莱克欧疗法公司美股招股说明书（2025-11-26版）

1,250,015 Shares of Common Stock This prospectus relates to the offer and resale from time to time of up to 1,250,015 shares, or the Shares, of common stock of Lexeo Therapeutics,Inc., a Delaware corporation, or the Company, par value $0.0001 per share, or the Common Stock, by the selling stockholder identified in thisprospectus, including its transferees, pledgees or donees or their respective successors, or the Selling Stockholder. The Shares are issuable upon theexercise of outstanding pre-funded warrants to purchase shares of Common Stock held by the Selling Stockholder, or the Pre-Funded Warrants. ThePre-Funded Warrants were issued by us in a private placement, or the Private Placement, pursuant to a securities purchase agreement between us and the The Selling Stockholder may sell any, all or none of the Shares and we do not know when or in what amount the Selling Stockholder may sell itsShares hereunder following the date of this prospectus. The Selling Stockholder may sell the Shares described in this prospectus in a number of different We are not selling any Shares under this prospectus and will not receive any of the proceeds from the sale of the Shares by the SellingStockholder. Upon any exercise of the Pre-Funded Warrants by payment of cash we will receive nominal proceeds equal to the exercise price of thePre-Funded Warrants. We will pay the expenses associated with registering the sales by the Selling Stockholder other than any underwriting discounts Our Common Stock is listed on The Nasdaq Global Market, or Nasdaq, under the symbol “LXEO”. On November25, 2025, the last quoted saleprice for our Common Stock as reported on Nasdaq was $9.72 per share. We are an “emerging growth company” and a “smaller reporting company” as defined under the federal securities laws, and, as such, may elect tocomply with certain reduced public company reporting requirements for this prospectus and for future filings. See the section titled “Prospectus Investing in our securities involves a high degree of risk. Before buying any securities, you should carefully readthe discussion of the risks and uncertainties of investing in our securities described in the section titled “Risk Factors”beginning on page 6 of this prospectus, and under similar headings in any amendments or supplements to this You should rely only on the information contained in this prospectus or any prospectus supplement or amendment hereto. We have notauthorized anyone to provide you with different information. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities ordetermined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense. Table of Contents TABLE OF CONTENTS Incorporation by Reference Table of Contents ABOUT THIS PROSPECTUS This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or the SEC, using the“shelf” registration process. Under this shelf registration process, the Selling Stockholder and its permitted transferees may, from time to time, sell theshares offered by them as described in the section titled “Plan of Distribution.” We will not receive any proceeds from the sale by the Selling This prospectus provides you with a general description of the securities that may be offered. To the extent necessary, each time that the SellingStockholder offers and sells securities, we or the Selling Stockholder may provide a prospectus supplement to this prospectus that contains specificinformation about the securities being offered and sold and the specific terms of that offering. To the extent permitted by law, we may also authorize oneor more free writing prospectuses that may contain material information relating to these offerings. Such prospectus supplement or free writingprospectus may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency betweenthe information in this prospectus and the applicable prospectus supplement or free writing prospectus, you should rely on the prospectus supplement or Neither we nor the Selling Stockholder have authorized anyone to provide you with any information or to make any representations other thanthose contained, or incorporated by reference, in this prospectus, any applicable prospectus supplement or in any related free writing prospectus. Neitherwe nor the Selling Stockholder take any responsibility for, nor provide any assurance as to the reliability of, any other information that others may giveyou. This prospectus and any applicable prospectus supplement or any related free writing prospectus do not constitute an offer to sell or the solicitationof an offer to buy any securities other than the securities described in the applicable prospectus supplement or an offer to sell or the solicitation of anoffer to buy such securiti