This is a humanized IgG1 monoclonal antibody using the same sequences as the therapeutic antibody benralizumab. It specifically binds to the alpha chain of the interleukin 5 receptor (IL5R) expressed on eosinophils, basophils and certain mast cells. Unlike IL5 low-affinity binding, benralizumab exhibits high affinity binding to the domain I of the α-chain of IL5R, thus blocking its signaling and the proliferation of IL5-dependent cell lines. It hinders IL5 binding as well as hetero-oligomerization between the alpha and beta subunits of IL5R, thereby effectively obstructing signal transduction. Moreover, benralizumab is an afucosylated IgG in the CH2 region which confers enhanced affinity for FcγRIIIα present on natural killer cells, macrophages and neutrophils. This interaction triggers amplified apoptosis response in eosinophils through antibody-dependent cell-mediated cytotoxicity (ADCC). Benralizumab is indicated for maintenance treatment in patients with severe asthma and an eosinophilic phenotype.