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SCHEDULE 13D/A 0001802528 XXXXXXXX LIVE 9 Common Stock, $0.001 par value 01/22/2026 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 16261918.00 0.00 16261918.00 16261918.00 N 9.9 IA 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. 0001830382 N Fairmount Healthcare Fund II GP LLC a AF N DE 0.00 16261918.00 0.00 16261918.00 16261918.00 N 9.9 OO 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. Common Stock, $0.001 par value Cogent Biosciences, Inc. 275 Wyman Street 3rd Floor Waltham MA 02451 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. 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. 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. 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. 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 01/22/2026 /s/ Tomas Kiselak Tomas Kiselak, Managing Member 01/22/2026 Fairmount Healthcare Fund II GP LLC /s/ Peter Harwin Peter Harwin, Managing Member 01/22/2026 /s/ Tomas Kiselak Tomas Kiselak, Managing Member 01/22/2026