Efficacy and safety of an oral combination therapy of niraparib and etoposide in platinum resistant/refractory ovarian cancer: a single arm, prospective, phase II study

Objective Non-platinum chemotherapy is used in platinum resistant/refractory ovarian cancer patients but offers limited efficacy, especially in those who develop platinum resistance after <= 2 lines of platinum based chemotherapy. This phase II study aimed to evaluate the efficacy and safety of oral niraparib plus etoposide in platinum resistant/refractory ovarian cancer. Methods Platinum resistant/refractory ovarian cancer patients after <= 2 lines of platinum based chemotherapy, histologically confirmed as non-mucinous epithelial ovarian cancer, regardless of biomarker status, were eligible. Patients received niraparib with a starting dose of 200 mg/100 mg alternate once a day, and oral etoposide of 50mg once a day, on days 1-20 of 30 days per cycle for a maximum of 6-8 cycles, followed by niraparib until disease progression or intolerable toxicity. The primary endpoint was investigator assessed progression free survival. Results 29 patients were enrolled from 22 May 2020 to 3 February 2023; 26 patients were included in the efficacy analysis set as per protocol. Median progression free survival was 4.2 months (95% confidence interval (CI) 3.9 to 4.4). Overall response rate was 26.9% (95% CI 8.7 to 45.2). Disease control rate was 57.7% (95% CI 37.3 to 78.0). Overall response rate in patients with a BRCA mutation and homologous recombination deficiency was 50% and 41.7%, respectively. Median progression free survival in patients with primary platinum resistance was 4.5 months (95%CI 3.6 to 5.3). 29 patients were included in the safety analysis set, and 8 (28%) patients experienced treatment related adverse events of grade >= 3. There was no treatment related discontinuation. Conclusions Niraparib combined with etoposide showed evidence of antitumor activity in platinum resistant/refractory ovarian cancer after <= 2 lines of platinum based chemotherapy, particularly in patients with a BRCA mutation, homologous recombination deficiency, or primary platinum resistance. This once-a-day oral combination was a convenient option.