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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(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)

X0202 SCHEDULE 13D/A 0001802528 XXXXXXXX LIVE 10 Common Stock, $0.001 par value 03/31/2026 false 0001622229 19240Q201 Cogent Biosciences, Inc. 275 Wyman Street 3rd Floor Waltham MA 02451 Ms. Erin O'Connor (267) 262-5300 Fairmount Funds Management LLC 200 Barr Harbor Drive, Suite 400 West Conshohocken PA 19428 0001802528 N Fairmount Funds Management LLC a AF N DE 0.00 15356918.00 0.00 15356918.00 15356918.00 N 8.6 IA The securities beneficially owned consist of (a) 5,503,418 shares of common stock, $0.001 par value ("Common Stock"), and (b) 9,853,500 shares of Common Stock issuable upon conversion of 39,414 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"). Row 13 is based on 179,162,320 shares of Common Stock outstanding as of March 31, 2026, consisting of (i) 162,308,820 shares of Common Stock outstanding as of February 17, 2026, as reported in the Company's most recent Annual Report on Form 10-K, (ii) 7,000,000 shares of Common Stock issued upon the conversion of 28,000 shares of Series A Preferred Stock held by Fund II on March 31, 2026 and (ii) 9,853,500 shares of Common Stock underlying the 39,414 shares of Series A Preferred Stock owned by Fund II. 0001830382 N Fairmount Healthcare Fund II GP LLC a AF N DE 0.00 15356918.00 0.00 15356918.00 15356918.00 N 8.6 OO The securities beneficially owned consist of (a) 5,503,418 shares of Common Stock, and (b) 9,853,500 shares of Common Stock issuable upon conversion of 39,414 shares of Series A Convertible Preferred Stock directly held by Fund II. Row 13 is based on 179,162,320 shares of Common Stock outstanding as of March 31, 2026, consisting of (i) 162,308,820 shares of Common Stock outstanding as of February 17, 2026, as reported in the Company's most recent Annual Report on Form 10-K, (ii) 7,000,000 shares of Common Stock issued upon the conversion of 28,000 shares of Series A Preferred Stock held by Fund II on March 31, 2026 and (ii) 9,853,500 shares of Common Stock underlying the 39,414 shares of Series A Preferred Stock owned by Fund II. Common Stock, $0.001 par value Cogent Biosciences, Inc. 275 Wyman Street 3rd Floor Waltham MA 02451 This Amendment No. 10 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, Amendment No. 8 filed on November 17, 2025 and Amendment No. 9 filed on January 22, 2026 (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. 10 shall have the meanings ascribed to them in the Statement. Unless amended or supplemented below, the information in the Statement remains unchanged. Item 3 of the Schedule 13D is hereby amended and supplemented as follows: On March 31, 2026, Fund II delivered to the Company a notice of conversion pursuant to Section 6.4 of the Certificate of Designations of Preferences, Rights and Limitations of Series A Non-Voting Convertible Preferred Stock (the "Certificate of Designations") to convert 28,000 shares of Series A Preferred Stock into 7,000,000 shares of Common Stock, in accordance with the terms of the Certificate of Designations. The conversion was effected for no cash consideration pursuant to the Certificate of Designations. The information in rows 11 and 13 of each of the cover pages (including the explanatory note in the "Comments") of this Amendment No. 10 is incorporated by reference herein. The information in rows 7 through 10 of each of the cover pages of this Amendment No. 10 is incorporated by reference herein. In aggregate, the Reporting Persons have voting and dispositive power over 15,356,918 shares of Common Stock, which is comprised of (a) 5,503,418 shares of Common Stock and (b) 9,853,500 shares of Common Stock currently issuable upon conversion of 39,414 shares of Series A Preferred Stock. Item 5(c) of the Schedule 13D is hereby supplemented as follows: On March 31, 2026, Fund II sold in a block trade a total of 7,000,000 shares of Common Stock at a price of $34.66 per share. 99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 to the Schedule 13D filed with the SEC on November 17, 2025) Fairmount Funds Management LLC /s/ Peter Harwin Peter Harwin, Managing Member 03/31/2026 /s/ Tomas Kiselak Tomas Kiselak, Managing Member 03/31/2026 Fairmount Healthcare Fund II GP LLC /s/ Peter Harwin Peter Harwin, Managing Member 03/31/2026 /s/ Tomas Kiselak Tomas Kiselak, Managing Member 03/31/2026