IL5 and eosinophilic granulomatosis with polyangiitis: Mepolizumab was the first registered (in 2004) anti–IL-5 biologic for the treatment of severe eosinophilic asthma (SEA), before validation in other conditions including CRSwNP, hypereosinophilic syndrome (HES), and eosinophilic granulomatosis with polyangiitis (EGPA).