AZ, Merck’s PARP Inhibitor Shines in Phase 3 Prostate Cancer Trial

Last week, AstraZeneca announced that its blockbuster PARP inhibitor, Lynparza (olaparib), registered encouraging results in a prostate cancer trial, which could potentially help consolidate its position in the therapeutic area.

AstraZeneca and Merck & Co., Inc.’s (known as MSD outside the US and Canada) Lynparza is the world’s first PARP inhibitor that has been greenlighted for four different cancers—ovarian breast, pancreatic, and prostate cancers. In May 2020, the drug was FDA authorized to treat HRR-gene mutated metastatic, castration-resistant prostate cancer (mCRPC), becoming only the second PARP inhibitor approved for this indication.

Metastatic Castration-Resistant Prostate Cancer

Prostate cancer is the second most common type of cancer in men. It is often driven by the male sex hormone (androgens), including testosterone. Since the androgen receptor aids in the survival of many prostate cancer cells, it is a common anti-cancer target.

mCRPC is a condition where cancer metastasizes to other parts of the body despite androgen deprivation therapy. Despite the increasing number of available treatments for patients with mCRPC, the five-year survival remains low.

PROpel Trial (NCT03732820)

PROpel is a randomized, double-blind, multi-center Phase 3 trial that evaluates the efficacy, safety, and tolerability of Lynparza versus placebo when given in addition to abiraterone in men with mCRPC who had not received prior chemotherapy or new hormonal agents (NHAs) in the 1st-line setting.

The latest interim results from the Phase 3 PROpel trial showed that, compared to the hormonal agent abiraterone, a standard of care (SOC), a statistically significant radiographic progression-free survival (rPFS) was observed previously untreated mCRPC patients when the SOC was combined with Lynparza.

Besides, the interim analysis also showed a trend towards improved overall survival (OS). However, the data are still immature, and the trial will continue to assess OS as a key secondary endpoint. The safety and tolerability were consistent with the known profiles of each medicine.

“Today, men with metastatic castration-resistant prostate cancer have limited options in the 1st-line setting, and sadly often the disease progresses after initial treatment with current standards of care,” said Susan Galbraith, Executive Vice President, Oncology R&D, AstraZeneca.

“These exciting results demonstrate the potential for Lynparza with abiraterone to become a new 1st-line option for patients regardless of their biomarker status and reach a broad population of patients living with this aggressive disease. We look forward to discussing the results with global health authorities as soon as possible,” she added.

“We are encouraged by the PROpel results and the clinical benefit Lynparza in combination with abiraterone demonstrated versus abiraterone alone as a 1st-line treatment option for men with metastatic castration-resistant prostate cancer. Today’s results build on MSD and AstraZeneca’s commitment to bring Lynparza earlier in lines of treatment and to more patients with advanced prostate cancer,” said Roy Baynes, Senior Vice President and Head of Global Clinical Development, Chief Medical Officer, MSD Research Laboratories.

Lynparza’s potential rivals—GSK’s Zejula, Pfizer’s Talzenna, and Clovis Oncology’s Rubraca are all currently evaluated in Phase 3 trials as first-line treatments for metastatic prostate cancer. It will be interesting to see how these PARP inhibitors compete in this area in the near future.

Author

Rajaneesh K. Gopinath