D1.352 - Assessment of the Efficacy of Mepolizumab in Modulating Disease Activity in Eosinophilic Granulomatosis with Polyangiitis: A 12-Month Analysis Evaluating the Birmingham Vasculitis Activity Score

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare condition that affects multiple systems in the body. It is defined as both a hypereosinophilic illness and an ANCA-associated vasculitis. The condition is characterised by vessel inflammation and increased levels of eosinophils, which are the key factors leading to organ damage. Mepolizumab, an anti-IL-5 monoclonal antibody, has been included both in the Evidence-Based Guideline for the diagnosis and management of eosinophilic granulomatosis with polyangiitis and in the 2022 update of the European Alliance of Associations for Rheumatology (EULAR) recommendations as a treatment to reduce disease activity and improve patient outcomes.  This study evaluates the efficacy of mepolizumab in altering the Birmingham Vasculitis Activity Score (BVAS, version 3) over a 12-month period.

The 2022 American College of Rheumatology/EULAR Classification Criteria for EGPA were applied to confirm the diagnosis. BVAS scores were recorded at baseline (T0) and at follow-up intervals of 3 months (T3), 6 months (T6), and 12 months (T12) following the initiation of mepolizumab therapy at a dose of 300 mg administered subcutaneously q4w.

The Shapiro-Wilk test was used to assess the normality of the age distribution within the patient cohort. Changes in BVAS over time were analyzed using Friedman’s test. Post-hoc pairwise comparisons were performed using the Wilcoxon signed-rank test to identify specific time points with significant differences in BVAS scores. To control for multiple comparisons, Bonferroni correction was applied to adjust the p-values. Statistical significance was defined as  p < 0.05 after adjustment.

Thirteen patients (mean age 64.83 ± 9.19 years, female-to-male ratio 1.6:1) were included in the study. The Friedman test indicated a statistically significant difference in BVAS scores over time (chi^2 = 34.31 ,  p < 0.001 ).

Post-hoc pairwise comparisons, conducted using the Wilcoxon signed-rank test with Bonferroni correction, revealed significant reductions in BVAS between T0 and T3 ( p = 0.001 , Bonferroni-corrected  p = 0.0015 ), T0 and T6 ( p = 0.001 , Bonferroni-corrected  p = 0.0015 ), and T0 and T12 ( p = 0.001 , Bonferroni-corrected  p = 0.0015 ). No statistically significant difference was observed between T3 and T6 ( p = 0.039 , Bonferroni-corrected  p = 0.239 ), while a significant reduction was noted between T3 and T12 ( p = 0.002 , Bonferroni-corrected  p = 0.013 ).

Mepolizumab shows significant efficacy in reducing BVAS scores in EGPA patients over a 12-month treatment period. The substantial reduction in BVAS observed from baseline (T0) to later time points highlights the therapy’s robust impact on disease activity. Early improvements at 3 months were maintained through 6 and 12 months, indicating a stable and sustained benefit over time. These findings support the role of mepolizumab as a key therapeutic option for EGPA, providing consistent disease control over time. Nevertheless, further studies involving larger cohorts are essential to confirm these results, enhance the understanding of the treatment’s long-term effects, and optimize therapeutic strategies for broader patient populations.