•

a proposal to adopt the Agreement and Plan of Merger, dated as of October 14, 2025 (as it may be amended from time to time, the “Merger Agreement”), by and among BioCryst Pharmaceuticals, Inc. (“BioCryst”), Axel Merger Sub, Inc., a wholly owned subsidiary of BioCryst (“Merger Sub”), and Astria, under which Merger Sub will merge with and into Astria, with Astria surviving and becoming a wholly owned subsidiary of BioCryst (the “Merger”) (the “Merger Proposal”);

•

a proposal to cast a vote, on a non-binding, advisory basis, to approve the Merger-related named executive officer compensation as disclosed in the table entitled “Golden Parachute Compensation” and its accompanying footnotes which is included in the section of this proxy statement/prospectus entitled “The Merger—Interests of Astria’s Directors and Executive Officers in the Merger,” as required by Section 14A of the Securities Exchange Act of 1934, as amended, which was enacted as part of the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 (the “Compensation Proposal”); and

•

a proposal to approve one or more adjournments of the Special Meeting to a later date or dates if there are not sufficient votes for adoption of the Merger Proposal on the date on which the Special Meeting is held (the “Adjournment Proposal”).

Q:

What is the Merger?

A:

BioCryst, Merger Sub and Astria have entered into an Agreement and Plan of Merger, dated as of October 14, 2025 (as it may be amended from time to time, the “Merger Agreement”). Pursuant to the Merger Agreement, Merger Sub will merge with and into Astria, with Astria surviving and becoming a wholly owned subsidiary of BioCryst (the “Merger”). A copy of the Merger Agreement is attached as Annex A to this proxy statement/prospectus. Following the Merger, the shares of Astria Common Stock will be delisted from The Nasdaq Stock Market (“Nasdaq”) and thereafter will be deregistered under the Exchange Act. The BioCryst Common Stock issued in the Merger will be listed on Nasdaq.

Q:

Why am I receiving this proxy statement/prospectus?

A:

Astria is sending these materials to its stockholders to help them decide how to vote their shares of Astria Common Stock with respect to the matters to be considered at a special meeting of Astria’s stockholders (the “Special Meeting”).

Q:

What will holders of Astria Common Stock receive in the Merger?

A:

If the Merger is completed, each share of Astria Common Stock, excluding shares held by BioCryst, Astria or their wholly owned subsidiaries or dissenting stockholders, that is issued and outstanding immediately prior to the effective time of the Merger (the “Effective Time”), will be converted into the right to receive (i) 0.59 (the “Exchange Ratio”) of a share of BioCryst Common Stock and, if applicable, cash in lieu of fractional shares and (ii) $8.55 in cash, without interest (the “Per Share Cash Amount” and, together with the consideration described in clause (i), the “Merger Consideration”), subject to adjustment as described below and subject to applicable withholding taxes.

Q:

Will the value of the Merger Consideration change between the date of this proxy statement/prospectus and the Effective Time?

A:

Yes. Although the Exchange Ratio is fixed, the market value of the stock component of the Merger Consideration will fluctuate with the market price of the BioCryst Common Stock between the date of this proxy statement/prospectus and the completion of the Merger. Any change in the market price of BioCryst Common Stock after the date of this proxy statement/prospectus will change the value of the shares of BioCryst Common Stock that Astria’s stockholders will receive.

Q:

What will happen to the Series X Preferred Shares in the Merger?

A:

Pursuant to the Merger Agreement, at the Effective Time, each share of Series X Convertible Preferred Stock, par value $0.001 per share, of Astria (the “Series X Preferred Shares”) that is issued and outstanding as of immediately prior to the Effective Time will be converted into the right to receive the Merger Consideration payable in accordance with the Merger Agreement with respect to the aggregate number of shares of Astria Common Stock for which such Series X Preferred Share was convertible immediately prior to the Effective Time pursuant to the certificate of designation of the Series X Preferred Shares, without interest and subject to applicable withholding taxes, and without regard to any limitations on conversion contained in such certificate of designation.

Q:

What will happen to the Astria Pre-Funded Warrants in the Merger?

A:

Pursuant to the Merger Agreement, at the Effective Time, each of the pre-funded warrants to purchase shares of Astria Common Stock (“Astria Pre-Funded Warrants”) that is outstanding immediately prior to the Effective Time will, in accordance with its own terms, cease to be exercisable for Astria Common Stock and will be automatically converted into the right to receive the Merger Consideration with respect to the aggregate number of shares of Astria Common Stock for which such Astria Pre-Funded Warrant was exercisable immediately prior to the Effective Time, taking into account the “cashless exercise” terms that govern such Astria Pre-Funded Warrant, without interest and subject to applicable withholding taxes, and without regard to any limitations on exercise contained therein.

Q:

What will happen to the Astria Common Warrants in the Merger?

A:

Pursuant to the Merger Agreement, each of the warrants to purchase shares of Astria Common Stock, other than the Astria Pre-Funded Warrants (“Astria Common Warrants”), that is issued and outstanding as of immediately prior to the Effective Time will continue to be outstanding following the Effective Time according to its terms, except that (i) such Astria Common Warrant will cease to be exercisable for Astria Common Stock and will become exercisable solely in exchange for the Merger Consideration with respect to the aggregate number of shares of Astria Common Stock for which such Astria Common Warrant was exercisable for immediately prior to the Effective Time (including after taking into account any “cashless exercise” terms that govern such Astria Common Warrant if so elected by the holder thereof), without interest and subject to applicable withholding taxes, and without regard to any limitations on exercise contained therein, or (ii) at any time prior to the 30^th day following the Effective Time, the holder of such Astria Common Warrant may require Astria to purchase such Astria Common Warrant for an amount in cash equal to the Black Scholes Value of such Astria Common Warrant pursuant to Section 3(d) of the applicable Astria Common Warrant, in lieu of receiving any Merger Consideration described in clause (i).

Q:

What will happen to Astria Stock Options in the Merger?

