X0306 4 2017-03-29 0 0001501989 CytomX Therapeutics, Inc. CTMX 0001663758 McCourt Marion 151 OYSTER POINT BLVD SUITE 400 SOUTH SAN FRANCISCO CA 94080 1 0 0 0 Stock Option (right to buy) 17.00 2017-03-29 4 A 0 28000 0.00 A 2027-03-28 Common Stock 28000 28000 D 1/36th of the shares subject to the option vest on each monthly anniversary measured from March 31, 2017 (the "Vesting Commencement Date"), such that 100% of the shares subject to the option will be fully vested and exercisable on the third anniversary of the Vesting Commencement Date, subject to the Reporting Person's continued service to the Issuer through each such date. /s/ Cynthia J. Ladd, as Attorney-in-Fact for Marion McCourt 2017-03-31