This Phase 3 study has been designed to confirm that adding custirsen to cabazitaxel/prednisone treatment can slow tumor progression and enhance survival outcomes compared to standard cabazitaxel/prednisone treatment in men with metastatic castrate resistant prostate cancer (CRPC). This will be a randomized, open-label, multicenter, international trial. Treatment will consist of cabazitaxel/prednisone/custirsen vs. cabazitaxel/prednisone. A total of approximately 630 patients will be randomized with equal probability to the two arms.