Alumis Inc美股招股说明书(2025-04-04版)

Dear stockholders of Alumis Inc. and stockholders of ACELYRIN, Inc.: As previously announced, the board of directors of Alumis Inc. (“Alumis”) and the board of directors of ACELYRIN, Inc. (“ACELYRIN”), eachwith Alan Colowick and Patrick Machado recused, have approved the merger of ACELYRIN and Alumis. Alumis, ACELYRIN and Arrow Merger Sub,Inc (“Merger Sub”), entered into an Agreement and Plan of Merger, dated as of February6, 2025 (the “Merger Agreement”), pursuant to which MergerSub will merge with and into ACELYRIN, with ACELYRIN continuing as a direct wholly owned subsidiary of Alumis (the “Merger”). If the transaction is completed, ACELYRIN stockholders will have the right to receive, for each issued and outstanding share of common stock,par value $0.00001 per share, of ACELYRIN (“ACELYRIN common stock”) held by such stockholder immediately prior to the effective time of theMerger, 0.4274 shares of common stock, par value $0.0001 per share, of Alumis (“Alumis common stock”), without interest (the number of shares ofAlumis common stock issued in exchange for each share of ACELYRIN common stock, the “Exchange Ratio”), with cash paid in lieu of fractionalshares. Alumis stockholders will continue to own their existing shares of Alumis common stock. The Exchange Ratio is fixed and will not reflectchanges in the market price of ACELYRIN common stock or Alumis common stock between the date of signing of the Merger Agreement andconsummation of the Merger. We urge Alumis stockholders and ACELYRIN stockholders to obtain current stock price quotations for Alumis commonstock and ACELYRIN common stock. Immediately following the Merger, Alumis stockholders as of immediately prior to the Merger are expected to collectively own approximately55% of the combined company and ACELYRIN stockholders as of immediately prior to the Merger are expected to collectively own approximately45% of the combined company, in each case, calculated on a fully diluted basis as of January31, 2025. Alumis common stock and ACELYRINcommon stock are both currently traded on the Nasdaq Global Select Market under the symbols “ALMS” and “SLRN,” respectively. Upon completionof the Merger, the ACELYRIN common stock will cease to be traded on the Nasdaq Global Select Market. At the special meeting of Alumis stockholders to be held virtually on May 13, 2025, Alumis stockholders will be asked to vote on (i)a proposalto approve the issuance of shares of Alumis common stock to ACELYRIN stockholders, which is a condition to completion of the Merger (the “Alumisstock issuance proposal”), and (ii)a proposal to approve the adjournment from time to time of the Alumis virtual special meeting, if necessary, tosolicit additional proxies if there are not sufficient votes to approve the issuance of shares of Alumis common stock in the Merger (the “Alumisadjournment proposal”). At the special meeting of ACELYRIN stockholders to be held virtually on May 13, 2025, ACELYRIN stockholders will be asked to vote on (i)aproposal to adopt the Merger Agreement (the “ACELYRIN merger proposal”) and (ii)a proposal to approve the adjournment from time to time of theACELYRIN virtual special meeting, if necessary, to solicit additional proxies if there are not sufficient votes to adopt the Merger Agreement (the“ACELYRIN adjournment proposal”). Only holders of record of Alumis common stock on April 1, 2025 (including shares of Alumis common stock held through a bank, broker or othernominee that is a stockholder of record of Alumis) and holders of record of ACELYRIN common stock on April 1, 2025 (including shares ofACELYRIN common stock held through a bank, broker or other nominee that is a stockholder of record of ACELYRIN) are entitled to attend and voteat the virtual special meeting of Alumis stockholders or the virtual special meeting of ACELYRIN stockholders, respectively, or any adjournment orpostponement thereof. We cannot complete the Merger unless the ACELYRIN stockholders and the Alumis stockholders approve the respective proposals related to theMerger.Your vote is very important, regardless of the number of shares you own. Whether or not you expect to attend the Alumis virtual special meeting orACELYRIN virtual special meeting, as applicable, please vote your shares as promptly as possible by (1)accessing the internet website specified on yourproxy card, (2)calling the toll-free number specified on your proxy card, or (3)signing and returning all proxy cards that you receive in the postage-paidenvelope provided, so that your shares may be represented and voted at the Alumis virtual special meeting or the ACELYRIN virtual special meeting, asapplicable.If you are an Alumis stockholder, please note that a failure to vote your shares may result in a failure to establish a quorum for the Alumisvirtual special meeting. If you are an ACELYRIN stockholder, please note that a failure to vote your shares is the equivalent of a vote against theMerger. The Alumis board of dir