Immune deficiencies, infection, and systemic immune disorders
MEDI-563, a humanized anti–IL-5 receptor α mAb with enhanced antibody-dependent cell-mediated cytotoxicity function

https://doi.org/10.1016/j.jaci.2010.04.004Get rights and content

Background

Peripheral blood eosinophilia and lung mucosal eosinophil infiltration are hallmarks of bronchial asthma. IL-5 is a critical cytokine for eosinophil maturation, survival, and mobilization. Attempts to target eosinophils for the treatment of asthma by means of IL-5 neutralization have only resulted in partial removal of airway eosinophils, and this warrants the development of more effective interventions to further explore the role of eosinophils in the clinical expression of asthma.

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.

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.

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.

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.

Section snippets

Epitope mapping of MEDI-563

Extracellular IL-5Rα knockout mutants were engineered by substituting regions of full-length human IL-5Rα with corresponding segments of murine IL-5Rα and vice versa for knock-in mutants. Mutants were transiently expressed in HEK293F cells. HEK293F transfectants were incubated with 1 μg/mL MEDI-563 for 1 hour on ice in phosphate-buffered saline (PBS). After washing, cells were incubated with goat anti-human IgG–fluorescein isothiocyanate (Jackson ImmunoResearch Laboratories, West Grove, Pa) and

MEDI-563 interaction with IL-5Rα

MEDI-563 bound to recombinant human and cynomolgus monkey IL-5Rα extracellular domains with a dissociation constant of 11 and 42 pmol/L, respectively, whereas the F(ab) fragment bound with an approximately 100-fold lower affinity, as assessed by means of surface plasmon resonance (Table I). Consistent with the specific expression of IL-5Rα on human eosinophils and basophils among a large variety of hematopoietic cell types (Fig 1, A), MEDI-563 exclusively stained peripheral blood eosinophils

Discussion

IL-5 blockade in subjects with asthma has failed to improve parameters of lung function in response to allergen challenge despite rapid and near-complete depletion of eosinophils from peripheral blood and sputum.14, 15, 16, 17 However, a causal link between reduced eosinophil numbers and a reduction in exacerbation frequency and prednisone requirement has recently been demonstrated in subjects with severe refractory eosinophilic asthma.16, 17 Interestingly, results from 2 independent clinical

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    Supported by MedImmune, LLC, Gaithersburg, Md, and Biowa, Inc, Princeton, NJ.

    Disclosure of potential conflict of interest: R. Kolbeck, A. Kozhich, L. Peng, M. M. Damschroder, R. Woods, W. W. Dall'Acqua, G. L. Stephens, A. A. Humbles, D. Gossage, H. Wu, P. A. Kiener, N. A. Molfino, and A. J. Coyle are employed by MedImmune, LLC. J. L. Reed's husband is employed by MedImmune, LLC. C. R. Mackay is the Founder and Director of G2 Therapies. M. Koike and G.L. Spitalny are employed by Biowa, Inc. The rest of the authors have declared that they have no conflict of interest.

    J. L. Reed is currently affiliated with the US Food and Drug Administration, Center for Biologics Evaluation and Research, Rockville, Md.

    ∗∗

    P. A. Kiener is currently employed by Zyngenia, Inc, Gaithersburg, Md.

    ∗∗∗

    C. R. Mackay is currently affiliated with the Immunology and Stem Cell Labs, Faculty of Medicine, Nursing and Health Sciences, School of Biomedical Sciences, Monash University, Clayton, Victoria, Australia.

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