Background: Currently, 3 poly(ADP-ribose) polymerase inhibitors (PARPi) are approved by the US Food and Drug Administration for patients (pts) with epithelial ovarian, fallopian tube, or primary peritoneal cancer. Data evaluating real-world cost comparisons of these agents are scarce. The objectives of this study were to: (1) compare the monthly drug cost from paid claims of the 3 PARPis: niraparib, olaparib tablet, and rucaparib; and (2) determine out-of-pocket (OOP) expenses among pts receiving PARPi therapy for OC. Methods: In this retrospective study, we identified newly diagnosed pts with OC in the United States between January 2015 and December 2018 using the IBM ® MarketScan ® Commercial and Medicare Supplemental Databases. Pts who received no prior PARPi therapy and with more than one pharmacy claim in the 2018 calendar year were included. The mean monthly drug cost to the payer for niraparib, olaparib, and rucaparib was calculated by dividing a pt’s total drug cost by the number of months from the pt’s first drug prescription date to the last drug prescription date plus 1 month. The cost per month for each PARPi was calculated as the mean total cost/month/pt and consisted of the plan allowed amount and OOP cost. Results: Seventy-nine pts with OC received niraparib, 51 olaparib, and 30 rucaparib during the study period. Niraparib had the lowest mean cost per month ($11,723), compared with olaparib ($13,015) and rucaparib ($14,893), 11% and 27% higher, respectively. There were no statistically significant differences in pt demographics (age, index year, insurance, geographic region, population density, follow-up time, reason for ending follow-up) amongst the 3 PARPis studied. Niraparib had the lowest mean OOP cost per month ($106) compared with olaparib ($180) and rucaparib ($120), a 69% and 13% increase, respectively. Sensitivity analysis excluding pts who used a PARPi for less than 2 months yielded similar results with niraparib having the lowest total costs (olaparib and rucaparib were 13% and 34% higher, respectively). There was a more pronounced effect in OOP cost, with niraparib remaining the lowest (olaparib and rucaparib were 99% and 35% higher, respectively). Conclusion: Niraparib had the lowest total cost per month (both allowed plan amount and OOP expense) for pts with OC receiving PARPi therapy. Sponsorship: This study was sponsored by TESARO: A GSK Company, Waltham, MA, USA.