Updated Phase III data for Exelixis Inc.'s cabozantinib showed the compound did not improve survival in patients with medullary thyroid cancer, but the biotech says the data are not mature and that PFS and safety data suggest its compound could be competitive with AstraZeneca plc's Caprelsa vandetanib.

About 2,000 patients are diagnosed with MTC in the U.S. each year. The initial treatment is removal of the thyroid, after which some patients may have relatively indolent disease and others will experience highly progressive metastatic disease over the course of months. The exact proportion of patients with highly progressive disease is unknown.