Exelixis Submits XL880 Diligence Report to Glaxo...( -Submission initiates...)

-Submission initiates 90-day review period-

SOUTH SAN FRANCISCO, Calif., Sept. 14 /PRNewswire-FirstCall/ -- Exelixis, Inc. (Nasdaq: EXEL) today announced that the company has submitted a comprehensive data report relating to XL880 to GlaxoSmithKline (GSK). As announced in August 2007, GSK requested to initiate its review of XL880 before the compound reaches proof-of-concept as defined under the product development and commercialization agreement between the two companies. GSK now has 90 days to review the data package and determine if it will select the compound for further clinical development and commercialization.

"Both GSK and Exelixis have been very encouraged by the results seen to date in the comprehensive clinical program for XL880," said George A. Scangos, Ph.D, president and chief executive officer of Exelixis, Inc. "We have seen very encouraging signs of anti-tumor activity, and XL880 remains the only MET inhibitor for which there is human pharmacodynamic data demonstrating that the compound does inhibit MET in human tumors. The increasing recognition that MET is likely to play a role in the proliferation of many types of solid tumors, including lung, breast, and colon tumors, coupled with the demonstrated ability of XL880 to inhibit MET in humans, has generated considerable enthusiasm. We are pleased that GSK asked to review the data early in order to clarify ownership of the compound and expand XL880's position as what we believe is the most advanced MET inhibitor in clinical development."

Pursuant to the product development and commercialization agreement between Exelixis and GlaxoSmithKline, GlaxoSmithKline has the option, after completion of clinical proof-of-concept by E
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