Tesaro's niraparib could become a much-needed new maintenance therapy for women with recurrent ovarian cancer after a positive phase III trial.
The PARP inhibitor significantly improved progression-free survival (PFS) when compared to placebo in the ENGOT-OV16/NOVA study, which recruited patients with platinum-sensitive recurrent ovarian cancer.
At the moment, women with recurrent ovarian cancer typically receive multiple rounds of chemotherapy, with gaps in between to limit side effects.
In Europe two targeted drugs - Roche's Avastin (bevacizumab) and AstraZeneca's PARP inhibitor Lynparza (olaparib) - are approved for maintenance therapy but are of limited benefit. In the case of Avastin its benefit is modest - extending survival by a few months - while Lynparza can only be used in around 15% of patients (those who have a BRCA mutation).
Niraparib is particularly exciting because the phase III trial showed a significant improvement in PFS regardless of the patients' BRCA status, giving it an edge over Lynparza, which remains the only PARP inhibitor on the market. The data means it could be used in more than two-thirds of ovarian cancer patients, according to analysts.
The median PFS with niraparib was 21 months in BRCA-positive patients compared to 5.5 months for placebo. In the non-BRCA group there was still a benefit, with PFS of 9.3 months compared to 3.9 months among matched controls.
Tesaro's drug also significantly improved PFS in women with another form of mutation known as homologous recombination DNA repair deficiency (HRD). In this group, patients on the drug showed a PFS of 12.9 months, compared to 3.8 months for placebo.
"We have never seen such large benefits in PFS in recurrent ovarian cancer," said lead investigator Dr Mansoor Raza Mirza of Copenhagen University Hospital in Denmark, who said the results are "a breakthrough for patients".
Shares in Tesaro rocketed on the news of the results, particularly as the company has no close rivals as it chases the ovarian cancer maintenance indication. With Lynparza's use limited to BRCA-positive patients and AbbVie's veliparib and Pfizer's talazoparib being studied initially for breast cancer, Tesaro could be on its own in the market for some time.
The company has indicated it intends to file for approval of niraparib before the end of the year.