Common Stock, par value $0.001 per share

SCHOLAR ROCK HOLDING CORP

301 BINNEY STREET, CAMBRIDGE, MA, 02142

This Schedule 13D/A 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/A 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/A.

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/A set forth the aggregate number of shares of common stock and percentages of the shares of common stock beneficially owned by such Reporting Person and are incorporated by reference. The percentage set forth in each row 13 is based upon the sum of (i) 96,127,265 shares of common stock outstanding as of August 1, 2025, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025; (ii) 1,064,804 shares of common stock issuable upon the exercise of RD Warrants; and (iii) with respect to Dr. Akkaraju, 110,000 shares of common stock issuable upon the exercise of stock options within 60 days. The Reporting Persons' beneficial ownership of the Issuer's securities consists of (i) 5,302,810 shares of common stock directly held by Samsara LP; (ii) RD Warrants immediately exercisable for up to 1,064,804 shares of common stock directly held by Samsara LP; (iii) 500,439 shares of common stock directly held by Samsara Opportunity Fund; (iv) 13,500 shares of common stock held by Dr. Akkaraju; and (v) 110,000 vested stock options (right to buy) held by Dr. Akkaraju. 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/A set forth the number of shares of 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.

On October 3, Samsara LP also sold 33,508 shares in an open market transaction. These shares were held by Samsara 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. Except as set forth in the preceding sentence 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.

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.