ALUMIS INC. — Proxy Solicitation & Information Statement 2026

May 18, 2026

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UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

Filed by the Registrant	x
Filed by a party other than the Registrant	¨

Check the appropriate box:

¨ Preliminary Proxy Statement

¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

¨ Definitive Proxy Statement

x Definitive Additional Materials

¨ Soliciting Material under § 240.14a-12

Alumis Inc.

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

x No fee required

¨ Fee paid previously with preliminary materials

¨ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11

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Your Vote Counts! ALUMIS INC. 2026 Annual Meeting Vote by June 29, 2026 11:59 PM ET You invested in ALUMIS INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy materials for the stockholder meeting to be held on June 30, 2026. Vote Virtually at the Meeting June 30, 2026 9:00 A.M. (PACIFIC TIME) Virtually at: www.virtualshareholdermeeting.com/ALMS2026 Please check the meeting materials for any special requirements for meeting attendance. Smartphone users Point your camera here and vote without entering a control number For complete information and to vote, visit www.ProxyVote.com Control # V86686-P48503 Get informed before you vote View the Notice and Proxy Statement and our Annual Report on Form 10-K online OR you can receive a free paper or email copy of the material(s) by requesting prior to June 16, 2026. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. ALUMIS INC. 280 EAST GRAND AVENUE SOUTH SAN FRANCISCO, CA 94080

THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. Please follow the instructions on the reverse side to vote these important matters. Vote at www.ProxyVote.com Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Delivery Settings”. Voting Items Board Recommends V86687-P48503 1. To elect the three Class II director nominees named below to serve until the Company’s 2029 annual meeting of stockholders. For Nominees: 01) James B. Tananbaum, M.D. 02) Lynn Tetrault, J.D. 03) Zhengbin (Bing) Yao, Ph.D. 2. To ratify the appointment of PricewaterhouseCoopers LLP as the Company’s independent auditor for the Company’s fiscal year ending December 31, 2026. For