Pfizer Inc. (NYSE:PFE) announced that its Phase 3 TALAPRO-3 clinical trial met its primary endpoint, demonstrating that the combination of TALZENNA (talazoparib) and XTANDI (enzalutamide) significantly improved radiographic progression-free survival compared with placebo plus XTANDI in patients with homologous recombination repair (HRR) gene–mutated metastatic castration-sensitive prostate cancer.
The global study enrolled 599 patients across the United States, Canada, Europe, South America and the Asia-Pacific region. According to Pfizer, the results surpassed the trial’s pre-specified hazard ratio target of 0.63, with most participants remaining progression-free at the time of the analysis. The treatment combination showed consistent benefits among patients with both BRCA and non-BRCA HRR gene mutations.
An interim review also indicated a positive trend in overall survival, which is a key secondary endpoint. Additional secondary measures—including overall response rate, duration of response and time to prostate-specific antigen progression—also showed improvements. Pfizer said the safety profile of the combination remained consistent with the known profiles of the individual drugs, and no new safety concerns were identified.
The combination of TALZENNA and XTANDI is currently approved in about 60 countries for the treatment of HRR gene–mutated metastatic castration-resistant prostate cancer. The companies said they plan to engage with global regulators to discuss potential submissions aimed at expanding the therapy’s use to earlier stages of the disease.
HRR gene mutations occur in roughly 25% of metastatic prostate cancer cases and are associated with poorer outcomes and reduced responsiveness to standard therapies. Even with recent treatment advances, around 50% to 65% of patients with metastatic castration-sensitive prostate cancer progress to castration-resistant disease within two years.
Pfizer said the findings from the TALAPRO-3 study will be submitted for presentation at an upcoming medical conference.