X0306 4 2016-06-02 0 0001501989 CytomX Therapeutics, Inc. CTMX 0001207114 SHANNON TIMOTHY M 285 RIVERSIDE AVENUE SUITE 250 WESTPORT CT 06880 1 0 0 0 Common Stock 2016-06-02 4 S 0 41193 10.79 D 4422734 I See Footnote Common Stock 2016-06-03 4 S 0 18428 10.83 D 4404306 I See Footnote Common Stock 134 D These shares of Common Stock ("Shares") are held directly by Canaan IX L.P. The Reporting Person is a non-managing member of Canaan Partners IX LLC, the general partner of Canaan IX L.P. The Reporting Person does not have voting, investment or dispositive power over any of the Shares directly held by Canaan IX L.P. and disclaims beneficial ownership of the Shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that the Reporting Person is the beneficial owner of the Shares for purposes of Section 16 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or for any other purpose. The price reported in Column 4 is a weighted average price. These Shares were sold in multiple transactions at prices ranging from $10.55 - $11.09, inclusive. The Reporting Person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of Shares sold at each separate price within the range set forth in footnote (2) of this Form 4. The price reported in Column 4 is a weighted average price. These Shares were sold in multiple transactions at prices ranging from $10.585 - $11.08, inclusive. The Reporting Person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of Shares sold at each separate price within the range set forth in footnote (3) of this Form 4. Exhibit 24 - 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) By: /s/ Cynthia J. Ladd, Attorney-in-Fact 2016-06-06