Onyx down on Phase II RCC data

ONXX was off $13.47 (33%) to $27.34 on 17.8 million shares on Monday after it and partner Bayer (FSE:BAYG; BAY) reported mixed results from a placebo-controlled Phase II trial of BAY 43-9006 in 502 cancer patients. The compound met the primary endpoint of stable disease at 24 weeks in a subset of 202 advanced kidney cancer patients, but only eight of those patients had independently confirmed partial responses of 50% or more. In June, the companies reported interim results showing 13 of 106 evaluable patients had tumor shrinkage of at least 50% (see BioCentury Extra, Monday June 7, 2004). The interim results were not confirmed or independently reviewed.

After a 12-week induction phase in which all 202 RCC patients received 400 mg of BAY 43-9006 twice daily, 65 patients whose tumor burden was within 25% of their pretreatment measurements were randomized into a second 12-week placebo-controlled continuation of the study. Another 79 patients who had tumor shrinkage of 25% or more continued treatment in an open-label portion of the study, while patients with tumor growth of 25% or more were discontinued from the study. The companies said the study was not prospectively designed to monitor tumor response rates. Additional data from the trial will be presented at an upcoming scientific meeting. ...