GlaxoSmithKline is moving forward with plans to develop and commercialize Exelixis' small molecule cancer compound XL880, the companies announced Dec. 14.

The announcement comes roughly four months after the U.K. drug maker said it would accelerate development, ahead of proof-of-concept studies, of the small molecule inhibitor of kinases MET and VEGF (¹ Also see "GSK, Exelixis Expedite Review Of Lead MET Inhibitor" - Pink Sheet, 23 August, 2007.).

Under a deal signed by the companies in 2005, whereby GSK has the right to opt in on three of 12 compounds, GSK's review of XL880 would have taken place after proof-of-concept data became available.

"In the case of XL880, GSK requested in August 2007 to review the compound's data prior to achievement of proof-of-concept," the firms noted in a same-day news release.

"The exercise of the XL880 option confirms GSK's growing status as a world leader in the development of new oncology medicines for use in the treatment, prevention and supportive care of cancer patients," GSK Senior VP-Oncology Medicines Development Center Paolo Paoletti stated.

"The data we have seen from trials conducted by Exelixis have given us confidence in the potential of XL880 for treating diseases for which there is high unmet medical need."

XL880 is currently being evaluated in Phase II for treatment of papillary renal cell carcinoma, gastric cancer and head and neck cancer.

Interim data from an ongoing Phase II trial of XL880 in those indications have shown that 15 of 19 patients (79 percent) with measurable disease evaluable for tumor response had a decrease in tumor size ranging from 4 percent to 33 percent, including one patient with a partial response, based on RECIST criteria.

GSK's selection of XL880 entitles Exelixis to a $35 million milestone payment and additional payments upon the attainment of specific development and commercialization milestones.

The $35 million will be applied to repayment of an advance that GSK paid to Exelixis in 2005, the firms said.

Exelixis is also entitled to receive double-digit royalties on product sales if the compound is approved and commercialized, and will have certain co-promotion rights to XL880 in North America.

GSK declined to license a different compound, XL647, for the treatment of non-small cell lung cancer in July. Exelixis has said it will advance the Phase II EGFR inhibitor on its own (² Also see "GlaxoSmithKline Passes On Option For Exelixis’ XL647 Lung Cancer Candidate" - Pink Sheet, 26 July, 2007.).

-Brooke McManus (b.mcmanus@elsevier.com)

GSK Selects Exelixis’ Phase II MET Inhibitor XL880

More from Archive

More from Pink Sheet