A:

Pursuant to the Merger Agreement, at the Effective Time, each option to purchase shares of Astria Common Stock granted pursuant to Astria’s Amended and Restated 2008 Equity Incentive Plan, Astria’s Second Amended and Restated 2015 Stock Incentive Plan and Astria’s 2022 Inducement Stock Incentive Plan (each, an “Astria Stock Option”) that is outstanding immediately prior to the Effective Time and which has an exercise price that is less than $13.00 per share of Astria Common Stock underlying such Astria Stock Option (an “In-the-Money Option”), whether or not then exercisable or vested, will (i) become fully vested and exercisable and (ii) be canceled and, in exchange therefor, the holder thereof will be entitled to receive a payment in cash, subject to applicable withholding taxes, of an amount equal to the product of (a) the total number of shares of Astria Common Stock subject to such canceled In-the-Money Option immediately prior to the Effective Time and (b) the excess of (A) $13.00 over (B) the exercise price per share of Astria Common Stock subject to such canceled In-the-Money Option, without interest.

Q:

Will the Merger affect the ownership of shares of BioCryst Common Stock held by current BioCryst stockholders?

A:

No. BioCryst’s stockholders will continue to own their existing shares of BioCryst Common Stock after the Merger is completed.

Q:

When do you expect to complete the Merger?

A:

We expect to complete the Merger in January of 2026. However, we cannot assure you of when or if the Merger will be completed. We must first obtain the approval of the Merger Proposal from Astria’s stockholders and satisfy certain other closing conditions. For further information, please see the section entitled “The Merger Agreement—Conditions to the Consummation of the Merger.”

Q:

What am I being asked to vote on?

A:

Astria’s stockholders are being asked to vote on the following:

•

the Merger Proposal;

•

a proposal to cast a vote, on a non-binding, advisory basis, to approve the Merger-related named executive officer compensation as disclosed in the table entitled “Golden Parachute Compensation” and its accompanying footnotes which is included in the section of this proxy statement/prospectus entitled “The Merger—Interests of Astria’s Directors and Executive Officers in the Merger,” as required by Section 14A of the Exchange Act, which was enacted as part of the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 (the “Compensation Proposal”); and

•

a proposal to approve one or more adjournments of the Special Meeting to a later date or dates if there are not sufficient votes for adoption of the Merger Proposal on the date on which the Special Meeting is held (the “Adjournment Proposal”).

Q:

How does the Astria Board recommend that Astria’s stockholders vote at the Special Meeting?

A:

The Astria Board has unanimously (i) determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are fair to, and in the best interests of, Astria and the holders of Astria Common Stock, (ii) approved, adopted and declared advisable the Merger Agreement and the transactions contemplated thereby, including the Merger, in accordance with the requirements of the General Corporation Law of the State of Delaware (the “DGCL”) and (iii) resolved to recommend that Astria’s stockholders vote to approve the adoption of the Merger Agreement.

Q:

When and where is the Special Meeting?

A:

The Special Meeting will be held on January 21, 2026 at 9:00 a.m., Eastern Time, at 22 Boston Wharf Road, 10th Floor, Boston, Massachusetts 02210. Subject to space availability, all of Astria’s stockholders as of the Record Date or their duly appointed proxies may attend the Special Meeting. Since seating is limited, admission to the Special Meeting will be on a first-come, first-served basis. Registration and seating will begin 30 minutes prior to the start of the meeting.

Q:

What constitutes a quorum for the Special Meeting?

A:

The presence at the Special Meeting of holders of a majority in voting power of the shares of Astria Common Stock issued and outstanding and entitled to vote at the Special Meeting, present in person or represented by proxy, will constitute a quorum for the purposes of the Special Meeting. All shares of Astria Common Stock entitled to vote and present in person or represented by proxy, including abstentions, if any, will be treated as present for purposes of determining the presence or absence of a quorum for all matters voted on at the Special Meeting.

Q:

Who is entitled to vote at the special meeting?

A:

Astria has fixed the close of business on December 9, 2025 as the record date to determine which of Astria’s stockholders will be entitled to receive notice of and vote at the Special Meeting (the “Record Date”). Only Astria’s stockholders of record at the close of business on the Record Date will be entitled to notice of, and to vote at, the Special Meeting.

Q:

What is the vote required to approve each proposal at the Special Meeting?

A:

Approval of the Merger Proposal requires the affirmative vote of holders of not less than a majority of the outstanding shares of Astria Common Stock.

Q:

Are there any voting agreements with Astria’s existing stockholders?

A:

Yes. In connection with the execution of the Merger Agreement, the members of the Astria Board and the executive officers of Astria, in their capacities as stockholders of Astria, as well as certain other stockholders of Astria, entered into Voting and Support Agreements (the “Voting Agreements”), pursuant to which, among other things, they agreed (i) to vote their shares of Astria Common Stock in favor of the Merger Proposal and certain related matters and against alternative transactions and (ii) subject to certain exceptions, not to transfer such shares of Astria Common Stock prior to the earlier of the Effective Time and the termination of the Merger Agreement, without the prior written consent of BioCryst.

Q:

Why is my vote important?

A:

If you do not vote, it will be more difficult for Astria to obtain the necessary quorum to hold the Special Meeting and to obtain stockholder approval of the Merger Proposal, which is necessary to complete the Merger. The Astria Board recommends that Astria’s stockholders vote “FOR” the Merger Proposal, “FOR” the Compensation Proposal, and “FOR” the Adjournment Proposal.

Q:

How many votes do I have?

A:

As of the close of business on the Record Date, there were 57,084,838 shares of Astria Common Stock outstanding, all of which were entitled to notice of, and to vote at, the Special Meeting, held by approximately 18 holders of record. Each holder of shares of Astria Common Stock outstanding on the Record Date will be entitled to one vote for each share held of record.

Q:

What do I need to do now?

A:

After carefully reading and considering the information contained in this proxy statement/prospectus, including any documents incorporated into this proxy statement/prospectus by reference, and its annexes, please complete, sign, date and return the enclosed proxy card in the enclosed envelope or vote by telephone or the internet by following the instructions on your proxy card as soon as possible so that your shares will be represented at the Special Meeting.

Q:

How do I vote?

