August 13, 2025

Sean A. McCarthy, D.Phil.
President and Chief Executive Officer
CytomX Therapeutics, Inc.
151 Oyster Point Blvd., Suite 400
South San Francisco, CA 94080

       Re: CytomX Therapeutics, Inc.
           Registration Statement on Form S-3
           Filed August 7, 2025
           File No. 333-289365
Dear Sean A. McCarthy D.Phil.:

       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 Chris Edwards at 202-551-6761 with any questions.



                                                           Sincerely,

                                                           Division of
Corporation Finance
                                                           Office of Life
Sciences
cc:   Mark V. Roeder, Esq.