This prospectus filed by MEI Pharma, Inc. (the “Company”) relates to the resale, from time to time by the selling stockholders named in this prospectus, or the selling stockholders, of up to (i) 25,301,407 shares (the “PIPE Shares”) of common stock, par value $0.0000002 per share (the “Common Stock”), issued to the investors in the PIPE Offering (as defined herein), which includes 2,084,509 shares of Common Stock issued prior to the date hereof upon the exercise of Pre-Funded Warrants (as defined herein) issued to one investor, (ii) 3,938,360 shares of Common Stock issuable upon exercise of the pre-funded warrants (the “Pre-Funded Warrants”), issued to one of the investors in the PIPE Offering, to purchase up to 3,938,360 shares of Common Stock with an exercise price per share equal to $0.0001 (the “Pre-Funded Warrant Shares”), (iii) 1,461,989 shares of Common Stock issuable upon exercise of the warrants (the “Asset Manager Warrants”) to purchase up to 1,461,989 shares of Common Stock (the “Asset Manager Warrant Shares”), (iv) 438,597 shares of Common Stock issuable upon exercise of the warrants (the “Strategic Advisor Warrants”) to purchase up to 438,597 shares of Common Stock with an exercise price per share equal to $4.10 (the “Strategic Advisor Warrant Shares”), and (v) 1,169,591 shares of Common Stock issuable upon exercise of the warrants (the “Placement Agent Warrants”) to purchase up to 1,169,591 shares of Common Stock with an exercise price per share equal to $4.10 (the “Placement Agent Warrant Shares”). The Asset Manager Warrants are exercisable at various prices per share of Common Stock as follows: (i) 584,795 shares of Common Stock at an exercise price of $3.42 per share; (ii) 292,398 shares of Common Stock at an exercise price of $3.93 per share; (iii) 292,398 shares of Common Stock at an exercise price of $4.62 per share; and (iv) 292,398 shares of Common Stock at an exercise price of $5.13 per share.

Of the PIPE Shares, 23,216,898 were issued pursuant to those certain Securities Purchase Agreements (the “Securities Purchase Agreements”) dated July 17, 2025 between the Company and the investors named therein in a private placement offering (the “PIPE Offering”) that closed on July 22, 2025. The remaining 2,084,509 PIPE Shares were issued following that offering pursuant to the exercise of pre-funded warrants issued to one of the investors in the PIPE Offering. The Asset Manager Warrants were issued to the asset manager under that certain Asset Management Agreement (the “Asset Management Agreement”) between the Company and such asset manager dated July 22, 2025. The Strategic Advisor Warrants were issued to the strategic advisor pursuant to that certain Strategic Advisor Agreement (the “Strategic Advisor Agreement”) between the Company and the strategic advisor named therein dated July 22, 2025. The Placement Agent Warrants were issued to American Capital Partners, LLC, in connection with the PIPE Offering pursuant to that certain Placement Agency Agreement (the “Placement Agency Agreement”) with Titan Partners Group LLC, a division of American Capital Partners, LLC (“Titan”) dated July 17, 2025. We refer to the PIPE Shares, Pre-Funded Warrant Shares, Asset Manager Warrant Shares, Strategic Advisor Warrant Shares and Placement Agent Warrant Shares collectively as the “Securities” in this prospectus.

The selling stockholders may from time to time sell, transfer or otherwise dispose of any or all of the Securities in a number of different ways and at varying prices. See the “Plan of Distribution” section of this prospectus for more information.

We are not selling any shares of Common Stock in this offering, and we will not receive any proceeds from the sale of shares by the selling stockholders. We will, however, receive up to approximately $394 in gross proceeds if the Pre-Funded Warrants are exercised in full, $6 million in gross proceeds if the Asset Manager Warrants are exercised in full, $1.8 million in gross proceeds if the Strategic Advisor Warrants are exercised in full, and $4.8 million in gross proceeds if the Placement Agent Warrants are exercised in full.

Our Common Stock is currently traded on The Nasdaq Capital Market (“Nasdaq”) under the symbol “MEIP.” On September 4, 2025, the closing price as reported on Nasdaq was $4.27 per share.

The selling stockholders may offer all or part of the Securities for resale from time to time through public or private transactions, at either prevailing market prices or at privately negotiated prices.

This prospectus provides a general description of the securities being offered. You should read this prospectus and the registration statement of which it forms a part before you invest in any securities.

We are a “smaller reporting company” under federal securities laws and as such, have elected to comply with reduced public company reporting requirements for this prospectus and the documents incorporated by reference herein and may elect to comply with reduced public company reporting requirements in future filings. See “Summary - Implications of Being a Smaller Reporting Company.”

Investing in our securities involves significant risks. We strongly recommend that you read carefully the risks we describe in this prospectus and in any accompanying prospectus supplement, as well as the risk factors that are incorporated by reference into this prospectus from our filings made with the Securities and Exchange Commission. See “Risk Factors” on page 8 of this prospectus.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

This prospectus supplement, the accompanying base prospectus and the documents we have filed with the SEC that are incorporated by reference herein and therein contain forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). In addition, from time to time we or our representatives have made or will make forward-looking statements in various other filings that we make with the SEC or in other documents, including press releases or other similar announcements. Forward-looking statements concern our current plans, intentions, beliefs, expectations and statements of future economic performance. Statements containing terms such as “will,” “may,” “believe,” “do not believe,” “plan,” “expect,” “intend,” “estimate,” “anticipate” and other phrases of similar meaning are considered to be forward-looking statements.

