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The FDA has approved the use of abiraterone in combination with prednisone for the treatment of men with metastatic castration-resistant prostate cancer who have received prior chemotherapy containing docetaxel.


The drug, made by Centocor Ortho Biotech under the brand name Zytiga, is the first once-daily, oral therapy for metastatic prostate cancer and inhibits the production of androgen at three sources.


"This FDA approval represents a welcome new option in the treatment of metastatic prostate cancer," Howard Scher, MD, Chief of the Genitourinary Oncology Service, Sidney Kimmel Center for Urologic and Prostate Cancers at Memorial Sloan-Kettering Cancer Center, who was one of the co-lead investigators for the Phase III study, said in a news release.


"As a clinician, I believe the efficacy and safety profile of abiraterone acetate, as well as its oral, once-daily formulation, will help address the important need for additional therapeutic choices for men living with this serious disease."


Added another of the co-lead investigators for the trial, Professor Johann S. de Bono, MD, MSc, PhD, of the Institute of Cancer Research, Royal Marsden NHS Foundation Trust: "It's an exciting time for men with prostate cancer, and I believe that Zytiga will play an essential role in clinical practice."


Results of the pivotal Phase III, randomized, placebo-controlled, multicenter study showed that at the prespecified interim analysis, treatment with abiraterone in combination with prednisone resulted in a 35% reduction in the risk of death (14.8 vs 10.9 months) and a 3.9 month difference in median survival compared with placebo plus prednisone.


And in an updated analysis, the results were consistent with those from the interim analysis, with a 4.6-month difference between the two arms in median survival (15.8 vs 11.2 months).


At a predetermined number of events in the study, an interim analysis was conducted and it was determined that efficacy had been demonstrated. At that time, the study was unblinded at the recommendation of the Independent Data Monitoring Committee.


The most common adverse reactions (i.e., occurring in at least 5% of patients) reported in the clinical study were: joint swelling or discomfort, hypokalemia, edema, muscle discomfort, hot flush, diarrhea, urinary tract infection, cough, hypertension, arrhythmia, urinary frequency, nocturia, dyspepsia, and upper respiratory tract infection.


Company information notes that the drug should be used with caution in patients with a history of cardiovascular disease or with medical conditions that might be compromised by increases in hypertension, hypokalemia and fluid retention, and that safety has not been established in patients with LVEF less than 50% or NYHA Class III or IV heart failure. It is important to control hypertension and correct hypokalemia before and during treatment and to monitor blood pressure, serum potassium, and symptoms of fluid retention at least monthly.