October 23, 2018

Garry Menzel
Chief Executive Officer
TCR2 Therapeutics Inc.
100 Binney Street
Suite 710
Cambridge, MA 02142

       Re: TCR2 Therapeutics Inc.
           Amendment No. 1 to
           Draft Registration Statement on Form S-1
           Submitted October 10, 2018
           CIK No. 0001750019

Dear Mr. Menzel:

      We have reviewed your amended draft registration statement and have the
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 response.

      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 Registration Statement on Form S-1

Prospectus Summary, page 1

1.     We note your response to comment 2 but remain concerned that you lack a
sufficient basis
       to compare your product candidates to approved CAR-T therapies. Given
your early stage
       of development and the lack of head-to-head clinical trials, these
comparisons are
       inappropriate. Please revise the prospectus throughout to delete these
 Garry Menzel
FirstName LastNameGarry Menzel
TCR2 Therapeutics Inc.
Comapany NameTCR2 Therapeutics Inc.
October 23, 2018
Page 2
October 23, 2018 Page 2
FirstName LastName

2.       We note your response to comment 3 . Please delete the reference that
your T cell
         therapies are "first-in-class."
Management's Discussion and Results of Operations
Results of Operations
Research and Development Expenses, page 82

3.       Your updated disclosure in the amendment does not appear to fully
address comment 9.
         As previously requested, please provide the following:
           Clarify that platform development relates to preclinical expenses;
           Clarify whether TC-210 preclinical expenses only include the
external outsourced
            development costs;
           Separately present any material type of expenses included in "other
expenses"; and
           Explain in the last sentence of the paragraph under the table how
the disclosure is
            consistent with your statement on page 4 indicating that TC-210 is
your most
            advanced mono TRuC-T cell product candidate.
Preclinical Studies of TC-210, page 99

4.       Please revise the description of your pre-clinical study to clarify
that the CAR-T cells used
         in the study are not completely identical to approved CAR-T cell
therapies and clarify
         who engineered such cells. To the extent applicable, please revise the
description of any
         other studies in similar manner.
Choice of Forum, page 172

5.       We note your response to comment 12, including your statement in your
response letter
         that your amended and restated bylaws do not designate an exclusive
forum for causes of
         action arising under the Exchange Act. However, the scope of your
forum selection
         clause is unclear, in part because of the reference to "any derivative
action or
         proceeding...." If your state court exclusive forum provision does not
apply to actions
         arising under the Exchange Act, please state this clearly in your
prospectus and in your
         amended and restated bylaws.
 Garry Menzel
TCR2 Therapeutics Inc.
October 23, 2018
Page 3

       You may contact Sisi Cheng at 202-551-5004 or Mary Mast at 202-551-3613
if you have
questions regarding comments on the financial statements and related matters.
Please contact
Donald Field at 202-551-3680 or Dietrich King at 202-551-8071 with any other

FirstName LastNameGarry Menzel                           Sincerely,
Comapany NameTCR2 Therapeutics Inc.
                                                         Division of
Corporation Finance
October 23, 2018 Page 3                                  Office of Healthcare &
FirstName LastName