GlaxoSmithKline has been working to restrengthen in cancer, particularly through a multibillion-dollar purchase of Tesaro. The main drug from the buyout, Zejula, is now up for a priority review in late-stage ovarian cancer, which the company hopes will help it pick up a niche nod its rivals don't have.

The FDA has accepted GSK's application for the drug to treat patients with advanced ovarian, fallopian tube or primary peritoneal cancers who have had at least three prior chemotherapy regimens. The patients must also have a BRCA mutation or homologous recombination deficiency (HRD) for their cancers, and in the case of HRD cancers, must have progressed at least half a year from their last chemo treatment. 

The application is based on data in a trial called Quadra that found "clinically relevant activity" for the patients when treated with the drug. Investigators noted that the patients have few options, and that survival after the third line of treatment ranges from five months to nine months.  

Now, the FDA expects to hand down a decision by Oct. 24, and if Zejula can secure an approval, it'll be the only drug in its class of PARP inhibitors—a group that includes AstraZeneca and Merck's Lynparza as well as Clovis Oncology's Rubraca—that can tout the specific indication.  While Lynparza and Rubraca are also approved for BRCA-positive patients who have had multiple rounds of chemo, they're not cleared for those with HRD.

Zejula is an oral PARP inhibitor currently approved as a maintenance treatment for women with recurrent ovarian, fallopian tube or primary peritoneal cancers whose disease returns. In that market, it's jockeying with both Lynparza and Rubraca for positioning. Pfizer also last year won an approval for Talzenna, a fourth PARP inhibitor, to treat patients with germline BRCA-mutated HER2-negative locally advanced or metastatic breast cancer. 

Monday’s development comes as GSK looks to build up its cancer offerings after leaving the field years ago. In December, the drugmaker purchased Tesaro for $5.1 billion, getting Zejula and other pipeline meds.  

At the time, GSK R&D head Hal Barron said PARP inhibitors were "a more important therapeutic class than … currently appreciated." He reiterated that sentiment Monday, saying in a statement that GSK hopes "ongoing clinical trials will demonstrate that this medicine can benefit even more patients." 

After the buyout, GSK CEO Emma Walmsley said at the J.P. Morgan Healthcare Conference in January that the company’s oncology pipeline was "gaining strength" and should affect the company's growth outlook starting in 2020.

GSK exited oncology years ago as part of its massive asset swap with Novartis to bulk up in vaccines. But after Walmsley took over in 2017, she overhauled the company’s R&D and rolled out a plan that included a refocus on oncology. GSK has recently reconsidered its investment in areas such as respiratory amid the overhaul, executives have said.