X0306 4 2021-05-05 0 0001496323 IGM Biosciences, Inc. IGMS 0001787681 Chen Daniel ShinYu C/O IGM BIOSCIENCES, INC. 325 E. MIDDLEFIELD ROAD MOUNTAIN VIEW CA 94043 0 1 0 0 Chief Medical Officer Common Stock 2021-05-05 4 S 0 469 62.3156 D 116518 D The sale was effected pursuant to a Rule 10b5-1 trading plan entered into by the Reporting Person. This transaction was executed in multiple trades at prices ranging from $62.00 to $62.40. The price reported above reflects the weighted average sale price. The Reporting Person undertakes to provide upon request by the staff of the Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each separate sale price. /s/ Misbah Tahir, by power of attorney 2021-05-06