United States securities and exchange commission logo February 12, 2021 Andrew Robbins President and Chief Executive Officer Cogent Biosciences, Inc. 200 Cambridge Park Drive, Suite 2500 Cambridge, Massachusetts 02140 Re: Cogent Biosciences, Inc. Registration Statement on Form S-3 Filed February 9, 2021 File No. 333-252873 Dear Mr. Robbins: This is to advise you that we have not reviewed and will not review your registration statement. Please refer to Rules 460 and 461 regarding requests for acceleration. We remind you that the company and its management are responsible for the accuracy and adequacy of their disclosures, notwithstanding any review, comments, action or absence of action by the staff. Please contact Alan Campbell at 202-551-4224 with any questions. Sincerely, Division of Corporation Finance Office of Life Sciences cc: Ryan A. Murr