X0306 4 2016-04-05 0001501989 CytomX Therapeutics, Inc. CTMX 0001184126 GLUCK FREDERICK W 743 SAN YSIDRO ROAD SANTA BARBARA CA 91308 true Common Stock 2016-04-05 4 J 0 331643 0 A 331643 I By Frederick W. Gluck 1997 Family Trust dtd July 28, 1997 Common Stock 2016-04-05 4 J 0 17111 0 A 22111 I By Richlin Partners, LLC Common Stock 147791 D Common Stock 3200 I By spouse Pro rata distribution, in-kind and for no consideration, from CytomX Therapeutics Holdings, LLC of which the reporting person is a non-managing member. The reporting person is a trustee of Frederick W. Gluck 1997 Family Trust dtd July 28, 1997. Richlin Partners, LLC is an entity owned of record by the spouse of Frederick W. Gluck. Exhibit 24.1 - Power of Attorney (incorporated by reference to the Power of Attorney filed as Exhibit 24.1 to the Form 3 filed by the reporting person on October 7, 2015) /s/ Cynthia J. Ladd, attorney-in-fact 2016-06-21