property rights or may use our proprietary information in such a way as to invite litigation that could jeopardize or invalidate our intellectual property or proprietary information or expose us to potential litigation;

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collaborators may infringe the intellectual property rights of third parties, which may expose us to litigation and potential liability; and

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collaborations may be terminated and, if terminated, may result in a need for additional capital to pursue further development or commercialization of the applicable product candidates.

Collaboration agreements may not lead to development or commercialization of product candidates in the most efficient manner or at all. If a collaborator of ours is involved in a business combination, it could decide to delay, diminish or terminate the development or commercialization of any product candidate licensed to it by us.

We may have to alter our development and commercialization plans if we are not able to establish collaborations.

We will require additional funds to complete the development and potential commercialization of our product candidates. For some of our product candidates, we may decide to collaborate with pharmaceutical and biotechnology companies for the development and potential commercialization of those product candidates. Moreover, we intend to utilize a variety of types of collaboration arrangements for the potential commercialization of our product candidates outside the United States. Whether we reach a definitive agreement for a collaboration will depend, among other things, upon our assessment of the collaborator’s resources and expertise, the terms and conditions of the proposed collaboration and the proposed collaborator’s evaluation of a number of factors. Those factors may include:

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the design or results of clinical trials;

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the likelihood of approval by the FDA or comparable foreign regulatory authorities;

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the potential market for the subject product candidate;

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the costs and complexities of manufacturing and delivering such product candidate to patients;

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the potential for competing products;

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our patent position protecting the product candidate, including any uncertainty with respect to our ownership of our technology or our licensor’s ownership of technology we license from them, which can exist if there is a challenge to such ownership without regard to the merits of the challenge;

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the need to seek licenses or sub-licenses to third-party intellectual property; and

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industry and market conditions generally.

The collaborator may also consider alternative product candidates or technologies for similar indications that may be available for collaboration and whether such a collaboration could be more attractive than the one with us for our product candidate. We may also be restricted under future license agreements from entering into agreements on certain terms with potential collaborators. In addition, there have been a significant number of recent business combinations among large pharmaceutical companies that have resulted in a reduced number of potential future collaborators.

If we are unable to reach agreements with suitable collaborators on a timely basis, on acceptable terms, or at all, we may have to curtail the development of a product candidate, reduce or delay its development program or one or more of our other development programs, delay its potential commercialization or reduce the scope of any sales or marketing activities, or increase our expenditures and undertake development or commercialization activities at our own expense. If we elect to fund and undertake development or commercialization activities on our own, we may need to obtain additional expertise and additional capital, which may not be available to us on acceptable terms or at all. If we fail to enter into collaborations and do not have sufficient funds or expertise to undertake the necessary development and commercialization activities, we may not be able to further develop our product candidates or bring them to market and our business may be materially and adversely affected.

We rely on third parties to conduct all of our nonclinical studies and all of our clinical trials. If these third parties do not successfully carry out their contractual duties or meet expected deadlines, we may be unable to obtain regulatory approval for or commercialize any of our product candidates. If they do not perform satisfactorily, our business may be materially harmed.

We do not independently conduct nonclinical studies that comply with good laboratory practice (“GLP”) requirements. We also do not have the ability to independently conduct clinical trials of any of our product candidates. We rely on third parties, such as contract research organizations, clinical data management organizations, medical institutions and clinical investigators, to conduct our clinical trials of our product candidates and potential product candidates. Any of these third parties may terminate their engagements with us at any time. If we need to enter into alternative arrangements, it would delay our product development activities and increase our costs.

Our reliance on these third parties for clinical development activities limits our control over these activities but we remain responsible for ensuring that each of our studies is conducted in accordance with the applicable protocol, legal, regulatory and scientific standards. For example, notwithstanding the obligations of a contract research organization for a trial of one of our product candidates, we remain responsible for ensuring that each of our clinical trials is conducted in accordance with the general investigational plan and protocols for the trial and applicable regulatory requirements. While we will have agreements governing their activities, we control only certain aspects of their activities and have limited influence over their actual performance. The third parties with whom we contract for execution of our GLP studies and our clinical trials play a significant role in the conduct of these studies and trials and the subsequent collection and analysis of data. Although we rely on these third parties to conduct our GLP-compliant nonclinical studies and clinical trials, we remain responsible for ensuring that each of our nonclinical studies and clinical trials are conducted in accordance with applicable laws and regulations, and our reliance on the CROs does not relieve us of our regulatory responsibilities. The FDA and regulatory authorities in other jurisdictions also require us to comply with standards, commonly

referred to as good clinical practices (“GCPs”) for conducting, monitoring, recording and reporting the results of clinical trials to assure that data and reported results are accurate and that the trial subjects are adequately informed of the potential risks of participating in clinical trials. The FDA enforces these GCPs through periodic inspections of trial sponsors, principal investigators, clinical trial sites and institutional review boards. If we or our third-party contractors fail to comply with applicable GCP standards, the clinical data generated in our clinical trials may be deemed unreliable and the FDA may require us to perform additional clinical trials before approving our product candidates, which would delay the regulatory approval process. We cannot make assurances that, upon inspection, the FDA will determine that any of our clinical trials comply with GCP. We are also required to register clinical trials and post the results of completed clinical trials on a government-sponsored database, ClinicalTrials.gov, within certain timeframes. Failure to do so can result in fines, adverse publicity and civil and criminal sanctions.

Furthermore, the third parties conducting clinical trials on our behalf are not our employees, and except for remedies available to us under our agreements with such contractors, we cannot control whether or not they devote sufficient time and resources to our ongoing development programs. These contractors may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical trials or other drug development activities, which could impede their ability to devote appropriate time to our clinical programs. If these third parties do not successfully carry out their contractual duties, meet expected deadlines or conduct our clinical trials in accordance with regulatory requirements or our stated protocols, we may not be able to obtain, or may be delayed in obtaining, marketing approvals for our product candidates. If that occurs, we may not be able to, or may be delayed in our efforts to, successfully commercialize our product candidates. In such an event, our financial results and the commercial prospects for our product candidates could be harmed, our costs could increase and our ability to generate revenue could be delayed, impaired or foreclosed.

We also rely on other third parties to store and distribute drug supplies for our clinical trials. Any performance failure on the part of our distributors could delay clinical development or marketing approval of our product candidates or commercialization of any resulting products, producing additional losses and depriving us of potential product revenue.

We contract with third parties for the manufacture of clinical supplies of tebipenem HBr and expect to continue to do so in connection with any future commercialization and for any future clinical trials and commercialization of any potential product candidates. This reliance on third parties increases the risk that we will not have sufficient quantities of our product candidates or such quantities at an acceptable cost, which could delay, prevent or impair our development or commercialization efforts.

We do not currently have nor do we plan to build the internal infrastructure or capability to manufacture our product candidates for use in the conduct of our preclinical research, our clinical trials or for commercial supply. We currently rely on and expect to continue to rely on third-party contract manufacturers to manufacture supplies of our product candidates, and we expect to rely on third-party contract manufacturers to manufacture commercial quantities of any product candidate that we commercialize following approval for marketing by applicable regulatory authorities, if any. Reliance on third-party manufacturers entails risks, including:

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manufacturing delays if our third-party manufacturers give greater priority to the supply of other products over our product candidates or otherwise do not satisfactorily perform according to the terms of the agreement between us;

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the possible termination or nonrenewal of the agreement by the third-party at a time that is costly or inconvenient for us;

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the possible breach of the manufacturing agreement by the third-party;

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the failure of the third-party manufacturer to comply with applicable regulatory requirements; and

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the possible misappropriation of our proprietary information, including our trade secrets and know-how.

We currently rely on a small number of third-party contract manufacturers and one supplier for all of our required raw materials, drug substance and finished product for our preclinical research and clinical trials. We do not have long-term agreements with any of these third parties. We also do not have any current contractual relationships for the manufacture of commercial supplies of any of our product candidates. If any of our existing manufacturers should become unavailable to us for any reason, we may incur delays in identifying or qualifying replacements.

In addition, because some of our manufacturers have manufacturing facilities in Taiwan, their ability to provide us with adequate supplies of high-quality products on a timely and cost-efficient basis is subject to a number of additional risks and uncertainties, including political, social and economic instability and factors that could impact the shipment of supplies. If our manufacturers are unable to provide us with adequate supplies of high-quality products on a timely and cost-efficient basis, our operations would be disrupted and our net revenue and profitability would suffer.

Our third-party contract manufacturers are based in Asia. In the past, our third-party contract manufacturers have been subject to various supply chain disruptions. These supply chain disruptions have increased the price of certain materials due to the significant increase in costs of raw materials and shipping costs. Our ability to produce and timely deliver our products may be materially impacted in the future if these supply chain disruptions continue or worsen.

Further, a major catastrophe, such as an earthquake or other natural disaster, labor strike, or work stoppage at any of our manufacturing facilities, or a manufacturing facility of our suppliers or customers, could result in a prolonged interruption of our business. A disruption resulting from any one of these events could cause significant delays in shipments of our products and the loss of revenue and customers, which could have a material adverse effect on our financial position, results of operations, and cash flows. Our manufacturer's facilities in Japan are located in seismically-active areas.

If any of our product candidates are approved by any regulatory agency, we intend to enter into agreements with third-party contract manufacturers for the commercial production of those products. This process is difficult and time consuming and we may face competition for access to manufacturing facilities as there are a limited number of contract manufacturers operating under current good manufacturing practices (“cGMPs”) that are capable of manufacturing our product candidates. Consequently, we may not be able to reach agreement with third-party manufacturers on satisfactory terms, which could delay our commercialization.

Third-party manufacturers are required to comply with cGMPs and similar regulatory requirements outside the United States. Facilities used by our third-party manufacturers must be approved by the FDA after we submit an NDA and before potential approval of the product candidate. Similar regulations apply to manufacturers of our product candidates for use or sale in foreign countries. We do not control the manufacturing process and are completely dependent on our third-party manufacturers for compliance with the applicable regulatory requirements for the manufacture of our product candidates. The inability or failure of our manufacturers to successfully manufacture material that conforms to the strict regulatory requirements of the FDA and any applicable foreign regulatory authority, may require us to find alternative manufacturing facilities, which could result in delays in obtaining approval for the applicable product candidate. In addition, our manufacturers are subject to ongoing periodic unannounced inspections by the FDA and corresponding state and foreign agencies for compliance with cGMPs and similar regulatory requirements. Failure by any of our manufacturers to comply with applicable cGMPs or other regulatory requirements could result in sanctions being imposed on us, including fines, injunctions, civil penalties, delays, suspensions or withdrawals of approvals, operating restrictions, interruptions in supply and criminal prosecutions, any of which could significantly and adversely affect supplies of our product candidates and have a material adverse effect on our business, financial condition and results of operations.

Our current and anticipated future dependence upon others for the manufacture of our product candidates and potential product candidates may adversely affect our future profit margins and our ability to commercialize any products for which we receive marketing approval on a timely and competitive basis.

If we fail to comply with our obligations in the agreements under which we in-license or acquire development or commercialization rights to products, technology or data from or to third parties, we could lose rights that are important to our business.

We are a party to agreements with Meiji and GSK for tebipenem HBr, and have legacy agreements with Vertex Pharmaceuticals for SPR720 and Pfizer, Everest and PBB Distributions Limited for SPR206, and we may enter into additional agreements, including license agreements, with other parties in the future that impose diligence, development and commercialization timelines, milestone payments, royalties, insurance and other obligations on us.

For example, we have the Meiji License that gives us rights outside of the Meiji Territory to develop, manufacture, and commercialize tebipenem HBr as well as the right to use, cross-reference, file or incorporate by reference any information and relevant Meiji regulatory documentation to support any regulatory filings outside of the Meiji Territory. In addition, we have the right to develop, manufacture and have manufactured tebipenem HBr in the Meiji Territory solely for the purpose of furthering development, manufacturing and commercialization of tebipenem HBr outside of the Meiji Territory. In exchange for those rights, we are obligated to satisfy diligence requirements, including using commercially reasonable efforts to develop and commercialize tebipenem HBr and to implement a specified development plan, meeting specified development milestones and providing an update on progress on an annual basis. The Meiji License requires us to pay future milestone payments of up to $1.0 million upon the achievement of specified regulatory milestones and royalties of 1% of net sales on a product-by-product and country-by-country basis.

In addition, pursuant to our GSK License Agreement, we granted GSK an exclusive royalty-bearing license, with the right to grant sublicenses, under our intellectual property and regulatory documents and a sublicense under certain intellectual property of Meiji and Meiji’s regulatory documents to develop, manufacture and commercialize the GSK Licensed Products in the GSK Territory. Under the terms of the GSK License Agreement, we received an upfront payment of $66.0 million for GSK to secure rights to tebipenem pivoxil and tebipenem HBr, a $30.0 million milestone payment upon achievement of a development milestone in the third quarter of 2023, and are entitled to receive a $95.0 million development milestone payment that is payable in four equal semi-annual

installments, of which we received $23.8 million in the first quarter of 2024, the third quarter of 2024, the first quarter of 2025 and the third quarter of 2025. Remaining potential payments under the GSK License Agreement are milestone based and are (i) $25.0 million for GSK’s submission of a NDA with the FDA for tebipenem HBr, (ii) up to $101.0 million in commercial milestone payments, and (iii) up to $225.0 million in sales milestone payments. In addition to the milestones described above, GSK is obligated to pay royalties to us on annual net sales of GSK Licensed Products in the GSK Territory. Such royalties are 1% for annual sales up to $750.0 million each year and range from high single-digit percentages on annual net sales above $750.0 million each year to low double-digit percentages on annual net sales above $1,000.0 million each year.

We are responsible for the execution and costs of the follow-up Phase 3 clinical trial of tebipenem HBr. GSK is responsible for the execution and costs of additional further development, including Phase 3 regulatory filing and commercialization activities for tebipenem HBr in the balance of the GSK Territory outside of the United States. We will also be responsible for providing and paying for the clinical supply of tebipenem HBr while GSK will be responsible for the costs of the commercial supply of tebipenem HBr.

