SCHEDULE 13D

CUSIP No.

19240Q201

Name of reporting person

Fairmount Funds Management LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 16,261,918.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 16,261,918.00

Aggregate amount beneficially owned by each reporting person

16,261,918.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

9.9 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person:

The securities include (a) 5,503,418 shares of common stock, $0.001 par value ("Common Stock"), and (b) 10,758,500 shares of Common Stock issuable upon conversion of 43,034 shares of Series A Convertible Preferred Stock, par value $0.001 per share (the "Series A Preferred Stock") directly held by Fairmount Healthcare Fund II L.P. ("Fund II"). The securities exclude shares of Common Stock issuable upon conversion of shares of Series A Preferred Stock held directly by Fund II in excess of the beneficial ownership limitation of 9.9%. Row 13 is based on 164,264,062 shares of Common Stock outstanding as of January 22, 2026, consisting of (i) 142,376,529 shares of Common Stock outstanding as of November 5, 2025, as reported in the Company's most recent Quarterly Report on Form 10-Q, (ii) 11,129,033 shares of Common Stock sold in the Company's underwritten public offering, as reported in the Company's Current Report on Form 8-K filed on November 13, 2025, and (iii) 10,758,500 shares of Common Stock underlying the 43,034 shares of Series A Preferred Stock owned by Fund II, subject to the beneficial ownership limitation.

SCHEDULE 13D

CUSIP No.

19240Q201

Name of reporting person

Fairmount Healthcare Fund II GP LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 16,261,918.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 16,261,918.00

Aggregate amount beneficially owned by each reporting person

16,261,918.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

9.9 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person:

The securities include (a) 5,503,418 shares of Common Stock, and (b) 10,758,500 shares of Common Stock issuable upon conversion of 43,034 shares of Series A Preferred Stock directly held by Fund II. The securities exclude shares of Common Stock issuable upon conversion of shares of Series A Preferred Stock held directly by Fund II in excess of the beneficial ownership limitation of 9.9%. Row 13 is based on 164,264,062 shares of Common Stock outstanding as of January 22, 2026, consisting of (i) 142,376,529 shares of Common Stock outstanding as of November 5, 2025, as reported in the Company's most recent Quarterly Report on Form 10-Q, (ii) 11,129,033 shares of Common Stock sold in the Company's underwritten public offering, as reported in the Company's Current Report on Form 8-K filed on November 13, 2025, and (iii) 10,758,500 shares of Common Stock underlying the 43,034 shares of Series A Preferred Stock owned by Fund II, subject to the beneficial ownership limitation.

SCHEDULE 13D

Item 1.

Security and Issuer

(a)

Title of Class of Securities:

Common Stock, $0.001 par value

(b)

Name of Issuer:

Cogent Biosciences, Inc.

(c)

Address of Issuer's Principal Executive Offices:

275 Wyman Street, 3rd Floor, Waltham, MASSACHUSETTS , 02451.

Item 1 Comment:

This Amendment No. 9 amends and supplements the statement on Schedule 13D originally filed with the Securities and Exchange Commission on July 6, 2020, Amendment No. 1 filed on June 21, 2022, Amendment No. 2 filed on June 13, 2023, Amendment No. 3 filed on February 16, 2024, Amendment No. 4 filed on March 27, 2024, Amendment No. 5 filed on April 1, 2024, Amendment No. 6 filed on June 13, 2024, Amendment No. 7 filed on July 14, 2025 and Amendment No. 8 filed on November 17, 2025 (as amended, the "Statement" or the "Schedule 13D") by the Reporting Persons with respect to the Common Stock of Cogent Biosciences, Inc. (the "Company"). Unless otherwise defined herein, capitalized terms used in this Amendment No. 9 shall have the meanings ascribed to them in the Statement. Unless amended or supplemented below, the information in the Statement remains unchanged.

Item 5.

Interest in Securities of the Issuer

(a)

The information in rows 11 and 13 of each of the cover pages (including the explanatory note in the "Comments") of this Amendment No. 9 is incorporated by reference herein.

(b)

The information in rows 7 through 10 of each of the cover pages of this Amendment No. 9 is incorporated by reference herein. In aggregate, the Reporting Persons have voting and dispositive power over 16,261,918 shares of Common Stock, which is comprised of (a) 5,503,418 shares of Common Stock and (b) 10,758,500 shares of Common Stock currently issuable upon conversion of 43,034 shares of Series A Preferred Stock, reflecting the beneficial ownership limitation of 9.9% of the outstanding Common Stock. In total, the Reporting Persons currently own 67,414 shares of Series A Preferred Stock.

(c)

Item 5(c) of the Schedule 13D is hereby amended and supplemented as follows: On January 22, 2026, Fund II sold in a block trade a total of 3,500,000 shares of Common Stock at a price of $36.40 per share.

Item 7.

Material to be Filed as Exhibits.

99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 to the Schedule 13D filed with the SEC on November 17, 2025)

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.

Fairmount Funds Management LLC

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin, Managing Member
Date:	01/22/2026

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak, Managing Member
Date:	01/22/2026

Fairmount Healthcare Fund II GP LLC

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin, Managing Member
Date:	01/22/2026

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak, Managing Member
Date:	01/22/2026