Stelios Papadopoulos, Ph.D., a co-founder of Exelixis, has been a director since December 1994 and the Chair of the Board since January 1998. Dr. Papadopoulos retired as Vice Chairman of Cowen & Co., LLC in August 2006 after six years as an investment banker with the firm, where he focused on the biotechnology and pharmaceutical sectors. Prior to joining Cowen & Co., he spent 13 years as an investment banker at PaineWebber, Incorporated, where he was most recently Chairman of PaineWebber Development Corp., a PaineWebber subsidiary focusing on biotechnology. He joined PaineWebber in April 1987 from Drexel Burnham Lambert, where he was a Vice President in the Equity Research Department covering the biotechnology industry. Prior to Drexel, he was a biotechnology analyst at Donaldson, Lufkin & Jenrette.

Before coming to Wall Street in 1985, Dr. Papadopoulos was on the faculty of the Department of Cell Biology at New York University Medical Center. Dr. Papadopoulos was a co-founder of Anadys Pharmaceuticals, Inc., a publicly held biopharmaceutical company dedicated to improving patient care by developing novel medicines for the treatment of hepatitis C, acquired by Hoffmann-La Roche Inc. in November 2011. Dr. Papadopoulos served as a member of the board of directors of Anadys Pharmaceuticals from 2000 to 2011 and as its chairman in 2011, prior to its acquisition.

Dr. Papadopoulos has also served as a member of the board of directors of four other publicly held companies: Regulus Therapeutics Inc., a biopharmaceutical company focused on the development of medicines targeting microRNAs, since 2008, and as its chairman since 2013; Eucrates Biomedical Acquisition Corp., a special purpose acquisition company (SPAC) formed for the purpose of effecting a merger, share exchange, asset acquisition, share purchase, reorganization or similar business combination with one or more businesses, and as its chairman, since 2020; Biogen, Inc., a biopharmaceutical company focused on the treatment of serious diseases, from 2008 to June 2023, and as its chairman from 2014 to June 2023; and BG Medicine, Inc., a diagnostics company focused on the development and commercialization of cardiovascular diagnostic tests, from 2003 to 2018. Dr. Papadopoulos was also co-founder and member of the board of directors of Cellzome Inc., a privately held drug discovery company acquired by GlaxoSmithKline in May 2012.

In the not-for-profit sector, Dr. Papadopoulos is a co-founder and Chairman of Fondation Santé, a member of the board of visitors of Duke Medicine, and a member of the Global Advisory Board of the Duke Institute for Health Innovation. Dr. Papadopoulos holds an M.S. in Physics, a Ph.D. in Biophysics and an M.B.A. in Finance, all from New York University.