Novartis' LEE011 'priority' tag hastens showdown with Pfizer's Ibrance, but do safety concerns portend a blowout?

Novartis HQ cropped

Novartis’ CDK4/6 breast cancer drug is coming for Pfizer’s Ibrance--and quickly. But how much does the New York drug giant really have to worry?

Novartis said Tuesday that its candidate, LEE011, had snagged the FDA’s priority review tag, putting it in line for a speedy trip down the regulatory pathway. The Novartis med already had a breakthrough therapy designation from the regulator.

The pharma giant’s submission includes results presented last month at the ESMO 2016 Congress, which showed that the combo of LEE011 and the standard hormone therapy Femara could cut the risk of disease progression or death by 44%, compared with Femara alone. The study tested the drugs in women with cancers classified as hormone receptor positive and human epidermal growth factor receptor-2 negative.

Now, the company is one step closer to taking that data out into the field for a showdown with Ibrance, the hot-launching drug that won its own rapid FDA OK early last year. But while LEE011’s efficacy marks may measure up to Ibrance’s--Bernstein’s Tim Anderson last month called the meds “twins separated at birth” in respect to their Phase III results--it can’t say the same on the safety front.

Incidences of drug-induced liver damage and mild cardiac arrhythmias--as well as one drug-related sudden death--left Credit Suisse analysts wondering whether the FDA might slap a black box warning, its most serious, on the Novartis product after approval.

At the very least, Novartis itself is considering adding on “some additional monitoring” of patients using the med, which it believes it can do “in such a way that it does not create additional patient burden or physician burden,” Novartis’ global head of drug development, Vas Narasimhan, told investors on the company’s Q3 conference call.

Analysts, though, aren’t so sure. “While this safety burden may be acceptable in metastatic breast cancer, a large element of commercial potential lies" in patients earlier in the disease course, who've just had their tumors surgically removed, the Credit Suisse analysts wrote last month. “[W]e believe that this safety burden may not be acceptable for broader use,” they said. And Bernstein’s Anderson trimmed his sales estimates for LEE011 following Narasimhan’s comments.

Credit Suisse’s Vamil Divan, for one, believes the safety concerns might be so stunting for Novartis that it could even fall behind Eli Lilly, which is still working its way through the clinic with prospective rival abemaciclib. They “leave a door open for abemaciclib to potentially be the second-best agent in the class, or at least not being relegated to a distant third-place position well behind both Ibrance and LEE011,” he wrote in October.

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