AstraZeneca's Lynparza, armed with new FDA nod, aims to regain share from Tesaro's Zejula

Sorry, Tesaro. Lynparza can now fight back. The AstraZeneca drug—now shared with Merck & Co.—won its new, broader approval in ovarian cancer, putting it on more even footing in its race with Tesaro’s recent launch, Zejula.

The FDA gave its blessing Thursday not only for a new oral formulation of Lynparza, but for a new indication as a maintenance treatment—essentially, second-line therapy designed to keep cancer at bay as long as possible.

Even better, Lynparza snagged that approval not only in patients with BRCA gene mutations, the population it already targets, but in women without those mutations, a much larger group.

Till now, Tesaro’s Zejula—launched in April—had been the only drug in the PARP inhibitor class to boast such a large range of potential patients. Lynparza and the Clovis Oncology entry Rubraca were both approved only for BRCA patients, and only in those who’d relapsed after two prior rounds of therapy.

That edge had helped Zejula seize PARP market share lickety-split. But now, Tesaro analysts are saying they expect Lynparza, Rubraca and Zejula to split the market in three fairly even pieces. Clovis is in the process of seeking a maintenance approval itself.

When AstraZeneca filed for the maintenance approval, market-watchers guessed that AstraZeneca might go for the non-BRCA approval, despite the fact that its clinical trial in that setting, Solo-2, focused directly on women with mutations. That’s because Lynparza had some data in the non-BRCA group from a prior study; though that data only covered a subset in that earlier trial, called Study 19, the idea was that AstraZeneca could put it together with the Solo data for a broader nod.

AstraZeneca was tight-lipped about that prospect at the time, but that’s exactly what happened.

"Somewhat surprisingly, the approval is broader than the BRCA mutant population tested in the company's Solo-2 maintenance study, and is also based on a previous, all-comers study that was rejected by an FDA AdCom in 2014," Evercore ISI analyst Steven Breazzano said Thursday afternoon.

That’s obviously good for AstraZeneca, and for Merck, which inked an $8.7 billion partnership with AstraZeneca on the drug earlier this month. The two drugmakers are splitting Lynparza right down the middle, and testing the med in combination with Merck’s high-performing PD-1 checkpoint inhibitor Keytruda.

Not good, however, for Clovis and Tesaro. "As this puts AstraZeneca right up there in the broader second-line maintenance setting competing for patients, we view it as an incremental negative" for both of those companies, Breazzano added.

The advantage of that broader market had put Zejula in an early PARP lead—very early, considering AstraZeneca’s med launched in December 2014, and Tesaro rolled out Zejula just a few months ago. Tesaro CEO Lonnie Moulder said just last week that the product held a 60% piece of the PARP pie by the end of the second quarter. To date, more than 1,000 doctors have already prescribed Zejula, more than twice the number of doctors who’d prescribed Zejula’s rivals in their respective first quarters on the market launch, Moulder said.

Not so much anymore. "While we see pros and cons for each PARP inhibitor, we expect these differences to negate each other, resulting in relatively similar market shares in the second-line-plus maintenance setting," Leerink analyst Seamus Fernandez said in an investor note on the heels of the Thursday afternoon approval.

For those keeping score in the PARP field, however, Lynparza’s Solo-2 trial was seen as a strong indicator that it would snag the broader approval, if not as broad as that trial suggested. Its maintenance data showed it staved off cancer for a median 19.9 months, and, in a separate sensitivity analysis, gave the drug a 24.5 month survival advantage over standard of care.

It’s "always been a three-horse race," Brezzano said.