ImageneBio Inc美股招股说明书(2026-04-13版)

2,508,337 Shares of Common Stock This prospectus supplement supplements the prospectus dated April2, 2026 (the “Prospectus”), which forms a part of our registration statementon Form S-1 (No. 333-290108), as amended. This prospectus supplement is being filed to update and supplement the information in the Prospectus withcertain information contained in our Current Report on Form 8-K, filed with the Securities and Exchange Commission on April13, 2026 (the “CurrentReport”). Accordingly, we have attached the Current Report in relevant part to this prospectus 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 April10, 2026, the last reported sales price of ourCommon Stock was $4.74 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 FORM 8-K CURRENT REPORTPursuant to Section 13 OR 15(d)of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 12, 2026 IMAGENEBIO, INC. (Exact name of registrant as specified in its charter) 001-40287(CommissionFile Number) 81-1697316(I.R.S. EmployerIdentification No.) 12526 High Bluff Drive, Suite 345San Diego, California(Address of principal executive offices) 92130(Zip Code) 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 the Form 8-K filing 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 Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-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 Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of 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.☐ Item 1.01Entry into a Material Definitive Agreement. Securities Purchase Agreement On April12, 2026, ImageneBio, Inc., a Delaware corporation (the “Company”), entered into a Securities Purchase Agreement (the “PurchaseAgreement”) with certain institutional and accredited investors (the “Investors”), pursuant to which the Company agreed to sell and issue pre-fundedwarrants to purchase shares of the Company’s voting common stock, par value $0.001 (“Common Stock” and the shares subject to the pre-fundedwarrants, the “Warrant Shares”), in a private placement transaction (the “Private Placement”). The closing of the Private Placement is anticipated to occur on or about April14, 2026 (the “Closing”), subject to customary closing conditions. At theClosing, the Company has agreed to issue and sell pre-funded warrants to purchase up to 5,770,335 Warrant Shares at a purchase price of $5.199 perWarrant Share to the Investors for gross proceeds to the Company of approximately $30million pursuant to the Purchase Agreement. Th