Study results for enzalutamide vs. bicalutamide in prostate cancer published

Results from the Phase 2 TERRAIN trial of Astellas’ enzalutamide compared to bicalutamide in metastatic castration-resistant prostate cancer (CRPC) have been published.

The Phase 2 TERRAIN trial enrolled 375 patients in North America and Europe. The trial enrolled patients with metastatic prostate cancer whose disease progressed despite treatment with a luteinizing hormone-releasing hormone (LHRH) analogue therapy or following surgical castration. The primary endpoint of the trial was progression-free survival (PFS), defined as time from randomization to centrally confirmed radiographic progression, skeletal-related event, initiation of new anti-neoplastic therapy or death, whichever occurred first.

Median PFS was 15.7 months in the enzalutamide group

The TERRAIN study achieved its primary endpoint demonstrating a statistically significant increase in PFS for enzalutamide compared to bicalutamide. Median PFS was 15.7 months in the enzalutamide group compared to 5.8 months in the bicalutamide group. The observed adverse event profile of enzalutamide in TERRAIN appeared consistent with that from Phase 3 enzalutamide trials.

“TERRAIN is the first and largest head-to-head trial comparing enzalutamide with bicalutamide that evaluated both the efficacy and safety of these agents in the treatment of men with mCRPC,” said Claire Thom, Pharm D., senior vice president and oncology therapeutic head, Astellas.

The median time on treatment in TERRAIN was 11.7 months in the enzalutamide group versus 5.8 months in the bicalutamide group. Serious adverse events were reported in 31.1% of enzalutamide-treated patients and 23% of bicalutamide-treated patients. Individual Grade 3 or higher adverse events largely occurred at a similar rate between treatment groups, with the exception of hypertension (7.1% vs. 4.2%) and back pain (2.7% vs. 1.6%), which occurred more frequently in the enzalutamide treatment group. Grade 3 or higher cardiac events were reported in 5.5% of enzalutamide-treated patients versus 2.1% of bicalutamide-treated patients. Two seizures were reported in the enzalutamide group and one in the bicalutamide group.