The mano-a-mano between Pfizer's Ibrance and Novartis' LEE011 nears with early PhIII wrap-up

Pfizer’s breast cancer drug Ibrance sprinted onto the market last February, and it has shown no signs of slowing down since. But the CDK 4/6 drug, a first in its class, could soon be racing with a new rival.

Novartis is breathing down Ibrance’s neck with its own CDK 4/6 drug LEE011, also known as ribociclib. The Swiss drugmaker stopped its Phase III study early after an interim analysis found ribociclib hit its primary goal of significantly delaying progression of the disease.

The study tested ribociclib alongside Femara (letrozole) in post-menopausal women with cancers classified as hormone receptor positive and human epidermal growth factor receptor-2 negative, more commonly styled as HR+/HER2-. Full details of the study should be presented at a future cancer meeting.

Next up are discussions with regulators about submitting the drug for approval, Novartis said in a Wednesday statement.

That means ribociclib is a ways off from launch, giving Ibrance more time to solidify its place in that breast cancer niche. The Pfizer drug racked up $723 million in 2015 sales, and for Q1, delivered another $429 million --$30 million ahead of analyst estimates. That puts Ibrance on track to breach the blockbuster barrier this year, its first full year on the market.

As of February, 20,000 patients have taken the med, compared with 15,000 at the end of Q3 last year, and the number of healthcare practitioners who have prescribed it swelled from 4,000 to 5,000, Albert Bourla, Pfizer's president of vaccines, oncology and consumer health, told investors earlier this year.

Meanwhile, Pfizer can continue to advance its own research program aimed at broadening Ibrance use. Already, the drug has scored a second indication: It started out with a first-line approval in advanced HR+/HER2- cancer, alongside the aromatase inhibitor Femara (letrozole); as of February of this year, it was FDA-approved for use with AstraZeneca’s Faslodex (fulvestrant) in women whose disease has progressed after hormone therapy.

The company has a “very heavy” clinical program in other breast cancer uses, including three studies in early breast cancer.  Pfizer is also studying Ibrance in a variety of other cancers--38 and counting--including head and neck cancer that’s not linked to the human papillomavirus, as well as advanced pancreatic cancer. It’s fielding 88 studies in all.

"As you can see, we are investing heavily to stay ahead of the competition," Bourla said during the company’s Q4 earnings call.

Novartis’ ribociclib isn't the only potential Ibrance rival coming down the pipeline, either. Eli Lilly's ($LLY) abemaciclib has Phase II data due to read out this year. Pfizer appears to be less worried about the Lilly med, however; during that Q4 call, R&D chief Mikael Dolsten said abemaciclib’s clinical profile differs from Ibrance and ribociclib’s, and that the Lilly drug comes with some “significant” gastrointestinal side effects.

Lilly has its own arguments in favor of abemaciclib, however--including lower toxicity levels that allow for continuous daily dosing, Bernstein analyst Tim Anderson has pointed out. "If abemaciclib is shown to have a better clinical profile, then its late-entrant status would still spell trouble for Ibrance, threatening its primacy and worrying investors," he wrote.

- see the release from Novartis

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Image: Khadijah Carter, a mother with breast cancer, was featured in Pfizer’s Story Half Told awareness campaign.