UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No.     )*

Scholar Rock Holding Corporation

(Name of Issuer)

Common stock, $0.001 par value per share

(Title of Class of Securities)

80706P103

(CUSIP Number)

May 23, 2018

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☐ Rule 13d-1(b)

☐ Rule 13d-1(c)

☒ Rule 13d-1(d)

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Scholar Rock Holding Corporation (the “Issuer”)

620 Memorial Drive, 2nd Floor

Cambridge, MA 02139

This joint statement on Schedule 13G is filed by Timothy A. Springer (“Dr. Springer”) and TAS Partners LLC (“TAS”), who are together referred to herein as the “Reporting Persons.”

The Reporting Persons have entered into a Joint Filing Agreement, dated as of the date hereof, a copy of which is filed with this Schedule 13G as Exhibit 1 (which is incorporated herein by reference), pursuant to which the Reporting Persons have agreed to file this statement jointly in accordance with the provisions of Rule 13d-1(k) under the Act.

The business address of each of Dr. Springer and TAS is 36 Woodman Road, Newton, MA, 02467.

TAS is a Delaware limited liability company and Dr. Springer is a citizen of the United States.

Shares of Common Stock, $0.001 par value per share (the “Shares”)

80706P103

The percentages of beneficial ownership stated herein and on each Reporting Person’s cover page to this Schedule 13G are based on a total of 25,237,160 Shares outstanding as of November 1, 2018, as reported by the Issuer in its Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2018, filed by the Issuer with the Securities and Exchange Commission on November 8, 2018. The cover page to this Schedule 13G for each Reporting Person is incorporated by reference in its entirety into this Item 4. As of the date hereof, the Reporting Persons, in the aggregate, beneficially own 3,553,935 Shares, representing approximately 14.1% of such class of securities.

Dr. Springer is the beneficial owner of a total of 3,553,935 Shares, representing approximately 14.1% of the outstanding Shares and consisting of (i) 2,968,565 Shares held directly, (ii) 580,855 Shares held by TAS and (iii) 4,515 Shares issuable upon exercise of outstanding options exercisable within the 60-day period following December 31, 2018. Dr. Springer disclaims beneficial ownership of the Shares held by TAS, except to the extent of his pecuniary interest therein.

TAS is the beneficial owner of a total of 580,855 Shares, representing approximately 2.3% of the outstanding Shares. TAS holds all such Shares directly. Dr. Springer is the sole managing member of TAS.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: February 13, 2019

Exhibit 1

JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree, as of February 13, 2019, that only one statement containing the information required by Schedule 13G, and each amendment thereto, need be filed with respect to the ownership by each of the undersigned of shares of common stock, $0.001 par value per share of Scholar Rock Holding Corporation, and such statement to which this Joint Filing Agreement is attached as Exhibit 1 is filed on behalf of each of the undersigned.