Real-world safety and effectiveness of mepolizumab for patients with eosinophilic granulomatosis with polyangiitis in Japan: A 48-week interim analysis of the MARS study

Objectives The objective of the study is to assess real-world, long-term safety/effectiveness of mepolizumab for eosinophilic granulomatosis with polyangiitis (EGPA) in Japan.Methods The Mepolizumab long-term study to Assess Real-world Safety and effectiveness of EGPA in Japan (MARS) (GSK ID: 213684/NCT04551989) is an ongoing 96-week study of patients with EGPA who received four-weekly mepolizumab 300 mg subcutaneously for >= 96 weeks before study entry (baseline) and continued treatment. This interim analysis included safety from baseline to Week 48 (observation period) and clinical outcomes before mepolizumab and during the observation period.Results Of 118 patients enrolled, 29% (34/118) experienced adverse events (AEs), of which 13% (15/118) experienced serious AEs; none were considered mepolizumab related. The median oral corticosteroid (OCS) dose decreased from 6.9 (pre-mepolizumab) to 3.0 (baseline) and 2.0 mg/day (Weeks 45-48); the proportion of patients receiving no OCS increased from 8% to 32% and 38%, respectively. Patients experiencing clinical symptoms decreased from 94% (pre-mepolizumab) to 73% (baseline) and 67% (Week 48). During the observation period, 5% of patients experienced EGPA relapse; the rates of EGPA-related hospitalisations, EGPA-related emergency room/unscheduled visits, and asthma exacerbations were 0.05, 0.09, and 0.08 event/person-year, respectively.Conclusions The results of mepolizumab treatment for >= 144 weeks (before baseline plus observation) were consistent with the known safety profile and allowed OCS dose reduction while improving disease control versus pre-treatment among patients with EGPA.