X0508 4 2024-02-14 0 0001662579 C4 Therapeutics, Inc. CCCC 0001992219 Mossler Mark C/O C4 THERAPEUTICS, INC. 490 ARSENAL WAY #120 WATERTOWN MA 02472 0 1 0 0 Chief Accounting Officer 0 Common Stock 2024-02-14 4 A 0 18290 0 A 19790 D Stock Option (Right to Buy) 7.31 2024-02-14 4 A 0 27430 0 A 2034-02-13 Common Stock 27430 27430 D Represents restricted stock units ("RSUs"). Each RSU represents the contingent right to receive one share of the Issuer's Common Stock upon vesting and settlement. The RSUs shall vest in four equal annual installments following the grant date, with the first installment vesting on February 14, 2025. Includes 1,500 shares of Common Stock that were inadvertently omitted from the Form 3 filed by the Reporting Person on September 19, 2023. The shares underlying this option shall vest and become exercisable in sixteen equal quarterly installments following the grant date, with the first installment vesting on May 14, 2024. /s/ Jolie M. Siegel, Attorney-in-Fact 2024-04-10