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

<jats:title>ABSTRACT</jats:title> <jats:sec> <jats:title>Objectives</jats:title> <jats:p>The objective of the study is to assess real-world, long-term safety/effectiveness of mepolizumab for eosinophilic granulomatosis with polyangiitis (EGPA) in Japan.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>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.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>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.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>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.</jats:p> </jats:sec>