Pfizer has announced positive results from a phase 3 study of its PARP inhibitor Talzenna (talazoparib) in combination with Astellas-partnered androgen inhibitor Xtandi (enzalutamide) in metastatic castration-resistant prostate cancer (mCRPC).
mCRPC is a cancer that has spread beyond the prostate gland and has progressed despite medical or surgical treatment to lower testosterone.
Around 10-20% of prostate cancer patients develop mCRPC within five to seven years of diagnosis.
The results from Pfizer’s TALAPRO-2 study, presented at the 2023 American Society of Clinical Oncology Genitourinary Cancers Symposium, demonstrate a 37% improvement in radiographic progression-free survival (rPFS) compared to placebo plus Xtandi in mCRPC patients.
Clinically meaningful improvement in median rPFS was also observed across several subgroups, including those with HRR gene alterations.
Although the overall survival data from the mid-study analysis is still immature, it also shows a trend favouring the combination treatment, with final results set to be reported once the predefined number of survival events has been reached.
Neeraj Agarwal, professor of oncology and presidential endowed chair of cancer research at Huntsman Cancer Institute, University of Utah, and lead investigator for TALAPRO-2, said: “Novel hormone therapies dramatically changed outcomes for patients with mCRPC in the last decade, and the results from the TALAPRO-2 study show that the addition of [Talzenna] to the existing standard of care adds significant clinical benefit.”
Although neither Talzenna nor the combination have been approved by any regulatory agency for the treatment of mCRPC, the US Food and Drug Administration (FDA) has granted priority review for use of the combination treatment for this indication, with a decision from the agency expected this year.
As well as the FDA, data from TALAPRO-2 has been shared with the European Medicines Agency and other regulatory agencies to support regulatory filings.
Chris Boshoff, chief development officer, oncology and rare disease, Pfizer Global Product Development, said: “Patients with mCRPC need new treatment approaches that can improve outcomes and the rPFS results from TALAPRO-2, which appears to be the longest observed in a randomised trial in this setting, demonstrate the potential of the Talzenna and Xtandi combination, if approved, to become a new standard of care.”