SAN FRANCISCO –- March 6, 2012 — CytomX Therapeutics, Inc., a leader in the field of highly targeted monoclonal antibody therapies, today announced the appointment of Hoyoung Huh, M.D., Ph.D., as chairman of the Board of Directors. Former chairman Charles Homcy, M.D., venture partner at Third Rock Ventures, will continue to serve on the Board of Directors.

“We are very pleased that Hoyoung will be joining us at such a pivotal point in CytomX’s growth and evolution,” said Sean McCarthy, D. Phil., chief executive officer of CytomX. “His extensive experience leading biotech companies and his proven expertise in forging strategic corporate relationships are an invaluable addition. I look forward to working closely with Hoyoung, Charles and our full board to advance our strategic agenda as we develop a pipeline of innovative Probody™ therapeutics and move our first candidates into development.”

Dr. Huh currently serves as chairman of the Geron Corporation, where he has also held executive chairman and director positions, and on the Board of Directors for Addex Pharmaceuticals and BayBio. Dr. Huh has been involved in the formation, management and financing of more than 20 successful entities across the U.S., Europe and Asia. He was previously president, CEO and chairman of BiPar Sciences, Inc., which was acquired by Sanofi-aventis for $500 million in 2009. Dr. Huh also served as chairman of Epizyme, Inc. and has held board positions with Facet Biotech and Nektar Therapeutics, where he was the chief operating officer. Previously, Dr. Huh was a partner at McKinsey & Company. Dr. Huh holds a B.S. in biochemistry from Dartmouth College, an M.D. from Cornell University Medical College and a Ph.D. from Cornell University/Sloan-Kettering Institute.

“CytomX’s highly differentiated platform brings a transformational approach to biologics targeting,” said Dr. Huh. “I am delighted to join as chairman of the board and work closely with this visionary leadership team to realize the full potential of the Probody™ platform.”