October 4, 2018

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

       Re: TCR2 Therapeutics Inc.
           Draft Registration Statement on Form S-1
           Submitted September 7, 2018
           CIK No. 0001750019

Dear Mr. Menzel:

       We have reviewed your 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
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

Draft Registration Statement on Form S-1

Prospectus Summary, page 1

1.     Without limitation and by example, we note the following statements:

           "[w]e... believe that our product candidates will have better
efficacy and safety than
           currently approved chimeric antigen receptor T cell (CAR-T)
therapies for CD19-
           positive B-cell hematological malignancies";
           "we have observed greater efficacy, longer persistence and less
cytokine release
 Garry Menzel
FirstName LastNameGarry Menzel
TCR2 Therapeutics Inc.
Comapany 2018
October 4, NameTCR2 Therapeutics Inc.
Page 2
October 4, 2018 Page 2
FirstName LastName
             compared to CAR-T cells";
             "[w]e believe that these properties will translate into a more
effective and safer T cell
             therapy for patients with cancer";
             "[o]ur core format, in which we target a single cancer antigen, is
known as a mono
             TRuC-T cell which we believe will be effective in patients based
on our preclinical
             "we have shown better efficacy, longer persistence and lower
cytokine release
             compared to existing CAR-T cell therapies bearing the same tumor
antigen binding
             domains"; and
             "[i]n our preclinical studies we have demonstrated better efficacy
and persistence of
             TRuC-T cells compared to CAR-T cells while also exhibiting lower
levels of cytokine

         Statements regarding efficacy and safety are determinations that only
the FDA has the
         authority to make. Please revise your disclosure here and throughout
the prospectus to
         eliminate any suggestion that your product candidates have been or
will ultimately be
         determined safe and effective or to have demonstrated safety and
efficacy for purposes of
         granting marketing approval by the FDA or a comparable agency.
2.       We note your comparisons to approved CAR-T therapies. Please advise
how you are able
         to make these comparisons given your pre-clinical stage and the lack
of any head-to-head
         clinical trials or, alternatively, delete these comparisons.
3.       Please tell us the basis for your belief that your therapies
constitute "the next generation"
         of therapies for patients suffering from cancer. In addition, please
tell us the basis for
         your belief that your therapies will be "first-in-class."
4.       Please name the gene editing company you reference on page 3 and
explain its
         significance to your business.
Our Pipeline, page 4

5.       Please delete the "Clinical" column and revise to add a column for
each of Phase 1, Phase
         2 and Phase 3. Additionally, please delete the "Undisclosed" and
"Multiple Programs"
         rows as those references appear premature.
6.       Please refer to the "Discovery," "Lead Optimization" and "IND
Enabling" columns.
         Please advise how "IND Enabling" differs from pre-clinical.
Additionally, please advise
         what is the difference between "Discovery" and "Lead Optimization." To
the extent you
         retain these columns rather than just "Discovery" and "Pre-Clinical"
columns, please add
         detailed footnotes to the table to explain each development phase
clearly so that investors
         can appreciate the differences between the phases.
 Garry Menzel
FirstName LastNameGarry Menzel
TCR2 Therapeutics Inc.
Comapany 2018
October 4, NameTCR2 Therapeutics Inc.
October 4, 2018 Page 3
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FirstName LastName
Implications of Being an Emerging Growth Company , page 7

7.       Please supplementally provide us with copies of all written
communications, as defined in
         Rule 405 under the Securities Act, that you, or anyone authorized to
do so on your behalf,
         present to potential investors in reliance on Section 5(d) of the
Securities Act, whether or
         not they retain copies of the communications.
Our bylaws to be effective upon the consummation of this offering designate
certain courts, page

8.       Please revise the risk factor to identify the actions for which the
United States District
         Court for the District of Massachusetts will be the exclusive forum.
In this regard, we
         note your disclosure on page 165 that such court will be the exclusive
forum for Securities
         Act claims.
Management's Discussion and Results of Operations
Results of Operations
Research and Development Expenses, page 82

