X0508 4 2026-02-13 0 0001662579 C4 Therapeutics, Inc. CCCC 0002040313 Mahaney Paige C4 THERAPEUTICS, INC. 490 ARSENAL WAY, SUITE 120 WATERTOWN MA 02472 0 1 0 0 Chief Scientific Officer 0 Common Stock 2026-02-13 4 A 0 240000 0 A 339356 D Common Stock 2026-02-14 5 M 0 E 7050 0 A 339356 D Common Stock 2026-02-14 4 F 0 2446 1.89 D 336910 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 as follows: (i) 120,000 RSUs shall vest in three equal annual installments following the grant date, with the first installment vesting on February 13, 2027, and (ii) 120,000 RSUs shall vest in full on February 13, 2029, subject to potential acceleration upon achievement of certain performance milestones. Reflects the acquisition of shares of Common Stock upon vesting of a previously disclosed grant of RSUs. The grant of RSUs was initially reported in Table I of the Forms 4 filed by the Reporting Person on February 18, 2025. Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of RSUs and does not represent a sale by the Reporting Person. /s/ Shagha Russell, Attorney-in-Fact 2026-02-18