If we fail to comply with our obligations to Meiji, GSK, or any of our other partners, our counterparties may have the right to terminate these agreements, in which event we might not be able to develop, manufacture or market any product candidate that is covered by these agreements, which could materially adversely affect the value of the product candidate being developed under any such agreement. Termination of these agreements or reduction or elimination of our rights under these agreements may result in our having to negotiate new or reinstated agreements with less favorable terms or cause us to lose our rights under these agreements, including our rights to important intellectual property or technology.

Risks Related to Our U.S. Government Contracts and to Certain Grant Agreements

Our use of government funding for certain of our programs adds complexity to our research and commercialization efforts with respect to those programs and may impose requirements that increase the costs of commercialization and production of product candidates developed under those government-funded programs.

We have received significant non-dilutive financing from various government agencies for the further development of our product candidates. Such funding sources may pose risks to us not encountered in other commercial contracts, including significant regulatory compliance risks. Contracts funded by the U.S. government and its agencies include provisions that reflect the government’s substantial public policy and compliance requirements, and substantial rights and remedies, many of which are not typically found in commercial contracts, including powers of the government to:

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terminate agreements, in whole or in part, for any reason or no reason;

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reduce or modify the government’s obligations under such agreements without the consent of the contractor;

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claim rights, including intellectual property rights, in products and data developed under such agreements;

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audit contract-related costs and fees, including allocated indirect costs;

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suspend the contractor from receiving new contracts pending resolution of alleged violations of procurement laws or regulations;

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impose U.S. manufacturing requirements for products that embody inventions conceived or first reduced to practice under such agreements;

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suspend or debar the contractor or grantee from doing future business with the government;

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control and potentially prohibit the export of products; and

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pursue criminal or civil remedies under the False Claims Act (the “FCA”), the False Statements Act and similar remedy provisions specific to government agreements.

We may not have the right to prohibit the U.S. government from using certain technologies developed by us, and we may not be able to prohibit third-party companies, including our competitors, from using those technologies in providing products and services to the U.S. government. The U.S. government generally takes the position that it has the right to royalty-free use of technologies that are developed under U.S. government contracts.

In addition, government contracts and grants, and subcontracts and subawards awarded in the performance of those contracts and grants, normally contain additional requirements that may increase our costs of doing business, reduce our profits, and expose us to liability for failure to comply with these terms and conditions. These requirements include, for example:

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specialized accounting systems unique to government awards;

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mandatory financial audits and potential liability for price adjustments or recoupment of government funds after such funds have been spent;

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public disclosures of certain award information, which may enable competitors to gain insights into our research program; and

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mandatory socioeconomic compliance requirements, including labor standards, anti-human-trafficking, non-discrimination and affirmative action programs, energy efficiency and environmental compliance requirements.

If we fail to maintain compliance with these requirements, we may be subject to potential contract or FCA liability and to termination of our contracts.

U.S. government agencies have special contracting requirements that give them the ability to unilaterally control our contracts.

U.S. government contracts typically contain unfavorable termination provisions and are subject to audit and modification by the government at its sole discretion, which will subject us to additional risks. These risks include the ability of the U.S. government to unilaterally:

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audit and object to our government contract-related costs and fees, and require us to reimburse all such costs and fees;

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suspend or prevent us for a set period of time from receiving new contracts or extending our existing contracts based on violations or suspected violations of laws or regulations;

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cancel, terminate or suspend our contracts based on violations or suspected violations of laws or regulations;

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terminate our contracts if in the government’s interest, including if funds become unavailable to the applicable governmental agency;

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reduce the scope and value of our contract; and

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change certain terms and conditions in our contract.

The U.S. government will be able to terminate any of its contracts with us, either for convenience or if we default by failing to perform in accordance with or to achieve the milestones set forth in the contract schedules and terms. Termination-for-convenience provisions generally enable us to recover only our costs incurred or committed and settlement expenses on the work completed prior to termination. Except for the amount of services received by the government, termination-for-default provisions do not permit these recoveries and would make us liable for excess costs incurred by the U.S. government in procuring undelivered items from another source.

Our business is subject to audit by the U.S. government and other potential sources for grant funding, including under our contracts with BARDA and NIAID and a negative outcome in an audit could adversely affect our business.

U.S. government agencies such as the Department of Health and Human Services (“DHHS”) and the Defense Contract Audit Agency (the “DCAA”) routinely audit and investigate government contractors. These agencies review a contractor’s performance under its contracts, cost structure and compliance with applicable laws, regulations and standards.

The DHHS and the DCAA also review the adequacy of, and a contractor’s compliance with, its internal control systems and policies, including the contractor’s purchasing, property, estimating, compensation and management information systems. Any costs found to be improperly allocated to a specific contract will not be paid, while such costs already paid must be refunded. If an audit uncovers improper or illegal activities, we may be subject to civil and criminal penalties and administrative sanctions, including:

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termination of contracts;

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forfeiture of profits;

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suspension of payments;

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fines; and

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suspension or prohibition from conducting business with the U.S. government.

In addition, we could suffer serious reputational harm if allegations of impropriety were made against us, which could cause our stock price to decrease.

Laws and regulations affecting government contracts make it more expensive and difficult for us to successfully conduct our business.

We must comply with numerous laws and regulations relating to the formation, administration and performance of government contracts, which can make it more difficult for us to retain our rights under our government contracts. These laws and regulations affect how we conduct business with government agencies. Among the most significant government contracting regulations that affect our business are:

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the Federal Acquisition Regulations (the “FAR”) and agency-specific regulations supplemental to the FAR, which comprehensively regulate the procurement, formation, administration and performance of government contracts;

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business ethics and public integrity obligations, which govern conflicts of interest and the hiring of former government employees, restrict the granting of gratuities and funding of lobbying activities and include other requirements such as the Anti-Kickback Statute and the Foreign Corrupt Practices Act;

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export and import control laws and regulations; and

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laws, regulations and executive orders restricting the use and dissemination of information classified for national security purposes and the exportation of certain products and technical data.

These requirements change frequently, such as through appropriations bills or executive orders. Any changes in applicable laws and regulations could restrict our ability to maintain our existing BARDA and other government contracts and obtain new contracts, which could limit our ability to conduct our business and materially adversely affect our results of operations.

Provisions in our U.S. government contracts, including our contracts with BARDA, may affect our intellectual property rights.

Certain of our activities have been funded, and may in the future be funded, by the U.S. government, including through our contracts with BARDA. When new technologies are developed with U.S. government funding, the government obtains certain rights in any resulting patents, including the right to a nonexclusive license authorizing the government to use the invention and rights that may permit the government to disclose our confidential information to third parties and to exercise “march-in” rights. The government can exercise its march-in rights if it determines that action is necessary because we fail to achieve practical application of the U.S. government-funded technology, because action is necessary to alleviate health or safety needs, to meet requirements of federal regulations or to give preference to U.S. industry. In addition, U.S. government-funded inventions must be reported to the government, U.S. government funding must be disclosed in any resulting patent applications, and our rights in such inventions may be subject to certain requirements to manufacture products in the United States.

Risks Related to Our Intellectual Property

If we are unable to obtain and maintain sufficient patent protection for our technology or our product candidates, or if the scope of the patent protection is not sufficiently broad, our competitors could develop and commercialize technology and products similar or identical to ours, and our ability to successfully commercialize our technology and product candidates may be adversely affected.

Our success depends in large part on our ability to obtain and maintain patent protection in the United States and other countries with respect to our proprietary chemistry technology and product candidates. If we do not adequately protect our intellectual property, competitors may be able to use our technologies and erode or negate any competitive advantage that we may have, which could harm our business and ability to achieve profitability. To protect our proprietary position, we file patent applications in the United States and abroad related to our novel technologies and product candidates that are important to our business. The patent application and approval process is expensive and time-consuming. We may not be able to file and prosecute all necessary or desirable patent applications at a reasonable cost or in a timely manner. We may also fail to identify patentable aspects of our research and development before it is too late to obtain patent protection.

The patent position of biotechnology and pharmaceutical companies generally is highly uncertain. No consistent policy regarding the breadth of claims allowed in biotechnology and pharmaceutical patents has emerged to date in the United States or in many foreign jurisdictions. In addition, the determination of patent rights with respect to pharmaceutical compounds and technologies commonly involves complex legal and factual questions, which has in recent years been the subject of much litigation. As a result, the issuance, scope, validity, enforceability and commercial value of our patent rights are highly uncertain. Furthermore, changes in patent laws in the United States, including those made by the America Invents Act of 2011, may affect the scope, strength and enforceability of our patent rights or the nature of proceedings which may be brought by us related to our patent rights.

Our pending and future patent applications may not result in patents being issued which protect our technology or product candidates, in whole or in part, or which effectively prevent others from commercializing competitive technologies and products. Changes in either the patent laws or interpretation of the patent laws in the United States and other countries may diminish the value of our patents or narrow the scope of our patent protection.

The laws of foreign countries may not protect our rights to the same extent or in the same manner as the laws of the United States. For example, in the United States, there is an exception for one’s own publication of an invention prior to filing a patent application for the invention. Most other countries have no such exception and any publication prior to filing is an absolute bar to patentability. Publications of discoveries in the scientific literature often lag behind the actual discoveries, and patent applications in the United States and other jurisdictions are typically not published until 18 months after filing, or in some cases not at all. Therefore, we cannot be certain that we were the first to make the inventions claimed in our patents or pending patent applications, or that we were the first to file for patent protection of such inventions. As a result of the America Invents Act of 2011, the United States transitioned to a first-inventor-to-file system in March 2013, under which, assuming the other requirements for patentability are met, the first inventor to file a patent application is entitled to the patent. However, as a result of the lag in the publication of patent applications following filing in the United States, we are still not be able to be certain upon filing that we are the first to file for patent protection for any invention. Moreover, we may be subject to a third-party pre-issuance submission of prior art to the U.S. Patent and Trademark Office (“USPTO”) or become involved in opposition, derivation, reexamination, inter partes review or interference proceedings, in the United States or elsewhere, challenging our patent rights or the patent rights of others. An adverse determination in any such submission, proceeding or litigation could reduce the scope of, or invalidate, our patent rights, allow third parties to commercialize our technology or product candidates and compete directly with us, without payment to us, or result in our inability to manufacture or commercialize products without infringing third-party patent rights.

Due to the war in Ukraine and sanctions between the United States and Russia, patents and patent applications in Russia, the Eurasian Patent Organization (“EAPO”) and Ukraine currently have an uncertain fate. Unless the conflict with Ukraine ends quickly it is unlikely our Russian and EAPO patent and patent applications will remain in effect. Ukraine is currently under martial law and not processing patent applications. It is expected all patent deadlines in Ukraine will be extended.

Even if our patent applications issue as patents, they may not issue in a form that will provide us with any meaningful protection, prevent competitors from competing with us or otherwise provide us with any competitive advantage. Our competitors may be able to circumvent our owned or licensed patents by developing similar or alternative technologies or products in a non-infringing manner. Our competitors may seek to market generic versions of any approved products by submitting Abbreviated New Drug Applications (“ANDAs”) to the FDA in which they claim that patents owned or licensed by us are invalid, unenforceable and/or not infringed. Alternatively, our competitors may seek approval to market their own products similar to or otherwise competitive with our products. In these circumstances, we may need to defend and/or assert our patents, including by filing lawsuits alleging patent infringement. In any of these types of proceedings, a court or other agency with jurisdiction may find our patents invalid and/or unenforceable. Even if we have valid and enforceable patents, these patents still may not provide protection against competing products or processes sufficient to achieve our business objectives.

The issuance of a patent is not conclusive as to its inventorship, scope, validity or enforceability, and our owned and licensed patents may be challenged in the courts or patent offices in the United States and abroad. Such challenges may result in loss of exclusivity or freedom to operate or in patent claims being narrowed, invalidated or held unenforceable, in whole or in part, which could limit our ability to stop others from using or commercializing similar or identical technology and products, or limit the duration of the patent protection of our technology and products. In addition, given the amount of time required for the development, testing and regulatory review of new product candidates, patents protecting such candidates might expire before or shortly after such candidates are commercialized.

We may become involved in lawsuits to protect or enforce our patents or other intellectual property, which could be expensive, time consuming and unsuccessful.

Competitors may infringe our patents, trademarks, copyrights or other intellectual property, or those of our licensors. To counter infringement or unauthorized use, we may be required to file infringement claims, which can be expensive and time consuming and divert the time and attention of our management and scientific personnel. Any claims we assert against perceived infringers could provoke these parties to assert counterclaims against us alleging that we infringe their patents. In addition, in a patent infringement proceeding, there is a risk that a court will decide that a patent of ours is invalid or unenforceable, in whole or in part, and that we do not have the right to stop the other party from using the invention at issue. There is also a risk that, even if the validity of such patents is upheld, the court will construe the patent’s claims narrowly or decide that we do not have the right to stop the other party from using the invention at issue on the grounds that our patents do not cover the invention. An adverse outcome in a litigation or proceeding involving our patents could limit our ability to assert our patents against those parties or other competitors, and may curtail or preclude our ability to exclude third parties from making and selling similar or competitive products. Any of these occurrences could adversely affect our competitive business position, business prospects and financial condition. Similarly, if we assert trademark infringement claims, a court may determine that the marks we have asserted are invalid or unenforceable, or that the party against whom we have asserted trademark infringement has superior rights to the marks in question. In this case, we could ultimately be forced to cease use of such trademarks.

In any infringement litigation, any award of monetary damages we receive may not be commercially valuable. Furthermore, because of the substantial amount of discovery required in connection with intellectual property litigation, there is a risk that some of our confidential information could be compromised by disclosure during litigation. Moreover, there can be no assurance that we will have sufficient financial or other resources to file and pursue such infringement claims, which typically last for years before they are concluded. Even if we ultimately prevail in such claims, the monetary cost of such litigation and the diversion of the attention of our management and scientific personnel could outweigh any benefit we receive as a result of the proceedings.

