The FDA has approved an oral, once-daily medication for use in combination with prednisone for the treatment of men with metastatic castration-resistant prostate cancer (CRPC) who have received prior chemotherapy.

Abiraterone acetate (Zytiga) is an oral androgen biosynthesis inhibitor that works by inhibiting the CYP17 enzyme complex.

“This FDA approval represents a welcome new option in the treatment of metastatic prostate cancer,” said study investigator Howard Scher, MD, Chief of the Genitourinary Oncology Service at the Sidney Kimmel Center for Urologic and Prostate Cancers at Memorial Sloan-Kettering in New York.  The drug “will help address the important need for additional therapeutic choices for men living with this serious disease.”

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Dr. Scher and his colleagues conducted a Phase 3 study in 13 countries. The study included 1,195 men with CRPC previously treated with one or two chemotherapy regimens, at least one of which contained docetaxel. Treatment with abiraterone acetate resulted in a 35% reduction in the risk of death and a 36% increase in median survival (14.8 vs. 10.9 months) compared with placebo.

Patients who received abiraterone acetate and low-dose prednisone/prednisolone also showed significant improvements in secondary study endpoints when compared to the prednisone/prednisolone plus placebo group. For example, the median time to PSA progression was 10.2 months for the abiraterone acetate group compared with 6.6 months for the placebo group.

The abiraterone acetate group had an increase in radiographic progression-free survival (mean 5.6 vs. 3.6 months for the placebo group). Total PSA response, defined as a 50% or greater decrease from baseline, was achieved in 38% of patients treated with abiraterone acetate compared with 10% in the placebo group.

The most common adverse reactions (occurring in more than 5% of patients) reported were joint swelling or discomfort, hypokalemia, edema, muscle discomfort, hot flush, diarrhea, UTI, cough, hypertension, arrhythmia, urinary frequency, nocturia, dyspepsia and upper respiratory tract infection.