Stelios Papadopoulos, Ph.D., a co-founder of Exelixis, has been a director since December 1994 and has served as Chair of the Board since January 1998. Dr. Papadopoulos retired as Vice Chairman of Cowen & Co., LLC in 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. Earlier, he held equity research roles at Drexel Burnham Lambert and 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 focused on improving patient care by developing novel medicines for the treatment of hepatitis C, acquired by F. Hoffmann-La Roche Ltd. in 2011. Dr. Papadopoulos served as a member of its board of directors from 2000 to 2011 and as its Chairman in 2011, prior to the acquisition. Dr. Papadopoulos serves as a member of the board of directors of Ovid Therapeutics, Inc. a publicly held biopharmaceutical company focused on developing small-molecule medicines for brain conditions, since 2025, and as co-founder and Chairman of the board of directors of Epikast, Inc., a privately held company focused on providing sales, medical affairs, market access, patient engagement and other services to pharmaceutical companies, since 2023. He previously served as a member of the board of directors of Regulus Therapeutics Inc., a publicly held biopharmaceutical company focused on the development of medicines targeting microRNAs, from 2008 to 2025, and as Chairman from 2013 to 2025, Biogen, Inc., a publicly held biopharmaceutical company focused on the treatment of serious diseases, from 2008 to 2023, and as its Chairman from 2014 to 2023, and Eucrates Biomedical Acquisition Corp., a special purpose acquisition company (SPAC) as its Chairman, from 2020 to 2023. Dr. Papadopoulos was also co-founder and member of the board of directors of Cellzome Inc., a privately held drug discovery company acquired by GSK plc in 2012. Dr. Papadopoulos is a co-founder and Chairman of Fondation Sant, and previously served as 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.