Rhythm Pharmaceuticals Inc美股招股说明书(2025-07-10版)

Common Stock We are offering 2,058,824 shares of our common stock. Our common stock is listed on the Nasdaq Global Market under the symbol “RYTM.” On July9, 2025,the last reported sale price for our common stock on the Nasdaq Global Market was $89.00 per share. INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE THE “RISK FACTORS” ON PAGES-6OF THIS PROSPECTUS SUPPLEMENT AND IN THE DOCUMENTS INCORPORATED BYREFERENCE IN THIS PROSPECTUS SUPPLEMENT CONCERNING FACTORS YOU SHOULDCONSIDER BEFORE INVESTING IN OUR COMMON STOCK. Neither the Securities and Exchange Commission nor any state securities commission has approved ordisapproved of these securities or passed upon the accuracy or adequacy of this prospectus supplement or theaccompanying prospectus. Any representation to the contrary is a criminal offense. Per Share ofCommon StockTotalPublic offering price$85.00$175,000,040Underwriting discounts and commissions$5.10$10,500,002Proceeds to us, before expenses$79.90$164,500,038(1) (1)We have also agreed to reimburse the underwriters for certain of their expenses. See “Underwriting”beginning on pageS-17of this prospectus supplement for more information about these arrangements. We have granted the underwriters the right to purchase up to an additional 308,823 shares of ourcommon stock from us at the public offering price, less underwriting discounts and commissions. Theunderwriters may exercise this right at any time, in whole or in part, within 30days following the date ofthis prospectus supplement. The underwriters expect to deliver the shares against payment on or about July 11, 2025. Joint Book-Running Managers Canaccord Genuity Citizens Capital Markets The date of this prospectus supplement is July 9, 2025 TABLE OF CONTENTS PageProspectus SupplementABOUT THIS PROSPECTUS SUPPLEMENTS-1CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSS-3PROSPECTUS SUPPLEMENT SUMMARYS-4THE OFFERINGS-5RISK FACTORSS-6USE OF PROCEEDSS-8DIVIDEND POLICYS-9DILUTIONS-10MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCESS-12UNDERWRITINGS-17LEGAL MATTERSS-25EXPERTSS-25WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCES-26 PageProspectusABOUT THIS PROSPECTUS1WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE2THE COMPANY3RISK FACTORS4USE OF PROCEEDS5DESCRIPTION OF CAPITAL STOCK6DESCRIPTION OF DEBT SECURITIES10DESCRIPTION OF OTHER SECURITIES17GLOBAL SECURITIES18PLAN OF DISTRIBUTION22LEGAL MATTERS23EXPERTS23 ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts. The first part is this prospectus supplement, which describes the terms ofthe offering of the securities offered hereby and also adds to and updates the information contained in theaccompanying prospectus and the documents incorporated by reference into this prospectus supplement andthe accompanying prospectus. The second part is the accompanying prospectus, which provides moregeneral information, some of which may not apply to this offering and some of which may have beensupplemented or superseded by information in this prospectus supplement or documents incorporated ordeemed to be incorporated by reference into this prospectus supplement that we filed with the SECsubsequent to the date of this prospectus supplement. To the extent that there is any conflict between theinformation contained in this prospectus supplement, on the one hand, and the information contained in theaccompanying prospectus or any document incorporated by reference herein or therein, on the other hand,you should rely on the information in this prospectus supplement or any free writing prospectus. If anystatement in one of these documents is inconsistent with a statement in another document having a laterdate — for example, a document incorporated by reference in this prospectus supplement — the statement inthe document having the later date modifies or supersedes the earlier statement. This prospectus supplement and the accompanying prospectus are part of a registration statement thatwe filed with the Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process.Under this shelf registration process, we may offer from time to time various securities, including thecommon stock that we are offering under this prospectus supplement and the accompanying prospectus.Such registration statement also includes exhibits that provide more detail on the matters discussed in thisprospectus supplement and the accompanying prospectus. You should read this prospectus supplement, theaccompanying prospectus, including the information incorporated by reference, the exhibits filed with theSEC, and any free writing prospectus that we have authorized for use in connection with this offering, intheir entirety before making an investment decision. You should rely only on the information contained in this prospectus supplement, the accompanyingprospectus or incorporated herein or therein by reference and in any free writing prospectus that we haveauthorized for use in