A:

An Astria stockholder may vote by proxy or in person at the Special Meeting. If you hold your shares of Astria Common Stock in your name as a stockholder of record, you may use one of the following methods to submit a proxy as an Astria stockholder:

•

through the internet by visiting www.fcrvote.com/ATXSSM and following the instructions, using the control number provided on your proxy card;

•

by telephone by calling 1-866-402-3905 and following the recorded instructions, using the control number provided on your proxy card; or

•

by mail by completing, signing, dating and returning the proxy card in the enclosed envelope, which requires no additional postage if mailed in the United States.

Q:

If my shares of Astria Common Stock are held in “street name” by my bank, broker or other nominee, will my bank, broker or other nominee automatically vote my shares for me?

A:

If an Astria stockholder’s shares are held in “street name” by a bank, broker or other nominee, that stockholder should check the voting form used by that firm to determine how to vote. You may not vote shares held in “street name” by returning a proxy card directly to Astria or by voting in person at the Special Meeting unless you provide a letter from the record holder of your shares confirming your beneficial ownership, which you must obtain from your bank, broker or other nominee.

Q:

What will happen if I return my proxy without indicating how to vote?

A:

If any proxy card is returned without indication as to how to vote, the shares of Astria Common Stock represented by that proxy card will be voted as recommended by the Astria Board.

Q:

May I change or revoke my vote after I have delivered my proxy?

A:

If you hold stock in your name as a stockholder of record, you may change or revoke your vote or revoke any proxy at any time before it is voted by (i) completing, signing, dating and returning a proxy card with a later date, (ii) voting by telephone or the internet at a later time than your original vote (but before the internet and telephone voting deadline), (iii) delivering a written revocation letter to Astria’s Corporate

Q:

Do I need identification to attend the Special Meeting in person?

A:

If you hold your shares of Astria Common Stock in your name as a stockholder of record and you wish to attend the Special Meeting, please bring your proxy card to the Special Meeting. You should also bring valid photo identification. If you are not an Astria stockholder of record or if your shares are held in “street name” by a bank, broker or other nominee, please bring a letter from the record holder of your shares confirming your beneficial ownership and a valid photo identification in order to be admitted to the meeting. A copy or printout of a brokerage statement will not be sufficient without a signed letter from the bank, broker or other nominee through which you beneficially own Astria Common Stock. Astria reserves the right to refuse admittance to anyone without proper proof of share ownership and without valid photo identification.

Q:

Are Astria’s stockholders entitled to appraisal rights?

A:

If the Merger is completed, holders of record and beneficial owners of Astria Common Stock who (1) do not vote in favor of the Merger Proposal; (2) continuously hold (in the case of holders of record) or continuously own (in the case of beneficial owners) their applicable shares of Astria Common Stock through the effective date of the Merger; (3) properly demand appraisal of their applicable shares; (4) meet certain statutory requirements as described in this proxy statement/prospectus; and (5) do not withdraw their demands or otherwise lose their rights to appraisal, will be entitled to seek appraisal of their shares in connection with the Merger in accordance with Section 262 of the DGCL. The requirements for perfecting and exercising appraisal rights are described in additional detail in the section of this proxy statement/prospectus entitled “Appraisal Rights,” which description is qualified in its entirety by Section 262 of the DGCL, the full text of which is available at https://delcode.delaware.gov/title8/c001/sc09/index.html#262.

Q:

What are the material U.S. federal income tax consequences of the Merger to Astria’s stockholders?

A:

The receipt of cash and BioCryst Common Stock in exchange for Astria Common Stock in the Merger will be a taxable transaction for U.S. federal income tax purposes. In general, if you are a U.S. Holder (as defined below), you will recognize capital gain or loss in an amount equal to the difference between (i) the fair market value of the Merger Consideration received and (ii) your tax basis in the Astria Common Stock exchanged pursuant to the Merger. In general, if you are a Non-U.S. Holder (as defined below), you will not be subject to U.S. federal income taxation on any gain realized unless you have certain connections to the United States, but you may be subject to backup withholding unless you comply with certain certification procedures or otherwise establish a valid exemption from backup withholding.

Q:

What should I do if I hold my shares of Astria Common Stock in book-entry form?

A:

If you are a holder of book-entry shares representing eligible Astria Common Stock held through a broker, bank or other nominee that is a member institution of The Depository Trust Company (“DTC”), an exchange agent will transmit to DTC or its nominees as soon as practicable after the Effective Time, upon surrender of such shares held of record by DTC or its nominees in accordance with DTC’s customary surrender procedures, the Merger Consideration, including the shares of BioCryst Common Stock issuable to you, the Per Share Cash Amount and cash in lieu of any fractional shares, in each case, that DTC has the right to receive, and DTC or its nominees will credit to your account at your broker, bank or other nominee, your applicable portions of that Merger Consideration.

Q:

What should I do if I receive more than one set of voting materials?

A:

Astria’s stockholders may receive more than one set of voting materials, including multiple copies of this proxy statement/prospectus and multiple proxy cards or voting instruction cards. For example, if you hold shares of Astria Common Stock in more than one brokerage account, you will receive a separate voting instruction card for each brokerage account in which you hold such shares. If you are a holder of record of Astria Common Stock and your shares are registered in more than one name, you will receive more than one proxy card. Please complete, sign, date and return each proxy card and voting instruction card that you receive or otherwise follow the voting instructions set forth in this proxy statement/prospectus to ensure that you vote every share of Astria Common Stock that you own.

Q:

What happens if I sell my shares of Astria Common Stock after the Record Date for the Special Meeting but before the Special Meeting?

A:

The Record Date is earlier than the date of the Special Meeting and the date that the Merger is expected to be completed. If you transfer your shares of Astria Common Stock after the Record Date but before the date of the Special Meeting, you will retain your right to vote at the Special Meeting (provided that such shares remain outstanding on the date of the Special Meeting), but you will not have the right to receive any Merger Consideration for the transferred shares of Astria Common Stock. You will only be entitled to receive the Merger Consideration in respect of shares of Astria Common Stock that you hold at the Effective Time.

Q:

Are there risks involved in undertaking the Merger?

A:

Yes. You should read and carefully consider the risk factors set forth in the section entitled “Risk Factors” beginning on page 17.

Q:

What happens if the Merger is not completed?

