United States securities and exchange commission logo

                             July 9, 2020

       Barry Labinger
       Chief Executive Officer
       Checkmate Pharmaceuticals, Inc.
       245 Main Street, 2nd Floor
       Cambridge, MA 02142

                                                        Re: Checkmate
Pharmaceuticals, Inc.
                                                            Amendment No. 1 to
                                                            Draft Registration
Statement on Form S-1
                                                            Submitted June 23,
                                                            CIK No. 0001651431

       Dear Mr. Labinger:

             We have reviewed your amended draft 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 providing the requested
information and either submitting
       an amended draft registration statement or publicly filing your
registration statement on
       EDGAR. 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

             After reviewing the information you provide in response to these
comments and your
       amended draft registration statement or filed registration statement, we
may have additional

       Amendment No. 1 to Draft Form S-1 submitted June 23, 2020

       Prospectus Summary, page 1

   1.                                                   We note your revisions
in response to prior comment 1. Please further revise to eliminate
                                                        the references that
remain throughout the document, such as the "generally manageable
                                                        safety profile we have
observed to date" on page 2 and similar reference on page 3,
                                                        "robust anti-tumor
activity" on pages 3 and 102, and "maintaining a continued acceptable
                                                        safety profile of
CMP-001" on pages 34 and 88.
   2.                                                   We note your response
to prior comment 2 and that you do not intend to rely upon the
                                                        comparisons to other
studies that evaluated neoadjuvant PD-1 blockade as a monotherapy
 Barry Labinger
Checkmate Pharmaceuticals, Inc.
July 9, 2020
Page 2
      or in combination with ipilimumab to support marketing approval of
CMP-001. In light of
      this fact, and the fact that it remains unclear whether there were
significant variables
      between your studies and those against which you are drawing the
comparisons, we
      continue to object to your statement that studies of your candidate
"compare favorably"
      with the other studies. We will not object if you include disclosure in
your Business
      section stating the results from the other studies, but please revise to
remove the
        You may contact Vanessa Robertson at 202-551-3649 or Lisa Vanjoske at
if you have questions regarding comments on the financial statements and
matters. Please contact Courtney Lindsay at 202-551-7237 or Mary Beth Breslin
at 202-551-
3625 with any other questions.

FirstName LastNameBarry Labinger
                                                         Division of
Corporation Finance
Comapany NameCheckmate Pharmaceuticals, Inc.
                                                         Office of Life
July 9, 2020 Page 2
cc:       Ben Marsh
FirstName LastName