lass=""h4"">Background
Periphera
l b
lood eosinophi
lia and
lung mucosa
l eosinophi
l infi
ltration are ha
llmarks of bronchia
l asthma. IL-5 is a critica
l cytokine for eosinophi
l maturation, surviva
l, and mobi
lization. Attempts to target eosinophi
ls for the treatment of asthma by means of IL-5 neutra
lization have on
ly resu
lted in partia
l remova
l of airway eosinophi
ls, and this warrants the deve
lopment of more effective interventions to further exp
lore the ro
le of eosinophi
ls in the c
linica
l expression of asthma.
lass=""h4"">Objective
We sought to develop a novel humanized anti–IL-5 receptor α (IL-5Rα) mAb with enhanced effector function (MEDI-563) that potently depletes circulating and tissue-resident eosinophils and basophils for the treatment of asthma.
lass=""h4"">Methods
We used surface plasmon resonance to determine the binding affinity of MEDI-563 to FcγRIIIa. Primary human eosinophils and basophils were used to demonstrate antibody-dependent cell-mediated cytotoxicity. The binding epitope of MEDI-563 on IL-5Rα was determined by using site-directed mutagenesis. The consequences of MEDI-563 administration on peripheral blood and bone marrow eosinophil depletion was investigated in nonhuman primates.
lass=""h4"">Results
MEDI-563 binds to an epitope on IL-5Rα that is in close proximity to the IL-5 binding site, and it inhibits IL-5–mediated cell proliferation. MEDI-563 potently induces antibody-dependent cell-mediated cytotoxicity of both eosinophils (half-maximal effective concentration = 0.9 pmol/L) and basophils (half-maximal effective concentration = 0.5 pmol/L) in vitro. In nonhuman primates MEDI-563 depletes blood eosinophils and eosinophil precursors in the bone marrow.
lass=""h4"">Conclusions
MEDI-563 might provide a novel approach for the treatment of asthma through active antibody-dependent cell-mediated depletion of eosinophils and basophils rather than through passive removal of IL-5.