Avidity Biosciences Inc美股招股说明书(2025-09-12版)

Table of Contents PROSPECTUS SUPPLEMENT(To Prospectus dated May9, 2024) 15,000,000 Shares Common Stock We are offering 15,000,000 shares of our common stock. Our common stock is listed on the Nasdaq Global Market under the symbol “RNA.” On September 11, 2025, the last reported sales price of ourcommon stock on the Nasdaq Global Market was $41.04 per share of common stock. Investing in our common stock involves risks. See the section titled “Risk Factors” beginning onpageS-6of this prospectus supplement and thedocuments incorporated by reference into this prospectus supplement. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passedupon the accuracy or adequacy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminaloffense. (1)See the section titled “Underwriting” for additional information regarding compensation payable to the underwriters. We have granted the underwriters an option for a period of 30 days to purchase up to anadditional 2,250,000shares of common stock from us at thepublic offering price, less the underwriting discounts and commissions. The underwriters expect to deliver the shares of common stock to purchasers on September 15, 2025. Joint Bookrunning Managers WellsFargoSecurities Table of Contents TABLE OF CONTENTS Prospectus Supplement About This Prospectus SupplementProspectus Supplement SummaryRisk FactorsCautionary Note Regarding Forward-Looking StatementsUse of ProceedsDilutionUnderwritingLegal MattersExpertsWhere You Can Find More Information; Incorporation By Reference Prospectus About this ProspectusWhere You Can Find More Information; Incorporation by ReferenceThe CompanyRisk FactorsCautionary Note Regarding Forward-Looking StatementsUse of ProceedsDividend PolicyDescription of Capital Stock Description of Debt Securities Table of Contents ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplement and the accompanying prospectus dated May9, 2024 are part of an automatic registration statement that we filed withthe Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process. This prospectus supplement and the accompanying prospectusrelate to the offer by us of shares of our common stock to certain investors. We provide information to you about this offering of shares of our commonstock in two separate documents that are bound together: (1)this prospectus supplement, which describes the specific details regarding this offering; and(2)the accompanying prospectus, which provides general information, some of which may not apply to this offering. Generally, when we refer to this“prospectus supplement,” we are referring to both documents combined. If information in this prospectus supplement is inconsistent with theaccompanying prospectus, you should rely on this prospectus supplement. However, if any statement in one of these documents is inconsistent with astatement in another document having a later date—for example, a document incorporated by reference in this prospectus supplement or theaccompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement as our business, financialcondition, results of operations and prospects may have changed since the earlier dates. You should read this prospectus supplement, the accompanyingprospectus, the documents and information incorporated by reference in this prospectus supplement and the accompanying prospectus, and any freewriting prospectus that we have authorized for use in connection with this offering when making your investment decision. You should also read andconsider the information in the documents we have referred you to under the headings “Where You Can Find More Information; Incorporation byReference.” You should rely only on information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectusor any free writing prospectus prepared by or on behalf of us or to which we have referred you. We have not, and the underwriters have not, authorizedanyone to provide you with information that is different. We are offering to sell and seeking offers to buy shares of our common stock only injurisdictions where offers and sales are permitted. The information contained in this prospectus supplement, the accompanying prospectus, thedocuments and information incorporated by reference in this prospectus supplement and the accompanying prospectus, and any free writing prospectusthat we have authorized for use in connection with this offering are accurate only as of their respective dates, regardless of the time of delivery of thisprospectus supplement or of any sale of our common stock. In this prospectus supplement, unless the context otherwise indicates, the terms “Avidity,” the “Company,” “we,” “our” and “us” or similar termsrefer to Avidity Biosciences, Inc