Effectiveness and safety of mepolizumab in combination with corticosteroids in patients with eosinophilic granulomatosis with polyangiitis

BACKGROUND: Mepolizumab (MPZ), an anti-interleukin-5 antibody, is effective for the treatment of eosinophilic granulomatosis with polyangiitis (EGPA). However, its effectiveness has not been adequately evaluated in real-world clinical practice. In this study, we assessed the effectiveness and safety of MPZ (300 mg) for relapsing/refractory EGPA resistant to corticosteroids (CS) for 1 year in real-world settings. METHODS: We administered MPZ (300 mg) to 16 patients with relapsing/refractory EGPA resistant to CS (Post-MPZ). We also retrospectively collected data from the same patients for the 12 months before the administration of MPZ (Pre-MPZ). The primary endpoint was the 12-month remission rate after MPZ administration and the secondary endpoints were the Birmingham vasculitis activity score (BVAS), vasculitis damage index (VDI), eosinophil counts, changes in concomitant CS doses/concomitant immunosuppressant use, MPZ retention rate, and incidence of adverse events. The clinical course was compared between Pre-MPZ and Post-MPZ. RESULTS: The 12-month remission rate after the initiation of MPZ was 75%. No change was observed in BVAS, eosinophil count, or concomitant CS dose over time in the Pre-MPZ group, whereas all these parameters were significantly decreased over time in the Post-MPZ group. The number of patients using concomitant immunosuppressant also decreased over time in the Post-MPZ group. VDI did not increase in either group. The MPZ retention rate was 100% and only three patients (18.8%) had infections. Changes in BVAS, eosinophil count, and cumulative concomitant CS dose were significantly lower in the Post-MPZ group than in the Pre-MPZ group. There was no significant difference in the changes in VDI between the groups. CONCLUSION: This study demonstrated that MPZ is effective and safe for EGPA. Furthermore, MPZ decreases disease activity, increases remission rate, and has a CS-sparing effect.