If we are sued for infringing intellectual property rights of third parties, or otherwise become involved in disputes regarding our intellectual property rights, such litigation could be costly and time consuming and could prevent or delay us from developing or commercializing our product candidates.

Our commercial success depends, in part, on our ability to develop, manufacture, market and sell our product candidates and use our proprietary chemistry technology without infringing the intellectual property and other proprietary rights of third parties. Numerous third-party U.S. and non-U.S. issued patents and pending applications exist in the area of antibacterial treatment, including compounds, formulations, treatment methods and synthetic processes that may be applied towards the synthesis of antibiotics. If any of their patents or patent applications cover our product candidates or technologies, we may not be free to manufacture or market our product candidates as planned.

There is a substantial amount of intellectual property litigation in the biotechnology and pharmaceutical industries, and we may become party to, or threatened with, litigation or other adversarial proceedings regarding intellectual property rights with respect to our technology or product candidates, including interference proceedings before the USPTO. Intellectual property disputes arise in a number of areas including with respect to patents, use of other proprietary rights and the contractual terms of license arrangements. Third parties may assert claims against us based on existing or future intellectual property rights. The outcome of intellectual property litigation is subject to uncertainties that cannot be adequately quantified in advance. With respect to our Meiji License of certain know-how and regulatory documents concerning tebipenem pivoxil, we are neither a party to, nor an express third-party beneficiary of, the letter agreements, which were signed in January 2017 and in February 2022, between Meiji and Global Pharma consenting to Meiji’s arrangements with us. As such, if any dispute among the parties were to occur, our direct enforcement rights with respect to the letter agreements may be limited or uncertain.

If we are found to infringe a third party’s intellectual property rights, we or our third-party collaborators could be forced, including by court order, to cease developing, manufacturing or commercializing the infringing product candidate or product. Alternatively, we or they may be required to obtain a license from such third party in order to use the infringing technology and continue developing, manufacturing or marketing the infringing product candidate. However, we or such collaborators may not be able to obtain any required license on commercially reasonable terms or at all. Even if we were able to obtain a license, it could be non-exclusive, thereby giving our competitors access to the same technologies licensed to us. In addition, we could be found liable for monetary damages, including treble damages and attorneys’ fees if we are found to have willfully infringed a patent. A finding of infringement could prevent us from commercializing our product candidates or force us to cease some of our business operations, which could materially harm our business. Claims that we or our third-party collaborators have misappropriated the intellectual property, confidential information or trade secrets of third parties could have a similar negative effect on our business.

We may be subject to claims that we or our employees, consultants or contractors have misappropriated the intellectual property of a third party, or claims asserting ownership of what we regard as our own intellectual property.

Many of our employees, consultants and contractors are currently, or were previously, employed at universities or other biotechnology or pharmaceutical companies, including our competitors or potential competitors. Although we try to ensure that these individuals do not use the intellectual property and other proprietary information or know-how of others in their work for us, we may be subject to claims that we or these individuals have used or disclosed such intellectual property or other proprietary information. Litigation may be necessary to defend against these claims.

In addition, while we typically require our employees, consultants and contractors who may be involved in the development of intellectual property to execute agreements assigning such intellectual property to us, we may be unsuccessful in executing such an agreement with each party who in fact develops intellectual property that we regard as our own. To the extent that we fail to obtain such assignments or such assignments are breached, we may be forced to bring claims against third parties, or defend claims they may bring against us, to determine the ownership of what we regard as our intellectual property. If we fail in prosecuting or defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights or personnel. Even if we are successful in prosecuting or defending against such claims, litigation could result in substantial costs and be a distraction to our management and scientific personnel.

If we are unable to protect the confidentiality of our trade secrets, the value of our technology could be materially adversely affected and our business would be harmed.

In addition to seeking patents for some of our technology and products, we also rely on trade secrets, including unpatented know-how, technology and other proprietary information, in seeking to develop and maintain a competitive position. We seek to protect these trade secrets, in part, by entering into non-disclosure and confidentiality agreements with parties who have access to them, such as our consultants, independent contractors, advisors, corporate collaborators, outside scientific collaborators, contract manufacturers, suppliers and other third parties. We, as well as our licensors, also enter into confidentiality and invention or patent assignment agreements with employees and certain consultants. Any party with whom we have executed such an agreement may breach that agreement and disclose our proprietary information, including our trade secrets, and we may not be able to obtain adequate remedies for such breaches. Enforcing a claim that a party illegally disclosed or misappropriated a trade secret is difficult, expensive and time-consuming, and the outcome is unpredictable. In addition, if any of our trade secrets were to be lawfully obtained or independently developed by a competitor, we would have no right to prevent such third party, or those to whom they communicate such technology or information, from using that technology or information to compete with us. If any of our trade secrets were to be disclosed to or independently developed by a competitor, our business and competitive position could be harmed.

We have registered trademarks and pending trademark applications. Failure to enforce our registered marks or secure registration of our pending trademark applications could adversely affect our business.

We have registered our trademarks for our name and logo in the United States and other countries and have a number of pending trademark applications in the United States and other countries. As of September 30, 2025, we have two registered U.S. trademarks, 23 registered foreign trademarks, and no pending foreign trademark applications. If our registered trademarks are invalidated, we may be unable to exclusively use our name or logo in certain jurisdictions or may need to change our name or logo in certain jurisdictions, which could affect our business. If we do not secure registrations for our pending trademark applications, we may encounter more difficulty in enforcing them against third parties, which could adversely affect our business.

We have applied to register our product candidate name as a trademark in the United States, where it has been allowed for registration, and have applied to register the mark in three foreign jurisdictions. We have also applied to register additional product candidate names as trademarks in the United States. When we file trademark applications for our product candidates, those applications may not be allowed for registration, and registered trademarks may not be obtained, maintained, or enforced. During trademark registration proceedings in the United States and foreign jurisdictions, we may receive rejections. We are given an opportunity to respond to those rejections, but we may not be able to overcome such rejections. In addition, in the USPTO and in comparable agencies in many foreign jurisdictions, third parties are given an opportunity to oppose pending trademark applications and to seek to cancel registered trademarks. Opposition or cancellation proceedings may be filed against our trademarks, and our trademarks may not survive such proceedings.

In addition, any proprietary name we propose to use with any product candidate in the United States must be approved by the FDA, regardless of whether we have registered it, or applied to register it, as a trademark. The FDA typically conducts a review of proposed product names, including an evaluation of potential for confusion with other product names. If the FDA objects to any of our proposed proprietary product names, we may be required to expend significant additional resources in an effort to identify a suitable proprietary product name that would qualify under applicable trademark laws, not infringe the existing rights of third parties and be acceptable to the FDA.

Risks Related to Regulatory Approval and Other Legal Compliance Matters

If we are not able to obtain, or if there are delays in obtaining, required regulatory approvals, we will not be able to commercialize our product candidates, and our ability to generate revenue will be materially impaired.

Our product candidates and the activities associated with their development and commercialization, including their design, testing, manufacture, safety, efficacy, recordkeeping, labeling, storage, approval, advertising, promotion, sale and distribution, are subject to comprehensive regulation by the FDA and other regulatory agencies in the United States and by comparable foreign regulatory authorities, with regulations differing from country to country. Failure to obtain marketing approval for a product candidate will prevent us from commercializing the product candidate.

We have only limited experience in filing and supporting the applications necessary to gain marketing approvals and have relied on third-party contract research organizations to assist us in this process.

The time required to obtain approval, if any, by the FDA and comparable foreign authorities is unpredictable but typically takes many years following the commencement of clinical trials and depends upon numerous factors, including the substantial discretion of the regulatory authorities. In addition, approval policies, regulations, or the type and amount of clinical data necessary to gain approval may change during the course of a product candidate’s clinical development and may vary among jurisdictions. We have not

obtained regulatory approval for any product candidate and it is possible that none of our product candidates we seek to develop in the future will ever obtain regulatory approval. Neither we nor any future collaborators are permitted to market any of our product candidates in the United States until we or they receive regulatory approval of an NDA from the FDA.

In order to obtain approval to commercialize a product candidate in the United States or abroad, we or our collaborators must demonstrate to the satisfaction of the FDA or foreign regulatory agencies, that such product candidates are safe and effective for their intended uses. Results from nonclinical studies and clinical trials can be interpreted in different ways. Even if we believe that the nonclinical or clinical data for our product candidates are promising, such data may not be sufficient to support approval by the FDA and other regulatory authorities. The FDA may also require us to conduct additional nonclinical studies or clinical trials for our product candidates either prior to or post-approval, and it may otherwise object to elements of our clinical development program.

An NDA must include extensive preclinical and clinical data and supporting information to establish the product candidate’s safety and efficacy for each desired indication. The NDA must also include significant information regarding the chemistry, manufacturing and controls for the product candidate. Foreign regulatory authorities have differing requirements for approval of drugs with which we must comply with prior to marketing. Obtaining marketing approval for marketing of a product candidate in one country does not ensure that we will be able to obtain marketing approval in other countries, but the failure to obtain marketing approval in one jurisdiction could negatively affect our ability to obtain marketing approval in other jurisdictions. The FDA or any foreign regulatory bodies can delay, limit or deny approval of our product candidates or require us to conduct additional nonclinical or clinical testing or abandon a program for many reasons, including:

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the FDA or the applicable foreign regulatory agency’s disagreement with the design or implementation of our clinical trials;

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negative or ambiguous results from our clinical trials or results that may not meet the level of statistical significance required by the FDA or comparable foreign regulatory agencies for approval;

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serious and unexpected drug-related side effects experienced by participants in our clinical trials or by individuals using drugs similar to our product candidates;

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our inability to demonstrate to the satisfaction of the FDA or the applicable foreign regulatory body that our product candidates are safe and effective for the proposed indication;

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the FDA’s or the applicable foreign regulatory agency’s disagreement with the interpretation of data from nonclinical studies or clinical trials;

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our inability to demonstrate the clinical and other benefits of our product candidates outweigh any safety or other perceived risks;

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the FDA’s or the applicable foreign regulatory agency’s requirement for additional nonclinical studies or clinical trials;

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the FDA’s or the applicable foreign regulatory agency’s disagreement regarding the formulation, labeling and/or the specifications for our product candidates; or

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the potential for approval policies or regulations of the FDA or the applicable foreign regulatory agencies to significantly change in a manner rendering our clinical data insufficient for approval.

Of the large number of drugs in development, only a small percentage complete the FDA or foreign regulatory approval processes and are successfully commercialized. The lengthy review process as well as the unpredictability of future clinical trial results may result in our failing to obtain regulatory approval, which would significantly harm our business, financial condition, results of operations and prospects.

Even if we eventually receive approval of an NDA or foreign marketing application for our product candidates, the FDA or the applicable foreign regulatory agency may grant approval contingent on the performance of costly additional clinical trials, often referred to as Phase 4 clinical trials, and the FDA may require the implementation of a REMS which may be required to ensure safe use of the drug after approval. The FDA or the applicable foreign regulatory agency also may approve a product candidate for a more limited indication or patient population than we originally requested, and the FDA or applicable foreign regulatory agency may not approve the labeling that we believe is necessary or desirable for the successful commercialization of a product candidate. Any delay in obtaining, or inability to obtain, applicable regulatory approval would delay or prevent commercialization of that product candidate and would materially adversely impact our business and prospects.

A fast track designation may not actually lead to a faster development or regulatory review or approval process.

We have received fast track designation for tebipenem HBr for the treatment of cUTI, including pyelonephritis, as well as fast track designation for SPR720 for treatment of adult patients with NTM-PD, and we may seek fast track designation for one or more of our other product candidates in the future. If a drug is intended for the treatment of a serious condition and nonclinical or clinical data demonstrate the potential to address unmet medical need for this condition, a drug sponsor may apply for fast track designation by the FDA for the particular indication under study. If fast track designation is obtained, the FDA may initiate review of sections of an NDA before the application is complete. This “rolling review” is available if the applicant provides and the FDA approves a schedule for the remaining information. If we seek fast track designation for a product candidate, we may not receive it from the FDA. However, even if we receive fast track designation, fast track designation does not ensure that we will receive marketing approval or that approval will be granted within any particular timeframe. We may not experience a faster development or regulatory review or approval process with fast track designation compared to conventional FDA procedures. In addition, the FDA may withdraw fast track designation if it believes that the designation is no longer supported by data from our clinical development program. Fast track designation alone does not guarantee qualification for the FDA’s priority review procedures. Additionally, the FDA has designated tebipenem HBr as a Qualified Infectious Disease Product (“QIDP”) for the treatment of cUTI, community-acquired pneumonia (“CABP”) and diabetic foot infections (“DFI”) under the Generating Antibiotic Incentives Now (“GAIN”) Act. Among other benefits of a QIDP designation, the first marketing application for the QIDP-designated indication qualifies for priority review by the FDA. Further, if tebipenem HBr is approved for the treatment of cUTI, CABP or DFI, the FDA’s QIDP designation previously granted to tebipenem HBr for those indications will entitle the drug product to receive a one-time five-year extension to any non-patent exclusivity period awarded to tebipenem HBr in the United States, such as a five-year New Chemical Entity exclusivity granted under the Hatch-Waxman Act, among other possible periods of regulatory exclusivity that would qualify for a GAIN exclusivity extension. The QIDP designation for tebipenem HBr, however, does not guarantee a faster development process or ensure FDA approval.

Priority review designation by the FDA may not lead to a faster regulatory review or approval process and, in any event, does not assure FDA approval.

If the FDA determines that a product candidate intended to treat a serious disease, if approved, would provide a significant improvement in safety or effectiveness of the treatment of the disease, the FDA may designate the drug application for that product candidate for priority review. A priority review designation means that the goal for the FDA to review the marketing application is six months from the date of NDA acceptance for filing, rather than the standard review period of ten months from the date of NDA acceptance for filing. A priority review designation does not necessarily mean a faster regulatory review process or necessarily confer any advantage with respect to approval compared to conventional FDA procedures. Receiving a priority review designation from the FDA does not guarantee approval of the drug application within the six-month review cycle or any time thereafter.

