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AstraZeneca, Merck target broad use of Lynparza in prostate cancer as PARP rivals Pfizer, J&J, Clovis loom

September 24, 2021 Angus Liu

Building on an FDA nod last year for Lynparza in some previously treated patients with prostate cancer, AstraZeneca and Merck are now trumpeting first-in-class positive data from a clinical trial that could open a broader market for the PARP inhibitor. 

Lynparza plus Johnson & Johnson’s Zytiga prolonged the time to tumor progression or death over Zytiga alone in men with previously untreated metastatic, castration-resistant prostate cancer (CRPC) regardless of their homologous recombination repair (HRR) mutation status, AZ and Merck said Friday. All patients also received corticosteroids. 

The positive readout, which came from a planned interim analysis of the phase 3 PROpel trial, has made Lynparza the first PARP inhibitor to show clinical benefit in this first-line setting. Even though the data are immature, the companies plan to take them to regulators, Susan Galbraith, AZ’s oncology R&D head, said in a statement.

It’s no surprise the companies are in a hurry to open a dialog with regulators. All other marketed PARP meds—including two by entrenched prostate cancer players—are targeting front-line metastatic CRPC.

RELATED: ASCO: AstraZeneca, Merck to expand Lynparza’s blockbuster territory with big early breast cancer showing

Thanks to an FDA green light last May, Lynparza is already cleared for the treatment of HRR-mutated metastatic CRPC following prior treatment with Pfizer and Astellas’ Xtandi or Zytiga. Another accelerated approval the FDA handed to Clovis Oncology last May gave rival PARP inhibitor Rubraca a path into the third-line treatment of BRCA-mutant, metastatic CRPC. BRCA mutations are a type of HRR deficiency.

But the race to conquer the first-line market is heating up among PARP players. J&J’s Janssen unit—which holds the rights to Zejula in prostate cancer through a 2016 licensing deal with its inventor, Tesaro—is pairing the PARP inhibitor with Zytiga plus prednisone in patients who didn’t get any prior treatment in the phase 3 MAGNITUDE trial, which covers all comers with or without HRR gene alterations.

As for Clovis’ Rubraca, investigators at the National Cancer Institute recently launched a phase 3 trial dubbed CASPAR to test whether combining the drug with Xtandi outperforms Xtandi alone in the front-line treatment of metastatic CRPC.

RELATED: AstraZeneca and Merck’s Lynparza pressures Clovis’ Rubraca with prostate cancer OK

What’s more, Pfizer’s Talzenna, which is only approved to treat BRCA-mutated breast cancer, is now in the phase 3 TALAPRO-2 trial in prostate cancer. Pfizer is collaborating with Astellas to test Talzenna in combination with Xtandi.

Lynparza is leading the PARP inhibitor field, with sales of $1.13 billion in the first six months of 2021, marking 15% year-over-year growth at constant currencies. With the latest prostate cancer win and recent positive data for use in patients with high-risk early breast cancer after surgery, the drug seems to be on a strong growth path. And Zytiga  brought in $1.2 billion in worldwide sales in the first half of the year, despite generic erosion and competition from newer meds.

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