Even though it says the regulatory timetable for cabozantinib in metastatic prostate cancer hasn't changed, Exelixis Inc. is paying a heavy price for news that spooked investors the day after Halloween.

Based on feedback from FDA in August, Exelixis thought it was in agreement with the agency about the design of a Phase III trial intended to show cabozantinib (XL184) can reduce bone pain in patients with metastatic prostate cancer. But sometime in October, according to the company, the agency reversed its position on the trial's endpoints.