ERA 223: A phase 3 trial of radium-223 dichloride (Ra-223) in combination with abiraterone acetate (abiraterone) and prednisone in the treatment of asymptomatic or mildly symptomatic chemotherapy-naïve patients (pts) with bone predominant metastatic castration-resistant prostate cancer (mCRPC).

TPS5082 Background: Ra-223, a first-in-class alpha-emitting radiopharmaceutical targeting bone metastases, reduced risk of death by 30% and delayed time to first symptomatic skeletal event (SSE) versus placebo (15.6 vs 9.8 mo; HR = 0.66) in phase 3 ALSYMPCA (Parker et al. NEJM 2013, Sartor et al. Lancet Oncol 2014). Ra-223 favorable safety profile and lack of significant toxicity support combining it with other agents. Abiraterone improved radiologic progression-free survival (rPFS) and overall survival (OS) (Ryan et al. NEJM 2012) in chemotherapy-naive men with mCRPC; it has no overlapping toxicity with Ra-223. This study investigates efficacy and safety of Ra-223 + abiraterone versus abiraterone alone in chemotherapy-naive pts with mCRPC to bone. Methods: This phase 3, double-blind, placebo-controlled, multinational trial (ERA 223, NCT02043678) will randomize ~ 800 pts with asymptomatic or mildly symptomatic chemotherapy-naive, bone-predominant mCRPC 1:1 to receive abiraterone (oral 1000 mg daily) and p...