Amendment to Schedule 13D Filing for Cogent Biosciences, Inc.

This filing is an amendment (Amendment No. 10) to the Schedule 13D originally filed on July 6, 2020, by Fairmount Funds Management LLC and Fairmount Healthcare Fund II GP LLC (the "Reporting Persons") regarding the Common Stock of Cogent Biosciences, Inc. On March 31, 2026, Fund II converted 28,000 shares of Series A Preferred Stock into 7,000,000 shares of Common Stock. Concurrently, on the same date, Fund II sold these 7,000,000 shares in a block trade at $34.66 per share. Following these transactions, the Reporting Persons collectively hold 15,356,918 shares of Common Stock, representing 8.6% of the class, with voting and dispositive power over these shares. The filing details the number of shares held directly and the number issuable upon conversion of preferred stock, based on a total of 179,162,320 shares outstanding as of March 31, 2026.