德菲尼姆疗法公司美股招股说明书（2026-06-24版）

We are offering 20,588,236 of our common shares, without par value, at a public offering price of$34.00 per share. Our common shares are listed on the Nasdaq Global Select Market (“Nasdaq”) under the symbol“DFTX”. The last reported sale price of our common shares on Nasdaq on June23, 2026 was Investing in our securities involves a high degree of risk. See “Risk Factors” beginning onpageS-9of this prospectus supplement, page 8 of the accompanying prospectus andunder similar headings in the documents incorporated by reference into this prospectus We are an “emerging growth company” under applicable Securities and Exchange Commissionrules and are subject to reduced public company reporting requirements. See “Prospectus Neither the Securities and Exchange Commission nor any state or other securitiescommission has approved or disapproved of these securities or determined if this We have granted the underwriters an option to purchase up to an additional 3,088,235 commonshares from us at the public offering price, less the underwriting discounts and commissionspayable by us. This option is exercisable, in whole or in part, for a period of 30days following the Delivery of the common shares is expected to be made on or about June 25, 2026. BofASecurities Prospectus Supplement dated June 23, 2026 Table of contents Prospectus Supplement About this prospectus supplement This prospectus supplement and the accompanying prospectus are part of a “shelf” registrationstatement on Form S-3 that went effective upon filing with the Securities and ExchangeCommission (the “SEC”) on June28, 2024. Under this shelf registration process, we may sell any This prospectus supplement relates to the offering of our common shares. Before buying any ofsuch common shares, we urge you to carefully read this prospectus supplement, together withthe accompanying prospectus and the information incorporated by reference as described under This prospectus supplement describes the terms of this offering of common shares, and alsoadds to, and updates, information contained in the documents incorporated by reference into thisprospectus supplement. To the extent there is a conflict between the information contained in thisprospectus supplement, on the one hand, and the information contained in any documentincorporated by reference into this prospectus supplement that was filed with the SEC before the You should rely only on the information contained in or incorporated by reference in thisprospectus supplement, the accompanying prospectus and in any free writing prospectus that wehave authorized for use in connection with this offering. Neither we, nor any underwriter or dealerhas authorized anyone to provide you with different information. If anyone provides you withdifferent or inconsistent information, you should not rely on it. This prospectus supplement andthe accompanying prospectus do not constitute an offer to sell, or a solicitation of an offer topurchase, the common shares offered by this prospectus supplement in any jurisdiction to or fromany person to whom or from whom it is unlawful to make such offer or solicitation of an offer insuch jurisdiction. You should assume that the information appearing in this prospectus This prospectus supplement, the accompanying prospectus and the information incorporatedherein or therein by reference contain summaries of certain provisions contained in some of thedocuments described herein or therein, but reference is made to the actual documents forcomplete information. All of the summaries are qualified in their entirety by the actual documents. Except as otherwise indicated or unless the context otherwise requires, references to“Corporation,” “Company,” “we,” “us,” “our” or “Definium,” refer to Definium Therapeutics, Inc. and This prospectus supplement may contain references to our trademarks and trade names and totrademarks and trade names belonging to other entities. Solely for convenience, trademarks andtrade names referred to in this prospectus supplement may appear without the ® or ™ symbols,but such references are not intended to indicate, in any way, that their respective owners will not Prospectus supplement summary This summary highlights selected information contained elsewhere in this prospectussupplement, the accompanying prospectus or incorporated by reference herein or therein anddoes not contain all of the information that you need to consider in making your investmentdecision. You should carefully read the entire prospectus supplement, the accompanyingprospectus and any related free writing prospectus, including the risks of investing in our commonshares, discussed under the heading “Risk Factors” in this prospectus supplement, the Overview We are a late-stage clinical biopharmaceutical company developing a new generation oftherapeutics intended to address underlying causes of psychiatric and neurological disorders. Ourmission is to forge a new era of psychiatry by ap