Forward-looking statements are based on our assumptions and are subject to known and unknown risks and uncertainties that could cause actual results to differ materially from those reflected in or implied by these forward-looking statements. Factors that might cause actual results to differ include, among others, those set forth under “Risk Factors” in this prospectus supplement and those discussed in “Management’s Discussion and Analysis of Financial Condition and Results of Operation” in our most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q and in our future periodic reports filed with the SEC, all of which are incorporated by reference herein. Readers are cautioned not to place undue reliance on any forward-looking statements contained in this prospectus supplement, the accompanying base prospectus or the documents we have filed with the SEC that are incorporated by reference herein and therein, which reflect management’s views and opinions only as of their respective dates. We assume no obligation to update forward-looking statements to reflect actual results, changes in assumptions or changes in other factors affecting such forward-looking statements, except to the extent required by applicable securities laws. You are advised, however, to consult any additional disclosures we have made or will make in the filings we make with the SEC, including reports on Forms 10-K, 10-Q and 8-K. All subsequent forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by the cautionary statements contained in this prospectus supplement, the accompanying base prospectus or any related issuer free writing prospectus.

This prospectus is part of a registration statement that we filed with the U.S. Securities and Exchange Commission, or the SEC, using a “shelf” registration process. By using a shelf registration statement, the selling stockholders may sell shares of our Common Stock from time to time and in one or more offerings as described in this prospectus and may provide a prospectus supplement to this prospectus that contains specific information about the shares of our Common Stock being offered and sold and the specific terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement or free writing prospectus may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement or free writing prospectus, you should rely on the prospectus supplement or free writing prospectus, as applicable. Before purchasing any shares of our Common Stock, you should carefully read both this prospectus and any applicable prospectus supplement and free writing prospectuses, together with the additional information described under the heading “Where You Can Find More Information.”

Neither we, the selling stockholders nor any underwriter has authorized anyone to provide you with any information or to make any representations other than those contained in this prospectus, any applicable prospectus supplement or any free writing prospectuses prepared by or on behalf of us or to which we have referred you. Neither we, the selling stockholders nor any underwriter takes responsibility for, and can provide no assurances as to the reliability of, any other information that others may give you. Neither we nor the selling stockholders will make an offer to sell the shares of our Common Stock in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus and any applicable prospectus supplement to this prospectus is accurate only as of the date on its respective cover, that the information appearing in any applicable free writing prospectus is accurate only as of the date of that free writing prospectus and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless indicated otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference in this prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

This prospectus includes summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or are incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described under the heading “Where You Can Find More Information.”

The terms “MEI Pharma,” the “Company,” “our,” “us” and “we,” as used in this prospectus, refer to MEI Pharma, Inc., a Delaware corporation, and its subsidiaries unless we state otherwise or the context indicates otherwise.

An investment in our Common Stock involves a high degree of risk. Before deciding whether to invest in our Common Stock, you should carefully consider the risks described below and discussed under the sections captioned “Risk Factors” contained in our most recent Annual Report on Form 10-K, as well as in any of our subsequent Quarterly Reports on Form 10-Q, which are incorporated by reference herein in their entirety, together with other information in this prospectus, the information and documents incorporated by reference in this prospectus, and in any prospectus supplement or free writing prospectus that we have authorized for use in connection with this offering. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be seriously harmed. This could cause the trading price of our Common Stock to decline, resulting in a loss of all or part of your investment.

Sales of a substantial number of shares of Common Stock could occur at any time, including sales by the selling stockholders under this prospectus. The issuance of new shares of Common Stock could result in resales of our shares of Common Stock by our current stockholders concerned about the potential ownership dilution of their holdings. In turn, these resales could have the effect of depressing the market price for our shares of Common Stock.

In order to raise additional capital, we may in the future offer additional shares of Common Stock or other securities convertible into or exchangeable for our shares of Common Stock that could result in further dilution to our current stockholders or result in downward pressure on the price of our Common Stock. We may sell our shares of Common Stock or other securities in any offering at prices that are higher or lower than the prices paid by the selling stockholders, and the investors purchasing shares or other securities in the future could have rights superior to existing stockholders. Moreover, to the extent that we issue options or warrants to purchase, or securities convertible into or exchangeable for, our shares of Common Stock in the future and those options, warrants or other securities are exercised, converted or exchanged, stockholders may experience further dilution.

There is no established public trading market for the Pre-Funded Warrants, Asset Manager Warrants, Strategic Advisor Warrants, or Placement Agent Warrants, and we do not expect a market to develop. In addition, we do not intend to apply to list the Pre-Funded Warrants, Strategic Advisor Warrants, or Placement Agent Warrants on any securities exchange or nationally recognized trading system. Without an active market, the liquidity of the Pre-Funded Warrants, Asset Manager Warrants, Strategic Advisor Warrants, and Placement Agent Warrants will be limited.

Until shares of Common Stock are acquired upon exercise of the Pre-Funded Warrants, Asset Manager Warrants, Strategic Advisor Warrants, or Placement Agent Warrants, holders of those warrants will have no rights with respect to the shares of Common Stock issuable upon exercise of such warrants. Upon exercise of the Pre-Funded Warrants, Asset Manager Warrants, Strategic Advisor Warrants, or Placement Agent Warrants, the holders will be entitled to exercise the rights of a holder of shares only as to matters for which the record date occurs after the issuance date for such shares of Common Stock.

We intend to use substantially all of the net proceeds from this offering to purchase Litecoin. Litecoin is a highly volatile asset that has traded between $59.26 and $146.61 per Litecoin on Coinbase in the 12 months ended July 3, 2025. More recently, during the second calendar quarter of 2025, Litecoin has traded between

$72.35 and $106.15 per Litecoin through June 30, 2025. In addition, Litecoin does not pay interest. The ability to generate a return on investment from the net proceeds of this offering will depend on whether there is appreciation in the value of Litecoin following our purchases. Future fluctuations in Litecoin’s trading prices may result in our converting Litecoin purchased with the net proceeds from this offering into cash with a value substantially below such net proceeds.

