ASCO GU 2017: Phase Ib study of apalutamide (APA) with abiraterone acetate (AA) and prednisone (P) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC): Update on safety and efficacy. 2 - Poster Session Highlights
Orlando, Florida USA (UroToday.com) This phase Ib study tested the feasibility and efficacy of combining apalutamide, an advanced AR blocker, with abiraterone acetate for patients with metastatic castrate-resistant prostate cancer (mCRPC). In 57 mCRPC patients , the investigators found 67% PSA response (≥50%) in androgen axis treatment naïve patients, compared to 15% in the pretreated patients. The most commonly reported adverse reactions were fatigue (42%), diarrhea (21%), and vomiting (21%). Only 1 patient discontinued the study due to grade 3 fatigue.
These results are comparable to the interim analysis from clinical trial NCT01650194, investigating the effect of combination therapy with abiraterone and enzalutamide, in which 76% of the patients had ≥50% PSA decline in a patient population with less metastatic burden. Apalutamide has similar pharmacologic characteristics as enzalutamide, but is thought to have several fold reduced central nervous system permeation. As such, the study results are favorable and the drug combination warrants further investigation.