Mepolizumab in patients with eosinophilic granulomatosis with polyangiitis reduced glucocorticoid dose and improved residual symptoms compared to conventional immunosuppressants: a retrospective observational study.

Mepolizumab (MPZ) is an anti-interleukin-5 monoclonal antibody used to treat eosinophilic granulomatosis with polyangiitis (EGPA). This study aimed to compare the efficacy of MPZ and conventional treatment (CT) for EGPA after maintenance therapy initiation. In this retrospective, observational study, patients diagnosed with EGPA meeting these criteria were included: prednisolone ≤ 20 mg/day, Birmingham Vasculitis Activity Score (BVAS) < 10, and MPZ or new CT initiation ≥ 6 months after initial treatment were included (MPZ: n = 16; CT: n = 16). BVAS, relapse-free survival, absolute eosinophil count, cumulative glucocorticoids (GC) dose, and GC toxicity index (GTI) were evaluated for up to 12 months. Multivariable linear regression for BVAS and logistic regression for relapse at 12 months were performed, adjusting for age, gender, disease duration, and baseline eosinophil count. In the MPZ group, BVAS at 12 months significantly decreased, while BVAS tended to be lower in the MPZ than in the CT group at 12 months. Participants achieving BVAS = 0 significantly increased in the MPZ group at 12 months. Relapse rates tended to be lower in the MPZ group. Absolute eosinophil counts decreased in the MPZ compared with the CT group from 1 to 12 months. Cumulative GC dose and GTI significantly decreased in the MPZ group vs. CT group. In multivariable analyses, the use of MPZ was suggestive of lower BVAS and lower odds of relapse at 12 months compared with CT, although these differences were not statistically significant. MPZ could be a potential treatment option for reducing GC or improving residual symptoms in patients with EGPA.