Exelixis says cabozantinib failed in Ph III prostate cancer trial

US biotech firm Exelixis (Nasdaq: EXEL) has posted disappointing top-line results from the final analysis of COMET-1, the Phase III pivotal trial of cabozantinib in men with metastatic castration-resistant prostate cancer (mCRPC) whose disease progressed after treatment with docetaxel as well as abiraterone and/or enzalutamide.

The trial did not meet its primary endpoint of demonstrating a statistically significant increase in overall survival (OS) for patients treated with cabozantinib as compared to prednisone. The median OS for the cabozantinib arm of the trial was 11.0 months versus 9.8 months for the prednisone arm (hazard ratio 0.90; 95% confidence interval 0.76 – 1.06; p value 0.212).

The COMET-1 results are the subject of ongoing analyses. Exelixis will submit additional data, including secondary and exploratory endpoints, for presentation at a future medical conference. Besides OS, the exploratory endpoint of progression-free survival (PFS) as assessed by the investigators is the only time-to-event-based endpoint for which data are available. Median PFS was 5.5 months for the cabozantinib arm of the trial versus 2.8 months for the prednisone arm (hazard ratio 0.50; 95% confidence interval 0.42 – 0.60; p value <0.0001). Safety data were consistent with those observed in earlier-stage trials of cabozantinib in mCRPC.