- AstraZeneca and partner Merck & Co. on Friday reported their drug Lynparza helped extend the lives of prostate cancer patients whose tumors had a specific genetic mutation, when compared to standard hormone treatment in a Phase 3 trial.
- The two companies didn't disclose details. But the results add to a growing body of evidence suggesting an emerging role in prostate cancer for a relatively new class of drugs called PARP inhibitors, already approved as ovarian and breast cancer treatments.
- This quarter, the Food and Drug Administration could approve both Lynparza and rival PARP blocker Rubraca for prostate cancer. Another, similar drug called Zejula may soon follow, as could results from a key test of Lynparza in patients newly diagnosed with the disease.
Slowly but surely, PARP inhibitors — drugs that block an enzyme that tumors use to repair their DNA — have amassed evidence proving their worth in multiple cancers.
After some early stumbles, four PARP blockers have won FDA approval since 2014: Lynparza, GlaxoSmithKline's Zejula, Clovis Oncology's Rubraca and Pfizer's Talzenna.
Those approvals came first in ovarian cancer, then breast cancer, and late last year, pancreatic cancer, a notoriously aggressive and tough tumor to treat.
Today's news from Merck and AstraZeneca, while lacking key details, is the latest evidence that the drugs could soon play a role in prostate cancer, the second most common cancer in American men.
The update comes from the PROfound trial, a 387-patient Phase 3 study in a genetic subset of prostate cancer patients who had failed at least two treatments. The two drugmakers reported last year that Lynparza had kept these patients' tumors from spreading for a median of 7.4 months, compared to 3.6 months for mainstay hormone therapies mainstay drugs like Xtandi and Zytiga — the first such result for a PARP inhibitor in a Phase 3 trial in prostate cancer. AstraZeneca and Merck filed for approval shortly thereafter, and a speedy review began in January.
While cancer drugs can be approved by showing they can hold tumors in check — a measure known as progression-free survival — extending lives is the gold standard for a cancer medicine. Today, the two drugmakers disclosed that Lynparza achieved that as well, compared to hormone therapy.
The data "reinforces its potential to change the treatment standard for patients with metastatic castration-resistant prostate cancer," said Roy Baynes, Merck Research Laboratories' chief medical officer and clinical development head, in a statement.
Though AstraZeneca and Merck didn't reveal the magnitude of that benefit, the results are still noteworthy. Lynparza is the first PARP inhibitor to show a survival benefit versus hormone therapy in prostate cancer, and that could help boost its prospects in a very competitive field, particularly against Rubraca. The FDA is reviewing both Lynparza and its Clovis rival in prostate cancer, and could approve both drugs this quarter.
SVB Leerink analyst Andrew Berens noted that an "overall survival advantage" for Lynparza "was not anticipated, and we believe should prove to be a significant commercial advantage" over Rubraca. Also in Lynparza's favor: the drug bested hormone therapy in a randomized trial, while Rubraca's best results come from a single-arm study, Berens wrote. Lynparza paces the PARP field, with $1.2 billion in sales in 2019.
Zejula is in the prostate cancer mix, too, having produced Phase 2 results last year. The FDA granted a Breakthrough Therapy designation to Zejula, which should speed up its review. Johnson & Johnson grabbed rights to Zejula in prostate cancer from Tesaro in 2016, two years before the biotech sold itself to GlaxoSmithKline.
The role of PARPs in prostate cancer, meanwhile, could grow as well. The Phase 3 PROPel trial, which tests Lynparza alongside hormone therapy in newly diagnosed prostate cancer patients, should produce results in 2021.