John P. Walker

Who is John P. Walker?

Mr. Walker is an experienced leader in the biotechnology industry and

has served as our Interim Chief Executive Officer since December 2006.

Mr. Walker serves as Chairman of the Board of Directors for Novacea and

for Renovis, Inc. He also serves on the Board of Directors of Affymax,

Inc. and Geron Corporation. During his 35-year career, Mr. Walker has

served as Chairman, CEO, or interim CEO of a number of biotechnology

and pharmaceutical companies, including KAI Pharmaceuticals and Guava

Technologies, Inc. From 1993 to 2001, he was Chairman, CEO, and a

director of AXYS Pharmaceuticals, Inc. and its predecessor company,

Arris Pharmaceutical Corporation. Prior to Arris, Mr. Walker was

Chairman and CEO of Vitaphore Corporation, a biomaterials company that

was sold to Union Carbide Chemical and Plastics Company, Inc. Mr.

Walker began his career with American Hospital Supply Corporation,

where he held a variety of general management, sales, and operational

positions. Mr. Walker also has served as President of American Medical

Systems and The Hospital Company.