Alumis Inc美股招股说明书(2026-01-06版)

Common stock We are offering $175,000,000 of shares of our common stock. Our common stock is traded on the Nasdaq Global Select Market under the symbol “ALMS.” On January 6, 2026, the lastreported sale price of our common stock on the Nasdaq Global Select Market was $16.23 per share. The final publicoffering price will be determined through negotiation between us and the lead underwriters in the offering and the recentmarket price used throughout this prospectus supplement may not be indicative of the actual offering price. We have two classes of common stock: the voting common stock offered hereby and non-voting common stock. We areoffering voting common stock in this offering, and unless otherwise noted, all references in this prospectus supplementand the accompanying prospectus to our “common stock” refer to our voting common stock. The rights of the holders ofcommon stock and non-voting common stock are identical, except with respect to voting and conversion. Each share ofcommon stock is entitled to one vote and is not convertible into any other class of our capital stock. Shares of non-votingcommon stock are non-voting, except as may be required by law. Each share of non-voting common stock may beconverted at any time into one share of common stock at the option of its holder, subject to the beneficial ownershiplimitations provided for in our amended and restated certificate of incorporation. See the section titled “Description ofCapital Stock” beginning on page12of the accompanying prospectus for more information on the rights of the holders ofour common stock and non-voting common stock. The non-voting common stock will not be listed for trading on anysecurities exchange. Investing in our common stock involves a high degree of risk. See “Risk Factors” beginning on pageS-6of thisprospectus supplement and in the documents incorporated by reference into this prospectus supplement. (1)See “Underwriters” beginning on pageS-18for additional information regarding underwriter compensation. We have granted the underwriters an option to purchase up to an additional $26,250,000of shares of common stock from usat the public offering price, less underwriting discounts and commissions, within 30days from the date of this prospectussupplement. See“Underwriting”for more information. The underwriters expect to deliver the shares to purchasers on or about, 2026. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of thesesecurities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Anyrepresentation to the contrary is a criminal offense. Joint book-running managersThe information in this preliminary prospectus supplement is not complete and may be changed. A registration statement relating to these securities has been filedwith the Securities and Exchange Commission and is effective. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sellthese securities, and they are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted. Morgan StanleyLeerink Partners Cantor January, 2026 TABLE OF CONTENTS ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts. The first part is this prospectus supplement, which describes the terms of thisoffering of common stock and also adds to and updates information contained in the accompanyingprospectusand the documents incorporated by reference into this prospectus supplement and theaccompanying prospectus. The second part, the accompanying prospectus dated August19, 2025, includingthe documents incorporated by reference therein, provides more general information. Generally, when werefer to this prospectus, we are referring to both parts of this document combined. To the extent there is aconflict between the information contained in this prospectus supplement, on the one hand, and theinformation contained in the accompanying prospectus or in any document incorporated by reference thatwas filed with the Securities and Exchange Commission (the “SEC”) before the date of this prospectussupplement, on the other hand, you should rely on the information in this prospectus supplement. If anystatement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in the accompanying prospectus—the statement in thedocument having the later date modifies or supersedes the earlier statement. We have not, and the underwriters have not, authorized anyone to provide any information other than thatcontained or incorporated by reference in this prospectus supplement, the accompanying prospectus or inany free writing prospectus that we have authorized for use in connection with this offering. We and theunderwriters take no responsibility for, and can provide no assurance as to the reliability of, any oth