COGT Cogent Biosciences Inc

Cogent Biosciences, Inc. (the “Issuer”).

200 Cambridge Park Drive, Suite 2500

Cambridge, Massachusetts 02140

This joint statement on Schedule 13G is being filed by TCG Crossover Fund I, L.P. (“TCG Crossover I”), TCG Crossover GP I, LLC (“TCG Crossover GP I” and together with TCG Crossover I, the “Reporting Entities”) and Chen Yu (the “Reporting Individual”). The Reporting Entities and the Reporting Individual are collectively referred to as the “Reporting Persons.” The Reporting Persons expressly disclaim status as a “group” for purposes of this Schedule 13G. The agreement among the Reporting Persons to file jointly in accordance with the provisions of Rule 13d-1(k)(1) under the Act is attached to this Statement as Exhibit 1. Other than those securities reported herein as being held directly by such Reporting Person, each Reporting Person disclaims beneficial ownership of all securities reported in this Statement except to the extent of such Reporting Person’s pecuniary interest therein.

The address of the principal business office of each Reporting Person is 705 High St., Palo Alto, CA 94301.

TCG Crossover GP I is a limited liability company organized under the laws of the State of Delaware. TCG Crossover I is a limited partnership organized under the laws of the State of Delaware. The Reporting Individual is a citizen of the United States of America.

Common Stock, $0.001 par value (“Common Stock”).

19240Q 201

Not applicable.

(a) Amount beneficially owned:

See Row 9 of the cover page for each Reporting Person and the corresponding footnotes.*

(b) Percent of class:

See Row 11 of the cover page for each Reporting Person and the corresponding footnotes.*

(c) Number of shares as to which the person has:

(i) Sole power to vote or to direct the vote

See Row 5 of the cover page for each Reporting Person and the corresponding footnotes.*

(ii) Shared power to vote or to direct the vote

See Row 6 of the cover page for each Reporting Person and the corresponding footnotes.*

(iii) Sole power to dispose or to direct the disposition of

See Row 7 of the cover page for each Reporting Person and the corresponding footnotes.*

(iv) Shared power to dispose or to direct the disposition of

See Row 8 of the cover page for each Reporting Person and the corresponding footnotes.*

Not applicable.

Under certain circumstances set forth in the limited partnership agreements of TCG Crossover I and the limited liability company agreement of TCG Crossover GP I, the general and limited partners or members, as the case may be, of each of such entities may be deemed to have the right to receive dividends from, or the proceeds from, the sale of securities of the Issuer owned by each such entity of which they are a partner or member, as the case may be.

Not applicable.

Not applicable.

Not applicable.

Not Applicable

Material to be Filed as Exhibits.

Exhibit 1 – Joint Filing Agreement.

SIGNATURE

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.

Dated: February 14, 2023

Exhibit 1

JOINT FILING AGREEMENT

The undersigned hereby agree that the foregoing statement on Schedule 13G is filed on behalf of each of the undersigned, and any amendments thereto executed by the undersigned shall be filed on behalf of each of the undersigned without the necessity of filing any additional joint filing agreement. The undersigned acknowledge that each is responsible for the timely filing of such statement on Schedule 13G and any amendments thereto, and for the completeness and accuracy of the information concerning him, her or it contained therein, but shall not be responsible for the completeness or accuracy of the information concerning the others of the undersigned, except to the extent that he, she or it knows or has reason to believe that such information is inaccurate or incomplete. This Joint Filing Agreement may be executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.

Dated: February 14, 2023

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