Exelixis, Inc. (NASDAQ:EXEL) today announced interim data from 51 patients with metastatic castration-resistant prostate cancer (CRPC) and bone metastases receiving a 40 mg daily dose of cabozantinib in an ongoing non-randomized expansion (NRE) cohort of a phase 2 randomized discontinuation trial. The data suggest that the 40 mg daily dose has similar clinical activity to the 100 mg daily dose previously reported from this trial for key parameters, including reduction of metastatic bone and soft tissue disease, and reduction of bone-related pain and narcotic use, with apparent improvement in adverse event rates and tolerability. Johann de Bono, M.D., Ph.D., leader of the prostate cancer targeted therapy team at The Institute of Cancer Research, London, and honorary consultant at The Royal Marsden NHS Foundation Trust, and an investigator on the trial, presented the data today in an oral presentation session on prostate cancer at the European Society for Medical Oncology (ESMO) 2012 Annual Meeting (Abstract #897O) in Vienna, Austria. “The results presented today at ESMO are consistent with interim data previously reported for the 40 mg cohort of an ongoing investigator-sponsored trial evaluating low-dose cabozantinib in men with CRPC and bone metastases,” said Michael M. Morrissey, Ph.D., president and chief executive officer of Exelixis. “The data suggest that the 40 mg daily dose has activity with respect to a number of key metrics, including bone and soft tissue responses, as well as changes in pain scores and narcotic use. Additionally, the 40 mg daily dose appears to be well-tolerated in patients with metastatic CRPC.” The interim results reported today include data from 51 men enrolled in the 40 mg NRE cohort of an ongoing phase 2 randomized discontinuation trial. All patients had bone metastases on bone scan and 41% had measurable soft tissue disease. All patients had received prior docetaxel, 67% had received prior abiraterone or enzalutamide (MDV3100), and 25% had received prior cabazitaxel. Bone-directed therapies such as zoledronic acid, denosumab, and radionuclides were used in 45%, 41% and 6% of patients, respectively. Seventy-one percent of patients had received at least 2 prior lines of therapy for CRPC. Clinically significant pain, defined as baseline pain score by Brief Pain Inventory (BPI) ≥4, was present in 53% of patients, with 45% of these patients receiving chronic narcotic administration.