Pfizer Inc. today announced that the first participant has been dosed in TALAPRO-3, a global, randomized, double-blind, placebo-controlled Phase 3 clinical trial. The study will evaluate the efficacy and safety of talazoparib, an oral poly (ADP-ribose) polymerase (PARP) inhibitor, in combination with enzalutamide, an androgen receptor inhibitor, compared with placebo plus enzalutamide in men with DNA damage response (DDR)-deficient metastatic castration-sensitive prostate cancer (mCSPC). The first patient was dosed at a site in Glendale, California.

“The prognosis for men with advanced prostate cancer has significantly improved since the introduction of novel hormone therapies, but additional therapeutic options are needed for the approximately 25 percent of men with tumors harboring DNA damage response (DDR) gene mutations, who may have poorer outcomes,” said Chris Boshoff, M.D., Ph.D., Chief Development Officer, Oncology, Pfizer Global Product Development. “By combining enzalutamide, which has a proven clinical benefit in men with metastatic castration-sensitive prostate cancer, with talazoparib, our PARP inhibitor that is active in DDR-mutated cancer, we may be able to offer a new treatment option that targets the underlying genetic mechanisms associated with DDR-mutated mCSPC.”

The TALAPRO-3 trial will enroll approximately 550 men with DDR-deficient mCSPC across 285 clinical trial sites in 28 countries. The primary endpoint of the study is radiographic progression-free survival (rPFS), and overall survival (OS) is a secondary endpoint. The anticipated primary completion date is late-2024.

“With the introduction of PARP inhibitors in the metastatic castration-resistant prostate cancer setting, it is important to explore how a combination approach may impact outcomes for men with metastatic castration-sensitive disease,” said Neeraj Agarwal, M.D., Professor of Oncology at the University of Utah School of Medicine, Senior Director for Clinical Research Innovation at Huntsman Cancer Institute and member of the TALAPRO-3 steering committee. “It’s exciting to be at the forefront of landmark studies like TALAPRO-3, which are helping to further our understanding of how different approaches may advance care for these men.”