Effectiveness, Tolerability, and Safety of Mepolizumab Injection Spacing in Patients With Eosinophilic Granulomatosis With Polyangiitis: A Retrospective Cohort Study

BACKGROUND/OBJECTIVE: This retrospective cohort study aimed to evaluate the effectiveness, tolerability, and safety of mepolizumab injection spacing for patients with eosinophilic granulomatosis with polyangiitis (EGPA). METHODS: We retrospectively evaluated the effectiveness, drug continuation rate, and safety of mepolizumab injection spacing in patients with EGPA between May 2018 and July 2024. We classified the study sample into the standard group (standard regimen) and the spacing group (which received injection spacing). The periods were defined as the standard interval period (the entire observation period for the standard group and the period before spacing in the spacing group) and the spacing interval period (the period after spacing). The effectiveness endpoint was the time to relapse, assessed using the Cox proportional hazards model with time-dependent covariates, and the safety endpoint was the incidence of adverse events. RESULTS: The analysis included 43 patients who received mepolizumab; among them, 10 had their mepolizumab injections spaced at 5-week (n=7) or 6-week (n=3) intervals. Eight patients experienced a relapse (7 and 1 during the standard and spacing interval periods, respectively), and 6 discontinued mepolizumab (4 and 2, respectively). Thus, the time to relapse and time to drug discontinuation showed no statistically significant difference between the standard and spacing interval periods. Rates of adverse events were similar in the 2 periods. CONCLUSIONS: Our findings suggest that mepolizumab injection spacing is a well-tolerated treatment strategy for stable EGPA. It may be a viable and safe treatment option for the long-term use of biological agents for EGPA.