Healthcare Industry News:  XL999 

Biopharmaceuticals Oncology

 News Release - April 24, 2007

Exelixis Reinitiates Clinical Development of XL999 in Patients With Non-Small Cell Lung Cancer

SOUTH SAN FRANCISCO, Calif., April 24 (HSMN NewsFeed) -- Exelixis, Inc. (Nasdaq: EXEL ) has been notified that the U.S. Food and Drug Administration (FDA) has completed its review of a clinical trial protocol for XL999 in patients with non-small cell lung cancer (NSCLC) and has agreed that the trial may be initiated.

This clinical trial will evaluate XL999 in patients with NSCLC who have failed at least one previous therapy. The trial will have a dose-escalation format starting at 0.4 mg/kg dosed weekly, while monitoring patients for potential cardiovascular events. Results from this Phase 1 clinical trial could provide Exelixis with the opportunity to move directly into a late stage clinical trial if XL999 demonstrates anti-tumor activity with an acceptable side-effect profile in this well-defined NSCLC patient population.

"We have worked closely with the FDA to reinitiate the clinical development of XL999 and believe that the approved protocol will enable us to assess both safety and preliminary anti-tumor activity of the compound in patients with NSCLC," said George A. Scangos, PhD, president and chief executive officer of Exelixis. "In the previous Phase 2 clinical trial of XL999 in NSCLC patients, nine patients participated, of whom two had partial responses and one had prolonged stable disease. We believe that these data warrant further evaluation of XL999 in this patient population, and we expect to begin enrolling patients in the new clinical trial this summer."

About XL999

XL999 is a potent inhibitor of key receptor tyrosine kinases (RTKs) implicated in the development and maintenance of tumor vasculature and in the proliferation of some tumor cells. It inhibits the FGFR, VEGFR and PDGFR RTKs and also is a potent inhibitor of FLT3, an important driver of leukemia cell proliferation in some patients with acute myelogenous leukemia (AML). Additional data from XL999 Phase 2 clinical trials will be presented in a poster at the 43rd Annual Meeting of the American Society of Clinical Oncology (ASCO). The conference is taking place June 1-5, 2007 in Chicago.

XL999 was previously evaluated in Phase 1 and 2 clinical trials in which cardiovascular adverse events were observed. These observations caused Exelixis to suspend new patient enrollment in the ongoing XL999 clinical trials in November 2006. The FDA subsequently placed the clinical program on partial clinical hold in December 2006. The previous Phase 1 and 2 clinical trials will not be re-initiated at this time. Given acceptance by the FDA of the new clinical trial protocol for XL999 in patients with NSCLC, the XL999 development program will now focus on this indication.

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 GlaxoSmithKline, Bristol-Myers Squibb Company, Genentech, Wyeth Pharmaceuticals and Sankyo. For more information, please visit the company's web site at

This press release contains forward-looking statements, including without limitation statements related to the future development and potential efficacy of XL999 and the expected timing of the initiation of the clinical trial of XL999. Words such as "believes," "anticipates," "plans," "expects," "intends," "will," "slated," "goal" 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. 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, risks related to the lengthy, costly and uncertain process of clinical testing of XL999 and the potential failure to demonstrate safety and efficacy and the therapeutic and commercial potential of XL999. These and other risk factors are discussed under "Risk Factors" and elsewhere in Exelixis' Annual Report on Form 10-K for the year ended December 29, 2006 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.

Source: Exelixis

Issuer of this News Release is solely responsible for its content.
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