United States securities and exchange commission logo




                                                                                
                               December 7, 2022

       Thomas R. Cannell, D.V.M.
       Chief Executive Officer
       Sesen Bio, Inc.
       245 First Street, Suite 1800
       Cambridge, MA 02142

                                                        Re: Sesen Bio, Inc.
                                                            Amendment No. 1 to 
Registration Statement on Form S-4
                                                            Filed November 22, 
2022
                                                            File No. 333-267891

       Dear Thomas R. Cannell:

             We have reviewed your amended registration statement and have the 
following
       comments. In some of our comments, we may ask you to provide us with 
information so we
       may better understand your disclosure.

              Please respond to this letter by amending your registration 
statement and providing the
       requested information. If you do not believe our comments apply to your 
facts and
       circumstances or do not believe an amendment is appropriate, please tell 
us why in your
       response.

              After reviewing any amendment to your registration statement and 
the information you
       provide in response to these comments, we may have additional comments. 
Unless we note
       otherwise, our references to prior comments are to comments in our 
November 10, 2022 letter.

       Amendment No. 1 to Registration Statement on Form S-4

       Cover Page

   1.                                                   It appears that the 
shares to be sold in the Carisma pre-closing financing are included in
                                                        the shares to be 
registered in this registration statement. The investors in the Carisma pre-
                                                        closing financing made 
their investment decision in a private offering and, therefore, the
                                                        sale must close 
privately. Please remove the Carisma pre-closing financing shares from
                                                        the registration 
statement.
       Carisma Business, page 234

   2.                                                   We note your revisions 
in response to comment 17. Please revise the first chart on page
                                                        240 to remove the 
reference to the "therapeutic efficacy" of Carisma's approach.
 Thomas R. Cannell, D.V.M.
Sesen Bio, Inc.
December 7, 2022
Page 2
Carisma's Pipeline Programs, page 235

3.    We note your response to prior comment 19 and re-issue. Please explain 
why CT-0525
      is sufficiently material to Carisma's business to warrant inclusion in 
the pipeline table.
Carisma's Strategy, page 237

4.    We note your response to prior comment 18 and re-issue in part. Please 
revise your
      statement on page 237 that you intend to "[r]apidly advance" CT-0508 
through clinical
      development to remove any implication that Carisma will be able to 
advance its product
      candidates in a rapid or accelerated manner.
       You may contact Vanessa Robertson at 202-551-3649 or Sasha Parikh at 
202-551-3627 if
you have questions regarding comments on the financial statements and related 
matters. Please
contact Dillon Hagius at 202-551-7967 or Ada D. Sarmento at 202-551-3798 with 
any other
questions.



                                                             Sincerely,
FirstName LastNameThomas R. Cannell, D.V.M.
                                                             Division of 
Corporation Finance
Comapany NameSesen Bio, Inc.
                                                             Office of Life 
Sciences
December 7, 2022 Page 2
cc:       Steven J. Abrams, Esq.
FirstName LastName