United States securities and exchange commission logo





                           May 7, 2021

       Steven Shallcross
       Chief Executive Officer and Chief Financial Officer
       Synthetic Biologics, Inc.
       9605 Medical Center Drive, Suite 270
       Rockville, Maryland 20850

                                                        Re: Synthetic
Biologics, Inc.
                                                            Registration
Statement on Form S-3
                                                            Filed May 3, 2021
                                                            File No. 333-255726

       Dear Mr. Shallcross:

              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 Dillon
Hagius at 202-551-7967 with any questions.




                           Sincerely,


                           Division of Corporation Finance

                           Office of Life Sciences
       cc:                                              Leslie Marlow