The US Food and Drug Administration (FDA) has approved Tesaro’s Zejula (niraparib) for the treatment of ovarian cancer. 

The poly-ADP ribose polymerase (PARP) inhibitor is now available as a maintenance therapy for recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer in those patients who have partially or completely responded to platinum-based chemotherapy.

The approval has come three months early for the US firm which is now looking to launch Zejula in April of this year. The drug remains under review in Europe although a launch is expected by the end of 2017.

Although not the first PARP inhibitor to reach the market, Zejula is the first to market in the maintenance therapy indication.

AstraZeneca’s Lynparza (olaparib) earned the first-of-its-kind-to-market accolade when it was approved as a monotherapy for ovarian cancer by both the FDA and the European Medicines Agency in 2014.

Lynparza generated sales of $218 million last year – a number Tesaro is likely to replicate with Zejula which analysts have predicted will reach peak revenues of $2 billion.

Alongside Lynparza are a number of other competitors for Zejula in the ovarian cancer market. Clovis Oncology’s Rubraca (rucaparib) has been approved in advanced ovarian cancer in conjunction with a BRCA test,  whilst Pfizer’s talazoparib and AbbVie’s veliparib are both in late-stage development.

Tesaro is making moves to bolster Zejula’s portfolio in response, developing the drug in a number of different uses, including first-line ovarian cancer maintenance therapy in combination with a PD-1 inhibitor; together with Roche’s Avastin (bevacizumab) in patients with first recurrence of ovarian cancer; in combination with Merck’s Keytruda (pembrolizumab) in metastatic triple-negative breast cancer; and plus a PD-1 inhibitor in several lung cancer indications.

One indication that doesn’t look too promising for Tesaro is in BRCA-positive breast cancer where a number of patients in the chemotherapy arm of its BRAVO study have dropped out.