MBX生物科学公司美股招股说明书(2025-09-25版)

Common Stock We are offering 11,108,055 shares of our common stock. Our common stock is listed on the Nasdaq Global Select Market, or Nasdaq, under the symbol “MBX”. OnSeptember 24, 2025, the last reported sale price of our common stock on Nasdaq was $20.10 per share. We are an “emerging growth company” and a “smaller reporting company” under the federal securities lawsand, as such, we have elected to comply with certain reduced public company reporting requirements for thisprospectus and for future filings. Investing in our common stock involves a high degree of risk. Before buying any shares, you shouldread carefully the discussion of the material risks of investing in our common stock under the heading “RiskFactors” starting on page11of this prospectus and the documents incorporated by reference herein. Neither the Securities and Exchange Commission nor any state securities commission has approved ordisapproved of these securities, or passed upon the adequacy or accuracy of this prospectus. Anyrepresentation to the contrary is a criminal offense. Per shareTotalPublic offering price$18.00$199,944,990Underwriting discounts and commissions$1.08$11,996,699Proceeds, before expenses, to MBX Biosciences, Inc.$16.92$187,948,291(1) (1)See “Underwriting” beginning on page29of this prospectus for additional information regarding underwriting compensation. We have granted the underwriters an option for a period of 30 days to purchase an additional 1,666,208 sharesof our common stock from us at the public offering price, less underwriting discounts and commissions. The underwriters expect to deliver the shares of common stock to purchasers on September 26, 2025. Oppenheimer & Co. Prospectus dated September 24, 2025. TABLE OF CONTENTS We incorporate by reference important information into this prospectus. You may obtain theinformation incorporated by reference without charge by following the instructions under "Where You CanFind More Information." You should carefully read this prospectus as well as additional informationdescribed under "Incorporation of Certain Information by Reference," before deciding to invest in ourcommon stock. We have not, and the underwriters have not, authorized anyone to provide any information or to make anyrepresentation other than those contained in this prospectus, any amendment or supplement to this prospectus or anyfree writing prospectuses prepared by or on behalf of us or to which we have referred you. We and the underwriterstake no responsibility for, and can provide no assurance as to the reliability of, any other information that others maygive you. This prospectus is an offer to sell only the shares of common stock offered hereby, but only undercircumstances and in jurisdictions where it is lawful to do so. The information contained in this prospectus, anyamendment or supplement to this prospectus or any applicable free writing prospectus is current only as of its date,regardless of its time of delivery or any sale of shares of our common stock. Our business, financial condition,results of operations and prospects may have changed since that date. For investors outside the United States: We have not, and the underwriters have not, done anything that wouldpermit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purposeis required, other than in the United States. Persons outside the United States who come into possession of thisprospectus must inform themselves about, and observe any restrictions relating to, the offering of the shares ofcommon stock and the distribution of this prospectus outside the United States. Market data and certain other statistical information used throughout this prospectus are based on independentindustry publications, governmental publications, reports by market research firms, or other independent sourcesthat we believe to be reliable sources. Industry publications and third-party research, surveys, and studies generallyindicate that their information has been obtained from sources believed to be reliable, although they do notguarantee the accuracy or completeness of such information. We are responsible for all of the disclosure containedin this prospectus, and we believe that these sources are reliable; however, we have not independently verified theinformation contained in such publications. While we are not aware of any misstatements regarding any third-partyinformation presented in this prospectus, their estimates, in particular, as they relate to projections, involvenumerous assumptions, are subject to risks and uncertainties, and are subject to change based on various factors,including those discussed under the section entitled “Risk factors” and elsewhere in this prospectus. Some data arealso based on our good faith estimates. We intend to apply for various trademarks that we use in connection with the operation of our business. Thisprospectus may also contain trademarks, s