X0508 4 2025-10-20 0001501989 CytomX Therapeutics, Inc. CTMX 0002094324 Lester Rachael C/O CYTOMX THERAPEUTICS, INC. 151 OYSTER POINT BLVD., SUITE 400 SOUTH SAN FRANCISCO CA 94080 true Chief Business Officer false Stock Option (Right to Buy) 3.74 2025-10-20 4 A 0 650000 0 A 2035-10-19 Common Stock 650000 650000 D 25% of the shares subject to the option vest on the one year anniversary measured from October 20, 2025 (the "Vesting Commencement Date"), and 1/48th of the shares will vest monthly thereafter, such that 100% of the shares subject to the option will be fully vested and exercisable on the fourth anniversary of the Vesting Commencement Date, subject to the Reporting Person's continued service to the Issuer through each such date. /s/ Christopher Ogden, as Attorney-in-Fact for Rachael Lester 2025-10-29