United States securities and exchange commission logo March 9, 2021 Nassim Usman, Ph.D. Chief Executive Officer Catalyst Biosciences, Inc. 611 Gateway Blvd. Suite 710 South San Francisco, CA 94080 Re: Catalyst Biosciences, Inc. Registration Statement on Form S-3 Filed March 4, 2021 File No. 333-253874 Dear Dr. Usman: 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 Jason Drory at 202-551-8342 with any questions. Sincerely, Division of Corporation Finance Office of Life Sciences cc: Stephen B. Thau, Esq.