In June, AstraZeneca revealed that in a phase 3 trial, its Lynparza had pared down the risk of disease worsening or death in breast cancer patients by 42%. And that showing apparently impressed the FDA.

The agency Wednesday accepted the British drugmaker’s approval application and granted the medication its "priority review" tag. That means it’ll be a hasty trip for Lynparza—which AZ shares with Merck—through the regulatory review process. Regulators set a decision date in the first quarter of 2018, AZ said. 

The "priority" nod comes on the back of study data showing that Lynparza—right now approved in ovarian cancer and ovarian cancer maintenance—shrank tumors in 60% of the HER2-negative breast cancer patients with BRCA1 or BRCA2 mutations. And importantly, it proved effective among patients with triple-negative breast cancer, a notoriously difficult-to-treat form of the disease.

If Lynparza can bring home an FDA nod, it’ll be the first PARP inhibitor to venture outside of the ovarian cancer arena. And that’ll open it up to sales its competitors—Clovis Oncology’s Rubraca and Tesaro’s Zejula—can’t currently touch.

That’s not to say they aren’t working on it, though, making AZ’s potential head start all the more critical. Rubraca is in phase 2 studies for breast cancer and triple negative breast cancer, and Tesaro and Merck are testing a Zejula-Keytruda triple negative breast cancer combo that’s also in phase 2.

Meanwhile, AstraZeneca is hoping that August’s ovarian cancer maintenance approval can help Lynparza steal share back from Zejula, which has been steamrolling since its April launch. Both drugs now bear go-aheads in women without BRCA gene mutations.