Lilly's cancer med abemaciclib hits survival mark, but can it stand up to Ibrance and Kisqali?

Eli Lilly
Eli Lilly's abemaciclib, if approved, will need to find some sort of marketing edge to compete as the third-to-market therapy in the CDK 4/6 class of breast-cancer fighters.

Eli Lilly’s chances of snagging an abemaciclib approval as wide as those of its rivals are looking even better, thanks to new survival data announced on Monday. But analysts are still questioning whether that’s enough to help the third-to-market CDK 4/6 med hang with its competition.

In a phase 3 trial of the drug in previously untreated patients with HR-positive, HER2-negative breast cancer, abemaciclib nailed its primary endpoint, demonstrating significant improvement in progression-free survival. The performance follows up on last month’s positive results from Lilly’s other key trial, a test in patients whose cancer had come back after a first round of treatment.

With those two sets of positive data in hand, the Indianapolis drugmaker is “assured of a product label with the same breadth” as that of Pfizer’s Ibrance and Novartis’ Kisqali, Bernstein analyst Tim Anderson predicted in a Monday note to clients. But that may not be enough to ensure abemaciclib’s success.

Considering that Lilly’s prospect will launch more than two years behind Ibrance, approved in February 2015, and more than half a year behind Kisqali, which snagged its FDA green light last month, the med will have to put some differentiating factors on display, Anderson said. And one of those factors—a different toxicity profile—isn’t necessarily something to brag about.

While abemaciclib can be dosed daily and continuously—compared with Ibrance, which patients need to stop for a week after every three weeks of therapy, to dodge neutropenia risks—it also comes with frequent, low-grade diarrhea. That’s a side effect that could prove particularly burdensome in a drug patients will take for either many months in the metastatic setting or a couple of years in the adjuvant setting, Anderson figures.

“Even if low-grade—may influence physician/patient choice adversely,” he wrote. “It is not the kind of differentiation a manufacturer seeks.”

Instead, the way Anderson sees it, Lilly should focus on efficacy, particularly on data showing whether abemaciclib can “produce more frequent and more durable tumor responses that translate to longer PFS.” Should the second-line trial, dubbed MONARCH 2, show a higher response rate and longer response duration for abemaciclib compared with its nemeses, Lilly’s med “may indeed secure its differentiation claim and even step ahead of” Kisqali.

For now, though, Wall Street isn’t baking that prospect into forecasts. Bernstein’s $1.3 billion 2021 sales prediction for the med matches consensus and assumes “no real differentiation” for the drug, Anderson wrote.