Pfizer's Ibrance lead gets bigger with Eli Lilly's abemaciclib delay

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Pfizer’s ($PFE) breast cancer therapy Ibrance is the drug to beat in its brand-new class, CDK4/6 inhibitors, but Novartis ($NVS) and Eli Lilly ($LLY) are both aiming for a serious race.

Unfortunately for Lilly, its contender just hit a pothole.

When a trial monitoring committee checked interim data on Lilly’s abemaciclib, the drug had not met its goal for efficacy yet. Instead, the committee said the trial--which combines abemaciclib with the hormone therapy fulvestrant--should go on. Lilly had been hoping, and many analysts expecting, that the drug would perform well enough to stop the trial early.

That’s what happened with an Ibrance trial, PALOMA3, last year in previously treated patients. Same with Novartis’ ribociclib, whose MONALEESA-2 study was halted on interim analysis.

This means the abemociclib combo data will be delayed until next year. More importantly, it means that Lilly won’t be able to use that data for an FDA filing by the fourth quarter of 2016 as it had expected. And that, in turn, could delay a launch to 2018.

That puts abemaciclib way behind Ibrance, which won a speedy FDA approval in February 2015. Since then, its sales have soared. For the second quarter, Ibrance hauled in $514 million, beating analyst estimates. The drug has been successful enough to dig into sales of Novartis’ well established Afinitor, analysts say.

Meanwhile, Novartis’ own CDK4/6 is also likely to beat abemaciclib to market. Just last week, ribociclib, also known as LEE011, won a breakthrough designation from the FDA for first-line use alongside Femara, which offers a speedy route to approval. That app involves the MONALEESA-2 trial that was halted early.

With Lilly’s delay, that puts Ibrance and ribociclib in two-way battle for share for quite some time, assuming ribociclib can launch fairly soon. Ibrance won’t have to defend its share against two rivals till 2018.

Plus, though Pfizer and Novartis are both on track for new indications--in previously treated patients, solo treatments, among others--Pfizer remains in the lead there.

And then there’s this wrinkle: The abemaciclib trial was restricted to patients who hadn’t been treated previously with another CDK4/6 drug, and that could narrow its market when it finally wins approval.

The Lilly drug “will be fourth or fifth line with around 20% [response rate], approximately comparable to other drugs in that same situation,” Sally Church, who covers the oncology field in her Biotech Strategy Blog, told Endpoints. “Will the FDA want more efficacy or equivalent?  I think Lilly are in a risky position.”

- see the Lilly release

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