Yesterday, Exelixis (NASDAQ: EXEL) announced positive data from the Phase 3 EXAM trial of cabozantinib in medullary thyroid cancer (MTC) demonstrating a 2.8-fold increase in progression-free survival (PFS) compared to placebo with a hazard ratio of 0.28. Patients in the treatment arm experienced median PFS of 11.2 months compared to 4 months in the placebo arm, an increase well above and beyond the 75% increase expected when the trial was designed. The EXAM trial was conducted under SPA and enrolled 330 patients with unresectable, locally advanced, or metastatic MTC. Full data will be presented at an upcoming medical conference. MTC does not have as many treatment options as other thyroid cancers, and the possibility that a new small molecule will be available for patients marks a significant advance in treatment. Cabozantinib is a promiscuous kinase inhibitor, targeting both VEGFR2 and MET, resulting in a decrease in tumor angiogenesis and metastasis. This is particularly important as the prognosis for metastatic MTC is much worse than other metastatic thyroid cancers.

While MTC is the most clinically advanced indication for cabozantinib, the drug is being investigated in a variety of other malignancies including prostate cancer, ovarian cancer, and hepatocellular carcinoma, among others. Exelixis plans to submit the NDA for MTC on a rolling basis with completion in the first half of 2012. The EXAM trial and NDA are major value-drivers for Exelixis as the company moves its first clinical candidate into the regulatory approval phase for one indication. With the aggressive clinical program in castration resistant prostate cancer receiving a large portion of management attention and other cancers in clinical study as well, investors already other indications to look toward for future value. The FDA’s response to a cabozantinib NDA in the coming year will be of primary importance to investors as this small molecule’s entry into the marketplace for MTC could just be the beginning of its use in a variety of cancers.

Disclosure: No position.