Zejula was the lead compound of U.S. cancer specialist Tesaro, which GSK acquired for $5.1 billion last year. Zejula brought in sales of 57 million pounds ($73.59 million) in the second quarter.
The FDA nod was based on a trial that showed the benefit of using Zejula to treat tumors whether or not the women had mutated BRCA genes which hamper DNA repairs, but also in women with a wider range of genetic mutations, grouped together under the term homologous recombination deficiency (HRD).
Currently, AstraZeneca and Merck & Co's Lynparza is seen as a leading PARP inhibitor, a class of medicines to which Zejula belongs, with analysts forecasting average sales of $3.1 billion for 2023.
Zejula, approved in 2017 by the FDA, is expected to achieve about 870 million pounds ($1.12 billion) in revenue that year.
Both Lynparza and Zejula have shown promise in ovarian cancer patients with BRCA and HRD mutations. With the approval, GSK has now become the first to be allowed to market its treatment in the HRD setting.
The approval underscores the potential of PARP inhibitors for use across a wider gene pool and beyond ovarian cancer.
Other approved PARP inhibitors include Pfizer's Talzenna and Clovis Oncology's Rubraca. Abbvie is testing an experimental compound called veliparib.
The approval is also a boost to GSK's comeback into cancer therapies. The drugmaker had sold its approved oncology drugs to Novartis in 2014.