A:

If the Merger is not completed, Astria’s stockholders will not receive the Merger Consideration. Instead, each of Astria and BioCryst will remain an independent public company and BioCryst Common Stock and Astria Common Stock will continue to be separately listed on Nasdaq.

Q:

Whom should I contact if I have questions?

A:

If you have any questions about the proxy materials or if you need assistance submitting your proxy or voting your shares, or need additional copies of this proxy statement/prospectus or the enclosed proxy card, please contact Astria’s Corporate Secretary at Astria Therapeutics, Inc., 22 Boston Wharf Road, 10th Floor, Boston, Massachusetts 02210, Attention: Corporate Secretary, or Astria’s proxy solicitor, Alliance Advisors, LLC, at 1-844-202-6294.

Q:

Where can I find more information about BioCryst and Astria?

A:

You can find more information about BioCryst and Astria from the various sources described under the section entitled “Where You Can Find More Information.”

•

increase the combined company’s vulnerability to adverse general economic or industry conditions;

•

limit the combined company’s flexibility in planning for, or reacting to, changes in the combined company’s business or the industry in which it operates;

•

make the combined company more vulnerable to increases in interest rates, as it is expected that borrowings under the Expected Loan Agreement will accrue interest at variable, uncapped rates, such that increases in interest rates will increase the associated interest payments that the combined company is required to make on outstanding borrowings;

•

require the combined company to dedicate a portion of its cash flow from operations to interest payments, limiting the availability of cash for other purposes;

•

limit the combined company’s ability to obtain additional financing or refinancing in the future for working capital or other purposes; and

•

place the combined company at a competitive disadvantage compared to its competitors that have less indebtedness.

•

Holders of Astria Common Stock: Based on 57,084,838 shares of Astria Common Stock issued and outstanding as of the Record Date and the Exchange Ratio, it is expected that BioCryst will issue approximately 33,680,054 shares of BioCryst Common Stock to holders of Astria Common Stock.

•

Holders of Series X Preferred Shares: Based on 5,184,591 shares of Astria Common Stock underlying 31,107 Series X Preferred Shares that were outstanding as of the Record Date and the Exchange Ratio, it is expected that BioCryst will issue approximately 3,058,908 shares of BioCryst Common Stock to holders of Series X Preferred Shares.

•

Holders of Astria Pre-Funded Warrants: Based on 921,093 shares of Astria Common Stock underlying Astria Pre-Funded Warrants that were outstanding as of the Record Date and the Exchange Ratio, it is expected, after taking into account the cashless exercise provisions of such Astria Pre-Funded Warrants, that BioCryst will issue approximately 543,402 shares of BioCryst Common Stock to holders of Astria Pre-Funded Warrants.

•

Holders of Astria Common Warrants: Based on 4,954,096 shares of Astria Common Stock underlying Astria Common Warrants (other than the shares underlying such Astria Common Warrants, which, as of such date, are known to Astria to constitute Elected Warrants) that were outstanding as of the Record Date and the Exchange Ratio, and assuming that none of the holders thereof elect to receive the Black Scholes Value of such Astria Common Warrants in lieu of Merger Consideration, it is expected, after taking into account the cashless exercise provisions of such Astria Common Warrants, that BioCryst will issue approximately 1,126,537 shares of BioCryst Common Stock to holders of such Astria Common Warrants.

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the expected benefits of the Merger and BioCryst’s ability to recognize the benefits of the Merger;

•

the anticipated timing of the Closing;

•

the anticipated financial impact of the Merger;

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BioCryst’s performance following the Closing, including future financial and operating results;

•

anticipated approval and commercialization of navenibart;

•

pharmaceutical research and development, such as drug discovery, preclinical and clinical development activities and related timelines;

•

expected HAE portfolio revenue growth and addressable markets;

•

anticipated benefits, performance, and competitive positioning of, and market size for, navenibart;

•

potential best-in-class profile of product candidates (including navenibart); and

•

BioCryst’s and Astria’s plans, objectives, expectations, intentions, growth strategies and other statements that are not historical facts.

•

the occurrence of any event, change or other circumstances that could give rise to the right of one or both of the parties to terminate the Merger Agreement;

•

the outcome of any legal proceedings that may be instituted against BioCryst or Astria;

•

the failure to obtain Astria’s stockholders’ approval of the Merger Proposal or to satisfy any of the other conditions to the Merger on a timely basis or at all;

•

the possibility that the anticipated benefits of the Merger, including anticipated synergies, are not realized when expected or at all, including as a result of the impact of, or problems arising from, the integration of the two companies or as a result of the strength of the economy and competitive factors in the areas where BioCryst and Astria do business;

•

the significant indebtedness BioCryst expects to incur in connection with the Merger and the need to generate sufficient cash flows to service and repay such debt;

•

the possibility that the Merger may be more expensive to complete than anticipated;

•

diversion of management’s attention from ongoing business operations and opportunities;

•

potential adverse reactions or changes to business or employee relationships, including those resulting from the announcement or completion of the Merger;

•

risks relating to the potential dilutive effect of shares of BioCryst Common Stock to be issued in the Merger;

•

BioCryst’s HAE portfolio and revenue growth expectations may not be achieved due to, among other risks, risks related to government actions, including that decisions and other actions, including as they relate to pricing for navenibart, may not be taken when expected or at all, or that the outcomes of such decisions and other actions may not be in line with BioCryst’s current expectations;

•

the U.S. Food and Drug Administration (“FDA”), or other applicable regulatory agencies, may not provide regulatory clearances or approval for navenibart on the expected timeline or at all, may impose certain restrictions, warnings, or other requirements on products and product candidates (including navenibart), may impose a clinical hold with respect to navenibart, or may withhold, delay, or withdraw market approval for products and product candidates (including navenibart);

•

that navenibart, if approved, may not achieve market acceptance;

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sustainability of profitability and positive cash flow, and anticipated cash balance, may not meet management’s expectations;

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statements and projections regarding financial guidance and goals and the attainment of such goals may differ from actual results based on market factors and BioCryst’s ability to execute its operational and budget plans;

•

actual financial results may not be consistent with expectations, including that revenue, operating expenses and cash usage may not be within management’s expected ranges;

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ongoing and future preclinical and clinical development of product candidates may take longer than expected and may not have positive results;

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the outcome of preclinical testing and early clinical trials may not be predictive of the success of later clinical trials;

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and other factors that may affect future results of BioCryst, Astria and the combined company.

