Safety and effectiveness of mepolizumab therapy in remission induction therapy for eosinophilic granulomatosis with polyangiitis: a retrospective study

OBJECTIVES: To investigate the safety and effectiveness of mepolizumab (MPZ), an anti-interleukin-5 antibody, as remission induction therapy for severe eosinophilic granulomatosis with polyangiitis (EGPA). METHODS: The clinical courses of patients with severe EGPA over 6 months were retrospectively investigated and compared between patients treated with high-dose corticosteroid (CS) plus MPZ therapy (MPZ group, n = 7) and those treated with high-dose CS plus intravenous cyclophosphamide (IVCY) pulse therapy (IVCY group, n = 13). The primary endpoints were the MPZ retention rate and the IVCY completion rate. The secondary endpoints were adverse events and changes in the Birmingham Vasculitis Activity Score (BVAS), Vascular Damage Index (VDI), eosinophil counts, and concomitant CS doses, and the extent and rates of these changes were compared between the MPZ and IVCY groups. RESULTS: Regarding the primary endpoints, the MPZ retention rate was 100%, and the IVCY completion rate was 61.5%. Regarding the secondary endpoints, adverse events were detected in 2/7 patients (28.6%) in the MPZ group and 7/13 patients (53.8%) in the IVCY group. BVAS and eosinophil counts significantly decreased in both groups at and after month 1, but there was no significant difference in the magnitude of changes between the two groups. VDI scores did not significantly increase in either group, and the degree of changes did not significantly differ between the two groups. Although concomitant CS doses significantly decreased at and after month 1 in both groups, the rates of decrease in CS doses at and after month 3 were significantly higher in the MPZ group. CONCLUSIONS: This study suggested that the use of MPZ as remission induction therapy for severe EGPA might be safe and effective for controlling disease activity and reducing CS doses. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13075-022-02845-3.