Since the end of the study observation period (2021), mepolizumab has become the only biologic currently approved for EGPA [24–26], and increasing evidence from both clinical and real-world studies has emerged in support of the use of biologics targeting IL-5 signalling (e.g. mepolizumab, benralizumab and reslizumab) to control disease and reduce OCS use [10–12, 17, 28, 36–44]. The gene discussed is IL5; the disease is eosinophilic granulomatosis with polyangiitis.