Exelixis has announced that it will begin the pivotal Phase III ‘306 trial of cabozantinib in patients with metastatic castration-resistant prostate cancer by the end of 2011.

The double-blind ‘306 trial is expected to enrol 246 CRPC patients, who will be randomised 1:1 to receive either cabozantinib or mitoxantrone / prednisone.

The alleviation of bone pain will be the primary endpoint of the study, while secondary endpoints include overall survival rate and bone scan response.

An earlier Phase II trial with cabozantinib demonstrated favourable effects on bone and soft tissue lesions, and in the relief of bone metastasis-related pain in castration-resistant prostate cancer patients.