X0306 4 2022-07-19 0 0001501989 CytomX Therapeutics, Inc. CTMX 0001682735 Peterson Amy C. C/O CYTOMX THERAPEUTICS, INC. 151 OYSTER POINT BLVD., STE. 400 SOUTH SAN FRANCISCO CA 94080 0 1 0 0 EVP, Chief Development Officer Common Stock 2022-07-19 4 A 0 20000 0.00 A 70153 D Common Stock 2022-07-20 4 S 0 7463 1.4220 D 62690 D Represents Performance Stock Units ("PSUs") initially granted on October 24, 2021 that were subject to a performance-based vesting condition. The first milestone vesting condition was determined to be satisfied upon which 50% of the PSUs vested. Includes 40,000 restricted stock units. Reflects the adjusted total which includes the purchase of 3,732 shares under the Cytomx Therapeutics Employee Stock Purchase Plan on May 31, 2022. The shares were sold solely to satisfy tax or other government withholding obligations in connection with the vesting of shares subject to a PSU of the Issuer. /s/ Lloyd Rowland, as Attorney-in-Fact for Amy C. Peterson 2022-07-21