Pfizer Inc. and Astellas Pharma Inc.'s phase 4 study of XTANDI, plus abiraterone acetate and prednisone as compared to treatment with just abiraterone acetate and prednisone, did not meet its primary endpoint.

The primary endpoint of the trial was improvement in progression-free survival in patients with chemotherapy-naïve metastatic castration-resistant prostate cancer, whose prostate-specific antigen has previously progressed on XTANDI.

XTANDI is approved by the U.S. FDA for the treatment of patients with metastatic castration-resistant prostate cancer.

Pfizer and Astellas jointly commercialize XTANDI in the U.S. and Astellas has responsibility for manufacturing and all additional regulatory filings globally, as well as commercializing XTANDI outside the U.S.