Abiraterone Acetate: A Review of Its Use in Patients with Metastatic Castration-Resistant Prostate Cancer

Sheridan M. Hoy

Abiraterone acetate (Zytiga(®)) is an orally administered, selective inhibitor of the 17α-hydroxylase and C17,20-lyase enzymatic activities of cytochrome P450 (CYP) 17. CYP17 is required for androgen biosynthesis, with androgen receptor signalling crucial in the progression from primary to metastatic prostate cancer. Abiraterone acetate is approved in the European Union and the US, in combination with prednisone or prednisolone, for the treatment of men with metastatic castration-resistant prostate cancer (CRPC). When administered in combination with prednisone in a placebo-controlled, multinational phase III study, abiraterone acetate significantly prolonged overall survival and radiographic progression-free survival (rPFS) in men with metastatic CRPC who had previously received docetaxel. In men with metastatic CRPC who had not previously received chemotherapy participating in a placebo-controlled, multinational phase III study, there was a strong trend towards an overall survival benefit, a significant prolongation in rPFS and significant delays in clinical decline, the need for chemotherapy and the onset of pain observed. Given the nature of the therapy, the overall tolerability profile of abiraterone acetate, in combination with prednisone, was acceptable in men with metastatic CRPC. Abiraterone acetate is associated with hypokalaemia, hypertension, and fluid retention or oedema, secondary to its mechanism of action, and with cardiac adverse events and hepatotoxicity; however, in the phase III studies the incidences of the most frequently reported grade 3 or 4 adverse events of special interest were relatively low. Although the final overall survival data in men with metastatic CRPC who have not previously received chemotherapy are awaited, current evidence indicates that abiraterone acetate is a useful option for the treatment of metastatic CRPC.