United States securities and exchange commission logo August 16, 2021 Fred M. Schwarzer Chief Executive Officer and President IGM Biosciences, Inc. 325 E. Middlefield Road Mountain View, California 94043 Re: IGM Biosciences, Inc. Registration Statement on Form S-3 Filed August 9, 2021 File No. 333-258644 Dear Mr. Schwarzer: This is to advise you that we have not reviewed and will not review your registration statement. 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 Alan Campbell at 202-551-4224 with any questions. Sincerely, Division of Corporation Finance Office of Life Sciences cc: Jennifer Knapp