Novartis’ breast cancer drug Kisqali so far hasn’t lived up to expectations, and the drugmaker’s hoping some strong new data in metastatic patients will help. Can the numbers actually boost the drug’s sales? Depends on how doctors decide to use them.

Novartis unveiled the results Sunday at the American Society of Clinical Oncology annual meeting, showing that among patients with HR-positive, HER2-negative breast cancer, adding Kisqali to fulvestrant kept the disease at bay for nearly eight months longer than fulvestrant alone.

That’s "among the biggest improvements since the induction of hormonal therapy some 45 years ago," study investigator Dennis Slamon, M.D., Ph.D., said.

The results covered women who hadn’t been treated before and those whose disease had progressed after one line of treatment.

In previously untreated patients, the Kisqali-fulvestrant combo staved off disease for a median 20.5 months, compared with just 12.8 months for solo fulvestrant. And investigators estimated that nearly 70% of women in that first-line subgroup still hadn’t seen their disease progress at a median follow-up of 16.5 months.  

Up to this point, "the dogma has been that these patients should receive hormonal therapy first, and then if they progress on that, then you give the combination," Slamon said. Now, though, these data set "a new potential standard for patients that have not seen prior hormonal therapy," he said.

Whether Kisqali’s performance in this trial translates to earlier use in the real world, though, remains to be seen.

"I’d like to tell you I think it’s going to be used a lot more given these data, but just given what I’ve seen in the past, it’s going to be interesting" to see how prescribing patterns play out, Slamon said. He pointed to Roche blockbuster Herceptin, which physicians—"who tend to be quite conservative in their approach"—continued to hold back until after further lines of chemo, even after data rolled out supporting its first-line use.

Novartis, for one, is hoping to see doctors run with the new data—and bolster Kisqali’s sales in the process. While its rival drug Ibrance, a Pfizer blockbuster, had a big head start on its in-class rivals, analysts still predicted that Kisqali and Eli Lilly player Verzenio could crack the $1 billion mark at their respective sales peaks. So far, though, Kisqali has failed to gain major traction—so much so that CEO Vas Narasimhan, before stepping into the company’s top spot, included jump-starting the product on his list of the top three challenges he’d face as helmsman.

Meanwhile, positive new breast cancer data on Ibrance and Verzenio have continued to boost the profile of the CDK 4/6 class as a whole—and, in turn, expand sales prospects for all three players. "I think it’s been remarkable, since we initially did the first studies, how consistent the data have been across all members of the class," Slamon said, adding that the results the class has put up so far show that "this is an important new therapeutic approach."

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