GSK widens the market for Zejula as FDA signs off on the PARP inhibitor for use in ovarian cancer patients without BRCA mutations
GSK has vastly expanded its market for cancer therapy Zejula — the crown jewel at the heart of its $5 billion acquisition of Tesaro — by winning FDA approval for the drug in a large subset of patients with ovarian cancer.
The approval comes for women with advanced epithelial ovarian, fallopian tube, or primary peritoneal cancer who experienced a complete or partial response to first-line platinum-based chemotherapy — accounting for approximately 80% of all ovarian cancer patients.
Previously, the drug’s use was limited to a subset of such cancer patients who carry BRCA mutations — the remaining 20%.
“This approval is highly anticipated as a potential inflection for Zejula, which has been lagging its main competitor Lynparza,” SVB Leerink’s Geoffrey Porges said.
Every other drug in its class — including AstraZeneca and partner Merck’s Lynparza and Clovis Oncology’s Rubraca — are only eligible to treat ovarian cancer patients with BRCA mutations as a monotherapy in first-line maintenance therapy settings.
“Women with advanced ovarian cancer have a five-year survival rate of less than 50%,” said Hal Barron, GSK’s chief scientific officer in a statement. “This expanded indication means that many more women with this devastating disease can receive earlier treatment with Zejula, which can extend the time it takes for their cancer to progress.”
Hal Barron at Endpoints News’ UKBIO19 event in London, October 2019
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Akin to GSK’s Zejula, Lynparza and Rubraca are poly-ADP ribose polymerase (PARP) inhibitors. PARP is a protein used by damaged cells to initiate repair, and by thwarting it, the class of drugs is engineered to prevent cancer cells from repairing themselves, thereby catalyzing their destruction.
While drug developers have primarily relied on BRCA mutations to identify patients who can benefit from this family of therapies, scientists have suggested that defects in other genes involved in DNA repair — which render cells cancerous — could be prime targets too.
As the second-to-market drug in the class, and viewed as lacking differentiation, Zejula only generated ~25% of the revenue Lynparza did last year — £229 million versus £921 million, noted Porges, adding that GSK management has indicated Zejula currently only has a minority share (15-20%) in the front-line setting, with the majority share taken by Lynparza.
Given the coronavirus pandemic, the Zejula launch in the new indication will likely be impacted. Porges forecast £371 million in sales for Zejula by the end of 2020, predicting it would rise to £851 million by 2025.
This new approval for Zejula was based on the results of the 733-patient, placebo-controlled PRIMA study.
Data on the median progression-free survival for the trial population showed the drug induced a statistically significant improvement of 13.8 months compared with 8.2 months for those receiving placebo.