Pfizer has announced positive top-line results from a phase 3 study of Talzenna (talazoparib), an oral poly ADP-ribose polymerase (PARP) inhibitor, in combination with Xtandi (enzalutamide) in men with metastatic castration-resistant prostate cancer (mCRPC), with or without homologous recombination repair (HRR) gene mutations.
The phase 3 TALAPRO-2 study is a two-part, two-cohort, multicentre, randomised, double-blind, placebo-controlled study that enrolled 1,095 patients with mCRPC (with no systemic treatments initiated after documentation of mCRPC) at sites in Europe, the US, Canada, South America and the Asia-Pacific region.
The study met its primary endpoint with a statistically significant and clinically meaningful improvement in radiographic progression-free survival (rPFS) compared with placebo plus Xtandi.
Results also showed a trend toward improved overall survival – a key secondary endpoint – at the time of the analysis, but this data is not yet mature, the company noted.
Benefits were also observed in other secondary endpoints, including investigator assessed rPFS, prostate specific antigen (PSA) response, time to PSA progression, and overall response rate. Additional secondary endpoints are being analysed.
Crucially, at the time of top-line analysis, the safety of the combination treatment was ‘generally consistent’ with the known safety profile of each medicine, Pfizer reported.
mCRPC is a cancer that has spread beyond the prostate gland and has progressed, despite medical or surgical treatment to lower testosterone. Approximately 10% to 20% of prostate cancer patients develop mCRPC within five to seven years of diagnosis.
Commenting on the positive results, Chris Boshoff, chief development officer, oncology and rare disease, Pfizer Global Product Development, said: “Xtandi is a global standard of care, with overall survival demonstrated in mCRPC, non-metastatic CRPC, and mCSPC.
“We are very pleased with the strong findings from TALAPRO-2, and although no definitive conclusions can be made across trials, the rPFS appears to be the longest observed in a randomised trial in this setting. This data highlights the potential for Talzenna in combination with Xtandi, if approved, to become a new standard of care for mCRPC, irrespective of HRR gene mutation status. We look forward to discussing the data with global health authorities.”
The company outlined its plans to submit detailed results from the study for presentation at a near-term medical congress. The data will also be shared with global regulatory authorities to potentially support a regulatory filing.