GSK's Zejula racks up first-line maintenance win in ovarian cancer, even in non-BRCA patients

GlaxoSmithKline laid out $5.1 billion last year for Tesaro and its key PARP inhibitor, Zejula, and with some new first-line ovarian cancer data it has another chance to prove the deal was worth it.

Zejula will have to stand up to AstraZeneca and Merck's rival med Lynparza, which has a lead in that market, thanks to a December approval for first-line, BRCA-mutated patients after platinum chemo. But the GSK drug's data win covers patients without BRCA mutations, too, giving it a chance to win a chunk of the market Lynparza doesn't yet own.

GSK Monday reported that in the phase 3 Prima trial, Zejula topped placebo at fending off cancer's advance in patients who responded to one round of platinum-based chemo, regardless of their BRCA status. And with the drug's sales now lagging far behind Lynparza's, an approval outside of BRCA-mutated patients could help.

Lynparza won a quick approval as first-line maintenance therapy in ovarian cancer patients with germline BRCA mutations thanks to "remarkable" data unveiled last fall, Jefferies analyst Peter Welford wrote in a Monday note to clients. The AstraZeneca/Merck drug reduced the risk of disease progression or death by a whopping 70%, and 60% of women taking the drug in the trial went at least three years without a relapse.

That's a tough act to follow. But Welford's team is “encouraged” by Zejula's results and awaits “detailed data to determine commercial implications.” GSK said it’ll release the full data at an upcoming medical meeting.

RELATED: AstraZeneca, Merck's Lynparza plows ahead in ovarian cancer with $1B-plus approval, phase 3 data

As Welford noted, 35% of ovarian cancer patients have non-gBRCA homologous recombination deficiencies, and Zejula has a chance to become the first med in the class to show benefit for that group.

About 300,000 women are diagnosed with ovarian cancer each year globally, GSK estimates. But “only about 15% of patients are currently eligible to receive PARP inhibitors as their initial therapy,” R&D head Hal Barron said in a Monday statement.  

“These exciting data demonstrate that Zejula has the potential to significantly benefit even more women with this devastating cancer,” he added.

RELATED: GlaxoSmithKline, looking to pump up in new favorite oncology, buys Tesaro for $5.1B 

GSK acquired Tesaro in a $5.1 billion deal last December, getting Zejula and a handful of pipeline prospects. Zejula originally won approval back in March 2017 as a second-line maintenance treatment for patients with epithelial ovarian, fallopian tube or primary peritoneal cancer who'd relapsed after one treatment round but then responded to platinum-based chemotherapy. Clovis Oncology's Rubraca carries a second-line maintenance nod as well.

Some market watchers panned the Tesaro acquisition, but GSK insisted the potential market for PARP inhibitors wasn’t fully appreciated. 

GSK made the move after exiting oncology in 2015 through a massive asset swap with Novartis. In that deal, GSK bulked up in vaccines and offloaded its cancer assets. More recently, it's changed course and is working to restrengthen in oncology.

RELATED: GSK wins speedy FDA Zejula review in ovarian cancer niche

Since the Tesaro buyout, GSK has been working to make the most of Zejula, which generated £42 million in the first quarter after the deal closed on January 22. GSK recently scored an FDA priority review for the med in an ovarian cancer niche where its rivals don’t have approvals. AstraZeneca and Merck's Lynparza pulled in $647 million last year.