August 15, 2019

Fred Schwarzer
Chief Executive Officer and President
IGM Biosciences, Inc.
325 E. Middlefield Road
Mountain View, CA 94043

       Re: IGM Biosciences, Inc.
           Amendment No. 1 to
           Draft Registration Statement on Form S-1
           Submitted August 9, 2019
           CIK No. 0001496323

Dear Mr. Schwarzer:

      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 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
comments.

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

Capitalization Table, page 61

1.     Please revise your filing to consistently provide the aggregate number
of common stock
       shares that the outstanding convertible preferred stock will
automatically convert to
       immediately prior to the completion of the offering. For example, page 8
states that
       91,150,325 shares of common stock will be issued upon conversion and
page 61 states
       that 86,290,538 shares of common stock will be issued.
2.     Please revise your filing to provide a consistent explanation of what is
included in the pro
       forma financial information. For example, footnote one to the table on
page 10 states the
       pro forma column gives effect to the issuance of 20,000,000 shares of
the Company's
 Fred Schwarzer
IGM Biosciences, Inc.
August 15, 2019
Page 2
         Series C convertible preferred stock. In addition to this transaction,
the pro forma
         explanation preceding the Capitalization Table also provides for the
automatic conversion
         of all outstanding shares of convertible preferred stock. The pro
forma financial
         information explanation as provided in Note 2 to the Notes to the
Consolidated Financial
         Statements for the six months ended June 30, 2019 and 2018 is also for
the two events,
         issuance of Series C convertible preferred stock and automatic
conversion of all
         outstanding convertible preferred stock. Please revise your filing
accordingly.
       You may contact Christine Torney at 202-551-3652 or Sharon Blume at
202-551-3474 if
you have questions regarding comments on the financial statements and related
matters. Please
contact Julia Griffith at 202-551-3267 or Justin Dobbie at 202-551-3469 with
any other
questions.



FirstName LastNameFred Schwarzer                             Sincerely,
Comapany NameIGM Biosciences, Inc.
                                                             Division of
Corporation Finance
August 15, 2019 Page 2                                       Office of
Healthcare & Insurance
FirstName LastName