In EGPA, Wechsler et al. reported that mepolizumab, an anti-interleukin-5 monoclonal antibody, effectively reduced glucocorticoid dose, achieved remission, and maintained remission, and that no significant induced deadly adverse events were observed in the group with mepolizumab compared with that in the placebo group [4]. This evidence concerns the gene IL5 and eosinophilic granulomatosis with polyangiitis.