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the Merger Proposal;

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the Compensation Proposal; and

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the Adjournment Proposal.

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through the internet by visiting www.fcrvote.com/ATXSSM and following the instructions, using the control number provided on your proxy card;

•

by telephone by calling 1-866-402-3905 and following the recorded instructions, using the control number provided on your proxy card; or

•

by mail by completing, signing, dating and returning the proxy card in the enclosed envelope, which requires no additional postage if mailed in the United States.

•

the Merger Consideration is comprised of $8.55 in cash and 0.59 of a share of BioCryst Common Stock, giving Astria’s stockholders immediate value and liquidity at closing of the Merger as a result of the cash portion of the Merger Consideration, as well as the ability to participate in any future increase in the value of the combined company following the closing of the Merger by virtue of their ownership of BioCryst Common Stock;

•

the Merger Consideration reflects an implied value of $13.00 per share based on BioCryst’s 20-day VWAP of $7.54 as of October 8, 2025 (which reflects the method of calculation of such VWAP that was agreed between Astria and BioCryst), and represented a premium of approximately 53% over the closing stock price per share of Astria Common Stock on October 13, 2025 (the last trading day before the public announcement of the Merger Agreement), and 71% over Astria Common Stock’s 20-day VWAP as of October 13, 2025 (the last trading day before the public announcement of the Merger Agreement);

•

the potentially complementary nature of navenibart, Astria’s lead product candidate and a potential long-acting injectable treatment for HAE, with BioCryst’s ORLADEYO product, the first oral HAE treatment, as well as BioCryst’s successful development and launch of ORLADEYO, experience which the Astria Board believes could increase the probability that navenibart will have a successful commercial launch, if approved for marketing;

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the Astria Board’s understanding, based on the due diligence conducted by Astria’s senior management and its outside financial and legal advisors, of BioCryst’s business, operations, assets and liabilities, financial condition, earnings, including the market for ORLADEYO, strategy and future prospects;

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the Astria Board’s review and analysis, with the assistance of its financial advisor, of potential strategic alternatives, regional licensing opportunities and alternative transaction partners to identify the opportunity that would, in the view of the Astria Board, create the most value for Astria’s stockholders;

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the Astria Board’s belief, after its review of strategic alternatives and discussions with Astria’s senior management and its financial and legal advisors, that the Merger is more favorable to Astria’s stockholders than the potential value that might have resulted from other strategic alternatives available to Astria;

•

the Astria Board’s belief that, as a result of arm’s-length negotiations with BioCryst, Astria and its representatives negotiated the highest Exchange Ratio and Per Share Cash Amount to which BioCryst was willing to agree, and that the other terms of the Merger Agreement, taken as a whole, include the most favorable terms to Astria in the aggregate to which BioCryst was willing to agree;

•

progress made by Astria throughout the negotiation process with BioCryst with respect to the valuation of Astria: from $11.50 per share implied value in BioCryst’s initial indication of interest to $13.00 per share implied value in the Merger Agreement, which the Astria Board believed was the greatest implied value to which BioCryst was willing to agree;

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the assessment of the Astria Board, grounded in its clinical development and commercialization experience and a deep understanding of Astria’s business, with the assistance of Astria’s senior management and its financial and legal advisors, of Astria’s standalone plan and other strategic alternatives available to Astria for enhancing value over the long term and the potential risks, rewards and uncertainties associated with Astria’s standalone plan and such other alternatives, and the belief of the Astria Board that the Merger offered greater benefits, with reduced risks, as compared to the value that could reasonably be expected to be obtained from Astria’s standalone plan and other alternatives available to Astria;

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the significant capital needed for Astria to complete the clinical development of its product candidates and, if approved for marketing, successfully commercialize them, and the potential that adequate additional financing may not be available on acceptable terms, or at all, or that the terms of any financing may adversely affect the holdings or the rights of Astria’s stockholders, including as a result of the dilution of Astria’s stockholders’ ownership interests or terms that include liquidation or other preferences, or contain restrictive covenants that limit Astria’s ability to take specific actions that could adversely impact its ability to conduct its business;

•

the challenges of successfully commercializing Astria’s product candidates, if approved for marketing, including, among other things, the ability to develop any drug device combination for navenibart, STAR-0310 or any future product candidates, the need to either develop a sales and marketing organization or outsource these functions to third parties, the ability to obtain, both domestically and abroad, coverage from third-party payors, including government health administration authorities and private health coverage insurers, and the ability to gain sufficient market acceptance by physicians, patients, third-party payors and others in the medical community;

•

the current financial market conditions and historical market prices, volatility and trading information with respect to the Astria Common Stock and the risk that Astria may be unable to secure funding on acceptable terms in the future;

•

the current and prospective business climate in the industry in which Astria and BioCryst operate, including the increasing number of current and likely competitors of Astria and BioCryst, and the related challenges faced in commercializing product candidates in general and, in particular, product candidates for treating HAE;

•

with the addition of navenibart, BioCryst’s portfolio will include both an oral product and a long-acting injectable product candidate for HAE, allowing for a more individualized approach to serving patients and the opportunity to offer patients both oral and injectable therapies;

•

the Astria Board’s view that the combined company will be led by an experienced senior management team from BioCryst with significant experience in the HAE market, and that Jill Milne, Astria’s Chief Executive Officer, will join the BioCryst Board effective as of the Closing; and

•

the financial analyses of Evercore reviewed with Astria Board on October 13, 2025, and the opinion of Evercore, dated October 13, 2025, addressed to the Astria Board as to the fairness, from a financial point of view and as of the date of such opinion, to the holders of Astria Common Stock of the Merger Consideration, as more fully described below under the caption “—Opinion of Astria’s Financial Advisor.”

