July 25, 2019

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

       Re: IGM Biosciences, Inc.
           Draft Registration Statement on Form S-1
           Submitted June 28, 2019
           CIK No. 0001496323

Dear Mr. Schwarzer:

       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
Overview, page 1

1.     We note your disclosure that "IgM antibodies have inherent properties
that we believe
       may enable them to improve upon the efficacy and safety of IgG
antibodies in multiple
       therapeutic applications." Since none of your product candidates has
received FDA
       approval, it is premature to suggest or imply that they are safe and
effective. We also note
       other examples of statements regarding safety and efficacy in the table
on page 79 and the
       disclosure on pages 87 and 90. Please revise your disclosure regarding
safety and
       efficacy in the summary and throughout your prospectus to clarify this
 Fred Schwarzer
FirstName LastNameFred Schwarzer
IGM Biosciences, Inc.
Comapany NameIGM Biosciences, Inc.
July 25, 2019
July 25, 2019 Page 2
Page 2
FirstName LastName
2.       Briefly explain technical terms where they are first used in your
disclosure. For example,
         explain what "IgM" and "IgG" mean and how the two antibodies differ.
3.       Please include in the summary the information that appears on page 83
in the Business
         section to the effect that a generally effective treatment for most
         Lymphoma patients already exists.
Our Strategy, page 3

4.       Please briefly provide us with or explain the basis for your statement
that you are a global
         leader in the development of IgM antibodies for therapeutic use.
Emerging Growth Company Status, page 5

5.       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.
Risk Factors, page 11

6.       We note that there are references to foreign regulators and foreign
markets throughout the
         Risk Factors and other sections of your prospectus. Please revise to
explain what non-
         U.S. markets, if any, you plan to enter, and what steps you have taken
in attaining the
         necessary regulatory approvals.
7.       Please revise your disclosure pertaining to the risks associated with
patents to clarify that
         you have relatively few patents, and many patent applications, at this
point in your
Use of Proceeds, page 58

8.       Please revise to clarify whether you believe the net proceeds will be
sufficient to complete
         the Phase 1 clinical trials for your two product candidates, and if
not, how far into those
         trials you expect the proceeds to last.
Results of Operations
Research and Development Expenses, page 68

9.       We note you incurred over $7 million in direct clinical trials
expenses as of December 31,
         2018 even though none of your product candidates had reached phase 1
clinical trials.
         Please expand your disclosures to explain what these expenses are
considering they are
         larger than your preclinical trials expenses. In your revised
disclosures, consider the
         description of research and development expenses already included on t
page 66, as
 Fred Schwarzer
FirstName LastNameFred Schwarzer
IGM Biosciences, Inc.
Comapany NameIGM Biosciences, Inc.
July 25, 2019
Page 3
July 25, 2019 Page 3
FirstName LastName
Critical Accounting Policies and Estimates
Fair Value of Common Stock, page 72

10.      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.
Business, page 74

11.      Please provide us a basis for statements that you have "the most
advanced research and
         development program focused on engineered therapeutic IgM antibodies;"
that your
         platform allows you "to create IgM antibodies with higher affinity and
avidity than
         naturally occurring IgM antibodies;" that your "platform also allows
us to utilize the
         strong and durable binding of IgM antibodies to kill cancer cells with
T cells, induce
         programmed death of cancer cells or deliver immune stimulating
cytokines to the region
         of the bound cell;" and that your "IgM platform creates significant
competitive advantages
         and can serve as the foundation for the development of a broad range
of IgM based
         therapeutic drugs."
Exclusive Jurisdiction, page 139

12.      Please disclose, if true, that your exclusive forum provision does not
apply to actions
         arising under the Securities Act or Exchange Act. Please also ensure
that the exclusive
         forum provision in the bylaws states this clearly, or tell us how you
will inform investors
         in future filings that the provision does not apply to any actions
arising under the
         Securities Act or Exchange Act.

13.      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.
 Fred Schwarzer
FirstName LastNameFred Schwarzer
IGM Biosciences, Inc.
Comapany NameIGM Biosciences, Inc.
July 25, 2019
Page 4
July 25, 2019 Page 4
FirstName LastName
        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
matters. Please contact Julia Griffith at (202) 551-3267 or Justin Dobbie at
(202) 551-3469 with
any other questions.


                                                           Division of
Corporation Finance
                                                           Office of Healthcare
& Insurance