- Treatment with Pfizer’s targeted cancer drug Talzenna, when combined with another called Xtandi, helped people with metastatic prostate cancer go longer without their disease progressing than those on Xtandi alone, the company said Thursday.
- The Food and Drug Administration is already reviewing data from Pfizer’s trial and is expected to decide whether to approve Talzenna in prostate cancer this year. Two other drugs of Talzenna’s type, AstraZeneca and Merck & Co.’s Lynparza and Clovis Oncology’s Rubraca, are currently approved for certain prostate cancers that have progressed following treatment.
- Known as PARP inhibitors, the drugs have come under FDA scrutiny, prompting withdrawals of Lynparza, Rubraca and GSK’s Zejula in some ovarian cancer settings. Clovis, which has struggled commercially amid lackluster Rubraca sales, has filed for bankruptcy protection.
In Pfizer’s study, called TALAPRO-2, the company tested Talzenna together with Xtandi, a drug it markets in the U.S. with Astellas, among prostate cancer patients whose disease has spread after initial testosterone-suppressing treatments. By itself, Xtandi can help patients on average live four months longer than those who don’t receive treatment, similar to the survival data for a competing drug, Johnson & Johnson’s Zytiga.
Results from TALAPRO-2 showed the Talzenna-Xtandi combination reduced the risk of death or disease progression by 37% when compared to Xtandi and a placebo. As more than half of participants in the combination arm are still alive or haven't experienced disease progression, trial investigators can’t yet calculate the median progression-free survival of patients on the two drugs. The median progression-free survival for Xtandi alone was nearly 22 months.
In patients with a gene mutation called homologous recombination repair deficiency, which trial investigators specified for a separate analysis as part of the study’s design, patients given the combination were 54% less likely to die or progress than those given Xtandi and a placebo.
Results were presented Thursday at a medical meeting.
If the FDA approves the combination, Pfizer could still find itself behind AstraZeneca and Merck & Co., which already have the Lynparza combination with Zytiga and steroids under regulatory review. The European Union OK’d the combination in December, based on the findings of the PROpel trial, in which the combination reduced the risk of death or progression by 33% when compared to Zytiga and steroids alone.
In December, the FDA delayed a decision on Lynparza combination by three months.
Even if Talzenna arrives behind Lynparza, an approval in prostate cancer could expand its use. Talzenna is only approved in a single breast cancer setting, as compared to the ovarian, breast, pancreatic and prostate cancer indications for which Lynparza has received a green light.
Approval also could help it stave off generic competition for Xtandi, if Pfizer and Astellas are able to build significant patents around the Talzenna combination. Xtandi’s main patents are due to expire in 2027.