Purpose

The purpose of this research study is to evaluate the progression-free survival (PFS) with XL184 as compared with placebo (an inactive substance) in subjects with unresectable, locally advanced, or metastatic medullary thyroid cancer (MTC). Subjects will be randomized to receive XL184 or placebo in a 2:1 ratio. XL184 is an investigational drug that inhibits VEGFR2, MET and RET, kinases implicated in tumor formation, growth and migration. The Clinical Steering Committee for this study, comprised of study doctors who specialize in medullary thyroid cancer, has provided guidance regarding the design of the study. The committee includes: Douglas Ball, MD, Barry Nelkin, PhD, Martin Schlumberger, MD and Steven Sherman, MD.