•

the calculation of the Exchange Ratio and the estimated number of shares of BioCryst Common Stock to be issued in the Merger;

•

the number and nature of the conditions to BioCryst’s and Astria’s respective obligations to complete the Merger and the likelihood that the Merger will be completed on a timely basis;

•

the absence of a financing contingency;

•

the rights of, and limitations on, Astria under the Merger Agreement to consider and engage in discussions regarding unsolicited acquisition proposals under certain circumstances, as more fully described in the section entitled “The Merger Agreement—No Solicitation of Competing Proposals”;

•

the limitations on the Astria Board’s ability to change its recommendation in favor of the Merger, as more fully described in the section entitled “The Merger Agreement—No Solicitation of Competing Proposals”;

•

the potential termination fee of $32.25 million payable by Astria to BioCryst if the Merger Agreement is terminated in certain circumstances, as more fully described in the sections entitled “The Merger Agreement—Termination of the Merger Agreement” and “The Merger Agreement—Termination Fee and Expenses”; and

•

pursuant to the Voting Agreements, certain stockholders of Astria have agreed, solely in their capacities as stockholders of Astria, to vote all of their shares of Astria Common Stock in favor of the Merger Proposal and against any alternative acquisition proposals, as more fully described in the section entitled “Voting and Support Agreements.”

•

the potential effect of the $32.25 million termination fee payable by Astria upon the occurrence of certain events in deterring other potential acquirors from proposing an alternative acquisition proposal that may be more advantageous to Astria’s stockholders;

•

the prohibition on Astria’s solicitation of alternative acquisition proposals during the pendency of the Merger;

•

the Exchange Ratio provides for a fixed number of shares of BioCryst Common Stock for each share of Astria Common Stock and, as such, holders of Astria Common Stock cannot be certain, at the time of the Special Meeting, of the market value of the Merger Consideration they will receive, and the possibility that holders of Astria Common Stock could be adversely affected by a decrease in the market price of BioCryst Common Stock before the closing of the Merger;

•

if the aggregate number of shares of BioCryst Common Stock to be issued in connection with the Merger will exceed 19.9% of the issued and outstanding shares of BioCryst Common Stock immediately prior to the Effective Time, the Exchange Ratio will be reduced, as more fully described in the section entitled “The Merger Agreement—Merger Consideration”;

•

as a result of the Merger, Astria will not realize the full value from the potential commercialization of navenibart, licensing of rights to navenibart in Europe and certain other ex-U.S. jurisdictions or any future development of STAR-0310;

•

the substantial expenses incurred or to be incurred by Astria in connection with the Merger;

•

the approval under the HSR Act required in connection with the Merger and the risk that such approval may not be received in a timely manner;

•

the risk of losing key Astria employees during the pendency of the Merger and thereafter;

•

the possible diversion of management attention and resources from the operation of Astria’s business or other strategic opportunities towards the completion of the Merger;

•

the Merger Agreement places certain restrictions on the conduct of Astria’s business prior to the completion of the Merger, which are customary for public company merger agreements involving biopharmaceutical companies, but which, subject to specific exceptions, could delay or prevent Astria from undertaking business opportunities that might arise during the pendency of the Merger or any other action it would otherwise take with respect to the operations of Astria absent the pendency of the Merger;

•

the potential for legal claims challenging the Merger;

•

the possible volatility of the trading price of Astria Common Stock and BioCryst Common Stock resulting from the announcement, pendency or completion of the Merger;

•

the Merger might not be consummated in a timely manner or at all;

•

the scientific, technical, regulatory and other risks and uncertainties associated with BioCryst’s development and commercialization of navenibart;

•

Astria’s cash continuing to deplete during the pendency of the Merger, which will reduce the potential value that would be available to Astria’s stockholders, should the Merger not be completed for any reason;

•

BioCryst may not have available sources of financing necessary to fund the Merger and the ongoing development of navenibart in addition to BioCryst’s existing pipeline of clinical and preclinical programs through upcoming value inflection points; and

•

the various other risks associated with the combined company and the transactions contemplated by the Merger Agreement, including those described in the sections entitled “Risk Factors” and “Cautionary Statement Concerning Forward-Looking Statements” in this proxy statement/prospectus.

•

reviewed certain publicly-available business and financial information relating to Astria and BioCryst that Evercore deemed to be relevant, including publicly-available research analysts’ estimates;

•

reviewed the Astria Forecasts (as defined and summarized in the section entitled “—Certain Unaudited Prospective Financial Information—Additional Unaudited Prospective Financial Information”), which consist of certain internal projected financial data relating to Astria, including projected utilization of net operating losses, prepared and furnished to Evercore by Astria’s management, as approved for Evercore’s use by Astria;

•

reviewed the BioCryst Forecasts (as defined and summarized in the section entitled “—Certain Unaudited Prospective Financial Information—Additional Unaudited Prospective Financial Information”), which consist of certain projected financial data relating to BioCryst prepared and furnished to Evercore by Astria’s management, as approved for Evercore’s use by Astria (which, together with the Astria Forecasts, are referred to as the “Forecasts”);

•

reviewed the Synergies Forecasts (as defined and summarized in the section entitled “—Certain Unaudited Prospective Financial Information—Additional Unaudited Prospective Financial Information”), which consist of certain estimates of the cost savings expected to result from the Merger, prepared and furnished to Evercore by Astria’s management, as approved for Evercore’s use by Astria;

•

discussed with Astria’s management their assessment of the past and current operations of Astria and BioCryst, the current financial condition and prospects of Astria and BioCryst, the Forecasts and the Synergies Forecasts (including Astria’s management’s views on the risks and uncertainties in achieving the Forecasts), and discussed with management of BioCryst their assessment of certain past and current operations of BioCryst, and the current financial condition and prospects of BioCryst;

•

reviewed the reported prices and the historical trading activity of the Astria Common Stock and the BioCryst Common Stock;

•

compared the stock market trading multiples of BioCryst with those of certain other publicly-traded companies that Evercore deemed relevant;

•

reviewed the financial terms and conditions of a draft, dated October 12, 2025, of the Merger Agreement; and

•

performed such other analyses and examinations and considered such other factors that Evercore deemed appropriate.