Historically, the crypto markets have been characterized by significant volatility in price, limited liquidity and trading volumes compared to sovereign currencies markets, relative anonymity, a developing regulatory landscape, potential susceptibility to market abuse and manipulation, compliance and internal control failures at exchanges, and various other risks inherent in its entirely electronic, virtual form and decentralized network. During times of market instability, we may not be able to sell our Litecoin at favorable prices or at all. Further, any Litecoin we hold with our custodians and transact with our trade execution partners does not enjoy the same protections as are available to cash or securities deposited with or transacted by institutions subject to regulation by the Federal Deposit Insurance Corporation or the Securities Investor Protection Corporation. Additionally, we may be unable to enter into term loans or other capital raising transactions collateralized by our unencumbered Litecoin or otherwise generate funds using our Litecoin holdings, including in particular during times of market instability or when the price of Litecoin has declined significantly. If we are unable to sell our Litecoin, enter into additional capital raising transactions using Litecoin as collateral, or otherwise generate funds using our Litecoin holdings, or if we are forced to sell our Litecoin at a significant loss, in order to meet our working capital requirements, our business and financial condition could be negatively impacted.

The introduction of a government-issued digital currency could eliminate or reduce the need or demand for private-sector issued crypto currencies, or significantly limit their utility. National governments around the world could introduce CBDCs, which could in turn limit the size of the market opportunity for cryptocurrencies, including Litecoin.

As Litecoin and other digital assets are relatively novel and the application of state and federal securities laws and other laws and regulations to digital assets is unclear in certain respects, it is possible that regulators in the United States or foreign countries may interpret or apply existing laws and regulations in a manner that adversely affects the price of Litecoin. The U.S. federal government, states, regulatory agencies, and foreign countries may also enact new laws and regulations, or pursue regulatory, legislative, enforcement or judicial actions, that could materially impact the price of Litecoin or the ability of individuals or institutions such as us to own or transfer Litecoin.

If Litecoin is determined to constitute a security for purposes of the federal securities laws, the additional regulatory restrictions imposed by such a determination could adversely affect the market price of Litecoin and in turn adversely affect the market price of our common stock. Moreover, the risks of us engaging in a Litecoin treasury strategy could create complications due to the lack of experience that third parties have with companies engaging in such a strategy, such as increased costs of director and officer liability insurance or the potential inability to obtain such coverage on acceptable terms in the future.

Under Sections 3(a)(1)(A) and (C) of the 1940 Act, a company generally will be deemed to be an “investment company” for purposes of the 1940 Act if (1) it is, or holds itself out as being, engaged primarily, or proposes to engage primarily, in the business of investing, reinvesting or trading in securities or (2) it is engaged, or proposes to engage, in the business of investing, reinvesting, owning, holding or trading in securities and it owns or proposes to acquire investment securities having a value exceeding 40% of the value of its total assets (exclusive of U.S. government securities and cash items) on an unconsolidated basis.

While the SEC has not stated a view as to whether Litecoin is or is not a “security” for purposes of the federal securities laws, a determination by the SEC or a court of competent jurisdiction that Litecoin is a security could lead to our meeting the definition of “investment company” under the 1940 Act, if the portion of our assets that consists of investments in Litecoin exceeds the 40% limit prescribed in the 1940 Act, which would subject us to significant additional regulatory requirements that could have a material adverse effect on our business and operations and may also require us to change the manner in which we conduct our business.

We intend to monitor our assets and income in order to conduct our business activities in a manner such that we do not fall within the definition of “investment company” under the 1940 Act or would qualify under one of the exemptions or exclusions provided by the 1940 Act and corresponding SEC rules. If Litecoin is determined to be a security for purposes of the federal securities laws, we would take steps to reduce our holdings of Litecoin as a percentage of our total assets. These steps may include, among others, selling Litecoin that we might otherwise hold for the long term and deploying our cash in assets that are not considered to be investment securities under the 1940 Act, in which case we may be forced to sell our Litecoin at unattractive prices. We may also seek to acquire additional assets that are not considered to be investment securities under the 1940 Act, and we may need to incur debt, issue additional equity or enter into other financing arrangements that are not otherwise attractive to our business. Any of these actions could have a material adverse effect on our results of operations and financial condition. Moreover, we can make no assurance that we would successfully be able to take the necessary steps to avoid meeting the definition of “investment company” under the 1940 Act and becoming subject to its requirements. If Litecoin is determined to constitute a security for purposes of the federal securities laws, and if we are not able to come within an available exemption or exclusion under the 1940 Act, then we would have to register as an investment company and require us to change the manner in which we conduct our business. In addition, such a determination could adversely affect the market price of Litecoin and in turn adversely affect the market price of our common stock.

Mutual funds, exchange-traded funds and their directors and management are subject to extensive regulation as “investment companies” and “investment advisers” under U.S. federal and state law; this regulation is intended for the benefit and protection of investors. We do not currently comply with and do not intend to voluntarily comply with these laws and regulations. This means, among other things, that the execution of or changes to our Litecoin strategy, our use of leverage, the manner in which our Litecoin is custodied, our ability to engage in transactions with affiliated parties and our operating and investment activities generally are not subject to the extensive legal and regulatory requirements and prohibitions that apply to investment companies and investment advisers. Consequently, our board of directors has broad discretion over the investment, leverage and cash management policies it authorizes, whether in respect of our Litecoin holdings or other activities we may pursue, and has the power to change our current policies, including our strategy of acquiring and holding Litecoin. See “Use of Proceeds.”

