Multinational phase 3 trial of abemaciclib plus abiraterone in patients with metastatic castration-resistant prostate cancer

The double-blind, placebo-controlled phase 3 CYCLONE 2 trial (89 centers in 12 countries) included 393 adult patients with metastatic castration-resistant prostate cancer (mCRPC). Patients were randomized to standard abiraterone and prednisone or prednisolone plus either abemaciclib (n=206) or placebo (n=187). The median age was 70.0 years (IQR 63.0-76.0). The primary endpoint of radiographic progression-free survival was not met, with rPFS events in 45% of patients in the abiraterone plus abemaciclib group and 51% of patients in the abiraterone plus placebo group. The median rPFS was 22.0 months versus 20.3 months. The authors conclude that inmCRPC dual inhibition of CDK4/6 and the androgen receptor pathway did not improve rPFS compared with inhibion of the androgen receptor pathway alone.