On June 17, 2025, the FDA announced the creation of a new voucher program to expedite the development and approval of new drug products. Vouchers issued under the new program, which is known as the Commissioner’s National Priority Voucher (“CNPV”) Program, may reportedly be redeemed by sponsors to shorten the review time of an NDA from approximately 10 to 12 months to one to two months. The FDA has indicated that the new CNPV process will convene experts from the FDA’s offices for a team-based review rather than using the standard review system of a drug application being sent to numerous FDA offices. Clinical information will be reviewed by a multidisciplinary team of physicians and scientists who will pre-review the submitted information and convene for a one-day meeting. Vouchers under this program will reportedly be given to companies aligned with U.S. national priorities. As with the FDA’s other programs for expediting review and approval of new drug products, even if we were to avail ourselves of this new program, there is no guarantee it would result in approval of our marketing applications or that such approval, if granted, would be on an expedited basis.

While we have negotiated an SPA agreement with the FDA relating to our pivotal Phase 3 clinical trial of tebipenem HBr in patients with cUTI, including acute pyelonephritis, this agreement does not guarantee approval of tebipenem HBr or any other particular outcome from regulatory review of the clinical trial or the product candidate.

On July 31, 2023, the Company announced that it received written agreement from the FDA, under an SPA, on the design and size of PIVOT-PO, a pivotal Phase 3 clinical trial of tebipenem HBr in patients with cUTI, including acute pyelonephritis. The FDA’s SPA process is designed to allow the FDA to evaluate the proposed design and size of clinical trials that are intended to form the primary basis for determining a drug product’s efficacy, among other eligible protocols. Upon specific written request by a clinical trial sponsor, the FDA will evaluate the planned protocol and respond to a sponsor’s questions regarding, among other things, primary efficacy endpoints, trial conduct and data analysis. The FDA ultimately assesses whether the protocol design and planned analysis of the trial adequately address scientific and regulatory requirements for the particular purposes identified by the sponsor, which in this case was that the PIVOT-PO protocol can be considered an adequate and well-controlled study in support of our future resubmission of the tebipenem HBr marketing application. All agreements between the FDA and the sponsor regarding an SPA must be clearly documented in writing, either in the form of an SPA letter or minutes of a meeting between the sponsor and the FDA at which the SPA agreement was reached.

However, an SPA agreement does not guarantee approval of a product candidate, and even if the FDA agrees to the design, execution and analysis proposed in protocols reviewed under the SPA process, the FDA may revoke or alter its agreement in certain circumstances. In particular, an SPA agreement is not binding on the FDA if public health concerns emerge that were unrecognized at the time of the SPA agreement, if other new scientific concerns regarding product safety or efficacy arise, if the sponsor fails to comply with the agreed upon trial protocols or modifies such protocols without prior FDA agreement, or if the relevant data, assumptions or information provided by the sponsor change or are found to be false or omit relevant facts. In addition, even after an SPA agreement is finalized, the SPA agreement may be modified, and such modification will be deemed binding on the FDA review division, except under the circumstances described above, so long as the FDA and the sponsor agree in writing to modify the protocol and such modification is intended to improve the study.

The FDA retains significant latitude and discretion in interpreting the terms of an SPA agreement, as well as the data and results obtained from any study that is the subject of the SPA agreement. We cannot assure you that our pivotal Phase 3 clinical trial will succeed, or that the SPA agreement will ultimately be binding on the FDA or will result in any FDA approval of tebipenem HBr. We expect that the FDA will review our compliance with the protocol that is subject to the SPA agreement, and, as with all NDA reviews, evaluate the results of the trial and conduct inspections of some of the sites where the trial will be conducted. We cannot assure you that the FDA will deem each of the clinical trial sites to have complied with applicable laws and regulations, and negative inspection results could significantly delay or prevent any potential approval for tebipenem HBr. If the FDA revokes or alters its agreement under the SPA, or interprets the data collected from the clinical trial differently than we do, the FDA may not deem the data sufficient to support an application for regulatory approval, which could materially adversely affect our business, financial condition and results of operations.

We may seek orphan drug designation for one or more of our product candidates. We may not be able to obtain or maintain orphan drug designations for any of our product candidates, and we may be unable to take advantage of the benefits associated with orphan drug designation, including the potential for market exclusivity.

Regulatory authorities in some jurisdictions, including the United States, may designate drugs for relatively small patient populations as orphan drugs. Under the Orphan Drug Act of 1983 (the “Orphan Drug Act”), the FDA may designate a product as an orphan product if it is intended to treat a rare disease or condition, which is generally defined as a patient population of fewer than 200,000 individuals in the United States, or a patient population of greater than 200,000 individuals in the United States, but for which there is no reasonable expectation that the cost of developing the drug will be recovered from sales in the United States. There can be no assurance that the FDA will grant orphan designation for any indication for which we apply.

In the United States, orphan designation entitles a party to financial incentives such as opportunities for grant funding towards clinical trial costs, tax advantages and user-fee waivers. In addition, if a product candidate that has orphan drug designation subsequently receives the first FDA approval for the disease for which it has such designation, it is entitled to orphan drug exclusivity, which means that the FDA may not approve any other applications, including an NDA, to market the same drug for the same indication for seven years, except in limited circumstances, such as a showing of clinical superiority to the product with orphan drug exclusivity or where the manufacturer is unable to assure sufficient product quantity.

In March 2020, the FDA granted orphan drug designation for SPR720. However, in November 2025, we announced that we were ceasing development of SPR720. Even though we may seek orphan drug designation for other product candidates in the future, there is no assurance that we or any third party partner we may have in the future will obtain orphan drug designation and/or be the first to obtain marketing approval for any particular rare indication. Further, even if we obtain orphan drug designation for other product candidates, such designation may not effectively protect us from competition because different drugs can be approved for the same condition and the same drug can be approved for different conditions and potentially used off-label in the orphan indication. Even after an orphan drug is approved, the FDA can subsequently approve a competing drug for the same condition for several reasons, including, if the FDA concludes that the later drug is safer or more effective or makes a major contribution to patient care. Orphan drug designation neither shortens the development time or regulatory review time of a drug, nor gives the drug any advantage in the regulatory review or approval process.

The FDA and Congress may further reevaluate the Orphan Drug Act and its regulations and policies. This may be particularly true in light of a decision from the Court of Appeals for the 11th Circuit in September 2021. In Catalyst Pharms, Inc. v. Becerra(“Catalyst”), it was held that, for the purpose of determining the scope of orphan drug exclusivity, the term “same disease or condition” in the statute means the designated “rare disease or condition” and could not be interpreted by the FDA to mean the “indication or use.” Thus, the court concluded, orphan drug exclusivity applies to the entire designated disease or condition rather than the approved “indication or use.” Although there have been legislative proposals to overrule this decision, they have not been enacted into law. On January 23, 2023, the FDA announced that, in matters beyond the scope of the Catalyst court order, the FDA will continue to apply its existing regulations tying orphan-drug exclusivity to the uses or indications for which the orphan drug is approved. More recently however, on February 14, 2025, a federal district court in Washington, D.C. fully embraced the reasoning of the Catalyst decision in another decision challenging the scope of orphan drug exclusivity. On April 17, 2025, the FDA appealed this decision to the U.S. Court of Appeals for the D.C. Circuit. The implications of this decision, and its impact on the FDA’s implementation of the Orphan Drug Act, are unclear at this point.

If approved for commercial marketing in the United States, our product candidates may face generic competition sooner than anticipated.

Even if we are successful in achieving regulatory approval to commercialize a product candidate, it may face competition from generic products earlier or more aggressively than anticipated, depending upon how well our future products perform in the U.S. prescription drug market. In addition to creating the 505(b)(2) NDA pathway, the Hatch-Waxman Amendments to the FDCA authorized the FDA to approve generic drugs that are the same as drugs previously approved for marketing under the NDA provisions of the statute pursuant to ANDAs. An ANDA relies on the preclinical and clinical testing conducted for a previously approved reference listed drug (“RLD”) and must demonstrate to the FDA that the generic drug product is identical to the RLD with respect to the active ingredients, the route of administration, the dosage form, and the strength of the drug and also that it is “bioequivalent” to the RLD. The FDA is prohibited by statute from approving an ANDA when certain marketing or data exclusivity protections apply to the RLD.

If the FDA ultimately approves tebipenem HBr for the treatment of cUTI, including pyelonephritis, caused by certain microorganisms in adult patients who have limited oral treatment options, we expect that it will be designated by the agency as an RLD and that it will be eligible for five-year new chemical entity exclusivity under the Hatch-Waxman provisions of the FDCA. This exclusivity period would block FDA from approving either a subsequent ANDA or 505(b)(2) NDA that references our future NDA, if approved. The qualified infectious disease product designation granted by FDA to this drug product and indication also make it eligible for a further five-year extension of that Hatch-Waxman exclusivity. We cannot predict the interest of potential generic competitors in the future market for such an approved treatment for cUTI, whether someone will attempt to invalidate our period of exclusivity or otherwise force the FDA to take other actions, or how quickly others may seek to come to market with competing products after the applicable exclusivity period ends. Future product candidates may also receive marketing exclusivity under the FDCA after approval that may similarly be subject to challenge or uncertainty.

If we or our partners are unable to obtain marketing approval in international jurisdictions, we will not be able to market our product candidates abroad.

In order to market and sell our product candidates in the European Union and many other jurisdictions, we or our partners must obtain separate marketing approvals and comply with numerous and varying regulatory requirements. Approval by the FDA does not ensure approval by regulatory authorities in other countries or jurisdictions, and approval by one regulatory authority outside the United States does not ensure approval by regulatory authorities in other countries or jurisdictions or by the FDA. The approval procedure varies among countries and can involve additional testing. In addition, clinical trials conducted in one country may not be accepted by regulatory authorities in other countries. Further, in April 2023, the European Commission issued a proposal to revise and replace the existing general pharmaceutical legislation. On June 4, 2025, after almost two years of negotiations among the EU Member States, the Council of the European Union adopted its position on the proposed overhaul of the EU general pharmaceutical legislative framework, which is known as the new Pharma Package. If adopted and implemented as currently proposed, these revisions will significantly change several aspects of drug development and approval in the European Union. The time required to obtain approval from regulatory authorities in other countries may differ substantially from that required to obtain FDA approval. The regulatory approval process outside the United States generally includes all of the risks associated with obtaining FDA approval. In addition, in many countries outside the United States, it is required that the product be approved for reimbursement before the product can be approved for sale in that country. We or our partners may not obtain approvals from regulatory authorities outside the United States on a timely basis or at all.

Further, we could face heightened risks with respect to obtaining marketing authorization in the United Kingdom as a result of the withdrawal of the United Kingdom from the European Union, commonly referred to as Brexit. The United Kingdom is no longer part of the European Single Market and EU Customs Union. As of January 1, 2025, the Medicines and Healthcare Products Regulatory Agency (“MHRA”) is responsible for approving all medicinal products destined for the U.K. market (i.e., Great Britain and Northern Ireland). On April 28, 2025, the U.K. Parliament adopted amendments to improve and strengthen the United Kingdom’s clinical trials regulatory regime; they will take effect on April 28, 2026. These changes were needed since the current U.K. requirements are based upon the now-repealed EU Clinical Trials Directive (2001/20/EC), which has been replaced by the European Clinical Trials Regulation (Regulation EU No 536/2014). Since the United Kingdom left the EU prior to the date on which the EU CTR took effect, the U.K. legal framework did not benefit from the same revisions as occurred at EU level.

If we receive regulatory approval for any of our product candidates, we will be subject to ongoing obligations and continuing regulatory review, which may result in significant additional expense. Our product candidates, if approved, could be subject to restrictions or withdrawal from the market, and we may be subject to penalties if we fail to comply with regulatory requirements or if we experience unanticipated problems with our product candidates, when and if approved.

Any product candidate for which we obtain marketing approval will also be subject to ongoing regulatory requirements for labeling, packaging, storage, distribution, advertising, promotion, record keeping and submission of safety and other post-market

information. For example, approved products, manufacturers and manufacturers’ facilities are required to comply with extensive FDA requirements, including ensuring that quality control and manufacturing procedures conform to cGMPs. As such, we and our contract manufacturers will be subject to continual review and periodic inspections to assess compliance with cGMPs. We and others with whom we work must continue to expend time, money and effort in all areas of regulatory compliance, including manufacturing, production and quality control. We will also be required to report certain adverse reactions and production problems, if any, to the FDA and to comply with requirements concerning advertising and promotion for our products.

In addition, even if marketing approval of a product candidate is granted, the approval may be subject to limitations on the indicated uses for which the product may be marketed, may be subject to significant conditions of approval or may impose requirements for costly post-marketing testing and surveillance to monitor the safety or efficacy of the product. The FDA may also require a REMS as a condition of approval of our product candidates, which could include requirements for a medication guide, physician communication plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. The FDA closely regulates the post-approval marketing and promotion of drugs to ensure that drugs are marketed only for the approved indications and in accordance with the provisions of the approved labeling and regulatory requirements. The FDA also imposes stringent restrictions on manufacturers’ communications regarding off-label use and if we do not restrict the marketing of our products only to their approved indications, we may be subject to enforcement action for off-label marketing.

