Other unresolved questions include (1) whether 300 mg/4 weeks instead of 100 mg/4 weeks is necessary for all patients with EGPA [94]; (2) whether mepolizumab can be combined with immunosuppressive agents, such as RTX [115]; (3) whether mepolizumab can be combined with other biological agents, such as anti-IgE antibody and anti-IL-4/IL-13 receptor antibody [116]; (4) whether mepolizumab suppresses organ damage over the long term; and (5) whether mepolizumab ultimately improves the prognosis for EGPA. Here, IL4 is linked to eosinophilic granulomatosis with polyangiitis.