IDEAYA生物科学美股招股说明书(2026-06-09版)

5,555,556 Shares of Common Stock Pre-funded Warrants to Purchase 5,555,576 Shares of Common Stock IDEAYA Biosciences, Inc. is offering 5,555,556 shares of its common stock and, in lieu of offering shares of its common stock to certaininvestors, pre-funded warrants to purchase 5,555,576 shares of its common stock. The purchase price of each pre-funded warrant is theprice per share at which shares of common stock are being sold to the public in this offering, minus $0.0001, which is the exercise price ofeach pre-funded warrant. This prospectus supplement also relates to the offering of the shares of common stock issuable upon theexercise of such pre-funded warrants. Our common stock is listed on the Nasdaq Global Select Market under the symbol “IDYA.” The last reported sale price of our commonstock on the Nasdaq Global Select Market on June8, 2026 was $31.48 per share. We do not intend to list the pre-funded warrants on theNasdaq Global Select Market or any other national securities exchange or nationally recognized trading system. (1)See “Underwriting” for additional information regarding underwriting compensation. We have granted the underwriters the right to purchase up to 1,666,669 additional shares of common stock from us at the public offeringprice, less the underwriting discounts and commission, within 30 days from the date of this prospectus supplement. Investing in our common stock and pre-funded warrants involves significant risks. See the section titled “Risk Factors” onpageS-6 of this prospectus supplement and in the documents incorporated by reference in this prospectus supplementconcerning factors you should consider before investing in our common stock. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities orpassed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to thecontrary is a criminal offense. The underwriters expect to deliver the shares of common stock and pre-funded warrants to purchase shares of common stock topurchasers on or about June 10, 2026. TDCowen WedbushPacGrow June 8, 2026 Table of Contents Table of Contents Prospectus Supplement About this Prospectus SupplementProspectus Supplement SummaryThe OfferingRisk FactorsCautionary Statement RegardingForward-Looking StatementsMarket and Industry DataUse of ProceedsDividend PolicyDescription of Pre-Funded WarrantsDilutionMaterial U.S.Federal Income Tax ConsequencesUnderwritingLegal MattersExpertsWhere You Can Find More Information; Incorporation by Reference ProspectusABOUT THIS PROSPECTUSWHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCEABOUT IDEAYARISK FACTORSUSE OF PROCEEDSDESCRIPTION OF CAPITAL STOCKDESCRIPTION OF OTHER SECURITIESGLOBAL SECURITIESPLAN OF DISTRIBUTIONLEGAL MATTERSEXPERTS Table of Contents About this Prospectus Supplement This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering of commonstock and pre-funded warrants and also adds to and updates information contained in the accompanying prospectus and the documentsincorporated by reference into this prospectus supplement and the accompanying prospectus. The second part is the accompanyingprospectus dated May5, 2026, included in our registration statement on Form S-3 (File No.333-295560), along with the documentsincorporated by reference therein, which provides more general information, some of which may not apply to this offering. Generally, whenwe refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between theinformation contained in this prospectus supplement, on the one hand, and the information contained in the accompanying prospectus orin any document incorporated by reference that was filed with the Securities and Exchange Commission, or the SEC, before the date ofthis prospectus supplement, on the other hand, you should rely on the information contained in this prospectus supplement. If anystatement in one of these documents is inconsistent with a statement in another document having a later date—for example, a documentincorporated by reference in the accompanying prospectus—the statement in the document having the later date modifies or supersedesthe earlier statement. This prospectus supplement and the accompanying prospectus are part of a “shelf” registration statement that we filed with the SEC.Under this shelf registration process, we may offer from time to time various securities, of which this offering of shares of our commonstock and pre-funded warrants is a part. Such registration statement also includes exhibits that provide more detail on the mattersdiscussed in this prospectus supplement and the accompanying prospectus. You should read this prospectus supplement, theaccompanying prospectus, including the information incorporated by reference