PLX4032 was well tolerated at 960 mg BID, now confirmed as the maximum tolerated dose Complete response in 1 patient treated for 3 cycles Partial responses of greater than 30% tumor regression by RECIST criteria have been observed in 18 patients, with 15 patients showing responses of greater than 50% Minor responses in 6 patients showed tumor regression between 10% and 30%

Median progression-free survival (PFS) has not been achieved since it is too early in the study to report. However, the earlier reported interim median PFS for the Phase 1 dose escalation study has now increased to seven months as patients continue on treatment.

Drug-related adverse events were predominantly mild in severity and included rash, joint pain, photosensitivity and fatigue. Serious adverse events were observed in some patients after chronic treatment, including seven patients with cutaneous squamous cell carcinoma (keratoacanthoma subtype) that was removed by excision, while treatment with PLX4032 was continued. A risk management plan is in place for baseline evaluation of the skin and monitoring of all patients while on the extension study.

Since we have now confirmed the earlier Phase 1 results for PLX4032 in metastatic melanoma, we are moving quickly to advance this product candidate to pivotal trials, which we expect to start shortly, stated K. Peter Hirth, Ph.D., chief executive officer of Plexxikon. The results we are seeing with PLX4032, our most advanced selective kinase inhibitor, are encouraging in terms of both efficacy and safety. Our precision engineering of new drug candidates could confer a safety advantage compared to other less targeted agents, for cancer patients as well as for those patients suffering from other chronic diseases.

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