Rapport Therapeutics Inc美股市值招股说明书(2025-09-10版)

Prospectus Supplement to Prospectus dated July9, 2025 9,615,385 Shares Common Stock We are offering 9,615,385 shares of our common stock. Our common stock is listed on The Nasdaq Global Market under the symbol “RAPP.” On September9, 2025, the last reported saleprice of our common stock on The Nasdaq Global Market was $28.03per share. Investing in shares of our common stock involves significant risks. See the section titled “Risk Factors” beginning onpageS-8of this prospectus supplement and page 1 of the accompanying prospectus, and in the documents that areincorporated by reference herein. You should read the entire prospectus supplement and the accompanying prospectus,including any information incorporated by reference herein or therein, carefully before you make your investment decision. We are an “emerging growth company” and “smaller reporting company” under the U.S. federal securities laws and, as such, wehave elected to comply with certain reduced public company reporting requirements for this prospectus supplement and future filings. See“Prospectus Supplement Summary-Implications of Being an Emerging Growth Company and Smaller Reporting Company.” Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or determined if this prospectus supplement and the accompanying prospectus is truthful or complete. Anyrepresentation to the contrary is a criminal offense. (1)See the section titled “Underwriting” for additional information regarding compensation payable to the underwriters. The underwriters may also exercise their option to purchase up to an additional 1,442,307 shares of our common stock from us, atthe public offering price, less the underwriting discounts and commissions, for 30 days after the date of this prospectus supplement. The underwriters expect to deliver the shares against payment on or about September 11, 2025. GoldmanSachs&Co.LLC Table of Contents TABLE OF CONTENTSPROSPECTUS SUPPLEMENT ABOUT THIS PROSPECTUS SUPPLEMENTSPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTSPROSPECTUS SUPPLEMENT SUMMARYTHE OFFERINGRISK FACTORSUSE OF PROCEEDSDILUTIONDIVIDEND POLICYUNDERWRITINGLEGAL MATTERSEXPERTSWHERE YOU CAN FIND MORE INFORMATIONINCORPORATION OF CERTAIN INFORMATION BY REFERENCE Table of Contents ABOUT THIS PROSPECTUS SUPPLEMENT This document is part of the registration statement on FormS-3that we filed with the Securities and Exchange Commission (the“SEC”) using a “shelf” registration process, and consists of two parts. The first part is this prospectus supplement, including the documentsincorporated by reference herein, which describes the specific terms of this offering. The second part, the accompanying prospectus,including the documents incorporated by reference therein, gives more general information, some of which may not apply to this offering.Generally, when we refer to the “prospectus,” we are referring to both parts combined. This prospectus supplement and any free writingprospectus we authorize for use in connection with this offering may add to, update or change information in the accompanyingprospectus and the documents incorporated by reference into this prospectus supplement or the accompanying prospectus. If information in this prospectus supplement is inconsistent with the accompanying prospectus or with any document incorporatedby reference herein or therein that was filed with the SEC before the date of this prospectus supplement, you should rely on theinformation contained in this prospectus supplement; provided, that if any statement in one of these documents is inconsistent with astatement in another document having a later date, the statement in the document having the later date modifies or supersedes the earlierstatement. This prospectus supplement, the accompanying prospectus, the documents incorporated by reference into each and any freewriting prospectus we authorize for use in connection with this offering include important information about us, the shares and otherinformation you should consider before purchasing the shares. See the sections entitled “Incorporation of Certain Information byReference” and “Where You Can Find More Information” in this prospectus supplement. We have not and the underwriters have not authorized anyone to provide you with any information other than the informationcontained in this prospectus supplement and the accompanying prospectus, including the documents incorporated by reference hereinand therein, and any free writing prospectus we have authorized for use in connection with this offering. We take no responsibility for, andcan provide no assurances as to the reliability of, any information that is in addition to or different from that contained or incorporated byreference in this prospectus supplement and the accompanying prospectus. You should not assume that the information contained in thisprospectus supplement and the accompanying prospect