Real-world outcomes and corticosteroid sparing with mepolizumab for EGPA or HES

Eosinophilic granulomatosis with polyangiitis (EGPA) and hypereosinophilic syndrome (HES) are rare systemic inflammatory diseases with overlapping features. Mepolizumab, a humanized mAb targeting IL-5, has been approved for treatment of both conditions. However, real-world data on its clinical benefit in private practice settings remain limited.

We sought to evaluate oral corticosteroid (OCS) use, clinical outcomes, and end-organ manifestations post-mepolizumab initiation in private practice settings using electronic medical records.

This retrospective pre-post cohort study used data from the US-based Allergy Partners network electronic medical records (January 1, 2007, to August 17, 2023) to select patients with EGPA or HES who initiated mepolizumab (index date). Participants were 18 years and older (EGPA) or 12 years and older (HES) with 3 or more months of clinical activity pre- and postindex. Outcomes included OCS use and dose, clinical outcomes (response and remission), and end-organ damage manifestations.

Overall, 44 patients with EGPA and 16 patients with HES had significant reductions in OCS use and dose (P = .014 for trend over each 6-month period), with improvements in end-organ manifestations over a treatment period up to 2 years. Among patients with EGPA, clinical response, disease control, and remission rates increased significantly. In addition, 86.4% of patients with EGPA experienced an improvement in at least 1 of the outcome measures of OCS use, end-organ manifestations, or blood eosinophil count. Among patients with HES, end-organ manifestations were more common preindex (87.5%) than postindex (56.3%).

These findings highlight the long-term OCS-sparing effects of mepolizumab and suggest additional clinical benefits for patients with EGPA and HES in a private practice setting.