By Carl O’Donnell

(Reuters) – The U.S. Food and Drug Administration on Wednesday cleared expanded use of GlaxoSmithKline Plc’s Zejula as a first option to keep advanced ovarian cancer at bay in women who have responded to chemotherapy.

The approval, which does not limit the drug to women with certain genetic anomalies, should open up Zejula to expanded use in a larger patient population and could signal a similar opportunity for other drugs in the same class, known as PARP inhibitors.

PARP inhibitors work by blocking enzymes involved in repairing damaged DNA, thereby helping to kill cancer cells. They are a growing focus for drug research, with potential for use in breast, lung and prostate cancers.

Zejula is the first PARP inhibitor cleared for use on its own as a first-line maintenance therapy for ovarian cancer patients who do not have a mutation of the BRCA enzyme, which occurs in about 20% of women with ovarian cancer.

Maintenance therapy – meaning it is used to help keep cancer from recurring – can significantly boost sales because the drug is typically used for a longer duration.

The FDA nod will help Zejula better compete with rival PARP inhibitors, which include AstraZeneca and Merck & Co’s Lynparza and Clovis Oncology’s Rubraca.

Zejula was previously approved for use as a maintenance therapy in patients who had recurrent bouts of ovarian cancer and as a treatment for patients with specific genetic mutations who had previously been given multiple rounds of chemotherapy.

As first-line maintenance, it can now be used earlier in the course of the disease for patients who have responded to chemotherapy.

Wednesday’s approval marks a win for GSK’s deal-making strategy. It acquired Zejula with its 2019 purchase of drugmaker Tesaro Inc for $5.1 billion, at a time when investors were growing skeptical about the potential of its flagship drug.

“We are very excited,” said GSK research head and chief scientific officer Hal Barron. “We said at the time we acquired Tesaro that the PARP class was significantly underappreciated.”

Under Chief Executive Emma Walmsley, the London-based drugmaker has sold several assets, and bought others in fast-growing markets such as oncology, to try to rejuvenate growth as several of its older drugs face the loss of patent protection.

On Wednesday, GSK’s first-quarter profit beat analysts’ expectations due to strong demand for its blockbuster shingles vaccine and higher sales of some of its pain relief medicines during the coronavirus pandemic.

(Reporting by Carl O’Donnell; Editing by Bill Berkrot)