ImageneBio Inc美股招股说明书(2025-10-30版)

ImageneBio, Inc. 2,508,337 Shares of Common Stock This prospectus supplement supplements the prospectus dated September15, 2025 (the “Prospectus”), which forms a part of our registrationstatement on FormS-1(No.333-290108). This prospectus supplement is being filed to update and supplement the information in the Prospectus withcertain information contained in our Current Reports on Form8-K,filed with the Securities and Exchange Commission onOctober 10, 2025,October22, 2025andOctober29, 2025(collectively, the “Current Reports”). Accordingly, we have attached the Current Reports in relevant part to thisprospectus supplement. The Prospectus and this prospectus supplement relate to the proposed offer and resale or other disposition from time to time by the sellingstockholders identified in this prospectus of 2,508,337 shares of common stock, par value $0.001 per share, (the “Common Stock”) of ImageneBio, Inc. Our Common Stock is listed on the Nasdaq Capital Market under the ticker symbol “IMA.” On October29, 2025, the last reported sales price ofour Common Stock was $8.79 per share. This prospectus supplement should be read in conjunction with the Prospectus, including any amendments or supplements to it, which is to bedelivered with this prospectus supplement. This prospectus supplement is qualified by reference to the Prospectus, including any amendments orsupplements thereto, except to the extent that the information provided by this prospectus supplement supersedes information contained in theProspectus. This prospectus supplement is not complete without, and may not be delivered or used except in conjunction with, the Prospectus, including anyamendments or supplements to it. Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertaintiesdescribed in the section titled “Risk Factors” beginning on page 6 of the Prospectus, and under similar headings in anyamendments or supplements to the Prospectus. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, orpassed upon the accuracy or adequacy of this prospectus supplement. Any representation to the contrary is a criminal offense. UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549 CURRENT REPORTPursuant to Section 13 OR 15(d)of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 10, 2025 IMAGENEBIO, INC. (Exact name of registrant as specified in its charter) 001-40287(CommissionFile Number) Registrant’s telephone number, including area code: (858)345-6265 Check the appropriate box below if the Form8-Kfiling is intended to simultaneously satisfy the filing obligation of the registrant under any of thefollowing provisions: ☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)☐Soliciting material pursuant to Rule14a-12under the Exchange Act (17 CFR240.14a-12)☐Pre-commencementcommunications pursuant to Rule14d-2(b)under the Exchange Act (17 CFR240.14d-2(b))☐Pre-commencementcommunications pursuant to Rule13e-4(c)under the Exchange Act (17 CFR240.13e-4(c)) Securities registered pursuant to Section 12(b) of the Act: Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of thischapter) or Rule12b-2of the Securities Exchange Act of 1934(§240.12b-2of this chapter). Emerging growth company☒ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with anynew or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐ On October10, 2025, Jotin Marango, M.D., Ph.D., our Chief Financial Officer and principal financial officer, provided notice of his resignation,effective October20, 2025. Dr.Marango’s resignation was not due to any disagreement with the Company. We plan to conduct a search forDr.Marango’s replacement. SIGNATURE Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by theundersigned hereunto duly authorized. IMAGENEBIO, INC. UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549 FORM8-K CURRENT REPORTPursuant to Section13 OR 15(d)of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported):October 21, 2025 IMAGENEBIO, INC. (Exact name of registrant as specified in its charter) 001-40287(CommissionFile Number) Registrant’s telephone number, including area code:(858)345-6265 Not Applicable(Former Name or Former Address, if Changed Since Last Report) Check the appropriate box below if theForm8-Kfilingis intended to simultaneously satisfy the filing obligation of the registrant under any of thefollowing provisions: ☐Written communications pursuant to Rule 425 under the Securities Ac