The makers of Enzalutamide (Xtandi), Astellas Pharma US, Inc and Medivation, Inc have begun a Phase 4 clinical trial known as PLATO. The study is designed to evaluate the efficacy and safety of continued treatment with enzalutamide (Xtandi) plus abiraterone acetate (Zytiga) and prednisone as compared to treatment with Zytiga and prednisone alone in men who have not yet had chemotherapy treatment for advanced prostate cancer that has advanced following failed therapy with Xtandi.

This trial will be global; randomized; double blind; placebo-controlled and scheduled to enroll approximately 500 chemotherapy-naive men. All subjects will initially receive treatment with Xtandi. Those men who experience disease progression on Xtandi will be randomized to treatment with Xtandi plus Zytiga and prednisone or to Zytiga and prednisone. The primary endpoint of the trial is progression-free survival.

The trial will evaluate Xtandi at a dose of 160 mg taken orally once daily in combination with Zytiga at a dose of 1000 mg administered orally once da