Common Stock, $0.0001 par value per share

ALUMIS INC.

280 East Grand Avenue, South San Francisco, CA, 94080

This Schedule 13D is being filed on behalf of Samsara BioCapital, L.P. ("Samsara LP"), Samsara BioCapital GP, LLC ("Samsara GP"), Samsara Opportunity Fund, L.P. ("Samsara Opportunity Fund") Samsara Opportunity Fund GP, LLC ("Samsara Opportunity GP") and Dr. Srinivas Akkaraju ("Dr. Akkaraju"). Samsara LP, Samsara GP, Samsara Opportunity Fund, Samsara Opportunity GP and Dr. Akkaraju are collectively referred to herein as the "Reporting Persons." The agreement among the Reporting Persons to file this Schedule 13D jointly in accordance with Rule 13d-1(k) of the Securities Exchange Act of 1934, as amended, (the "Act") is attached hereto as Exhibit 99.1. Each of the Reporting Persons expressly disclaims the existence of a "group" for purposes of this Schedule 13D.

The address of the principal business office of each of the Reporting Persons is 628 Middlefield Road, Palo Alto, CA 94301.

The principal business of the Reporting Persons is venture capital investments. Dr. Akkaraju serves as the Managing Member of each of Samsara GP, which is the general partner of Samsara LP, and Samsara Opportunity GP, which is the general partner of Samsara Opportunity Fund.

During the last five years, none of the Reporting Persons was a party to a civil proceeding of a judicial of administrative body of competent jurisdiction or were subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Each of Samsara LP, Samsara GP, Samsara Opportunity Fund and Samsara Opportunity GP was organized in the state of Delaware and Dr. Akkaraju is a citizen of the United States.

Rows 11 and 13 of each Reporting Person's cover page to this Schedule 13D set forth the aggregate number of shares of voting common stock and percentages of the shares of voting common stock beneficially owned by such Reporting Person and are incorporated by reference. The percentage set forth in each row 13 is based upon 97,208,495 shares of voting common stock outstanding as of November 6, 2025, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (the "SEC") on November 13, 2025. The Reporting Persons' beneficial ownership of the Issuer's securities consists of (i) 4,491,731 shares of voting common stock directly held by Samsara LP; and (ii) 643,260 shares of voting common stock directly held by Samsara Opportunity Fund. Samsara GP is the sole general partner of Samsara LP and Dr. Akkaraju is the managing member of Samsara GP. Each of Samsara GP and Dr. Akkaraju possesses power to direct the voting and disposition of the securities held by Samsara LP. Samsara Opportunity GP is the sole general partner of Samsara Opportunity Fund and Dr. Akkaraju is the managing member of Samsara Opportunity GP. Each of Samsara Opportunity GP and Dr. Akkaraju possesses power to direct the voting and disposition of the securities held by Samsara Opportunity Fund.

Rows 7 through 10 of each Reporting Person's cover page to this Schedule 13D set forth the number of shares of voting common stock as to which such Reporting Person has the sole or shared power to vote or direct the vote and sole or shared power to dispose or to direct the disposition and are incorporated by reference.

Except as set forth below and elsewhere herein, none of the Reporting Persons has effected any transactions with respect to the securities of the Issuer during the past sixty days: On November 13, 2025, Samsara LP sold (i) 276,179 shares of voting common stock to Samsara Opportunity Fund in a private sale for $5.25 per share, and (ii) 33,460 shares in an open market transaction at $5.28 per share. These shares represented shares held by Samsara LP for the exclusive benefit of limited partners who had redeemed their respective interests in Samsara LP and in which neither Samsara GP nor Dr. Akkaraju had any economic interest.

No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, the securities beneficially owned by any of the Reporting Persons.

Not applicable.