Perceptive Advisors LLC and Joseph Edelman's Ownership in CytomX Therapeutics, Inc.

Perceptive Advisors LLC, Joseph Edelman, and Perceptive Life Sciences Master Fund, Ltd. have filed a Schedule 13G indicating their ownership in CytomX Therapeutics, Inc. Each of the Reporting Persons beneficially owns 9,680,185 shares of Common Stock, representing 5.9% of the outstanding shares. The shares are directly held by the Master Fund, with Perceptive Advisors serving as the investment manager and Mr. Edelman as the managing member. The filing certifies that the securities were not acquired for the purpose of influencing the control of the issuer. The filing was made pursuant to Rule 13d-1(c) and signed by Joseph Edelman on behalf of all Reporting Persons.