Acumen Pharmaceuticals Inc美股招股说明书(2026-04-01版)

Up to 10,833,331 shares of Common Stock This prospectus relates to the resale or other disposition from time to time by the selling stockholders identified in this prospectus,including their transferees, pledgees, donees or successors, of up to 10,833,331 shares of our common stock, par value $0.0001 pershare (the “Common Stock”) that we issued in a private placement completed on March 16, 2026 (the “Private Placement”). The selling stockholders may, from time to time, sell, transfer or otherwise dispose of any or all of their shares of Common Stockor interests in shares of Common Stock on any stock exchange, market or trading facility on which the shares are traded or in privatetransactions. These dispositions may be at fixed prices, at prevailing market prices at the time of sale, at prices related to the prevailingmarket price, at varying prices determined at the time of sale, or at negotiated prices. See “Plan of Distribution” which begins on page13. We do not know when or in what amount the selling stockholders may dispose of or offer for sale the shares covered by thisprospectus. We are not offering any shares of Common Stock under this prospectus. We will not receive any of the proceeds from the sale ofCommon Stock by the selling stockholders. All expenses of registration incurred in connection with this offering are being borne byus. The selling stockholders will bear all discounts and commissions, if any, and expenses incurred by them for brokerage, accounting,tax or legal services or any other expenses incurred in their sale of shares of Common Stock. Our Common Stock is listed on the Nasdaq Global Select Market under the symbol “ABOS.” On March 31, 2026, the lastreported sale price of our Common Stock was $2.36 per share. We may amend or supplement this prospectus from time to time by filing amendments or supplements as required. You shouldread the entire prospectus and any amendments or supplements carefully before you make your investment decision. Investing in our securities involves risks. See “Risk Factors” on page4, and any applicable prospectus supplement, andunder similar headings in the other documents that are incorporated by reference into this prospectus. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminaloffense. Prospectus datedApril 1, 2026 TABLE OF CONTENTS ABOUT THIS PROSPECTUSPROSPECTUS SUMMARYRISK FACTORSDESCRIPTION OF PRIVATE PLACEMENTDESCRIPTION OF CAPITAL STOCKDISCLOSURE REGARDING FORWARD-LOOKING STATEMENTSUSE OF PROCEEDSSELLING STOCKHOLDERSPLAN OF DISTRIBUTIONLEGAL MATTERSEXPERTSWHERE YOU CAN FIND MORE INFORMATIONINCORPORATION OF DOCUMENTS BY REFERENCE ABOUT THIS PROSPECTUS This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission (the“SEC”) using a “shelf” registration or continuous offering process. You should read this prospectus and the information and documents incorporated by reference carefully. Such documents containimportant information you should consider when making your investment decision. See “Where You Can Find More Information” and“Incorporation of Documents by Reference” in this prospectus. This prospectus may be supplemented from time to time to add, update or change information in this prospectus. Any statementcontained in this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statementcontained in such prospectus supplement modifies or supersedes such statement. Any statement so modified will be deemed toconstitute a part of this prospectus only as so modified, and any statement so superseded will be deemed not to constitute a part of thisprospectus. Neither we nor the selling stockholders have authorized any other person to provide you with different information. Ifanyone provides you with different or inconsistent information, you should not rely on it. No dealer, salesperson or other person isauthorized to give any information or to represent anything not contained in this prospectus, any applicable prospectus supplement orany related free writing prospectus. This prospectus is not an offer to sell securities, and it is not soliciting an offer to buy securities, inany jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus or anyprospectus supplement, as well as information we have filed with the SEC that is incorporated by reference, is accurate as of the dateon the front of those documents only, regardless of the time of delivery of this prospectus or any applicable prospectus supplement, orany sale of a security. Our business, financial condition, results of operations and prospects may have changed since those dates. This prospectus contains summaries of certain p