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,
Statement on Form S-3
                                                            Filed February 9,
                                                            File No. 333-252873

       Dear Mr. Robbins:

              This is to advise you that we have not reviewed and will not
review your registration

               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.


                          Division of Corporation Finance

                          Office of Life Sciences
       cc:                                              Ryan A. Murr