9.       With regard to the research and development expense table and
discussion on page 82,
         please address the following:
           Clarify why you are referring to clinical development when it
appears based on page 4
             that your product candidates are in the preclinical phase;
           Please revise the table to clarify that TC-210 is also in the
preclinical phase;
           Clarify, if such is the case, that the costs related to TC-210 only
include the external
             outsourced development costs;
           Separately present any material type of expense included in "other
expenses"; and
           Clarify your last sentence in the paragraph below the table which
states that you began
             focusing on the development of TC-210 as opposed to your TRuC-T
cell platform
             since the statement appears to conflict with your statement on
page 4 that indicates
             TC-210 is your most advanced mono TRuC-T cell product candidate.
Preclinical Studies of TC-210, page 99

10.      Please revise the descriptions of your various pre-clinical studies to
focus on the specific
         factual details of your studies and to remove all inappropriate
references to the efficacy or
         safety of your product candidates including all inappropriate
comparisons to approved
         CAR-T therapies.
Description of Capital Stock
Registration Rights, page 163

11.      Please disclose whether there are any maximum cash penalties under the
         rights agreements, as well as any additional penalties resulting from
delays in registering
         your common stock, if any. Refer to ASC 825-20-50-1.
 Garry Menzel
FirstName LastNameGarry Menzel
TCR2 Therapeutics Inc.
Comapany 2018
October 4, NameTCR2 Therapeutics Inc.
October 4, 2018 Page 4
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Choice of Forum, page 165

12.      We note that your forum selection provision identifies the Court of
Chancery of the State
         of Delaware as the exclusive forum for certain litigation, including
any "derivative
         action." Please disclose whether this provision applies to actions
arising under the
         Exchange Act. In that regard, we note that Section 27 of the Exchange
Act creates
         exclusive federal jurisdiction over all suits brought to enforce any
duty or liability created
         by the Exchange Act or the rules and regulations thereunder. If this
provision does not
         apply to actions arising under the Exchange Act, please also ensure
that the exclusive
         forum provision in your governing documents states this clearly.
Notes to Financial Statements
9. Stock-Based Compensation, page F-15

13.      Please tell us why you believe the expected volatility of 69.3% and
65.7% for 2016 and
         2017, respectively, is appropriate. In this regard, explain why you
believe each company
         is similar to you. Also, please tell us what volatility rate was used
in your valuations in
         2018. In your response, at a minimum, specifically tell us whether
these peer companies
         have any product revenues and the following information regarding
their development
           The number of product candidates in the pipeline
           The general therapeutic area of these product candidates, and
           The phase of development for those product candidates.

14.      Once you have an estimated offering price or range, please explain to
us how you
         determined the fair value of the common stock underlying your equity
issuances and the
         reasons for any differences between the recent valuations of your
common stock leading
         up to the IPO and the estimated offering price. This information will
help facilitate our
         review of your accounting for equity issuances including stock
compensation and
         beneficial conversion features.
Item 16. Exhibits and Financial Statement Schedules, page II-4

15.      Please file the royalty transfer agreement, as well as the related
royalty direction letter, as
         an exhibit to the registration statement or tell us why you are not
required to do so.

16.      Please provide us mockups of any pages that include any additional
pictures or graphics to
         be presented, including any accompanying captions. Please keep in
mind, in scheduling
         your printing and distribution of the preliminary prospectus, that we
may have comments
         after our review of these materials.
 Garry Menzel
TCR2 Therapeutics Inc.
October 4, 2018
Page 5
17.      We note you have filed certain exhibits pursuant to a request for
confidential treatment.
         We will provide any comments we have on your application for
confidential treatment
         under separate cover.
       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 4, 2018 Page 5                                         Office of
Healthcare & Insurance
FirstName LastName