title: Highly effective recombinant format of a humanized IgG-like bispecific antibody for cancer immunotherapy with retargeting of lymphocytes to tumor cells.
abstract: We previously reported the marked in vitro and in vivo antitumor activity of hEx3, a humanized diabody (small recombinant bispecific antibody) with epidermal growth factor receptor (EGFR) and CD3 retargeting. Here, we fabricated a tetravalent IgG-like bispecific antibody with two kinds of single-chain Fv (scFv), i.e. humanized anti-EGFR scFv and anti-CD3 scFv, that contains the same four variable domains as hEx3, on the platform of human IgG1 (hEx3-scFv-Fc). hEx3-scFv-Fc prepared from mammalian cells showed specific binding to both EGFR and CD3 target antigens. At one-thousandth (0.1-100 fmol/ml) of the dose of normal hEx3, hEx3-scFv-Fc showed intense cytotoxicity to an EGFR-positive cell line in a growth-inhibition assay using lymphokine-activated killer cells with the T-cell phenotype (T-LAK cells). The enhanced antitumor effect was more clearly observed when peripheral blood mononuclear cells (PBMCs) were used as effector cells, indicating the utility of IgG-like fabrication. These results suggested that the intense antitumor activity is attributable to the multivalency and the presence of the fused human Fc, a hypothesis that was supported by the results of flow cytometry, PBMC proliferation assay, and protein kinase inhibition assay. Furthermore, the growth inhibition effects of hEx3-scFv-Fc were considerably superior to those of the approved therapeutic antibody, cetuximab, which recognizes the same EGFR antigen even when using PBMCs as effector cells. The high potency of hEx3-scFv-Fc may translate into improved antitumor therapy and lower costs of production because of the smaller doses needed.
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan.
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Asano
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kawaguchi
authors.forename: Hidesuke
authors.initials: H
authors.lastname: Fukazawa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakanishi
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Umetsu
authors.forename: Hiroki
authors.initials: H
authors.lastname: Hayashi
authors.forename: Yu
authors.initials: Y
authors.lastname: Katayose
authors.forename: Michiaki
authors.initials: M
authors.lastname: Unno
authors.forename: Toshio
authors.initials: T
authors.lastname: Kudo
authors.forename: Izumi
authors.initials: I
authors.lastname: Kumagai
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000737:chemistry*; D017252:CD3 Complex / Q000737:chemistry; D016466:CHO Cells; D049109:Cell Proliferation; D006224:Cricetinae; D003412:Cricetulus; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry*; D007167:Immunotherapy / Q000379:methods*; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism*; D008954:Models, Biological; D009369:Neoplasms / Q000276:immunology / Q000473:pathology*
chemical_list: D018033:Antibodies, Bispecific; D017252:CD3 Complex; D007074:Immunoglobulin G; D066246:ErbB Receptors