Lilly revs up to challenge Pfizer, Novartis in breast cancer with abemaciclib 'priority' nod

If Lilly can snag an approval for abemaciclib, it'll enter the CDK 4/6 market, where Pfizer picked up more than $2 billion in sales last year.

Here comes the second challenger to Pfizer’s Ibrance.

On Monday, the FDA granted Eli Lilly’s abemaciclib a priority review, putting it on a quicker path to approval. If it can get there, it’ll become the third entrant in the CDK 4/6 class of breast-cancer fighters, behind Ibrance and Novartis’ Kisqali—a medication the agency greenlighted less than four months ago

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

Of course, abemaciclib will have its challenges as a third-to-market med—but it’s facing other hurdles, too. It’s triggered frequent, low-grade diarrhea in trials, a side effect that’s “not the kind of differentiation a manufacturer seeks,” as Bernstein analyst Tim Anderson put it in an April note to clients.

But as Barclays analyst Geoff Meacham pointed out in his own June note, adjusting dosage is an option for dealing with the diarrhea rates—though it remains to be seen if doing so “will be enough to spur greater than expected utilization.”

In his view, at least, ratcheting back the dose to 150 mg from 200 mg “mostly” puts adverse events “into the acceptable range overall without affecting median duration of response and largely clarifies the primary concern surrounding abemaciclib.”

If doctors agree, then that would be good news for Lilly, which is seeking a piece of the CDK 4/6 market, where Ibrance pulled in $2.14 billion for Pfizer last year. Bernstein analysts have pegged 2021 sales for the abemaciclib at $1.3 billion, assuming “no real differentiation” for the Lilly product. That’s just shy of the $1.6 billion Wall Street expects for Kisqali the following year.

RELATED: With Novartis' Kisqali, Pfizer faces its first in-class threat for Ibrance

Pfizer, meanwhile, has insisted it’s not afraid of a little competition.

“Every drug that tries to enter in this space has a very high bar to live up to in order to be as widely accepted and well received as Ibrance has been,” Mace Rothenberg, Pfizer’s chief development officer for oncology, said in an April interview. “We’re really committed to this area and retaining market leadership in this field.”

The way the company sees it, it’s got plenty of room to grow Ibrance even within its current HR-positive, HER2-negative breast cancer indications.

“Our initial strategy was to establish Ibrance as the standard of care with early adopting physicians,” Albert Bourla, president of Pfizer’s innovative health division, told investors on the drug giant’s fourth-quarter conference call in January. But “moving forward, we believe the growth will come from late adopters, many of whom have already prescribed Ibrance, but in a limited number of patients,” he added.