SAN DIEGO -- Researchers say that a new type of drug can help prevent advanced breast cancer from worsening, potentially providing an important new treatment option for women and a blockbuster product for Pfizer.
In a clinical trial, the drug cut by half the risk that cancer would worsen, or progress, researchers said Sunday. The median time before the disease progressed or the woman died was 20.2 months for those who received the drug, compared with 10.2 months for the control group.
"The magnitude of benefit we are seeing is not something commonly seen in cancer medicine studies," Richard Finn, a principal investigator in the study, said. Dr. Finn, an oncologist at the University of California, Los Angeles, called the results "quite groundbreaking."
The drug, known as palbociclib, also appeared to prolong survival but not by a statistically significant amount. Those who received the drug lived a median of 37.5 months compared with 33.3 months for those in the control group.
The results from the Phase 2, or midstage, study were presented Sunday in San Diego at the annual meeting of the American Association for Cancer Research. They are being closely watched on Wall Street, because palbociclib is considered a jewel in Pfizer's product pipeline, with analysts predicting annual sales of billions of dollars. Amgen is entitled to an 8 percent royalty on sales of the drug.
Strong as the results were, it is possible they will be a bit of a letdown to some investors.
That is partly because they were not quite as good as interim results presented about halfway through the trial. At that point, the difference in median progression-free survival was 26.1 months for palbociclib versus 7.5 months for the control group.
While Pfizer is in the lead to bring this new class of drugs to market, Novartis has begun late-stage testing of its own CDK 4/6 inhibitor. Eli Lilly is at an earlier stage, with some results for its drug scheduled to be presented at the cancer conference. While breast cancer is the initial focus, the drugs are being tested for other cancers.
The study, sponsored by Pfizer, involved 165 post-menopausal women who were receiving their initial treatment for recurring or metastatic breast cancer. The cancers were estrogen receptor-positive, meaning their growth was fueled by that hormone, but negative for Her2, a different protein.