•

Amicus Therapeutics, Inc.;

•

Apellis Pharmaceuticals, Inc.;

•

Ardelyx, Inc.;

•

Catalyst Pharmaceuticals, Inc.;

•

Harmony Biosciences Holdings, Inc.;

•

Krystal Biotech, Inc.;

•

Mirum Pharmaceuticals, Inc.;

•

PTC Therapeutics, Inc.; and

•

Travere Therapeutics, Inc.

(1)

The amounts in this table do not include Out-of-the-Money Options as, pursuant to the Merger Agreement, at the Effective Time, each Out-of-the-Money Option will be canceled for no consideration.

(2)

Pursuant to the Merger Agreement, at the Effective Time, each In-the-Money Option, whether or not then exercisable or vested, will (i) become fully vested and exercisable and (ii) be canceled and, in exchange therefor, the holder of such In-the-Money Option will be entitled to receive a payment in cash, subject to applicable withholding taxes, equal to the product of (a) the total number of shares of Astria Common Stock subject to such canceled In-the-Money Option immediately prior to the Effective Time and (b) the excess of (A) $13.00 over (B) the exercise price per share of Astria Common Stock subject to such canceled In-the-Money Option, without interest. The amounts in this column represent the product of such calculation for each respective individual.

*

Also a member of the Astria Board.

(1)

The amounts in this table do not include Out-of-the-Money Options as, pursuant to the Merger Agreement, at the Effective Time, each Out-of-the-Money Option will be canceled for no consideration.

(2)

Pursuant to the Merger Agreement, at the Effective Time, each In-the-Money Option, whether or not then exercisable or vested, will (i) become fully vested and exercisable and (ii) be canceled and, in exchange therefore, the holder of such In-the-Money Option will be entitled to receive a payment in cash, subject to applicable withholding taxes, equal to the product of (a) the total number of shares of Astria Common Stock subject to such canceled In-the-Money Option immediately prior to the Effective Time and (b) the excess of (A) $13.00 over (B) the exercise price per share of Astria Common Stock subject to such canceled In-the-Money Option, without interest. The amounts in this column represent the product of such calculation for each respective individual.

•

continuation of such Covered Employee’s monthly base salary (as defined in the Astria Severance Plan) for a severance period following such termination (a “Severance Period”) equal to 18 months in the case of Astria’s Chief Executive Officer and 12 months in the case of Astria’s other executive officers;

•

payment by Astria of a portion of the cost of Consolidated Omnibus Budget Reconciliation Act (“COBRA”) continuation of benefits coverage for the Covered Employee and their applicable dependents for no longer than the Covered Employee’s applicable Severance Period or until the Covered Employee commences new employment and is eligible for new plan coverage, if sooner, subject to certain conditions set forth in the Astria Severance Plan;

•

any unpaid annual bonus in respect of any completed bonus period which has ended prior to the date of the Covered Employee’s Change in Control Termination and which the Astria Board deems granted to the Covered Employee in its discretion pursuant to Astria’s contingent compensation program;

•

in the case of Astria’s Chief Executive Officer, a bonus amount equal to one-half of the average annual bonus paid to Astria’s Chief Executive Officer over the three calendar years preceding the calendar year in which the Change in Control Termination occurs, which bonus will be prorated to reflect the number of days served in the calendar year in which such Change in Control Termination occurs; and

•

full vesting of any unvested equity awards.

•

Jill C. Milne, Ph.D., President and Chief Executive Officer;

•

Christopher Morabito, M.D., Chief Medical Officer; and

•

Benjamin Harshbarger, J.D., Chief Legal Officer.

(1)

The severance amounts reported in the “Cash” column are attributable to double-trigger arrangements (i.e., the amounts are triggered by the “change in control” that will occur upon completion of the Merger and payment is conditioned upon the named executive officer’s qualifying termination of employment by Astria without “cause” or due to the executive officer’s resignation for “good reason,” in each case, within 12 months following the change in control). Pursuant to the Astria Severance Plan, these amounts are the sum of (i) in the case of Dr. Milne, 18 months’ base salary, and in the case of Dr. Morabito and Mr. Harshbarger, 12 months’ of the executive’s base salary, each at the rate in effect immediately prior to the executive’s Change in Control Termination, (ii) any unpaid annual bonus in respect of any completed bonus period which has ended prior to the date of such employee’s Change in Control Termination and which the Astria Board deems granted to such employee in its discretion pursuant to Astria’s contingent compensation program, and (iii) in the case of Dr. Milne, a bonus amount equal to one-half of the average annual bonus paid to Dr. Milne over the three calendar years preceding the calendar year in which the Change in Control Termination occurs, which bonus will be prorated to reflect the number of days served in the calendar year in which such Change in Control Termination occurs. In addition, this column also includes the guaranteed payout of the 2025 annual bonus payable pursuant to the terms of the Merger Agreement. Pursuant to the terms of the Merger Agreement, prior to the Closing, but not before January 1, 2026 (unless in connection with mitigation relating to Section 280G of the Code), Astria may pay 2025 annual bonuses to each eligible employee equal to the greater of (i) actual performance or (ii) 125% of such employee’s target annual bonus amount for 2025. However, if the Effective Time occurs on or prior to March 15, 2026 and Astria has not paid such 2025 annual bonuses to employees as of immediately prior to the Effective Time, on the Closing Date, BioCryst will, or will cause its subsidiaries to, make such 2025 annual cash bonus payments, net of applicable withholdings, to each employee employed by Astria or any of its subsidiaries immediately prior to the Effective Time in the same amounts. For the named executive officers, 125% of their 2025 annual bonus is equal to: $415,013 for Dr. Milne; $252,678 for Dr. Morabito; and $240,041 for Mr. Harshbarger.

