IDEAYA生物科学美股招股说明书(2026-05-05版)

Up to $350,000,000 Common Stock On January19, 2024, we entered into a sales agreement with Jefferies LLC, or Jefferies, relating to the offer and sale of shares of our commonstock, par value $0.0001 per share, having an aggregate sales price of up to $350,000,000 from time to time under this prospectus supplementand the accompanying prospectus through Jefferies acting as our sales agent. Under the sales agreement, we have offered and sold shares ofour common stock having an aggregate gross sales price of $193,447,003.19 through the date of this prospectus supplement pursuant to a priorprospectus supplement and prospectus. Accordingly, as of the date of this prospectus supplement, shares of our common stock having anaggregate gross sales price of up to $156,552,996.81 remain available for offer and sale pursuant to the sales agreement. Our common stock is listed on the Nasdaq Global Select Market under the symbol “IDYA.” On May1, 2026, the last reported sale price of ourcommon stock on the Nasdaq Global Select Market was $28.19 per share. Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectus will be made by any method permittedthat is deemed to be an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended, or theSecurities Act. Jefferies is not required to sell any specific amount of securities, but will act as our sales agent using commercially reasonableefforts consistent with its normal trading and sales practices, on mutually agreed terms between Jefferies and us. There is no arrangement forfunds to be received in any escrow, trust or similar arrangement. The compensation to Jefferies for sales of common stock pursuant to the sales agreement will be an amount up to 3.0% of the gross proceeds ofany shares of common stock sold under the sales agreement. In connection with the sale of the common stock on our behalf, Jefferies will bedeemed to be an “underwriter” within the meaning of the Securities Act and the compensation of Jefferies will be deemed to be underwritingcommissions or discounts. We have also agreed to provide indemnification and contribution to Jefferies with respect to certain liabilities, includingliabilities under the Securities Act or the Securities Exchange Act of 1934, as amended. Our business and an investment in our common stock involve significant risks. These risks are described under the caption“Risk Factors” beginning on page S-7 of this prospectus supplement and in the documents incorporated by reference in thisprospectus supplement or the accompanying prospectus concerning factors you should consider before investing in ourcommon stock. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of thesesecurities or passed upon the adequacy or accuracy of this prospectus supplement. Any representation to the contrary is acriminal offense. Jefferies May5, 2026 TABLE OF CONTENTSPROSPECTUS SUPPLEMENT PROSPECTUS Table of Contents ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplement is part of a registration statement that we have filed with the U.S. Securities and Exchange Commission, or the SEC,utilizing a “shelf” registration process. By using an automatic shelf registration statement, we may offer shares of our common stock having anaggregate offering price of up to $156,552,996.81 from time to time under this prospectus supplement at prices and on terms to be determined bymarket conditions at the time of offering. We provide information to you about this offering of shares of our common stock in two separate documents that are bound together: (1)thisprospectus supplement, which describes the specific details regarding this offering; and (2)the accompanying prospectus, which provides generalinformation, some of which may not apply to this offering. Generally, when we refer to this “prospectus,” we are referring to both documentscombined. If information in this prospectus supplement is inconsistent with the accompanying prospectus, you should rely on this prospectussupplement. However, if any statement in one of these documents is inconsistent with a statement in another document having a later date—forexample, a document incorporated by reference in this prospectus supplement—the statement in the document having the later date modifies orsupersedes the earlier statement as our business, financial condition, results of operations and prospects may have changed since the earlierdates. We have not, and Jefferies has not, authorized anyone to provide you with information, or to make any representation, different from thatcontained in or incorporated by reference in this prospectus supplement, the accompanying prospectus and any free writing prospectus preparedby or on behalf of us or to which we have referred you. We and Jefferies take no responsibility for, and can provide no assurance as to thereliability of,