We expect that substantially all of the Litecoin we acquire will be held in custody accounts at U.S.-based institutional-grade digital asset custodians. Security breaches and cyberattacks are of particular concern with respect to digital assets, including Litecoin. Litecoin and other blockchain-based cryptocurrencies and the entities that provide services to participants in the Litecoin ecosystem have been, and may in the future be, subject to security breaches, cyberattacks, or other malicious activities. For example, in October 2021 it was reported that hackers exploited a flaw in the account recovery process and stole from the accounts of at least 6,000 customers of the Coinbase exchange, although the flaw was subsequently fixed and Coinbase reimbursed affected customers. Similarly, in November 2022, hackers exploited weaknesses in the security architecture of the FTX Trading digital asset exchange and reportedly stole over $400 million in digital assets from customers. A successful security breach or cyberattack could result in:

Further, any actual or perceived data security breach or cybersecurity attack directed at other companies with digital assets or companies that operate digital asset networks, regardless of whether we are directly impacted, could lead to a general loss of confidence in the broader Litecoin ecosystem or in the use of the Litecoin network to conduct financial transactions, which could negatively impact us.

Attacks upon systems across a variety of industries, including industries related to Litecoin, are increasing in frequency, persistence, and sophistication, and, in many cases, are being conducted by sophisticated, well-funded and organized groups and individuals, including state actors. The techniques used to obtain unauthorized, improper or illegal access to systems and information (including personal data and digital assets), disable or degrade services, or sabotage systems are constantly evolving, may be difficult to detect quickly, and often are not recognized or detected until after they have been launched against a target. These attacks may occur on our systems or those of our third-party service providers or partners. We may experience breaches of our security measures due to human error, malfeasance, insider threats, system errors or vulnerabilities or other irregularities. In particular, we expect that unauthorized parties will attempt to gain access to our systems and facilities, as well as those of our partners and third-party service providers, through various means, such as hacking, social engineering, phishing and fraud. Threats can come from a variety of sources, including criminal hackers, hacktivists, state-sponsored intrusions, industrial espionage, and insiders. In addition, certain types of attacks could harm us even if our systems are left undisturbed. For example, certain threats are designed to remain dormant or undetectable, sometimes for extended periods of time, or until launched against a target and we may not be able to implement adequate preventative measures. Further, there has been an increase in such activities due to the increase in work-from-home arrangements. The risk of cyberattacks could also be increased by cyberwarfare in connection with the ongoing Russia-Ukraine and Israel-Hamas conflicts, or other future conflicts, including potential proliferation of malware into systems unrelated to such conflicts. Any future breach of our operations or those of others in the Litecoin industry, including third-party services on which we rely, could materially and adversely affect our financial condition and results of operations.

We will not receive any proceeds from the sale of Common Stock by the selling stockholders. All of the net proceeds from the sale of our Common Stock will go to the selling stockholders as described below in the sections entitled “selling stockholders” and “Plan of Distribution.” However, we will receive up to approximately $394 in gross proceeds if the Pre-Funded Warrants are exercised in full, $6 million in gross proceeds if the Asset Manager Warrants are exercised in full, $1.8 million in gross proceeds if the Strategic Advisor Warrants are exercised in full, and $4.8 million in gross proceeds if the Placement Agent Warrants are exercised in full. To the extent we receive proceeds from the exercise of the Pre-Funded Warrants, Asset Manager Warrants, Strategic Advisor Warrants and Placement Agent Warrants, we expect to use such proceeds to acquire Litecoin. We have agreed to bear the expenses relating to the registration of the Securities for the selling stockholders.

Shares of our Common Stock are traded on The Nasdaq Capital Market (“Nasdaq”) under the symbol “MEIP.” Other than a special dividend paid in November 2023, we have never declared or paid, and do not anticipate declaring, or paying in the foreseeable future, any cash dividends on our capital stock. Future determinations as to the declaration and payment of dividends, if any, will be at the discretion of our Board of Directors and will depend on then existing conditions, including our operating results, financial conditions, contractual restrictions, capital requirements, business prospects and other factors our Board of Directors may deem relevant.

Instead of paying cash dividends, we anticipate that all of our earnings will be used to provide working capital, to support our operations, and to finance the growth and development of our business. The payment of dividends is within the discretion of the Board of Directors and will depend on our earnings, capital requirements, financial condition, prospects, applicable Delaware law, which, among other requirements, provides that dividends are only payable out of retained earnings, and other factors our Board of Directors might deem relevant. There are no restrictions that currently limit our ability to pay dividends on our Common Stock other than those generally imposed by applicable Delaware law.

The descriptions of the Securities contained in this prospectus, together with any applicable prospectus supplements, summarize the material terms and provisions of the Securities being offered pursuant to this prospectus.

The following description of our Common Stock is a summary. This summary is qualified in its entirety by reference to the Delaware General Corporation Law (“DGCL”) and to the complete text of our Amended and Restated Certificate of Incorporation and Bylaws.

Our authorized capital stock consists of shares made up of:

Holders of our Common Stock are entitled to one vote per share for the election of directors and on all other matters that require stockholder approval. Holders of shares of Common Stock do not have any cumulative voting rights. Subject to any preferential rights of any outstanding preferred stock, in the event of our liquidation, dissolution or winding up, holders of our Common Stock are entitled to share ratably in the assets remaining after payment of liabilities and the liquidation preferences of any outstanding preferred stock. Our Common Stock does not carry any redemption rights or any preemptive or preferential rights enabling a holder to subscribe for, or receive shares of, any class of our Common Stock or any other securities convertible into shares of any class of our Common Stock. Holders of our Common Stock have the right to participate ratably in dividend distributions. The shares of our Common Stock offered hereby, when issued, will be fully paid and nonassessable.