(2)

The amounts reported in the “Equity” column are attributable to single-trigger arrangements (i.e., the amounts are triggered by the “change in control” that will occur upon completion of the Merger without a subsequent termination of employment). Pursuant to the Merger Agreement, at the Effective Time, each In-the-Money Option, whether or not then exercisable or vested, will (i) become fully vested and exercisable and (ii) be canceled and, in exchange therefor, the holder of such In-the-Money Option will be entitled to receive a payment in cash, subject to applicable withholding taxes, equal to the product of (a) the total number of shares of Astria Common Stock subject to such canceled In-the-Money Option immediately prior to the Effective Time and (b) the excess of (A) $13.00 over (B) the exercise price per share of Astria Common Stock subject to such canceled In-the-Money Option, without interest. The amounts in this column represent the product of such calculation for each respective individual (for the avoidance of doubt, only with respect to In-the-Money Options for which vesting will be accelerated as described in this paragraph). For Dr. Milne, the amount in this column also includes an estimate of the value of the initial equity grant that she expects to receive upon joining the BioCryst Board, equal to $500,000 prorated based on the effective date of her appointment relative to BioCryst’s next annual meeting of stockholders and payable 60% in stock options and 40% in restricted stock units. The amounts in this column do not include Out-of-the-Money Options as, pursuant to the Merger Agreement, at the Effective Time, each Astria Stock Option that is outstanding immediately prior to the Effective Time and which has an exercise price that is equal to or greater than $13.00 per share of Astria Common Stock underlying such option will be canceled for no consideration.

(3)

The amounts reported in the “Perquisites/Benefits” column are attributable to double-trigger arrangements (i.e., the amounts are triggered by the change in control that will occur upon completion of the Merger and payment is conditioned upon the named

(4)

Under the terms of the Astria Severance Plan, if the payments and benefits to a Covered Employee under the Astria Severance Plan or another plan, arrangement or agreement would subject the Covered Employee to the excise tax imposed by Section 4999 of the Code, then such payments will be reduced by the minimum amount necessary to avoid such excise tax, if such reduction would result in the Covered Employee receiving a higher net after-tax amount. The amounts reflected in this table do not reflect the application of any reduction in compensation or benefits pursuant to the terms of the Astria Severance Plan.

•

the stockholder or beneficial owner must not vote in favor of the Merger Proposal;

•

the stockholder or beneficial owner must deliver to Astria a written demand for appraisal of such holder’s or owner’s shares of Astria Common Stock before the vote on the Merger Proposal at the Special Meeting; and

•

the stockholder must continuously hold or the beneficial owner must continuously own the shares from the date of making the demand through the effective date of the Merger.

•

the shares of Astria Common Stock held by Astria as treasury stock and each share of Astria Common Stock held by BioCryst, Merger Sub or any wholly owned subsidiary of BioCryst or of Astria (collectively, the “Excluded Shares”), in each case will be cancelled and retired without consideration;

•

each outstanding share of Astria Common Stock (other than the Excluded Shares or Dissenting Shares (as defined below)) will be cancelled and converted into the right to receive (i) 0.59 of a share of BioCryst Common Stock and, if applicable, cash in lieu of fractional shares and (ii) $8.55 in cash, without interest, subject to adjustment as described below and subject to applicable withholding taxes; and

•

each Series X Preferred Share will be cancelled and converted into the right to receive the Merger Consideration payable with respect to the aggregate number of shares of Astria Common Stock for which such Series X Preferred Share was convertible into immediately prior to the Effective Time under the Certificate of Designation of Preferences, Rights and Limitations of Series X Convertible Preferred Stock of Astria, dated as of January 28, 2021 (the “Certificate of Designation”), without interest.

•

in the case of an In-the-Money Option, become fully vested and exercisable, and be canceled in exchange for the payment in cash of an amount equal to the product of (i) the total number of shares of Astria Common Stock subject to such canceled In-the-Money Option immediately prior to the Effective Time and (ii) the excess of (a) $13.00 over (b) the exercise price per share of Astria Common Stock subject to such canceled In-the-Money Option, without interest. From and after the Effective Time, each such In-the-Money Option will no longer be exercisable by the former holder and such holder shall only be entitled to receive such cash payment; and

•

in the case of an Out-of-the-Money Option, be canceled without any payment and have no further force or effect.

•

organization, good standing and corporate power;

•

corporate authority to enter into, deliver and perform the Merger Agreement, and the enforceability of the Merger Agreement;

•

actions by or filings with government bodies or consents from government bodies or other persons in connection with the execution and performance of the Merger Agreement or consummation of the transactions contemplated by the Merger Agreement;

•

the absence, as a result of the execution and performance of the Merger Agreement, of any conflict with or violation of their organizational documents, any conflict with or violation of applicable laws or government orders, any conflict with or breach or default under, or creation of any lien on any of their assets, or necessity of any authorization, consent, waiver, notice or similar action, in each case under any contract to which they are a party;

•

their capitalization and ownership of equity interests issued by them;

•

the organization and good standing of their respective subsidiaries;

•

SEC filings, reports, disclosure controls and procedures and financial statements;

•

the information supplied by such party for inclusion or incorporation by reference in this proxy statement/prospectus;

•

the absence of a Material Adverse Effect since December 31, 2024;

•

the absence of certain undisclosed liabilities;

•

compliance with applicable laws;

•

litigation;

•

intellectual property matters;

•

data protection and privacy matters;

•

tax matters;

•

FDA and other regulatory matters; and

•

brokerage commissions or similar fees due in connection with the transactions contemplated by the Merger Agreement.

•

ownership and capital structure of its subsidiaries;

•

the necessary approvals by the Astria Board in connection with the transactions contemplated by the Merger Agreement and the necessary vote of Astria’s stockholders in connection with the Merger Agreement;

•

holding of necessary permits and compliance with government orders;

•

the absence of certain material changes or events since December 31, 2024;

•

compliance with anti-corruption laws and requirements pertaining to trade controls or sanctions laws;

•

title to its properties and real property leases;

•

employee benefit plans and labor matters;

•

compliance with environmental laws;

•

certain material contracts and commitments to which Astria is a party to or bound by;

•

information technology matters;

•

certain transactions with affiliates;

•

insurance policies;

•

the receipt by the Astria Board of an opinion of a financial advisor in connection with the transactions contemplated by the Merger Agreement; and

•

the inapplicability of antitakeover statutes in connection with the transactions contemplated by the Merger Agreement.

•

the due authorization and valid issuance of the shares of BioCryst Common Stock to be issued in connection with the Merger;

•

BioCryst and its controlled affiliates not owning or having owned 15% or more of the capital stock of Astria; and