In rare slip, Pfizer steamroller Ibrance fails to show it helps patients live longer

More than two years ago, Pfizer’s Ibrance won an FDA nod to treat some breast cancer patients whose disease had progressed after endocrine therapy. But new study results suggest the drug may not actually help patients live longer.

On Monday, Pfizer said Ibrance, in combination with fulvestrant, had failed to outdo placebo-plus-fulvestrant in women with HR-positive, HER2-negative breast cancer. While results "demonstrated a positive trend in the hazard ratio favoring the Ibrance combination," they didn’t reach the statistical-significance mark.

Pfizer was quick to point to the "high bar" for statistical significance in this particular patient population, as well as Ibrance's advance in breast cancer treatment. "Ibrance in combination with endocrine therapy has transformed the treatment landscape for patients with HR-positive, HER2-negative metastatic breast cancer," Mace Rothenburg, M.D., Pfizer’s chief development officer for oncology, said in a statement.

Nicholas Turner, M.D., Ph.D., the study’s lead investigator, added that "the duration of the survival in hormone receptor-positive metastatic breast cancer patients, and the potential for subsequent therapies to confound overall survival outcomes, make demonstrating statistically significant improvement in overall survival extremely difficult."

The Ibrance-fulvestrant combo won a February 2016 approval from U.S. regulators after demonstrating that it could beat out the placebo-fulvestrant pairing at staving off cancer progression. All told, that data has helped Ibrance and fulvestrant win go-aheads in more than 80 countries, Pfizer said.

These days, though, Pfizer has in-class competitors eager to snatch up market share from the blockbuster seller. Novartis’ Kisqali hit the scene in March of last year, and Eli Lilly’s Verzenio followed six months later.

Still, the New York drugmaker retains a commanding market lead, thanks to a two-year head start. For this year’s first quarter, it pulled in $933 million, and it’s been prescribed to more than 120,000 patients worldwide.