The following summary of certain terms and provisions of the Pre-Funded Warrants, which if exercised, will become the Pre-Funded Warrant Shares that are being offered hereby, is not complete and is subject to, and qualified in its entirety by, the provisions of the Pre-Funded Warrant, the form of which is filed as an exhibit to the registration statement of which this prospectus forms a part. Prospective investors should carefully review the terms and provisions of the form of Pre-Funded Warrant for a complete description of the terms and conditions of the Pre-Funded Warrants.

Duration and Exercise Price. Each Pre-Funded Warrant will have an initial exercise price per share equal to $0.0001. The Pre-Funded Warrants will be immediately exercisable or otherwise in accordance with the terms of the Pre-Funded Warrant and may be exercised at any time until the Pre-Funded Warrants are exercised in full. The exercise price and number of shares of Common Stock issuable upon exercise is subject to appropriate adjustment in the event of stock dividends, stock splits, reorganizations or similar events affecting our Common Stock and the exercise price

Exercisability. The Pre-Funded Warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us a duly executed exercise notice accompanied by payment in full for the number of our shares of Common Stock purchased upon such exercise (except in the case of a cashless exercise as discussed below). A holder (together with its affiliates) may not exercise any portion of the Pre-Funded Warrant to the extent that the holder would own more than 4.99% of the outstanding shares of Common Stock immediately after exercise (or, upon election by a holder prior to the issuance of any Pre-Funded Warrant, 9.99%), except that upon at least 61 days’ prior notice from the holder to us, the holder may increase the amount of ownership of outstanding stock after exercising the holder’s Pre-Funded Warrants up to 9.99% of the number of our shares of Common Stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Pre-Funded Warrants. No fractional shares of Common Stock will be issued in connection with the exercise of a Pre-Funded Warrant. In lieu of fractional shares, the Company shall, at its election, either pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the exercise price or round up to the next whole share of Common Stock.

Cashless Exercise. In lieu of making the cash payment otherwise contemplated to be made to us upon such exercise in payment of the aggregate exercise price, the holder of the Pre-Funded Warrant may exercise, in whole

or in part, at such time by means of a “cashless exercise” through which the holder shall be entitled to receive upon such exercise the number of shares of Common Stock determined according to a formula set forth in the Pre-Funded Warrant.

Transferability. Subject to applicable laws, a Pre-Funded Warrant may be transferred at the option of the holder upon surrender of the Pre-Funded Warrant to us together with the appropriate instruments of transfer.

Exchange Listing. There is no trading market available for the Pre-Funded Warrants on any securities exchange or nationally recognized trading system. We do not intend to list the Pre-Funded Warrants on any securities exchange or nationally recognized trading system.

Right as a Stockholder. Except as otherwise provided in the Pre-Funded Warrants or by virtue of such holder’s ownership of Common Stock, the holders of the Pre-Funded Warrants do not have the rights or privileges of holders of our Common Stock, including any voting rights, until they exercise their Pre-Funded Warrants.

Fundamental Transaction. In the event of a fundamental transaction, as described in the Pre-Funded Warrants and generally including any reorganization, recapitalization or reclassification of our shares of Common Stock, the sale, transfer or other disposition of all or substantially all of our properties or assets, our consolidation or merger with or into another person, the acquisition of more than 50% of our outstanding Common Stock, or any person or group becoming the beneficial owner of 50% of the voting power represented by our outstanding shares of Common Stock, then, upon any subsequent exercise of the Pre-Funded Warrant, the holder shall have the right to receive, for each share underlying the Pre-Funded Warrant that would have been issuable upon such exercise immediately prior to the occurrence of such fundamental transaction, at the option of the holder, the number of shares of Common Stock of the successor or acquiring corporation or of the Company, if it is the surviving corporation, and any additional consideration (for purposes of this paragraph, the “Alternate Consideration”) receivable as a result of such fundamental transaction by a holder of the number of shares of Common Stock for which the Pre-Funded Warrant is exercisable immediately prior to such fundamental transaction. If holders of Common Stock are given any choice as to the securities, cash or property to be received in a fundamental transaction, then the holder shall be given the same choice as to the Alternate Consideration it receives upon any exercise of the Pre-Funded Warrant following such fundamental transaction. If the Company is not the surviving entity following a fundamental transaction, then at the option of the holder, the surviving entity shall deliver to the holder a security of the surviving entity in exchange for the Pre-Funded Warrant.

The following summary of certain terms and provisions of the Asset Manager Warrants, which if exercised, will become the Asset Manager Warrant Shares that are being offered hereby, is not complete and is subject to, and qualified in its entirety by, the provisions of the Asset Manager Warrant, the form of which is filed as an exhibit to the registration statement of which this prospectus forms a part. Prospective investors should carefully review the terms and provisions of the form of Asset Manager Warrant for a complete description of the terms and conditions of the Asset Manager Warrants.

Duration and Exercise Price. The Asset Manager Warrants are exercisable at various prices per share of Common Stock as follows: (i) 584,795 shares of Common Stock at an exercise price of $3.42 per share; (ii) 292,398 shares of Common Stock at an exercise price of $3.93 per share; (iii) 292,398 shares of Common Stock at an exercise price of $4.62 per share; and (iv) 292,398 shares of Common Stock at an exercise price of $5.13 per share. The Strategic Advisor Warrants are exercisable at any point on or prior to 5:00 p.m. on July 22, 2030 (the “AM Warrant Termination Date”).

