X0306 4 2021-01-07 0 0001789972 Cullinan Management, Inc. CGEM 0001575933 Hughes Owen C/O CULLINAN MANAGEMENT, INC. ONE MAIN STREET, SUITE 520 CAMBRIDGE MA 02142 1 1 0 0 President and CEO Stock Option (Right to Buy) 21.00 2021-01-07 4 A 0 433332 0.00 A 2031-01-06 Common Stock 433332 433332 D The option represents a right to purchase a total of 433,332 shares of the Issuer's Common Stock, 25% of which will become fully vested and exercisable on January 7, 2022, with the remaining shares vesting in equal monthly installments over the following three years (36 months), subject to the reporting person's continued employment with the Issuer. /s/ Jeffrey Trigilio, attorney-in-fact 2020-01-07