TALAPRO-2: A placebo-controlled phase III study of talazoparib (TALA) plus enzalutamide (ENZA) for patients with first-line metastatic castration-resistant prostate cancer (mCRPC).

Abstract

TPS264 Background: TALA is a poly(ADP-ribose) polymerase (PARP) inhibitor that inhibits PARP1/2 and traps PARP on DNA, preventing DNA damage repair (DDR) and causing death of cells with DDR mutations (eg BRCA1/2). TALA is approved in multiple countries for germline BRCA1/2-mutated HER2- advanced breast cancer. ENZA is an established therapy for CRPC. PARP1 activity has been shown to support AR function, suggesting that co-blockade of PARP1 may synergize with AR-directed therapy, regardless of DDR deficiency. A combination of TALA with ENZA in mCRPC may improve clinical outcomes in patients with or without DDR-deficient tumors. TALAPRO-2 (NCT03395197) is a 2-part study to evaluate efficacy, safety, pharmacokinetics, and patient (pt)-reported outcomes (PROs) of the combination. Methods: Enrollment goal is 1037 pts (19 pts, part 1 dose-finding; 1,018 pts, part 2 placebo-controlled). Key eligibility criteria: age ≥18 y, asymptomatic/mildly symptomatic mCRPC, ECOG performance status ≤1, no brain metastases, and no prior life-prolonging systemic therapy in nonmetastatic CRPC or mCRPC state. Prior docetaxel or novel hormonal therapy (excluding novel AR inhibitors) in castration sensitive (CSPC) setting is allowed. The randomized double-blind portion will evaluate safety, efficacy, and PROs of TALA (0.5 mg QD) + ENZA (160 mg QD) vs placebo + ENZA (160 mg QD). Randomization is stratified by prior NHT or docetaxel for CSPC (yes/no) and DDR mutation status (deficient vs nondeficient/unknown). The primary endpoint is radiographic progression-free survival (rPFS), defined as time to progression in soft tissue per RECIST v.1.1 or in bone per PCWG3 criteria or death. The key secondary endpoint is overall survival (OS). Efficacy will be assessed by radiography every 8 weeks up to week 25 and every 8–12 weeks thereafter. rPFS will be compared between two arms by a 1-sided stratified log-rank test. Pt recruitment is ongoing in multiple regions including US, Europe/Eastern Europe, Israel, South America, South Africa, and Asia Pacific region. This study was sponsored by Pfizer Inc. Clinical trial information: NCT03395197.