Exercisability. The Asset Manager Warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us, on or before the AM Warrant Termination Date, a duly executed exercise notice accompanied by payment in full for the number of our shares of Common Stock purchased upon such exercise (except in the case of a cashless exercise as discussed below). A holder (together with its affiliates) may not exercise any portion of the Asset Manager Warrant to the extent that the holder would own more 4.99% of the outstanding shares of Common Stock immediately after exercise (or, upon election by a holder prior to the issuance of any Pre-Funded Warrant, 9.99%), except that upon at least 61 days’ prior notice from the holder to us, the holder may increase or decrease the amount of ownership of outstanding stock after exercising the holder’s Asset Manager Warrants provided that in no event shall ownership exceed 9.99% of the number of our shares of Common Stock outstanding immediately after giving effect to the exercise, as such percentage

ownership is determined in accordance with the terms of the Asset Manager Warrants. No fractional shares of Common Stock will be issued in connection with the exercise of an Asset Manager Warrant. In lieu of fractional shares, at our election, we will either pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the exercise price or round up to the next whole share.

Cashless Exercise. In lieu of making the cash payment otherwise contemplated to be made to us upon such exercise in payment of the aggregate exercise price, the holder may elect instead to receive upon such exercise (either in whole or in part) the net number of shares of Common Stock determined according to a formula set forth in the Asset Manager Warrants.

Transferability. Subject to applicable laws, an Asset Manager Warrant may be transferred at the option of the holder upon surrender of the Asset Manager Warrant to us together with the appropriate instruments of transfer.

Exchange Listing. There is no trading market available for the Asset Manager Warrants on any securities exchange or nationally recognized trading system. We do not intend to list the Asset Manager Warrants on any securities exchange or nationally recognized trading system.

Right as a Stockholder. Except as otherwise provided in the Asset Manager Warrants or by virtue of such holder’s ownership of Common Stock, the holders of the Asset Manager Warrants do not have the rights or privileges of holders of our Common Stock, including any voting rights, until they exercise their Asset Manager Warrants.

The following summary of certain terms and provisions of the Strategic Advisor Warrants, which if exercised, will become the Strategic Advisor Warrant Shares that are being offered hereby, is not complete and is subject to, and qualified in its entirety by, the provisions of the Strategic Advisor Warrant, the form of which is filed as an exhibit to the registration statement of which this prospectus forms a part. Prospective investors should carefully review the terms and provisions of the form of Strategic Advisor Warrant for a complete description of the terms and conditions of the Strategic Advisor Warrants.

Duration and Exercise Price. Each Strategic Advisor Warrant will have an initial exercise price per share equal to $4.10. The Strategic Advisor Warrants will be immediately exercisable or otherwise in accordance with the terms of the Strategic Advisor Warrant and may be exercised at any time until July 22, 2030 (the “SA Warrant Termination Date”).

Exercisability. The Strategic Advisor Warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us, on or before the SA Warrant Termination Date, a duly executed exercise notice accompanied by payment in full for the number of our shares of Common Stock purchased upon such exercise (except in the case of a cashless exercise as discussed below). A holder (together with its affiliates) may not exercise any portion of the Strategic Advisor Warrant to the extent that the holder would own more than 4.99% of the outstanding shares of Common Stock immediately after exercise (or, upon election by a holder prior to the issuance of any Pre-Funded Warrant, 9.99%), except that upon at least 61 days’ prior notice from the holder to us, the holder may increase or decrease the amount of ownership of outstanding stock after exercising the holder’s Strategic Advisor Warrants provided that in no event shall ownership exceed 9.99% of the number of our shares of Common Stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Strategic Advisor Warrants. No fractional shares of Common Stock will be issued in connection with the exercise of a Strategic Advisor Warrant. In lieu of fractional shares, at our election, we will either pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the exercise price or round up to the next whole share.

Cashless Exercise. In lieu of making the cash payment otherwise contemplated to be made to us upon such exercise in payment of the aggregate exercise price, the holder may elect instead to receive upon such exercise (either in whole or in part) the net number of shares of Common Stock determined according to a formula set forth in the Strategic Advisor Warrants.

Transferability. Subject to applicable laws, a Strategic Advisor Warrant may be transferred at the option of the holder upon surrender of the Strategic Advisor Warrant to us together with the appropriate instruments of transfer.

Exchange Listing. There is no trading market available for the Strategic Advisor Warrants on any securities exchange or nationally recognized trading system. We do not intend to list the Strategic Advisor Warrants on any securities exchange or nationally recognized trading system.

Right as a Stockholder. Except as otherwise provided in the Strategic Advisor Warrants or by virtue of such holder’s ownership of Common Stock, the holders of the Strategic Advisor Warrants do not have the rights or privileges of holders of our Common Stock, including any voting rights, until they exercise their Strategic Advisor Warrants.

The following summary of certain terms and provisions of the Placement Agent Warrants, which if exercised, will become the Placement Agent Warrant Shares that are being offered hereby, is not complete and is subject to, and qualified in its entirety by, the provisions of the Placement Agent Warrant, the form of which is filed as an exhibit to the registration statement of which this prospectus forms a part. Prospective investors should carefully review the terms and provisions of the form of Placement Agent Warrant for a complete description of the terms and conditions of the Placement Agent Warrants.

Duration and Exercise Price. Each Placement Agent Warrant will have an initial exercise price per share equal to $4.10. The Placement Agent Warrants will be immediately exercisable or otherwise in accordance with the terms of the Placement Agent Warrant and may be exercised at any time until July 22, 2030. The exercise price and number of shares of Common Stock issuable upon exercise is subject to appropriate adjustment in the event of stock dividends, stock splits, reorganizations or similar events affecting our Common Stock and the exercise price.

Exercisability. The Placement Agent Warrants will be exercisable, at the option of the holder, in whole or in part, by delivering to us a duly executed exercise notice accompanied by payment in full for the number of our shares of Common Stock purchased upon such exercise (except in the case of a cashless exercise as discussed below). A holder (together with its affiliates) may not exercise any portion of the Placement Agent Warrant to the extent that the holder would own more than 4.99% (or, upon election by a Holder prior to the issuance of any Placement Agents Warrants, 9.99%) of the outstanding shares of Common Stock immediately after exercise, except that upon at least 61 days’ prior notice from the holder to us, the holder may increase or decrease the amount of ownership of outstanding stock after exercising the holder’s Placement Agent Warrants, provided that, the holder’s ownership may not exceed 9.99% of the number of our shares of Common Stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Placement Agent Warrants. No fractional shares of Common Stock will be issued in connection with the exercise of a Placement Agent Warrant. In lieu of fractional shares, at our election, we will either pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the exercise price or round up to the next whole share.

