PRESS RELEASE: Exelixis and Bristol-Myers Squibb Extend Research Deal

Exelixis and Bristol-Myers Squibb Extend Research Deal

SOUTH SAN FRANCISCO, Calif., Sept. 21 -- Exelixis, Inc. today announced that it has signed an extension of the company's research collaboration agreement with Bristol-Myers Squibb Company to develop and commercialize novel therapies targeted against the Liver X Receptor (LXR), a nuclear hormone receptor implicated in a variety of cardiovascular and metabolic disorders.

The collaboration, originally established in January of 2005 for a period of two years, has been extended at Bristol-Myers Squibb's request through January 12, 2009. Bristol-Myers Squibb also has retained the option to further extend the research collaboration by an additional year. Terms of the extension include additional research funding paid to Exelixis in the amount of $7.5M.

"Exelixis and Bristol-Myers Squibb have a history of working efficiently and productively together, and we have maintained this positive dynamic in our LXR collaboration," said Michael Morrissey, Ph.D., president of research and development at Exelixis. "In less than two years, we have made substantial progress in identifying and optimizing compounds that activate LXR, potentially providing new treatments for cardiovascular and metabolic diseases, which are diseases with increasing impact."

Under the terms of the collaboration, the two companies jointly identify drug candidates that are ready for Investigational New Drug Application-enabling studies. Bristol-Myers Squibb then undertakes further preclinical development and has responsibility for clinical development, regulatory, manufacturing and sales/marketing activities for such compounds.

About the Liver X Receptor

LXR activation by oxysterols (oxidized cholesterol) or by synthetic agonists initiates a cascade of cellular events that both increase "reverse cholesterol transport," thereby removing excess cholesterol from the body, and suppress inflammation. Elevated levels of oxysterols have been implicated in the progression of heart disease and plaque formation in the artery wall. LXR activation therefore directly targets two well-known risk factors of heart disease and provides a novel approach for decreasing the deposition of fat and lipids in the artery wall and suppressing the inflammatory damage associated with atherosclerosis. In animal models of heart disease, small molecule synthetic LXR ligands have been shown to cause regression of pre-existing atherosclerotic lesions. Thus, LXR may be a first-in-class target for therapies that directly target the pathology of atherosclerosis and coronary artery disease via a dual mechanism of reverse cholesterol transport and repression of inflammation.

About Exelixis

Exelixis, Inc. is a development-stage biotechnology company dedicated to the discovery and development of novel small molecule therapeutics for the treatment of cancer and other serious diseases. The company is leveraging its fully integrated drug discovery platform to fuel the growth of its development pipeline, which is primarily focused on cancer. Currently, Exelixis' broad product pipeline includes investigational compounds in phase 2 and phase 1 clinical development for cancer and renal disease. Exelixis has established strategic corporate alliances with major pharmaceutical and biotechnology companies, including GSK, Bristol-Myers Squibb, Genentech, Wyeth Pharmaceuticals and Daiichi-Sankyo. For more information, please visit the company's web site at

Forward Looking Statement

This press release contains forward-looking statements, including, without limitation, all statements related to the discovery, development and commercialization of therapies targeted against the Liver X Receptor (LXR), future performance under the collaboration and the value of LXR as a target for therapies for atherosclerosis and coronary artery disease. Words such as "potentially" "undertakes," "may" and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon Exelixis' current expectations. Forward-looking statements involve risks and uncertainties and past performance is not indicative of future results. Exelixis' actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, the risk that products candidates that appeared promising in early research do not demonstrate safety or efficacy in clinical trials; the ability of Exelixis to advance preclinical compounds into clinical development; the uncertainty of the FDA approval process; and the therapeutic and commercial value of Exelixis' compounds. These and other risk factors are discussed under "Risk Factors" and elsewhere in Exelixis' quarterly report on Form 10-Q for the quarter ended June 30, 2007 and other filings with the Securities and Exchange Commission. Exelixis expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in Exelixis' expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.