If a regulatory agency discovers previously unknown problems with a product, such as adverse events of unanticipated severity or frequency, or problems with the facility where the product is manufactured, or disagrees with the promotion, marketing or labeling of a product, it may impose restrictions on that product or us. In addition, if any product fails to comply with applicable regulatory requirements, a regulatory agency may:

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issue warning letters, untitled letters or impose holds on clinical trials if any are still on-going;

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mandate modifications to promotional materials or require provision of corrective information to healthcare practitioners;

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impose restrictions on the product or its manufacturers or manufacturing processes;

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impose restrictions on the labeling or marketing of the product;

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impose restrictions on product distribution or use;

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require post-marketing studies or clinical trials;

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require withdrawal of the product from the market;

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refuse to approve pending applications or supplements to approved applications that we submit;

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require recall of the product;

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require entry into a consent decree, which can include imposition of various fines (including restitution or disgorgement of profits or revenue), reimbursements for inspection costs, required due dates for specific actions and penalties for noncompliance;

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suspend or withdraw marketing approvals;

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refuse to permit the import or export of the product;

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seize or detain supplies of the product; or

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issue injunctions or impose civil or criminal penalties.

The FDA’s policies may change and additional government regulations may be enacted that could prevent, limit or delay marketing approval of our product candidates. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may lose any marketing approval that we may have obtained, which would adversely affect our business, prospects and ability to achieve or sustain profitability.

Our relationships with customers and third-party payors will be subject to applicable anti-kickback, fraud and abuse and other healthcare laws and regulations, which could expose us to criminal sanctions, civil penalties, contractual damages, reputational harm and diminished profits and future earnings.

Healthcare providers, physicians and third-party payors will play a primary role in the recommendation and prescription of any product candidates for which we may obtain marketing approval. Our future arrangements with third-party payors and customers will expose us to broadly applicable fraud and abuse and other healthcare laws and regulations that may constrain the business or financial arrangements and relationships through which we market, sell and distribute any products for which we obtain marketing approval and reimbursement. These laws and regulations include, for example, the false claims and anti-kickback statutes and regulations. At such

time as we market, sell and distribute any products for which we obtain marketing approval and reimbursement, it is possible that our business activities could be subject to challenge under one or more of these laws and regulations. Restrictions under applicable federal and state healthcare laws and regulations include the following:

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the federal healthcare Anti-Kickback Statute, among other things, prohibits persons from knowingly and willfully soliciting, offering, receiving or providing remuneration, directly or indirectly, in cash or in kind, to induce or reward either the referral of an individual for, or the purchase, order or recommendation of, any good or service for which payment may be made under federally funded healthcare programs such as Medicare and Medicaid. A person or entity does not need to have actual knowledge of the statute or specific intent to violate the statute in order to have committed a violation. In addition, the government may assert that a claim that includes items or services resulting from a violation of the federal Anti-Kickback Statute constitutes a false or fraudulent claim for purposes of the False Claims Act;

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the federal False Claims Act imposes criminal and civil penalties, which can be enforced by private citizens through civil whistleblower and qui tam actions, against individuals or entities for knowingly presenting, or causing to be presented, to the federal government, claims for payment that are false or fraudulent or making a false statement to avoid, decrease or conceal an obligation to pay money to the federal government;

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HIPAA imposes criminal and civil liability for executing a scheme to defraud any healthcare benefit program or for making any false statements relating to healthcare matters; as in the case of the federal healthcare Anti-Kickback Statute, a person or entity does not need to have actual knowledge of the statute or specific intent to violate the statute in order to have committed a violation;

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HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act, also imposes obligations on certain covered entities as well as their business associates that perform services involving the use or disclosure of protected health information, including mandatory contractual terms, with respect to safeguarding the privacy and security of protected health information, and requires notification to affected individuals and regulatory authorities of certain breaches of security of protected health information;

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the federal False Statements statute prohibits knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false statement in connection with the delivery of or payment for healthcare benefits, items or services;

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the federal Physician Payments Sunshine Act requires manufacturers of drugs, devices, biologics and medical supplies covered by Medicare or Medicaid to report, on an annual basis, to the DHHS, information related to payments and other transfers of value to physicians (defined to include doctors, dentists, optometrists, podiatrists, chiropractors and certain advanced non-physician health care practitioners), teaching hospitals, as well as ownership and investment interests held by physicians and their immediate family members;

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state and federal consumer protection laws, including the Federal Trade Commission Act, govern the collection, use, disclosure and protection of health and other personal information and could apply to our operations and the operations of our collaborators; and

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analogous state laws and regulations, such as state anti-kickback and false claims laws, may apply to sales or marketing arrangements and claims involving healthcare items or services reimbursed by non-governmental third-party payors, including private insurers, and some state laws require pharmaceutical companies to implement compliance programs and to track and report gifts, compensation and other remuneration provided to physicians, in addition to requiring drug manufacturers to report information related to payments to physicians and other healthcare providers or marketing expenditures and pricing information. State laws also govern the privacy and security of health information in some circumstances, and many such state laws differ from each other in significant ways and often are not preempted by HIPAA, thus complicating compliance efforts.

We will be required to spend substantial time and money to ensure that our business arrangements with third parties, and our business generally, comply with applicable healthcare laws and regulations. Even then, governmental authorities may conclude that our business practices, including arrangements we may have with physicians and other healthcare providers, do not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. If governmental authorities find that our operations violate any of these laws or any other governmental regulations that may apply to us, we may be subject to significant civil, criminal and administrative penalties, damages, imprisonment, fines, exclusion from government funded healthcare programs, such as Medicare and Medicaid, and we may be required to curtail or restructure our operations. Moreover, we expect that there will continue to be federal and state laws and regulations, proposed and implemented, that could affect our operations and business. The extent to which future legislation or regulations, if any, relating to healthcare fraud and abuse laws or enforcement, may be enacted or what effect such legislation or regulation would have on our business remains uncertain.

Recently enacted and future policies and legislation may increase the difficulty and cost for us to obtain marketing approval of and commercialize our product candidates and may affect the reimbursement made for any product candidate for which we receive marketing approval.

The pricing and reimbursement environment may become more challenging due to, among other reasons, policies advanced by the presidential administration, federal agencies, new healthcare legislation passed by the U.S. Congress or fiscal challenges faced by all levels of government health administration authorities. Among policy makers and payors in the United States and foreign countries, there is significant interest in promoting changes in healthcare systems with the stated goals of containing healthcare costs, improving quality and expanding access to healthcare. In the United States, the pharmaceutical industry has been a particular focus of these efforts and has been significantly affected by major legislative initiatives. We expect to experience pricing pressures in connection with the sale of any products for which we obtain marketing approval, due to the trend toward managed healthcare, the increasing influence of health maintenance organizations and additional legislative proposals. Resulting legislative, administrative, or policy changes from payors may reduce payments for any products for which we obtain marketing approval and could affect future revenues.

The Affordable Care Act (“ACA”) became law in the United States in March 2010 with the goals of broadening access to health insurance, reducing or constraining the growth of healthcare spending, enhancing remedies against fraud and abuse, adding new transparency requirements for the health care and health insurance industries and imposing additional health policy reforms. Provisions of ACA may negatively affect our future revenues. For example, the ACA requires, among other things, that annual fees be paid by manufacturers for certain branded prescription drugs, that manufacturers participate in a discount program for certain outpatient drugs under Medicare Part D, and that manufacturers provide increased rebates under the Medicaid Drug Rebate Program for outpatient drugs dispensed to Medicaid recipients. The ACA also addresses a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for line extensions and expands oversight and support for the federal government’s comparative effectiveness research of services and products.

Beginning on April 1, 2013, Medicare payments for all items and services under Part A and B, including drugs and biologicals, and most payments to plans under Medicare Part D were reduced by 2%, or automatic spending reductions, required by the Budget Control Act of 2011 (“BCA”), as amended by the American Taxpayer Relief Act of 2012. The BCA requires sequestration for most federal programs, excluding Medicaid, Social Security, and certain other programs. The BCA caps the cuts to Medicare payments for items and services and payments to Part D plans at 2%. As long as these cuts remain in effect, they could adversely affect payment for our product candidates, if approved for commercial marketing. We expect that additional state and federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for healthcare products and services, which could result in reduced demand for our product candidates or additional pricing pressures.

Moreover, there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products. There have been several U.S. Congressional inquiries and proposed bills designed to, among other things, bring more transparency to drug pricing, reduce the cost of prescription drugs under Medicare, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for drugs. Individual states in the United States have also become increasingly active in passing legislation and implementing regulations designed to control pharmaceutical product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. In December 2020, the U.S. Supreme Court held unanimously that federal law does not preempt the states’ ability to regulate pharmaceutical benefit managers (“PBMs”) and other members of the health care and pharmaceutical supply chain, an important decision that may lead to further and more aggressive efforts by states in this area. The Federal Trade Commission (“FTC”) in mid-2022 also launched sweeping investigations into the practices of the PBM industry, and published interim reports with its finding in mid-2024 and January 2025, that could lead to additional federal and state legislative or regulatory proposals targeting such entities’ operations, pharmacy networks, or financial arrangements, including in the current 2025-2026 congressional session. During the previous congressional session, numerous bipartisan PBM reforms were considered in both the Senate and the House of Representatives; they include diverse legislative proposals such as eliminating rebates; divorcing service fees from the price of a drug, discount, or rebate; prohibiting spread pricing; limiting administrative fees; requiring PBMs to report formulary placement rationale; promoting transparency. Significant efforts to change the PBM industry as it currently exists in the United States may affect the entire pharmaceutical supply chain and the business of other stakeholders, including biopharmaceutical developers like us. In September 2023, the FTC issued a policy statement articulating its view that certain “improper” patent listings by drug developers in FDA’s Orange Book represent an unfair trade practice and indicated that industry should be prepared for potential enforcement actions based on its analysis. The FTC followed that action in November 2023 by publicly calling out over 100 “improper” patent listings made by ten large pharmaceutical companies and initiating an FDA administrative process with respect to those patents. The controversy regarding the appropriateness of listing such patents has led to numerous lawsuits alleging anticompetitive conduct by biopharmaceutical companies. It remains to be seen whether the FTC under the Trump Administration will continue to prioritize the policy issue of “improper” patent listings or whether Congress may take any legislative actions related to this issue. Accordingly, regulatory and government interest in biopharmaceutical industry business practices continues to expand and pose a risk of uncertainty.

Further, in August 2022, President Biden signed into the law the Inflation Reduction Act (“IRA”). Among other things, the IRA has multiple provisions that may impact the prices of drug products that are both sold into the Medicare program and throughout the United States. A manufacturer of drugs covered by Medicare Parts B or D must now pay a rebate to the federal government if their drug product’s price increases faster than the rate of inflation. This calculation is made on a drug product by drug product basis and the amount of the rebate owed to the federal government is directly dependent on the volume of a drug product that is paid for by Medicare Parts B or D. Additionally, starting for payment year 2026, Centers for Medicare & Medicaid Services (“CMS”) will negotiate drug prices annually for a select number of single source Part D drugs without generic or biosimilar competition. With passage of the One Big Beautiful Bill Act on July 3, 2025, which was signed into law on July 4, 2025, Congress extended this exemption to drugs and biologics with multiple orphan drug designations.

The first cycle of negotiations for the Medicare Drug Price Negotiation Program commenced in the summer of 2023. On August 15, 2024, DHHS published the results of the first Medicare drug price negotiations for ten selected drugs that treat a range of conditions, including diabetes, chronic kidney disease, and rheumatoid arthritis. The prices of these ten drugs will become effective January 1, 2026. On January 17, 2025, CMS announced its selection of 15 additional drugs covered by Part D for the second cycle of negotiations by February 1, 2025. While there had been some questions about the Trump administration’s position on this program, CMS issued a public statement on January 29, 2025, declaring that lowering the cost of prescription drugs is a top priority of the new administration and CMS is committed to considering opportunities to bring greater transparency in the negotiation program. The second cycle of negotiations with participating drug companies will occur during 2025, and any negotiated prices for this second set of drugs will be effective starting January 1, 2027.

On June 6, 2023, Merck & Co. filed a lawsuit against DHHS and CMS asserting that, among other things, the IRA’s Drug Price Negotiation Program for Medicare constitutes an uncompensated taking in violation of the Fifth Amendment of the Constitution. Subsequently, a number of other parties, including the U.S. Chamber of Commerce, Bristol Myers Squibb Company, the PhRMA, Astellas, Novo Nordisk, Janssen Pharmaceuticals, Novartis, AstraZeneca, Boehringer Ingelheim, and Teva also filed lawsuits in various courts with constitutional and Administrative Procedure Act claims against the DHHS and CMS. There have been various decisions by the courts considering these cases since they were filed. The DHHS has generally won the substantive disputes in these cases or succeeded in getting claims dismissed for lack of standing. Most of these cases are now on appeal. On October 30, 2024, the U.S. Court of Appeals for the Third Circuit heard oral argument in three of these cases. In April 2025, the U.S. Court of Appeals for the Second Circuit and the U.S. Court of Appeals for the Third Circuit heard argument in an additional three cases. On May 8, 2025, the Third Circuit rejected AstraZeneca’s challenge to the Medicare price negotiation program, finding that the program did not violate the company’s due process rights under the constitution since there is no protected property interest in selling goods to Medicare beneficiaries at a price higher than what the government is willing to pay in reimbursement. We expect that litigation involving these and other provisions of the IRA will continue, with unpredictable and uncertain results. Accordingly, while it is currently unclear how the IRA will be effectuated, we cannot predict with certainty what impact any federal or state health reforms will have on us, but such changes could impose new or more stringent regulatory requirements on our activities or result in reduced reimbursement for our products, any of which could adversely affect our business, results of operations and financial condition.

More recently, on April 15, 2025, President Trump issued an executive order which directs DHHS to take steps to reduce the prices of pharmaceutical products. The order repeats many of the proposals advanced during the first Trump administration, including directing the FDA to streamline and improve its existing drug importation program so as to make it easier for states to obtain approval without sacrificing the safety or quality of drug products. Other provisions of the order relate to the 340B program. Specifically, one provision calls on the Secretary of DHHS to determine the hospital acquisition cost for covered outpatient drugs at hospital outpatient departments and to consider and propose any appropriate adjustments for Medicare payment. The other provision directs DHHS to condition grant funding to certain health centers on those centers passing through the 340B discounts they receive on insulin and injectable epinephrine products to patients who meet certain requirements. With respect to the IRA’s Medicare drug pricing program, the order, among other things, calls for alignment in “the treatment of small molecule prescription drugs with that of biological products, ending the distortion that undermines relative investment in small molecule prescription drugs, coupled with other reforms to prevent any increase in overall costs to Medicare and its beneficiaries.”

