X0306 4 2022-05-17 0 0001690585 Magenta Therapeutics, Inc. MGTA 0001816944 Humphrey Jeffrey C/O MAGENTA THERAPEUTICS, INC. 100 TECHNOLOGY SQUARE CAMBRIDGE MA 02139 0 1 0 0 Chief Medical Officer Stock Option (Right to Buy) 1.18 2022-05-17 4 A 0 50000 0.00 A 2032-05-16 Common Stock 50000 50000 D This option shall vest and become exercisable in three equal installments, each installment vesting every six months, over the 18 months following the vesting commencement date. The vesting commencement date is May 15, 2022. /s/ Cindy Driscoll, Attorney-in-Fact for Jeffrey Humphrey 2022-05-19