GlaxoSmithKline has a long way to go to catch rival AstraZeneca in the PARP inhibitor market, but a new FDA approval for its Zejula drug should help it gain some ground.
The US regulator has approved Zejula (niraparib) as a fourth-line treatment for women with recurrent ovarian, fallopian tube, or primary peritoneal cancer associated with a type of mutation known as homologous recombination deficiency (HRD).
Zejula can be used in women who have been treated with three or more prior chemotherapy regimens and whose tumours are HRD-positive, identified using a just-approved companion diagnostic from Myriad Genetics.
It makes GSK’s drug the only once-daily PARP inhibitor to be approved as a monotherapy for this patient group, according to the company, giving it an indication free of direct competition from AZ’s market-leading Lynparza (olaparib), Clovis Oncology’s Rubraca (rucaparib), and Pfizer’s recently-approved Talzenna (talazoparib).
“This represents the first time a PARP inhibitor has been approved for use in patients beyond those with a BRCA-positive…mutation as monotherapy in the late-line treatment setting,” said GSK in a statement.
Zejula – which GSK acquired as part of its $5.1bn takeover of Tesaro last year – is also approved as a maintenance therapy for adults with recurrent ovarian, fallopian tube, or primary peritoneal cancers whose tumours have completely or partially responded to platinum-based chemotherapy treatments.
GSK has high hopes for the drug, which made £99m ($128m) in sales in the first half of the year, and is also developing it for other indications including first-line maintenance of ovarian cancer. That is the indication that seems to accelerated the uptake of Lynparza, which made $520m in the first half of the year.
The new approval is based on the results of the QUADRA study, which enrolled women with BRCA- and as well as HRD-positive ovarian cancer. Zejula was found to demonstrate significant improvement in progression-free survival (PFS) for the women, regardless of their biomarker status.
Overall, the study showed a 24% objective response rate and a median duration of response of 8.3 months. In patients with BRCA mutations, the ORR was 39% for those with platinum-sensitive disease, 29% in platinum-resistant disease, and 19% in platinum-refractory disease.
In patients without BRCA mutations, but with a genomic instability score (GIS) of 42 or greater as determined by the Myriad diagnostic as well as platinum-sensitive disease, the ORR was 20%.
“Ovarian cancer has a high rate of recurrence, so there is a real need for therapies for women whose cancer has progressed through multiple lines of treatment and who have few or no options left,” said lead investigator Dr Kathleen Moore of the University of Oklahoma in the US.
“It’s meaningful to see that Zejula has been approved as a late-line treatment for women including those with and without BRCA mutations,” she added.