Further, on May 12, 2025, President Trump issued an additional executive order calling on pharmaceutical manufacturers to voluntarily reduce the prices of medicines in the United States. The Order directs the Secretary of DHHS to communicate most-favored-nation (“MFN”) price targets to pharmaceutical manufacturers to bring prices in line with comparably developed nations. The executive order further provides that if such actions do not lower the costs of pharmaceuticals, the Secretary of DHHS would pursue other actions, including proposing a rulemaking that imposes MFN pricing in the United States. Subsequently, on May 20, 2025, HHS indicated that the proposed MFN pricing will apply only to brand products without generic or biosimilar competition and the reference foreign countries will include only those in which the branded product similarly does not have generic or biosimilar competition. Second, DHHS indicated that the MFN target price will be the lowest price in a country that is a member of the Organisation for Economic Co-operation and Development (“OECD”) with a gross domestic product (“GDP”), per capita of at least 60% of the U.S. GDP per capita. Based on previous estimates, there are likely at least 22 OECD countries that would satisfy this criterion. The implications of these actions remain unclear and are likely to result in litigation if the administration pursues an MFN regulatory pricing requirement.

At the state level, individual states are increasingly aggressive in passing legislation and implementing regulations designed to control pharmaceutical and biological product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. This is increasingly true with respect to products approved pursuant to the accelerated approval pathway. State Medicaid programs and other payers are developing strategies and implementing significant coverage barriers, or refusing to cover these products outright, arguing that accelerated approval drugs have insufficient or limited evidence despite meeting the FDA’s standards for accelerated approval.

We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative or executive action, either in the United States or abroad. We expect that additional state and federal health care reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for health care products and services.

Changes in tax laws or in their implementation or interpretation could adversely affect our business and financial condition.

Income, sales, use or other tax laws, statutes, rules, or regulations could be enacted or amended at any time, which could affect our business or financial condition, including causing potentially adverse impacts to our effective tax rate, tax liabilities, and cash tax obligations. For example, the IRA was signed into law in August 2022, and the OBBBA was signed into law in July 2025. The IRA introduced new tax provisions, including a one percent excise tax imposed on certain stock repurchases by publicly traded companies. The one percent excise tax generally applies to any acquisition of stock by the publicly traded company (or certain of its affiliates) from a stockholder of the company in exchange for money or other property (other than stock of the company itself), subject to a de minimis exception. Thus, the excise tax could apply to certain transactions that are not traditional stock repurchases. The OBBBA contains numerous tax provisions that we are currently in the process of evaluating, and which may significantly affect our business or financial condition. The recent changes under the OBBBA include tax rate extensions and changes to the business interest deduction limitation, the expensing of domestic research and development expenditures (in contrast to the continued capitalization and amortization of foreign research and development expenditures), the bonus depreciation deduction rules, and the international tax framework. Regulatory guidance under the IRA, the OBBBA, and other tax-related legislation is and continues to be forthcoming, and such guidance could ultimately increase or lessen the impact of these laws on our business and financial condition. In addition, it is uncertain if and to what extent various states will conform to changes in federal tax legislation.

If we successfully commercialize one of our product candidates, failure to comply with our reporting and payment obligations under U.S. governmental pricing programs could have a material adverse effect on our business, financial condition and results of operations.

If we participate in the Medicaid Drug Rebate Program if and when we successfully commercialize a product candidate, we will be required to report certain pricing information for our product to the Centers for Medicare & Medicaid Services, the federal agency that administers the Medicaid and Medicare programs. We may also be required to report pricing information to the U.S. Department of Veterans Affairs. If we become subject to these reporting requirements, we will be liable for errors associated with our submission of pricing data, for failure to report pricing data in a timely manner, and for overcharging government payers, which can result in civil monetary penalties under the Medicaid statute, the federal civil False Claims Act, and other laws and regulations.

Additionally, the 2021 Consolidated Appropriations Act signed into law on December 27, 2020 incorporated extensive healthcare provisions and amendments to existing laws, which includes a requirement that all manufacturers of drug products covered under Medicare Part B report the product’s average sales price to DHHS beginning on January 1, 2022, subject to enforcement via civil money penalties. Increasingly there are state laws and regulations that require prescription drug price reporting or impose other restrictions designed to control pharmaceutical product pricing, such as price or patient reimbursement constraints and discounts.

Our employees, independent contractors, principal investigators, contract research organizations, consultants or vendors may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements.

We are exposed to the risk that our employees, independent contractors, principal investigators, contract research organizations, consultants or vendors may engage in fraudulent or other illegal activity. Misconduct by these parties could include intentional, reckless and/or negligent conduct or disclosure of unauthorized activities to us that violates: FDA regulations, including those laws requiring the reporting of true, complete and accurate information to the FDA; manufacturing standards; federal and state healthcare fraud and abuse laws and regulations; or laws that require the true, complete and accurate reporting of financial information or data. Specifically, sales, marketing and business arrangements in the healthcare industry are subject to extensive laws and regulations intended to prevent fraud, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting, marketing and promotion, sales commission, customer incentive programs and other business arrangements. Activities subject to these laws also involve the improper use or misrepresentation of information obtained in the course of clinical trials or creating fraudulent data in our preclinical studies or clinical trials, which could result in regulatory sanctions and

serious harm to our reputation. It is not always possible to identify and deter misconduct by our employees and other third parties, and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to be in compliance with such laws or regulations. Additionally, we are subject to the risk that a person could allege such fraud or other misconduct, even if none occurred. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business, including the imposition of civil, criminal and administrative penalties, damages, monetary fines, possible exclusion from participation in Medicare, Medicaid and other federal healthcare programs, contractual damages, reputational harm, diminished potential profits and future earnings, and curtailment of our operations, any of which could adversely affect our business, financial condition, results of operations or prospects.

Disruptions at the FDA and other government agencies from funding cuts, personnel losses, regulatory reform, government shutdowns and other developments could hinder our ability to obtain guidance from the FDA regarding our clinical development program and develop and secure approval of our product candidates in a timely manner, which would negatively impact our business.

The FDA and comparable regulatory agencies in foreign jurisdictions, such as the EMA and Committee for Medicinal Products for Human Use, play an important role in the development of our product candidates by providing guidance on our clinical development programs and reviewing our regulatory submissions, including INDs, requests for special designations and marketing applications. If these oversight and review activities are disrupted, then correspondingly our ability to develop and secure timely approval of our product candidates could be impacted in a negative manner.

For example, the loss of FDA leadership and personnel could lead to disruptions and delays in FDA guidance, review and approval of our product candidates. Pursuant to President Trump’s Executive Order 14210, “Implementing the President’s ‘Department of Government Efficiency’ Workforce Optimization Initiative,” the Secretary of DHHS announced on March 27, 2025, a reorganization and Reduction in Force (“RIF”) across the Department of approximately 20,000 employees (82,000 to 62,000), with FDA’s workforce of approximately 20,000 to decrease by 3,500 full-time employees. Subsequently, the FDA indicated that roughly a quarter of those employees who received RIF notices had been reinstated. On July 14, 2025, following litigation reaching the U.S. Supreme Court, the administration began to carry out these layoffs across DHHS, including the FDA. There are also ongoing deliberations within the administration and Congress over potentially substantial proposed cuts to the overall budget for DHHS and funding of the FDA for the 2026 federal fiscal year.

While the FDA’s review of marketing applications and other activities for new drugs and biologics is largely funded through the user fee program established under the Prescription Drug User Fee Act (“PDUFA”), it remains unclear how the administration’s RIF and budget cuts will impact this program and the ability of the FDA to provide guidance and review our product candidates in a timely manner. For example, while the FDA RIF did not reportedly specifically target FDA reviewers, many operations, administrative and policy staff that help support such reviews were affected and those losses could lead to delays in PDUFA reviews and related activities. There has been at least one report in which the FDA failed to meet a PDUFA goal date for approval of an NDA due to heavy workload and limited resources. In addition, while currently unclear, there is a risk that the RIF and budget cutbacks could threaten the integrity of the PDUFA program itself. That is because, for the FDA to obligate user fees collected under PDUFA in the first place, a certain amount of non-user fee appropriations must be spent on the process for the review of applications plus certain other costs during the same fiscal year.

There is also substantial uncertainty as to how regulatory reform measures being implemented by the Trump Administration across the government will impact the FDA and other federal agencies with jurisdiction over our activities. For example, since taking office, the President has issued a number of executive orders that could have a significant impact on the manner in which the FDA conducts its operations and engages in regulatory and oversight activities. These include Executive Order 14192, “Unleashing Prosperity Through Deregulation,” January 31, 2025; Executive Order 14212, “Establishing the President’s Make America Healthy Again Commission,” February 13, 2025; and Executive Order 14219, “Ensuring Lawful Governance and Implementing the President’s ‘Department of Government Efficiency’ Deregulatory Initiative,” February 21, 2025. If these or other orders or executive actions impose constraints on the FDA’s ability to engage in oversight and implementation activities in the normal course, our business may be negatively impacted.

Similarly, actions by the U.S. government have significantly disrupted the operations of U.S. government agencies such as the National Institutes of Health, National Science Foundation, Centers for Disease Control and Prevention, and FDA, which have traditionally provided funding for basic research, research and development, and clinical testing. These U.S. government actions have included, among other things, suspending, terminating and withholding of disbursements of funds owed under ongoing contracts, grants, and other financial assistance agreements; declining to continue multi-year research projects for additional annual budget periods; canceling or delaying solicitations for new contract, grant and other financial assistance awards; canceling or delaying proposal evaluation processes and issuance of such new awards; substantially reducing federal agency staff responsible for managing contract and financial assistance programs; eliminating agency information and resources for facilitating research activity; delaying or

terminating federal agency procedures for authorizing international transactions; initiating aggressive enforcement actions that may disrupt the operations of major research universities that are significant contributors to life sciences research in the U.S., and threatening access to federal agency contracts and other funding awards based on companies’ otherwise lawful corporate policies and choice of counsel. These U.S. government actions could, directly or indirectly, significantly disrupt, delay, prevent, or increase the costs of our research and product commercialization programs, including our ability to develop new product candidates, conduct clinical trials, implement research collaborations with other companies or institutions, and obtain approvals to market and sell new products.

In addition, government funding of the SEC and other government agencies on which our operations may rely, including those that fund research and development activities, is subject to the political process, which is inherently fluid and unpredictable. For example, over the last several years, the U.S. government has shut down several times and certain regulatory agencies, such as the FDA and the SEC, have had to furlough critical FDA, SEC and other government employees and stop critical activities. If a prolonged government shutdown occurs, it could significantly impact the ability of the FDA to timely review and process our regulatory submissions and could impact our ability to access the public markets and obtain necessary capital in order to properly capitalize and continue our operations.

At the same time, disruptions at the FDA and other government agencies may result from public health events similar to the COVID-19 pandemic. For example, during the pandemic, a number of companies announced receipt of complete response letters due to the FDA’s inability to complete required inspections for their applications. In the event of a similar public health emergency in the future, the FDA may not be able to continue its current pace and review timelines could be extended. Regulatory authorities outside the United States facing similar circumstances may adopt similar restrictions or other policy measures in response to a similar public health emergency and may also experience delays in their regulatory activities.

If any of the foregoing developments and others impact the ability of the FDA to provide us with guidance regarding our clinical development programs or delay the agency’s review and processing of our regulatory submissions, including INDs and NDAs/BLAs, our business would be negatively impacted. Further, any future government shutdown could impact our ability to access the public markets and obtain necessary capital in order to properly capitalize and continue our operations.

Finally, three decisions from the U.S. Supreme Court issued in July 2024 may lead to an increase in litigation against regulatory agencies that could create uncertainty and thus negatively impact our business. The first decision overturned established precedent that required courts to defer to regulatory agencies’ interpretations of ambiguous statutory language. The second decision overturned regulatory agencies’ ability to impose civil penalties in administrative proceedings. The third decision extended the statute of limitations within which entities may challenge agency actions. These cases may result in increased litigation by industry against regulatory agencies, including but not limited to the FDA and SEC, and may impact how such agencies choose to pursue enforcement and compliance actions. However, the specific, lasting effects of these decisions, which may vary within different judicial districts and circuits, are unknown. We also cannot predict the extent to which FDA and SEC regulations, policies, and decisions may become subject to increasing legal challenges, delays, and changes.

Changes in and uncertainty surrounding U.S. and international trade policies, particularly with respect to China, may adversely impact our business and operating results.

This past spring, the U.S. government initiated a series of tariff-related actions against U.S. trading partners. On April 2, 2025, President Trump issued an executive order announcing a “baseline” reciprocal tariff of 10% on all U.S. trading partners effective April 5, 2025, and higher individualized reciprocal tariffs on 57 countries (with certain product exemptions for pharmaceutical-related products, among others). Previously, the Trump administration had imposed a 25% tariff on Canada and Mexico for goods not covered by the United States-Mexico-Canada Agreement (“USMCA”) and tariffs equaling 20% on China. In response, several countries threatened retaliatory measures, including Canada and China, which then imposed retaliatory tariffs. Prior to when the country-specific reciprocal tariffs were scheduled to take effect, the Trump administration delayed the effective date of such tariffs for all countries except China to August 1, 2025. Later, the United States and China reached a framework agreement that ultimately resulted in the suspension of the higher reciprocal tariffs on China until November 11, 2025. Since the April announcement, several countries including the European Union, Japan, South Korea and the United Kingdom, among others, have reached deals with the U.S. that include reduced tariff rates to varying levels and other measures. On July 31, 2025, President Trump issued an Executive Order detailing new reciprocal tariff rates for individual countries that took effect on August 7, 2025. The new reciprocal rates, which are consistent with the rates reflected in the trade deals already announced, range from 10% to 41%. The new rates do not apply to Canada, China, Mexico and a few other countries. For China, the 10% baseline reciprocal tariff announced in April remains in effect, in addition to a minimum of an additional 20%. Regarding Canada and Mexico, the rate remains 25% for goods that are not covered by the USMCA for Mexico and, effective August 1, 2025, was increased to 35% on imports from Canada that are not covered by the USMCA. Sustained uncertainty about, or the further escalation of, trade and political tensions between the United States and China could result in a disadvantageous research and manufacturing environment in China, particularly for U.S. based companies, including retaliatory restrictions that hinder or potentially inhibit our ability to rely on CMOs and other service providers that operate in China. Certain countries have reached agreements with the U.S. that cap pharmaceutical tariffs at 15%. These include the European Union, Japan, South Korea and the United Kingdom.

