South San Francisco, California
April 15, 2002

Exelixis, Inc. (Nasdaq: EXEL) has identified and validated additional pesticide targets through its Genoptera joint venture with Bayer's crop protection division. Assay development and subsequent high throughput screening of these targets against Bayer's compound collection may lead to the development of superior pest control agents. The delivery of these targets has triggered an undisclosed milestone payment to Exelixis.

"The challenge of creating new generations of pesticides which can overcome pest resistance and safely and cost effectively ensure abundant crop yields will be facilitated by the research efforts of the Genoptera joint venture," stated George A. Scangos, Ph.D., president and chief executive officer of Exelixis. "The targets which have been identified through the collaboration are characterized with a high level of biological validation, and provide to our partner Bayer an excellent foundation for further research aimed at combating pest species.

Genoptera LLC is an Exelixis-Bayer joint venture with the aim of identifying novel targets and providing assays for the discovery of new crop protection substances, in particular the discovery of novel insecticides and nematicides. The 2000 joint venture included a $20 million up-front payment and performance-based milestone and royalty payments to Exelixis as well as $80 million in research funding over the course of the eight-year joint venture.

Exelixis, Inc. is a leading genomics-based drug discovery company focused on product development through its expertise in comparative genomics and model system genetics. These technologies provide a rapid, efficient and cost effective way to move from DNA sequence data to knowledge about the function of genes and the proteins they encode. The company's technology is broadly applicable to all life sciences industries including pharmaceutical, diagnostic, agricultural biotechnology and animal health. Exelixis has partnerships with Aventis CropScience, Bayer, Bristol-Myers Squibb, Elan Pharmaceuticals, Protein Design Labs, Schering-Plough Research Institute, Scios, Dow AgroSciences and Cytokinetics and is building its internal development program in the area of oncology.