Cashless Exercise. In lieu of making the cash payment otherwise contemplated to be made to us upon such exercise in payment of the aggregate exercise price, the holder may elect instead to receive upon such exercise (either in whole or in part) the net number of shares of Common Stock determined according to a formula set forth in the Placement Agent Warrants.

Transferability. Subject to applicable securities and other laws and procedures intended to ensure compliance with such laws, the Placement Agent Warrants may be transferred at the option of the holder upon surrender of the warrant to us together with the appropriate instruments of transfer, except that transferability of the Placement Agent Warrants is subject to applicable FINRA rules.

Exchange Listing. There is no trading market available for the Placement Agent Warrants on any securities exchange or nationally recognized trading system. We do not intend to list the Placement Agent Warrants on any securities exchange or nationally recognized trading system.

Right as a Stockholder. Except as otherwise provided in the Placement Agent Warrants or by virtue of such holder’s ownership of Common Stock, the holders of the Placement Agent Warrants do not have the rights or privileges of holders of our Common Stock, including any voting rights, until they exercise their Placement Agent Warrants.

Fundamental Transaction. In the event of a fundamental transaction, as described in the Placement Agent Warrants and generally including any reorganization, recapitalization or reclassification of our shares of Common

Stock, the sale, transfer or other disposition of all or substantially all of our properties or assets, our consolidation or merger with or into another person, the acquisition of more than 50% of our outstanding Common Stock, or any person or group becoming the beneficial owner of 50% of the voting power represented by our outstanding shares of Common Stock, the holders of the Placement Agent Warrants will be entitled to receive upon exercise of the Placement Agent Warrants the number of shares of Common Stock of the successor or acquiring corporation or of the Company, if it is the surviving corporation, and any additional consideration (for purposes of this paragraph, the “Alternate Consideration”) receivable as a result of such fundamental transaction by a holder of the number of shares of Common Stock for which the Placement Agent Warrant is exercisable immediately prior to such fundamental transaction. If holders of Common Stock are given any choice as to the securities, cash or property to be received in a fundamental transaction, then the holder shall be given the same choice as to the Alternate Consideration it receives upon any exercise of the Placement Agent Warrant following such fundamental transaction. If the Company is not the surviving entity following a fundamental transaction, then at the option of the holder, the surviving entity shall deliver to the holder a security of the surviving entity in exchange for the Placement Agent Warrant.

We are subject to the provisions of Section 203 of the DGCL regulating corporate takeovers. This statute prevents certain Delaware corporations, under certain circumstances, from engaging in a “business combination” with:

A “business combination” includes a merger or sale of more than 10% of our assets. However, the above provisions of Section 203 do not apply if:

Our transfer agent is Computershare Trust Company, N.A. located at 150 Royall Street, Canton, MA 02021.

The shares of Common Stock being offered by the selling stockholders are those previously issued to the selling stockholders, or those issuable upon exercise of previously issued warrants to purchase shares of Common Stock. We are registering the Securities in order to permit the selling stockholders to offer the Securities for resale from time to time.

The following table sets forth, based on information provided to us by or on behalf of the selling stockholders or known to us, the name of the selling stockholders and the number of shares of our Common Stock beneficially owned by the selling stockholders before and after this offering.

The table below lists the selling stockholders and other information regarding the beneficial ownership (as determined under Section 13(d) of the Exchange Act, and the rules and regulations thereunder) of the shares of Common Stock held by each of the selling stockholders.

The selling stockholders may sell all, some or none of their shares in this offering. See “Plan of Distribution.” The percentages of ownership of the selling stockholders in the below table is based upon 32,837,743 shares of common stock outstanding as of August 25, 2025.

Each selling stockholder of the Securities and any of their pledgees, assignees, and successors-in-interest may, from time to time, sell any or all of their securities covered hereby on the principal trading market or any other stock exchange, market or trading facility on which the Securities are traded or in private transactions. These sales may be at fixed or negotiated prices. A selling stockholder may use any one or more of the following methods when selling securities:

The selling stockholders may also sell securities under Rule 144 or any other exemption from registration under the Securities Act, if available, rather than under this prospectus.

Broker-dealers engaged by the selling stockholders may arrange for other brokers-dealers to participate in sales. Broker-dealers may receive commissions or discounts from the selling stockholders (or, if any broker-dealer acts as agent for the purchaser of securities, from the purchaser) in amounts to be negotiated, but, except as set forth in a supplement to this prospectus, in the case of an agency transaction not in excess of a customary brokerage commission in compliance with FINRA Rule 2121; and in the case of a principal transaction a markup or markdown in compliance with FINRA Rule 2121.

In connection with the sale of the securities or interests therein, the selling stockholders may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of the securities in the course of hedging the positions they assume. The selling stockholders may also sell securities short and deliver these securities to close out their short positions, or loan or pledge the securities to broker-dealers that in turn may sell these securities. The selling stockholders may also enter into option or other transactions with broker-dealers or other financial institutions or create one or more derivative securities which require the delivery to such broker-dealer or other financial institution of securities offered by this prospectus, which securities such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction).

