GlaxoSmithKline is seeking to accelerate its review of an Exelixis MET inhibitor, XL880, ahead of proof-of-concept, South San Francisco, Calif.-based Exelixis announced Aug. 23. Under the action, GSK could opt in to pursue further clinical development and commercialization of the anti-cancer compound earlier than anticipated, which could potentially move up the initiation of larger clinical trials in breast and lung cancer, Exelixis told "The Pink Sheet" DAILY.

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

The drug is currently being studied in two Phase II trials in hereditary papillary renal cell cancer and gastric cancer. Details of those trials have not been released, although the company said the renal cancer trial is evaluating two cohorts of 17 patients each, with the first fully enrolled and the second enrolling.

"These are relatively narrow indications," Exelixis said of the renal cell and gastric trials. "The implication here is ... it moves up the ability to get those larger trials started faster." The MET inhibitor has demonstrated dose-dependent tumor growth inhibition in preclinical models of breast cancer, colorectal cancer, non-small cell lung cancer and gioblastoma. It has been shown to cause substantial tumor regression in all models tested, according to Exelixis.

Exelixis expects to deliver data to GSK in mid-September, at which point GSK will begin its review to determine whether to continue development.

The request by GSK to expedite the review "reflects the high level of excitement around both the compound and the therapeutic potential of MET inhibition," the company said. The compound is believed to be the latest stage MET inhibitor in development, according to Exelixis.

The announcement comes shortly after GSK declined to license a different compound, XL647, from Exelixis for the treatment of non-small cell lung cancer. Exelixis said in July that it will advance the Phase II EGFR inhibitor ¹(Also see "GlaxoSmithKline Passes On Option For Exelixis’ XL647 Lung Cancer Candidate" - Pink Sheet, 26 July, 2007.)

- Jessica Merrill (j.merrill@elsevier.com)

GSK, Exelixis Expedite Review Of Lead MET Inhibitor

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