Management of Non-Severe Eosinophilic Granulomatosis with Polyangiitis without Immunosuppressants Using Mepolizumab: Clinical Implications

Background: To investigate whether long-term remission can be maintained with corticosteroids plus mepolizumab, without the addition of conventional immunosuppressants, following initial remission induction in patients with eosinophilic granulomatosis with polyangiitis (EGPA). Methods: We retrospectively recruited 72 EGPA patients treated at the National Hospital Organization Yokohama Medical Center (April 2022 to March 2025). Patients were categorized into an IS-combination group (immunosuppressant + corticosteroid + mepolizumab) and a non-IS group (corticosteroid + mepolizumab) on the basis of immunosuppressant use at mepolizumab initiation. Peripheral blood eosinophil counts, Birmingham Vasculitis Activity Score (BVAS), systemic corticosteroid dosage, remission induction rates, and duration of relapse-free period following the introduction of mepolizumab were compared. Results: Compared with the IS-combination group, the non-IS group was older at EGPA onset ( P  = 0.02), had a shorter interval from diagnosis to study entry ( P  = 0.004), had less myocardial involvement ( P  = 0.01), and had lower BVAS before treatment with mepolizumab ( P < 0.001). Immunosuppressant Use during initial treatment was 100% in the IS-combination group and 75% in the non-IS group ( P  = 0.001). The non-IS group achieved remission faster ( P  = 0.03), had a higher cumulative remission rate ( P  = 0.01), and had a higher relapse-free rate ( P  = 0.02). Conclusion: In non-severe EGPA, treatment with corticosteroids plus mepolizumab without concomitant immunosuppression should achieve earlier remission and maintain long-term disease control.