The European Commission has approved the Janssen-Cilag’s androgen biosynthesis inhibitor Zytig® (abiraterone acetate) as combination therapy with prednisone or prednisolone against metastatic castration-resistant prostate cancer (mCRPC) in adult men with progressive disease after docetaxel-based chemotherapy. Approval in Europe follows an accelerated regulatory review process by the European Medicines Agency. FDA approval of Zytig for the combination therapy against mCRPC was granted in May.
Approval of the drug in the U.S. and Europe have both triggered milestone payments to BTG. The firm will in addition receive royalties on worldwide sales of Zytig. BTG licensed worldwide rights to abiraterone acetate to Cougar Biotechnology (since acquired by Johnson & Johnson, which also owns Janssen), back in 2004. Meanwhile, Phase II trials with abiraterone acetate are ongoing in patients with breast cancer.
Both FDA and EU clearance of Zytig for the prostate cancer indication were based on Phase III trial data demonstrating that adding Zytig to prednisone or prednisolone therapy reduced the risk of death by 35.4% and improved median overall survival by 3.9 months to 14.8 months, when compared with prenisone or prednisolone therapy plus placebo. Subsequent updated analyses after a 20.2 month follow-up confirmed the initial findings, and showed that the Zytig combination increased median overall survival by 4.6 months. Data from the study also showed that more patients receiving Zytig also experienced pain relief.
Zytig therapy was in addition associated with a lower incidence of skeletal events including bone fracture, spinal cord compression, the need for palliative radiation to bone, or bone surgery. At six months 18% of patients receiving Zytig had experienced a skeletal event, compared with 28% of patients treated with placebo in addition to prednisone/prednisolone. At 12 months the figures were 30% and 40%, respectively, and at 18 months 35% and 40%.