Separately, in April 2025, the U.S. Department of Commerce initiated an investigation under Section 232 of the Trade Expansion Act of 1962 into the impact on U.S. national security of the imports of pharmaceuticals and pharmaceutical ingredients, including finished drug products, medical countermeasures, critical inputs such as active pharmaceutical ingredients, and key starting materials, and derivative products of those items. On September 25, 2025, via a post on Truth Social, President Trump announced that, beginning October 1, 2025, all branded or patented drugs imported in the U.S. would face a 100% tariff. At the same time, Trump indicated that these tariffs could be avoided by building pharmaceutical manufacturing facilities in the U.S. Thereafter, Trump delayed the October 1st effective date of the tariffs on branded or patented pharmaceutical products announcing that the Administration had now “begun preparing” tariffs on manufacturers that don’t build in the U.S. or enter into an MFN drug pricing agreement with the Trump administration.

As a result of changes in tariffs that have been announced and/or implemented, and the underlying uncertainty currently surrounding international trade, we could experience a negative impact to our costs of materials and production processes, and supply chain disruptions and delays as a result of any new tariff policies or trade restrictions. If we are unable to obtain necessary raw materials or product components in sufficient quantity and in a timely manner due to disruptions in the global supply chain caused by macroeconomic events and conditions, the development, testing and clinical trials of our product candidates may be delayed or infeasible, and regulatory approval or commercial launch of any resulting product may be delayed or not obtained, which could significantly harm our business. We cannot yet predict the effect of the recently imposed U.S. tariffs on imports, or the extent to which other countries will impose quotas, duties, tariffs, taxes or other similar restrictions upon imports or exports in the future, nor can we predict future trade policy or the terms of any renegotiated trade agreements and their impact on our business.

Risks Related to Employee Matters and Managing Growth

Our future success depends on our ability to retain our key executives and to attract, retain and motivate qualified personnel.

Our industry has experienced a high rate of turnover of management personnel in recent years. We are highly dependent on the development, regulatory, commercialization and business development expertise of principal members of our management, scientific and clinical team. Although we have formal employment agreements with our executive officers, these agreements do not prevent them from terminating their employment with us at any time.

In October 2024, we implemented a restructuring plan that reduced our workforce by approximately 39%. While we have confidence in our remaining employees, and our leadership team, including our current President, Chief Executive Officer and Chief Financial Officer, Ms. Rajavelu, who was appointed President and Chief Executive Officer effective as of May 2, 2025 following our separation with Mr. Shukla, the inherent uncertainty following this restructuring may cause concerns from third parties with whom we do business, and may increase the likelihood of turnover of other key officers and employees. Continued disruption caused by the transition or by the loss of ongoing services of any qualified scientific and management personnel could delay or prevent the successful development of our product candidates.

If we lose one or more of our named executive officers or key employees, our ability to implement our business strategy successfully could be seriously harmed. Furthermore, replacing executive officers and key employees may be difficult and may take an extended period of time because of the limited number of individuals in our industry with the breadth of skills and experience required to develop, gain regulatory approval of and commercialize product candidates successfully. Competition to hire from this limited pool is intense, and we may be unable to hire, train, retain or motivate these additional key personnel on acceptable terms given the competition among numerous pharmaceutical and biotechnology companies for similar personnel. We also experience competition for the hiring of scientific and clinical personnel from universities and research institutions. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development and commercialization strategy. Our consultants and advisors may be engaged by entities other than us and may have commitments under consulting or advisory contracts with other entities that may limit their availability to us. If we are unable to continue to attract and retain high quality personnel, our ability to develop and commercialize product candidates will be limited.

We undertook internal restructuring activities that could result in disruptions to our business or otherwise materially harm our results of operations or financial condition.

In October 2024, we announced a restructuring plan and implemented a workforce reduction. There can be no assurance that our restructuring will achieve the cost savings, operating efficiencies or other benefits that we may initially expect. Restructuring activities may also result in a loss of continuity, accumulated knowledge and inefficiency during transitional periods and thereafter. Further, internal restructurings can require a significant amount of time and focus from management and other employees, which may divert attention from operations.

If foreign approvals are obtained, we will be subject to additional risks in conducting business in international markets.

Even if we are able to obtain approval for commercialization of a product candidate in a foreign country, we will be subject to additional risks related to international business operations, including:

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potentially reduced protection for intellectual property rights;

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the potential for so-called parallel importing, which is what happens when a local seller, faced with high or higher local prices, opts to import goods from a foreign market (with low or lower prices) rather than buying them locally;

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unexpected changes in tariffs, trade barriers and regulatory requirements;

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economic weakness, including inflation, or political instability in particular foreign economies and markets;

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workforce uncertainty in countries where labor unrest is more common than in the United States;

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production shortages resulting from any events affecting a product candidate and/or finished drug product supply or manufacturing capabilities abroad;

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business interruptions resulting from geo-political conflicts, including war and terrorism, health epidemics or natural disasters, including earthquakes, hurricanes, typhoons, floods and fires; and

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failure to comply with Office of Foreign Asset Control rules and regulations and the Foreign Corrupt Practices Act.

These and other risks may materially adversely affect our ability to attain or sustain revenue from international markets.

Risks Related to Our Common Stock

The price of our common stock has been and, in the future, may continue to be volatile whether related or unrelated to our operations, which could result in a decline in value for our stockholders.

Our stock price may be volatile. The stock market in general and the market for smaller pharmaceutical and biotechnology companies in particular have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. As a result of this volatility, our stockholders may not be able to sell their shares at or above the price they paid for their shares. The market price for our common stock may be influenced by many factors, including:

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the success of existing or new competitive products or technologies;

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the timing of clinical trials of our product candidates;

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results of clinical trials of any of our product candidates;

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failure or discontinuation of any of our development programs;

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results of clinical trials of product candidates of our competitors;

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regulatory or legal developments in the United States and other countries;

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the perception of the pharmaceutical and biotechnology industry by the public, legislatures, regulators and the investment community;

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developments or disputes concerning patent applications, issued patents or other proprietary rights;

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the recruitment or departure of key personnel;

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the level of expenses related to any of our product candidates or clinical development programs;

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the results of our efforts to develop, in-license or acquire additional product candidates or products;

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actual or anticipated changes in estimates as to financial results or development timelines;

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announcement or expectation of additional financing efforts;

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sales of our common stock by us, our insiders or other stockholders;

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variations in our financial results or those of companies that are perceived to be similar to us;

•

changes in estimates or recommendations by securities analysts, if any, that cover our stock;

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changes in the structure of healthcare payment systems;

•

market conditions in the pharmaceutical and biotechnology sectors;

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general economic, industry and market conditions; and

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the other factors described in this “Risk Factors” section.

In addition, the stock market has experienced significant volatility, particularly with respect to pharmaceutical, biotechnology and other life sciences company stocks. The volatility of pharmaceutical, biotechnology and other life sciences company stocks often does not relate to the operating performance of the companies represented by the stock. In the past, securities class action litigation has often been initiated against companies following periods of volatility in their stock price, such as the two putative class action lawsuits filed in 2022 against us and certain of our former officers and the stockholder derivative actions filed in 2023 and 2024 against us and certain of our former officers. This type of litigation could result, and has in the past resulted, in substantial costs and divert our management’s attention and resources, and could also require us to make substantial payments to satisfy judgments or to settle litigation.

We have received a “Wells Notice” from the SEC contemplating a civil enforcement action, which could have a material adverse effect on our business, financial condition and results of operations, prospects, and/or our stock price.

On January 9, 2025, we responded to the “Wells Notice” from the Staff of the SEC, as further described in Part II, Item 1 “Legal Proceedings” of this Quarterly Report on Form 10-Q.

A Wells Notice is neither a formal charge of wrongdoing nor a final determination that the recipient has violated any law, but is a preliminary determination by the Staff to recommend to the SEC Commissioners that a civil enforcement action or administrative proceeding be brought against the recipients. If the SEC were to authorize an action against us and/or any of the identified individuals, it may seek an injunction or cease-and-desist order against future violations of provisions of the federal securities laws, the imposition of civil monetary penalties, disgorgement or other equitable relief within the SEC’s authority, or any combination of the foregoing. The SEC could also seek an order barring each identified individual from serving as an officer or director of a public company for a specified period of time.

We are cooperating with the SEC and have made a submission in response to the Wells Notice explaining why an enforcement action would not be appropriate. We cannot predict the results of the Investigation and the Wells Notice process and any corresponding enforcement action against us and/or any of the identified individuals, and the costs, timing and other potential consequences of responding and complying therewith with any certainty. The Investigation, and the Wells Notice process continues to be expensive and disruptive, and we are subject to indemnifying each of the individuals for their costs associated with the Wells Notices. Our insurance, to the extent maintained, may not cover all claims that may be asserted against us or the specified individuals, and we are unable to predict how long the Investigation will continue. An unfavorable outcome may have an adverse impact on our business, financial condition and results of operations, prospects, or our stock price. Any proceeding could also negatively impact our reputation among our stakeholders.

An active trading market for our common stock may not be sustained.

Although our common stock is listed on the Nasdaq GS, there is a risk that an active trading market for our shares may not continue to develop or be sustained. As a result, it may be difficult for our stockholders to sell their shares without depressing the market price for the shares, or at all.

In the past, we have failed to maintain certain continued listing requirements of the Nasdaq GS and could fail to maintain those requirements again in the future, which could negatively affect the market price of our common stock, our liquidity and our ability to raise capital. Our potential failure to meet the continued listing requirements of Nasdaq GS in the future could result in the delisting of our common stock.

Our common stock is listed on the Nasdaq GS, which imposes, among other requirements, a minimum $1.00 per share bid price requirement for continued inclusion on the Nasdaq GS pursuant to Nasdaq Listing Rule 5450(a)(1) (the “Bid Price Requirement”). The closing bid price for our common stock must remain at or above $1.00 per share to comply with the Bid Price Requirement for continued listing. On February 25, 2025, we received a deficiency letter (the “Notice”) from the Listing Qualifications Department of the Nasdaq Stock Market, LLC (“Nasdaq”) notifying us that, for the preceding 30 consecutive trading days, the closing bid price of our common stock was below the Bid Price Requirement. In accordance with Nasdaq Listing Rule 5810(c)(3)(A), we had until August 25, 2025, to regain compliance with the Bid Price Requirement. On June 12, 2025, we received a letter from Nasdaq notifying us that the closing bid price of our common stock was at least $1.00 per share for a minimum of 10 consecutive trading days and that we had regained compliance with the Bid Price Requirement. Our common stock continues to be eligible for listing on the Nasdaq GS.

There can be no assurance that we will be able to keep the closing bid price above $1.00 per share. If we fail to satisfy the continued listing requirements of Nasdaq GS, including the Bid Price Requirement, Nasdaq will provide us with another deficiency letter regarding the continued listing requirement. If we are unable to regain compliance with the Nasdaq Listing Rules in the future, Nasdaq will take steps to delist our common stock. Such a delisting from the Nasdaq GS could make trading our common stock more difficult for investors, potentially leading to declines in our share price and liquidity. If our common stock is delisted by the Nasdaq GS, our common stock may be eligible to trade on the Nasdaq Capital Market or an over-the-counter quotation system, where an investor may find it more difficult to sell our stock or obtain accurate quotations as to the market value of our common stock. We cannot assure you that our common stock, if delisted from the Nasdaq GS, will be listed on another national securities exchange or quoted on an over-the counter quotation system.

If securities or industry analysts do not publish research or publish inaccurate or unfavorable research about our business, our share price and trading volume could decline.

The trading market for our common stock relies in part on the research and reports that securities or industry analysts publish about us or our business. If only a few analysts provide coverage of us, the trading price of our stock would likely decline. If one or more of the analysts covering our business downgrade our stock or change their opinion of our stock, our stock price would likely decline. In addition, if one or more of these analysts cease coverage of our company or fail to regularly publish reports on us, we could lose visibility in the financial markets, which could cause our share price or trading volume to decline.

Unstable global economic and political conditions, including economic uncertainty tied to volatility in interest rates and inflation, credit and financial market instability, and uncertainty related to ongoing geopolitical conflicts, could adversely affect our business, financial condition, stock price and ability to raise capital. The global economy, in particular the financial markets, have recently experienced significant disruption and volatility, including without limitation, as a result of volatility in interest rates and inflation, capital markets volatility, currency rate fluctuations, volatility in commodity prices, decline in consumer confidence and economic growth, supply chain disruptions, banking disruptions, and uncertainty resulting from geopolitical events, including trade wars, civil and political unrest, wars and other armed conflicts. In addition, market, interest rate, and inflation volatility may increase our cost of financing or restrict our access to potential sources of future capital. Furthermore, our stock price may further decline due in part to the volatility of the stock market and any general economic downturn.

