Abiraterone acetate (trade name Zytiga) is a prodrug to the abiraterone, steroidal compound with antiandrogen activity and a 17 α-hydroxylase/C17,20-lyase (CYP17) inhibitor. It is indicated in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer. Abiraterone acetate is converted in vivo to abiraterone which inhibits CYP17, enzyme expressed in testicular, adrenal, and prostatic tumor tissues and required for androgen biosynthesis. Administration of this agent may suppress testosterone production by both the testes and the adrenals to castrate-range levels. Androgen sensitive prostatic carcinoma responds to treatment that decreases androgen levels. Androgen deprivation therapies, such as treatment with GnRH agonists or orchiectomy, decrease androgen production in the testes but do not affect androgen production by the adrenals or in the tumor.