ESMO: Pfizer's Ibrance flop in early breast cancer shouldn't hurt metastatic sales, exec says

Investigators are sifting through data to see whether certain populations benefited from two years of Ibrance treatment alongside standard endocrine therapy. (Pfizer)

Pfizer talked up Ibrance’s potential in early breast cancer for years before getting the bad news this May: The Pallas study, examining the drug in stage 2 and stage 3 patients with the HR-positive, HER2-negative form of the disease, was a flop.

But while the failure might represent a missed revenue opportunity, it shouldn’t hurt Ibrance’s ability to churn out sales in the metastatic setting, one exec says.

At a median follow-up of 23.7 months, adding Ibrance to post-surgery endocrine therapy hadn’t helped patients ward off invasive disease, according to an abstract of a study set to be presented at the European Society for Medical Oncology virtual meeting this weekend.

At the three-year mark, 88.2% of Ibrance patients were free of invasive disease, versus 88.5% of patients who received endocrine therapy alone.

RELATED: Pfizer's Ibrance misses shot at big new market with early breast cancer failure

“Clearly, we’re disappointed with the Pallas results,” said Andy Schmeltz, global president and general manager of Pfizer's oncology unit. “We were hopeful” based on “some of our earlier work in phase 2 that the outcome would be different, but this is why you do the study.”

So what was behind the miss? Investigators are still “very actively exploring potential reasons for why we have seen the outcome we did,” lead investigator Erica Mayer, M.D., said, and they’re looking for subgroups of patients who may have benefited.

One thing she did note, though, is that the median follow-up time was “quite short” at about two years.

“I really think that longer-term follow-up is very necessary when studying this patient population,” she said, noting that “we will need to follow these patients long term to really comprehensively understand the full impact of treatment exposure in this setting and watch as this data matures.”

In the meantime, though, Pfizer’s financial expectations haven’t been battered too badly, Schmeltz said. The company had projected Pallas as a $2 billion peak revenue opportunity, risk-adjusted at 50%, and “we’ve had enough other progress in our oncology pipeline and across the rest of Pfizer” to make up for that $1 billion hit to expectations.

RELATED: Lilly's Verzenio shows up Ibrance, hitting its goal in early breast cancer after Pfizer's drug faltered

Pfizer isn’t completely out of the woods, though. Shortly after it unveiled the Pallas failure, Eli Lilly—which makes Ibrance archrival Verzenio—announced it had pulled off a win in its own early breast cancer trial, albeit in a slightly different population.

The outcome led some analysts, including Cantor Fitzgerald’s Louise Chen, to wonder whether an adjuvant OK for Verzenio could shift doctors’ preferences away from Ibrance in the metastatic setting, where it boasts a wide lead over its Lilly nemesis. In 2019, Ibrance raked in $4.96 billion, compared to Verzenio’s $580 million.

But Schmeltz isn’t worried. “I’ve got to say that all our interactions with thought leaders, through market research with medical oncologists that treat breast cancer, they look at early breast cancer very differently from metastatic,” he said, adding that “we do not expect any impact on Ibrance’s … positioning or performance in the metastatic setting.”

Evercore ISI analyst Umer Raffat, for his part, agreed.

"Could this increase % share in metastatic? I doubt it," Raffat wrote in a note to clients following Lilly’s top-line release in June.