Cost-minimization analysis comparing eltrombopag vs romiplostim for adults with chronic immune thrombocytopenia

Abstract

BACKGROUND: Promacta (eltrombopag; EPAG) and Nplate (romiplostim; ROMI) have not been compared in head-to-head trials for treatment of chronic immune thrombocytopenia (cITP); however, indirect treatment comparisons have indicated similar efficacy and safety outcomes, and the drugs are generally accepted as therapeutic alternatives. OBJECTIVE: To determine which of the 2 therapies would result in the lowest overall cost from a US health plan perspective, under the assumption of equivalent clinical efficacy and safety. METHODS: A cost-minimization model was developed in Microsoft Excel. The model incorporated only costs that differ between the treatments, including drug acquisition, administration, and monitoring costs, over a 52-week horizon. Average dosing for EPAG and ROMI was taken from the long-term EXTEND trial and from a published meta-analysis of 14 clinical trials, respectively. ROMI is injectable and EPAG is oral, so only ROMI had administration costs. The model assumed patients used 25 mg EPAG tablets and the 250 µg vial size of ROMI. ROMI wastage was included in drug acquisition costs by rounding up average dose to the nearest whole vial. Monitoring requirements were determined from US prescribing information, with platelet monitoring assumed equal, and hepatic panel testing every 4 weeks for EPAG. The model was adjustable to commercial, Medicare, and Medicaid plan perspectives, with optional inclusion of drug wastage, monitoring, or administration costs. RESULTS: The base case used a commercial plan perspective, with average dosing of 51.5 mg/day for EPAG and 4.20 µg/kg/week for ROMI. The analysis found a cost difference per treated patient of $64,770 in favor of EPAG on an annual basis. Breakdown by unique costs for EPAG included drug-acquisition cost of $123,135 and monitoring cost of $705. Breakdown by unique costs for ROMI included drug-acquisition cost of $183,234, with wastage of $63,179 and administration cost of $5,377. Based on a hypothetical commercial plan with 1 million members and an estimated 11 patients with cITP receiving ROMI, potential annual savings for switching all patients from ROMI to EPAG is $712,473 or $0.06 per member per month. EPAG remained the less costly option for all plan types and assumptions. A sensitivity analysis found that the result was most sensitive to drug pricing and wastage inputs. CONCLUSIONS: Because of lower drug-acquisition costs (including drug wastage) and administration costs, treatment of cITP with EPAG is associated with a lower net cost per patient than ROMI.