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 50 mg 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.

Trial registration number NCT04217798