Predictive factors of favorable outcome for mepolizumab and corticosteroid treatment to for eosinophilic granulomatosis with polyangiitis(EGPA)

<bold>Background:</bold> The remission induction therapy for EGPA uses corticosteroid(CS) and immunosuppressive therapy. Mepolizumab(MEP), an anti-interleukin-5 monoclonal antibody is firstly introduced for the treatment of eosinophilic severe asthma, also known to be effective for treatment of EGPA. However, predictive factors of favorable outcome from CS and MEP treatment for the diseaseEGPA are unclear. Therefore, we report EGPA patients treated with CS and MEP to identify predictive factors of favorable outcome based on clinical findings. <bold>Methods:</bold> We retrospectively collected data of patients with EGPA between 2008 and 2022. ANCA values, eosinophils count, rhinosinusitis with nasal polyps, C-reactive protein(CRP), IgG at the point of diagnosis were evaluated. <bold>Results:</bold> Five patients (Age 45.1 (28-57) (mean (range)), male/female 2/3) achieved remission with corticosteroids alone (CS), 7 patients (Age 57 (55-66), male/female 4/3) achieved remission with MEP after corticosteroids CS (MEP), and 5 patients (Age 63 (55-71), male/female 3/2) failed to induce remission with CS and MEP(No Remission; NR). The presence of chronic rhinosinusitis with nasal polyps significantly differed between the groups (2/7/2 for CS/MEP/NR, p=0.0157). Initial eosinophil counts were significantly different between the groups (8067/15807/4879, p=0.0402). The rates of ANCA-positive patients, initial CRP values, and IgG values showed no significant differences. No apparent adverse events of MEP were found in any cases. <bold>Conclusions:</bold> Patients with EGPA with higher eosinophils and with chronic rhinosinusitis with nasal polyps might have more favorable outcome of MEP treatments.