Clinical Benefit of Mepolizumab in Eosinophilic Granulomatosis With Polyangiitis for Patients With and Without a Vasculitic Phenotype

OBJECTIVE: To evaluate mepolizumab's efficacy in eosinophilic granulomatosis with polyangiitis (EGPA) with and without a vasculitic phenotype. METHODS: The MIRRA study (NCT02020889/GSK ID: 115921) included adults with relapsing/refractory EGPA and 4 or more weeks of stable oral glucocorticoids (OG). Patients received mepolizumab (300 mg subcutaneously every 4 weeks) or placebo, plus standard of care for 52 weeks. This post hoc analysis assessed EGPA vasculitic phenotype using antineutrophil cytoplasmic antibody (ANCA) history, baseline Birmingham Vasculitis Activity Score (BVAS), and Vasculitis Damage Index (VDI) score. Coprimary endpoints included accrued remission over 52 weeks and proportion in remission at Week 36 and Week 48. Remission was defined as a BVAS equal to 0 and an OG dose of 4 or more mg/day of a prednisone equivalent. Types of relapses (vasculitis, asthma, and sino‐nasal) and EGPA vasculitic characteristics (by study remission status) were also assessed. RESULTS: A total of 136 patients were included (n = 68, mepolizumab and placebo). Irrespective of history of ANCA positivity status, baseline BVAS, or baseline VDI, the accrued remission duration and the proportion of patients in remission at Weeks 36 and 48 were greater with mepolizumab compared with placebo. With mepolizumab, remission at both Week 36 and Week 48 was achieved by 54% of patients with and 27% of patients without a history of ANCA positivity compared with 0% and 4%, respectively (placebo); 45% of patients with a BVAS of 0 and 22% of patients with BVAS of greater than 0 compared with 5% and 2%, respectively (placebo); and 29% of patients with a VDI score of less than 5 and 37% of patients with a VDI score of 5 or more compared with 6% and 0%, respectively (placebo). Mepolizumab reduced all types of relapses as compared with placebo. Baseline vasculitic characteristics (neuropathy, glomerulonephritis, alveolar hemorrhage, palpable purpura, and ANCA positivity) were generally similar among patients with and without remission. CONCLUSION: Mepolizumab is associated with clinical benefits for patients with and without a vasculitic EGPA phenotype.