Pfizer says PARP inhibitor succeeds in prostate cancer study

Dive Brief:

• Pfizer’s breast cancer drug Talzenna helped advanced prostate cancer patients in a clinical trial live longer without their disease progressing, a finding announced Tuesday that could help it compete with a rival medicine from AstraZeneca.
• The trial combined Talzenna with Pfizer’s marketed prostate cancer drug Xtandi in patients whose disease no longer respond to hormonal therapies and whose tumors have spread throughout the body. Patients receiving the combination were at least 30% less likely to die or have their disease worsen than those given Xtandi alone, Pfizer said.
• Talzenna is from a class of drugs called PARP inhibitors, which are now commonly used to treat ovarian and breast cancers. AstraZeneca’s PARP inhibitor Lynparza, the top-seller in the class, has gained Food and Drug Administration approval in prostate cancer, but only in patients with specific mutations who have progressed on Xtandi.

Dive Insight:

Prostate cancer is the second most common cause of cancer death among men, but survival rates have improved over time. In the most advanced stage, when the disease has stopped responding to standard testosterone-suppressing hormone therapy and has spread beyond the prostate, doctors have used chemotherapy to fight the disease. However, in the past decade two new hormone-blocking drugs, Xtandi and Johnson & Johnson’s Zytiga, have been approved to treat some of these more advanced patients.

PARP inhibitors are another new option. In patients with the specific mutations who have advanced following Xtandi or Zytiga treatment, Lynparza alone reduced the risk of progression by more than 50%, and in patients with a narrower subset of mutations reduced the risk of death by more than 31%.

Now Pfizer has positive data for a PARP inhibitor in a broader group of patients whose disease is less advanced. In the trial, dubbed TALAPRO-2, Talzenna was tested in combination with Xtandi against Xtandi alone in men whose cancer was showing signs of progression while taking hormone-suppressing drugs.

Pfizer didn’t release detailed data, but said the Talzenna-Xtandi combination exceeded a pre-specified benchmark of reducing the risk of progression by at least 30%, regardless of mutation status. On safety, patients receiving both drugs had side effects consistent with those of the two drugs taken individually, which include anemia, nausea, weakness and fatigue.

The company said the combination also showed a trend toward improved overall survival, but the difference was not yet statistically significant. Pfizer began enrolling patients in 2018, and patients with metastatic prostate cancer can live several years beyond initial diagnosis, making an overall survival calculation more difficult.

The company plans to release detailed data from TALAPRO-2 at an upcoming medical meeting and discuss the results with U.S. and international regulators for potential review.

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