Primary, secondary, and quality-of-life endpoint results from the phase III AFFIRM study of MDV3100, an androgen receptor signaling inhibitor.

Abstract

4519^ Background: MDV3100, a novel androgen receptor signaling inhibitor (ARSI), inhibits: 1) binding of androgens to AR, 2) AR nuclear translocation, and 3) association of AR with DNA. MDV3100 was active in a phase I-II trial enrolling pre- and post-docetaxel castration-resistant prostate cancer (CRPC) patients. The AFFIRM trial evaluated whether MDV3100 could provide benefit to men with post-docetaxel CRPC. Methods: In this double-blind, multinational phase III study, patients who had received docetaxel-based chemotherapy were randomized 2:1 to MDV3100 160 mg/day or placebo. Treatment with corticosteroids was allowed but not required. Patients were stratified by baseline ECOG and mean brief pain inventory score. The primary endpoint was overall survival (OS). Other efficacy endpoints included radiographic progression-free survival (rPFS), time to PSA progression (TTPP), soft tissue objective response (PR+CR), PSA response, and quality of life (QoL) response (FACT-P). Results: 800 patients were randomized to MDV3100 and 399 to placebo with respective median treatment durations of 8.3 and 3.0 months.Based on a planned interim analysis at 520 deaths, the Independent Data Monitoring Committee recommended the study be unblinded and placebo patients offered MDV3100. Efficacy results are presented (Table). The most common MDV3100 events with an incidence higher than placebo were fatigue (34% vs 29%), diarrhea (21% vs 18%), and hot flush (20% vs 10%). Grade >3 events of interest were cardiac disorders (0.9% MDV3100 vs 2% placebo), fatigue (6% MDV3100 vs 7% placebo), seizure (0.6% MDV3100 vs. 0% placebo), and LFT abnormalities (0.4% MDV3100 vs 0.8% placebo). Conclusions: MDV3100, a novel ARSI, is well-tolerated and significantly prolongs OS, slows disease progression, and improves QoL in men with post-docetaxel CRPC. [Table: see text]