Definition

A humanized immunoglobulin G1 (IgG1) monoclonal antibody directed against interleukin-5 (IL-5) with anti-asthmatic and potential immunosuppressive activity. Upon administration, mepolizumab selectively binds to IL-5, preventing it from associating with interleukin-5 receptor subunit alpha (IL5RA) on the surface of eosinophils and their progenitors. IL-5 plays a role in the regulation of eosinophil development from hematopoietic progenitors as well as eosinophil maturation, differentiation, mobilization, activation, and survival. IL-5 also play a role in the pathogenesis of some phenotypes of hypereosinophilic syndrome (HES).