X0306 4 2020-06-17 0 0001501989 CytomX Therapeutics, Inc. CTMX 0001387521 Meyers James R C/O CYTOMX THERAPEUTICS, INC. 151 OYSTER POINT BLVD., SUITE 400 SOUTH SAN FRANCISCO CA 94080 1 0 0 0 Stock Option (Right to Buy) 8.35 2020-06-17 4 A 0 20000 0.00 A 2030-06-16 Common Stock 20000 20000 D The underlying shares subject to the option vest and become exercisable as to 100% of the total number of shares subject to the option on the earlier of (i) the first anniversary of the grant date or (ii) the date of the 2021 Annual Meeting of the Issuer's stockholders, assuming continuous service as a director until such vesting date. /s/ Lloyd Rowland, as Attorney-in-Fact for James R. Meyers 2020-06-17