XTANDI was approved in August of 2012 for use in patients with metastatic CRPC who previously received docetaxel (chemotherapy). The label was expanded in September of 2014 to include men with metastatic CRPC who have not received chemotherapy (chemo-naïve). Metastatic CRPC is defined as a cancer that has spread beyond the prostate gland and has progressed despite testosterone-lowering therapies.
Medivation/Astellas reported U.S. XTANDI sales of $679 million in 2014, up from $392 million in 2013.
The Phase 2 TERRAIN trial compared progression-free survival (PFS) in patients taking 160 mg of enzalutamide versus 50 mg of bicalutamide, both in combination with luteinizing hormone-releasing hormone (LHRH). Medivation first revealed that XTANDI provides a longer duration of disease control in this setting compared to bicalutamide in late January, but this was the first look at details. The results, taken from 375 patients, showed an increase in median PFS for patients using enzalutamide (15.7 months) compared to bicalutamide (5.8 months). Similarly, the median time to PSA progression was 13.6 months longer with enzalutamide.
The multi-national, randomized, double-blind, placebo-controlled PREVAIL trial enrolled 1,717 patients to evaluate the risk of death with 160 mg enzalutamide versus placebo. Results showed a 23% reduction in risk of death (OS: HR 0.77; 95% CI 0.67–0.88; p=0.0002) as well as a 4-month improvement in overall survival, which compares favorably to a HR of 0.79 for Johnson & Johnson’s (JNJ) competing Zytiga.
Although use in both settings is already a reality given off-label prescribing, approval in these indications can reasonably be expected to increase sales of XTANDI, particularly in comparison to bicalutamide – the current standard of care in the setting.