NEJM publishes ZYTIGA plus prednisone Phase 3 trial data in metastatic castration-resistant prostate cancer

May 26 2011

A study titled "Abiraterone and Increased Survival in Metastatic Prostate Cancer," published in the May 26 issue of NEJM, found that patients with metastatic castration-resistant prostate cancer who have received prior chemotherapy containing docetaxel showed a significant improvement in overall survival when treated with ZYTIGA™ (abiraterone acetate) plus prednisone compared to patients treated with prednisone plus placebo.  The COU-AA-301 study was sponsored by Ortho Biotech Oncology Research & Development, unit of Cougar Biotechnology, Inc.

Results of the pivotal Phase 3, randomized, placebo-controlled, multicenter study showed that at pre-specified interim analysis, treatment with ZYTIGA in combination with prednisone resulted in a 35.4 percent reduction in the risk of death (14.8 months vs. 10.9 months [hazard ratio (HR) = 0.65; 95 percent CI: 0.54, 0.77; p<0.001]) and a 3.9 month difference in median survival compared to placebo plus prednisone.

The most common adverse events identified by the authors were fatigue, back pain, nausea, constipation, bone pain and arthralgia, which occurred at similar frequency in both arms.  Urinary tract infections were more frequent in the ZYTIGA arm.  Adverse events associated with elevated mineralocorticoid levels due to CYP17 inhibition (fluid retention and edema, hypokalemia and hypertension), as well as cardiac disorders and liver-function test abnormalities were deemed of special interest and were more common in the ZYTIGA arm.  Additional information is included in the Important Safety Information below.

"Given that men with metastatic castration-resistant prostate cancer have few options, we are pleased with the results of this rigorous study, which show that abiraterone acetate may extend survival in these patients," said Johann S. de Bono, MD, FRCP, MSc, PhD, The Institute for Cancer Research, The Royal Marsden NHS Foundation Trust, and lead author.  "The data indicate that abiraterone acetate has the potential to meet a significant unmet need for these patients."