Final Overall Survival and Molecular Data Associated with Clinical Outcomes in Patients Receiving Ipatasertib and Abiraterone in the Phase 3 IPATential150 Trial

BACKGROUND AND OBJECTIVE: In the phase 3 IPATential150 trial, ipatasertib addition to abiraterone significantly reduced the risk of disease progression in men with metastatic castration-resistant prostate cancer (mCRPC) with PTEN loss on immunohistochemistry (IHC), but not in the intention-to-treat (ITT) population. Here we report the final overall survival (OS) analysis and present results for prespecified and exploratory biomarker analyses. METHODS: Patients were randomized to receive ipatasertib (400 mg once daily) or placebo. All patients received abiraterone (1000 mg once daily) and prednisone (5 mg twice daily). OS was assessed in patients with PTEN loss on IHC and the ITT population. Exploratory biomarker analyses included PTEN status via next-generation sequencing (NGS) and other key genomic alterations. KEY FINDINGS AND LIMITATIONS: At final analysis (median follow-up 33.9 mo), ipatasertib addition did not improve OS for patients with PTEN loss in IHC (n = 521; stratified hazard ratio [sHR] 0.94, 95% confidence interval [CI] 0.76-1.17; p = 0.57) or the ITT population (n = 1101; sHR 0.91, 95% CI 0.79-1.07; not formally tested). Exploratory NGS assessments identified subgroups with genomic PTEN loss (n = 208) or PIK3CA/AKT1/PTEN alterations (n = 250), with potentially better outcomes from ipatasertib (HR 0.76, 95% CI 0.54-1.07; and HR 0.70, 95% CI 0.51-0.96, respectively). Limitations include the exploratory nature of the analysis, incomplete availability of NGS data, and potential intrapatient heterogeneity. CONCLUSIONS AND CLINICAL IMPLICATIONS: Ipatasertib addition to abiraterone did not improve OS for men with mCRPC, regardless of PTEN status on IHC. Exploratory biomarker analyses identified additional genomic alterations of potential clinical relevance for AKT blockade in mCRPC that require further validation in prospective studies.