April 4, 2019

Jason Gardner
Chief Executive Officer
Magenta Therapeutics, Inc.
100 Technology Square
Cambridge, MA 02139

       Re: Magenta Therapeutics, Inc.
           Draft Registration Statement on Form S-1
           Submitted March 29, 2019
           CIK No. 0001690585

Dear Dr. Gardner:

       This is to advise you that we do not intend to review your registration
statement.

        We request that you publicly file your registration statement no later
than 48 hours prior
to the requested effective date and time. 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 Tonya K. Aldave at (202) 551-3601 with any questions.



                                                             Sincerely,

                                                             Division of
Corporation Finance
                                                             Office of
Healthcare & Insurance
cc:    William D. Collins, Esq.