Exelixis has also discussed the trial design with European regulatory agencies. Exelixis is planning to initiate the Phase III trial of XL184 as a potential treatment for medullary thyroid cancer (MTC) this summer.
The Phase III trial will be a randomized, placebo-controlled, double-blinded study of XL184 as single-agent therapy in 315 patients with unresectable, locally advanced, or metastatic MTC. Patients will be randomized in a 2:1 ratio to receive XL184 or placebo administered as a daily oral dose. The primary endpoint will be duration of progression-free survival.
In a planned event-driven analysis, the study size provides 90% power to detect a 75% increase in progression-free survival in patients with documented progressive disease prior to study entry. Secondary endpoints will include overall survival, objective tumor response rate, and changes in serum biomarkers (carcinoembryonic antigen and calcitonin). It is expected that approximately 100 sites in 20 countries will participate in this study.