It is now accepted that castration-resistant prostate cancer (CRPC) is not really androgen-independent and continues to rely on androgen signaling. Abiraterone is an inhibitor of cytochrome P450 17A1 (CYP17A1) that impairs androgen-receptor signaling by depleting adrenal and intratumoral androgens. After studies showed improved survival with abiraterone, it was approved by the Food and Drug Administration for the treatment of metastatic castration-resistant prostate cancer (mCRPC).