The Phase III trial is a randomized, placebo-controlled, double-blinded study of XL184 as single-agent therapy in 315 patients with unresectable, locally advanced, or metastatic medullary thyroid cancer (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).
Additional secondary endpoints will be assessment of the potential relationship between germline and tumor DNA sequence alterations and the efficacy of XL184, as well as assessment of pharmacodynamics and pharmacokinetics of XL184.