If the disruption and volatility persist or heighten, it may impact our ability to raise sufficient additional capital on agreeable terms, if at all. If we are unable to raise sufficient additional capital, our business, financial condition, stock price and results of operations could be adversely affected, and we will need to implement cost reduction strategies, which could include delaying, reducing or altogether terminating both internal and external costs related to our operations and research and development programs. In addition, political developments impacting government spending and international trade, including changes in trade agreements, trade disputes, tariffs and investment restrictions, such as the ongoing trade dispute between the United States and China, may negatively impact markets and cause weaker macroeconomic conditions. These global economic and political factors could also strain certain of our suppliers and manufacturers, possibly resulting in supply disruptions or increased raw material or manufacturing costs, or adversely impacting their ability to manufacture clinical trial materials for our product candidates. Any of the foregoing could harm our business and we cannot anticipate all of the ways in which the current economic and geopolitical climate and financial market conditions could adversely impact our business.

We have broad discretion in the use of our cash reserves and may not use them effectively.

Our management has broad discretion in the application of our cash reserves and could spend these funds in ways that do not improve our results of operations or enhance the value of our common stock. The failure by our management to apply these funds effectively could result in financial losses that could have a material adverse effect on our business, cause the price of our common stock to decline and delay the development of our product candidates. Pending their use, we may invest our cash reserves in a manner that does not produce income or that loses value.

We are a smaller reporting company and the reduced disclosure requirements applicable to smaller reporting companies may make our common stock less attractive to investors.

We are subject to Section 404 of The Sarbanes-Oxley Act of 2002 (“Section 404”) and the related rules of the SEC, which generally require our management and independent registered public accounting firm to report on the effectiveness of our internal control over financial reporting. However, for so long as we remain a “smaller reporting company” (“SRC”) and non-accelerated filer, we intend to take advantage of certain exemptions from various reporting requirements, including, but not limited to, not being

required to comply with the auditor attestation requirements of Section 404. Once we do not meet the definition of a SRC and non-accelerated filer or, if prior to such date, we opt to no longer take advantage of the applicable exemption, we will be required to include an attestation report from our independent registered public accounting firm on the effectiveness of our internal controls over financial reporting. We could continue to qualify as a SRC and non-accelerated filer if the market value of our common stock held by non-affiliates is below $75.0 million (or $700.0 million if our annual revenue is less than $100.0 million) as of June 30 in any given year.

We have incurred and will continue to incur increased costs as a result of operating as a public company, and our management will be required to devote substantial time to compliance initiatives and corporate governance practices.

As a public company, we incur significant legal, accounting and other expenses that we did not incur as a private company. Sarbanes-Oxley, the Dodd-Frank Wall Street Reform and Consumer Protection Act, the listing requirements of the Nasdaq GS and other applicable securities rules and regulations impose various requirements on public companies, including establishment and maintenance of effective disclosure and financial controls and corporate governance practices. Our management and other personnel devote a substantial amount of time to these compliance initiatives. Moreover, these rules and regulations have increased our legal and financial compliance costs and have made some activities more time-consuming and costly. For example, these rules and regulations have made it more difficult and more expensive for us to obtain director and officer liability insurance, which could make it more difficult for us to attract and retain qualified members of our Board of Directors. These rules and regulations are often subject to varying interpretations, in many cases due to their lack of specificity, and, as a result, their application in practice may evolve over time as new guidance is provided by regulatory and governing bodies. This could result in continuing uncertainty regarding compliance matters and higher costs necessitated by ongoing revisions to disclosure and governance practices.

Failure to maintain effective internal controls in accordance with Section 404 of Sarbanes-Oxley in the future could have a material adverse effect on our ability to produce accurate financial statements and on our stock price.

Section 404 of Sarbanes-Oxley requires us, on an annual basis, to review and evaluate our internal controls. To maintain compliance with Section 404, we are required to document and evaluate our internal control over financial reporting, which is both costly and challenging. We will need to continue to dedicate internal resources, continue to engage outside consultants and follow a detailed work plan to continue to assess and document the adequacy of internal control over financial reporting, continue to improve control processes as appropriate, validate through testing that controls are functioning as documented and implement a continuous reporting and improvement process for internal control over financial reporting. If we identify one or more material weaknesses, it could result in an adverse reaction in the financial markets due to a loss of confidence in the reliability of our financial statements.

A significant portion of our total outstanding shares may be sold into the market at any time, which could cause the market price of our common stock to decline significantly, even if our business is doing well.

Sales of a substantial number of shares of our common stock in the public market could occur at any time. These sales, or the perception in the market that the holders of a large number of shares of common stock intend to sell shares, could reduce the market price of our common stock. Our outstanding shares of common stock may be freely sold in the public market at any time to the extent permitted by Rules 144 and 701 under the Securities Act, or to the extent that such shares have already been registered under the Securities Act and are held by non-affiliates of ours. Moreover, holders of a substantial number of shares of our common stock have rights, subject to conditions, to require us to file registration statements covering their shares or to include their shares in registration statements that we may file for ourselves or other stockholders. We also have registered all shares of common stock that we may issue under our equity compensation plans or that are issuable upon exercise of outstanding options. These shares can be freely sold in the public market upon issuance and once vested, subject to volume limitations applicable to affiliates. If any of these additional shares are sold, or if it is perceived that they will be sold, in the public market, the market price of our common stock could decline.

We do not anticipate paying any cash dividends on our capital stock in the foreseeable future. Accordingly, stockholders must rely on capital appreciation, if any, for any return on their investment.

We have never declared or paid cash dividends on our capital stock. We currently intend to retain all of our future earnings, if any, to finance the operation, development and growth of our business. To the extent that we enter into any future debt agreements, the terms of such agreements may also preclude us from paying dividends. As a result, capital appreciation, if any, of our common stock will be our stockholders’ sole source of gain for the foreseeable future.

Provisions in our corporate charter documents and under Delaware law could make an acquisition of us, which may be beneficial to our stockholders, more difficult and may prevent attempts by our stockholders to replace or remove our current management.

Provisions in our Amended and Restated Certificate of Incorporation, as amended, and Amended and Restated Bylaws may discourage, delay or prevent a merger, acquisition or other change in control of us that our stockholders may consider favorable, including transactions in which our stockholders might otherwise receive a premium for their shares. These provisions could also limit the price that investors might be willing to pay in the future for shares of our common stock, thereby depressing the market price of

our common stock. In addition, because our Board of Directors is responsible for appointing the members of our management team, these provisions may frustrate or prevent any attempts by our stockholders to replace or remove our current management by making it more difficult for stockholders to replace members of our Board of Directors. Among other things, these provisions:

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establish a classified Board of Directors such that all members of the board are not elected at one time;

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allow the authorized number of our directors to be changed only by resolution of our Board of Directors;

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limit the manner in which stockholders can remove directors from our Board of Directors;

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establish advance notice requirements for nominations for election to our Board of Directors or for proposing matters that can be acted on at stockholder meetings;

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require that stockholder actions must be effected at a duly called stockholder meeting and prohibit actions by our stockholders by written consent;

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limit who may call a special meeting of stockholders;

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authorize our Board of Directors to issue preferred stock without stockholder approval, which could be used to institute a “poison pill” that would work to dilute the stock ownership of a potential hostile acquirer, effectively preventing acquisitions that have not been approved by our Board of Directors; and

•

require the approval of the holders of at least 75% of the votes that all of our stockholders would be entitled to cast to amend or repeal certain provisions of our Amended and Restated Certificate of Incorporation, as amended, or Amended and Restated Bylaws.

Moreover, because we are incorporated in Delaware, we are governed by the provisions of Section 203 of the Delaware General Corporation Law (the “DGCL”), which prohibits a person who owns 15% or more of our outstanding voting stock from merging or combining with us for a period of three years after the date of the transaction in which the person acquired 15% or more of our outstanding voting stock, unless the merger or combination is approved in a prescribed manner. This could discourage, delay or prevent someone from acquiring us or merging with us, whether or not it is desired by, or beneficial to, our stockholders.

In addition, our Amended and Restated Certificate of Incorporation, as amended, to the fullest extent permitted by law, provides that the Court of Chancery of the State of Delaware will be the exclusive forum for: any derivative action or proceeding brought on our behalf; any action asserting a breach of fiduciary duty; any action asserting a claim against us arising pursuant to the DGCL, our Amended and Restated Certificate of Incorporation, as amended, or our Amended and Restated Bylaws; or any action asserting a claim against us that is governed by the internal affairs doctrine. This exclusive forum provision does not apply to suits brought to enforce a duty or liability created by the Exchange Act. It could apply, however, to a suit that falls within one or more of the categories enumerated in the exclusive forum provision and asserts claims under the Securities Act, inasmuch as Section 22 of the Securities Act creates concurrent jurisdiction for federal and state courts over all suits brought to enforce any duty or liability created by the Securities Act or the rule and regulations thereunder. There is uncertainty as to whether a court would enforce such provision with respect to claims under the Securities Act, and our stockholders will not be deemed to have waived our compliance with the federal securities laws and the rules and regulations thereunder.

This choice of forum provision may limit a stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with us or any of our directors, officers, or other employees, which may discourage lawsuits with respect to such claims. Alternatively, if a court were to find the choice of forum provisions contained in our Amended and Restated Certificate of Incorporation, as amended, to be inapplicable or unenforceable in an action, we may incur additional costs associated with resolving such action in other jurisdictions, which could harm our business, results of operations and financial condition.

Provisions in our Amended and Restated Certificate of Incorporation, as amended, and other provisions of Delaware law could limit the price that investors are willing to pay in the future for shares of our common stock.

We may become involved in securities litigation that could divert management’s attention and harm our business, and insurance coverage may not be sufficient to cover all costs and damages.

Securities litigation often follows certain significant business activities, such as the announcement of a strategic restructuring, or the announcement of negative events, such as negative results from clinical trials. We may be exposed to such litigation even if no wrongdoing occurred. We have in the past, and may in the future, become subject to securities litigation. For example, two putative class action lawsuits were filed in 2022 against us and certain of our former officers and stockholder derivative actions were filed in 2023 and 2024 against us and certain of our former officers. Litigation is usually expensive and diverts management’s attention and resources, which could adversely affect our business and cash resources and our ability to execute on our partnership with GSK to eventually commercialize tebipenem HBr, or the ultimate value our stockholders receive in such partnership or other opportunity.

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds.

None.

Item 3. Defaults Upon Senior Securities.

None.

Item 4. Mine Safety Disclosures.

Not Applicable.

Item 5. Other Information.

Director and Officer Trading Arrangements

None of our directors or officers adopted or terminated a Rule 10b5-1 trading arrangement or a non-Rule 10b5-1 trading arrangement (as such terms are defined in Items 408(a) and 408(c) of Regulation S-K, respectively) during the quarterly period covered by this report.

Item 6. Exhibits


Exhibit Number	Exhibit Description	Filed with this Report	Incorporated by Reference herein from Form or Schedule	Filing Date	SEC File / Registration Number

3.1	Amended and Restated Certificate of Incorporation of the Registrant		Form 8-K (Exhibit 3.1)	11/6/2017	001-38266

3.2	Certificate of Amendment to the Amended and Restated Certificate of Incorporation of the Registrant		Form 8-K (Exhibit 3.1)	8/18/2021	001-38266

3.3	Amended and Restated Bylaws of the Registrant		Form 10-Q (Exhibit 3.1)	11/13/2023	001-38266

31	Certification of Principal Executive Officer and Principal Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002	X

32*	Certification pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, by Principal Executive Officer and Principal Financial Officer	X

101.INS	XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document	X

101.SCH	Inline XBRL Taxonomy Extension Schema Document	X

101.CAL	Inline XBRL Taxonomy Extension Calculation Linkbase Document	X

101.DEF	Inline XBRL Taxonomy Extension Definition Linkbase Document	X

101.LAB	Inline XBRL Taxonomy Extension Label Linkbase Document	X

101.PRE	Inline XBRL Taxonomy Extension Presentation Linkbase Document	X

104	Cover Page Interactive Data File (embedded within the Inline XBRL document)	X

* The certification attached as Exhibit 32 that accompanies this Quarterly Report on Form 10-Q is not deemed filed with the Securities and Exchange Commission and is not to be incorporated by reference into any filing of Spero Therapeutics, Inc. under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, whether made before or after the date of this Form 10-Q, irrespective of any general incorporation language contained in such filing.


Delaware	46-4590683

(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)

675 Massachusetts Avenue, 14th Floor Cambridge, Massachusetts	02139

(Address of principal executive offices)	(Zip Code)


Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, $0.001 par value per share	SPRO	The Nasdaq Global Select Market


Large accelerated filer	☐	Accelerated filer	☐
Non-accelerated filer	☒	Smaller reporting company	☒
		Emerging growth company	☐


	SPERO THERAPEUTICS, INC.

Date: November 13, 2025	By:	/s/ Esther Rajavelu
		Esther Rajavelu
		President, Chief Executive Officer, Chief Financial Officer and Treasurer
		(Principal Executive Officer, Principal Financial Officer and Principal Accounting Officer)


☒	QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934


☐	TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to


		Page
	PART I – FINANCIAL INFORMATION
Item 1.	Financial Statements (Unaudited)	5
	Condensed Consolidated Balance Sheets as of September 30, 2025 and December 31, 2024	5
	Condensed Consolidated Statements of Operations and Comprehensive Loss for the three and nine months ended September 30, 2025 and 2024	6
	Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2025 and 2024	7
	Condensed Consolidated Statements of Stockholders’ Equity for the three and nine months ended September 30, 2025 and 2024	8
	Notes to Unaudited Condensed Consolidated Financial Statements	9
Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	31
Item 3.	Quantitative and Qualitative Disclosures About Market Risk	41
Item 4.	Controls and Procedures	42

	PART II – OTHER INFORMATION
Item 1.	Legal Proceedings	43
Item 1A.	Risk Factors	44
Item 2.	Unregistered Sales of Equity Securities and Use of Proceeds	84
Item 3.	Defaults Upon Senior Securities	85
Item 4.	Mine Safety Disclosures	85
Item 5.	Other Information	85
Item 6.	Exhibits	86

Signatures		87