The selling stockholders and any broker-dealers or agents that are involved in selling the securities may be deemed to be “underwriters” within the meaning of the Securities Act in connection with such sales. In such event, any commissions received by such broker-dealers or agents and any profit on the resale of the securities purchased by them may be deemed to be underwriting commissions or discounts under the Securities Act. Each selling stockholder has informed the Company that it does not have any written or oral agreement or understanding, directly or indirectly, with any person to distribute the securities.

We are required to pay certain fees and expenses incurred by the Company incident to the registration of the Securities. The Company has agreed to indemnify the selling stockholders against certain losses, claims, damages and liabilities, including liabilities under the Securities Act.

We are obligated to maintain the effectiveness of this registration statement until all of the PIPE Shares, Pre-Funded Warrant Shares, and Strategic Advisor Warrant Shares, registered pursuant to it (i) have been sold, thereunder or pursuant to Rule 144, or (ii) may be sold without volume or manner-of-sale restrictions pursuant to Rule 144 and without the requirement for the Company to be in compliance with the current public information

requirement under Rule 144. Pursuant to the terms of the Placement Agent Warrants, we are also obligated to register the Placement Agent Warrant Shares. The resale Securities will be sold only through registered or licensed brokers or dealers if required under applicable state securities laws. In addition, in certain states, the resale Securities covered hereby may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from the registration or qualification requirement is available and is complied with.

Under applicable rules and regulations under the Exchange Act, any person engaged in the distribution of the resale securities may not simultaneously engage in market making activities with respect to the shares of Common Stock for the applicable restricted period, as defined in Regulation M, prior to the commencement of the distribution. In addition, the selling stockholders will be subject to applicable provisions of the Exchange Act and the rules and regulations thereunder, including Regulation M, which may limit the timing of purchases and sales of the shares of Common Stock by the selling stockholders or any other person. We will make copies of this prospectus available to the selling stockholders and have informed them of the need to deliver a copy of this prospectus to each purchaser at or prior to the time of the sale (including by compliance with Rule 172 under the Securities Act).

The validity of the securities being offered hereby will be passed upon for us by Morgan, Lewis & Bockius LLP, Philadelphia, Pennsylvania. Certain partners of Morgan, Lewis & Bockius LLP own a number of shares of our common stock which represent less than 0.1% of the total outstanding common stock.

The consolidated financial statements of MEI Pharma, Inc. incorporated by reference in this Prospectus have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report. Such financial statements are incorporated by reference in reliance upon the report of such firm, given their authority as experts in accounting and auditing.

The consolidated financial statements of MEI Pharma, Inc. as of June 30, 2023 and for the year then ended, incorporated by reference in this prospectus and in the registration statement, have been so incorporated in reliance on the report of BDO USA, P.C., an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The SEC allows us to “incorporate by reference” the information we file with it, which means that we can disclose important information to you by referring you to those documents instead of having to repeat the information in this prospectus. The information incorporated by reference is considered to be part of this prospectus, and because we are a smaller reporting company, later information that we file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future filings (including those made after the initial filing of the registration statement of which this prospectus is a part and prior to the effectiveness of such registration statement) we will make with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act until the termination of the offering of the shares covered by this prospectus.

As a smaller reporting company, we also are incorporating by reference any future information filed (rather than furnished) by us with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, after the date of the initial filing of the registration statement of which this prospectus is a part and before the effective date of the registration statement and after the date of this prospectus until the termination of the offering. Any statements contained in a previously filed document incorporated by reference into this prospectus is deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus, or in a subsequently filed document also incorporated by reference herein, modifies or supersedes that statement.

Notwithstanding the foregoing, unless specifically stated to the contrary, none of the information that is not deemed “filed” with the SEC, including information furnished under Items 2.02 or 7.01 of any Current Report on Form 8-K, will be incorporated by reference into, or otherwise included in, this prospectus.

We make available, free of charge, through our website at https://meipharma.com/ under “Investor and Media” our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. Information contained on our website is not incorporated by reference into this prospectus and should not be considered part of this prospectus or any applicable prospectus supplement. In addition, the SEC maintains an Internet website that contains reports, proxy and information statements, and other information that we file with the SEC at www.sec.gov. You may also obtain, free of charge, a copy of any of these documents (other than exhibits to these documents unless the exhibits are specifically incorporated by reference into these documents or referred to in this prospectus) by writing or calling us at the following address and telephone number.

You should rely only on the information incorporated by reference or provided in this prospectus or any prospectus supplement. We have not authorized anyone to provide you with different information. Neither we nor the selling stockholders are making an offer of the Common Stock in any state where the offer is not permitted. You should not assume that the information in this prospectus or in the documents incorporated by reference is accurate as of any date other than the date on the front of this prospectus or those documents.

We are subject to the information requirements of the Exchange Act, and in accordance with the Exchange Act, file annual, quarterly and special reports, proxy statements and other information with the SEC. These documents may be accessed through the SEC’s electronic data gathering, analysis and retrieval system, or EDGAR, via electronic means, including the SEC’s home page on the Internet (www.sec.gov). Our corporate website address is https://meipharma.com/. Information contained on or accessible through our website is not a part of this prospectus, and the inclusion of our website address in this prospectus is an inactive textual reference only.

This prospectus is part of the registration statement on Form S-3 we filed with the SEC under the Securities Act and does not contain all the information set forth in the registration statement. Whenever a reference is made in this prospectus to any of our contracts, agreements or other documents, the reference may not be complete and you should refer to the exhibits that are a part of the registration statement or the exhibits to the reports or other documents incorporated by reference into this prospectus for a copy of such contract, agreement or other document.

We have not authorized any dealer, salesperson or other person to give any information or represent anything not contained in this prospectus. You must not rely on any unauthorized information. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus does not offer to sell any securities in any jurisdiction where it is unlawful. Neither the delivery of this prospectus, nor any sale made hereunder, shall create any implication that the information in this prospectus is correct after the date hereof.