title: Suppression of leukemia expressing wild-type or ITD-mutant FLT3 receptor by a fully human anti-FLT3 neutralizing antibody.
abstract: FMS-like tyrosine kinase 3 (FLT3), a class III receptor tyrosine kinase, is expressed at high levels in the blasts of approximately 90% of patients with acute myelogenous leukemia (AML). Internal tandem duplications (ITDs) in the juxtamembrane domain and point mutations in the kinase domain of FLT3 are found in approximately 37% of AML patients and are associated with a poor prognosis. We report here the development and characterization of a fully human anti-FLT3 neutralizing antibody (IMC-EB10) isolated from a human Fab phage display library. IMCEB10 (immunoglobulin G1 [IgG1], kappa) binds with high affinity (KD=158 pM) to soluble FLT3 in enzyme-linked immunosorbent assay (ELISA) and to FLT3 receptor expressed on the surfaces of human leukemia cell lines. IMC-EB10 blocks the binding of FLT3 ligand (FL) to soluble FLT3 in ELISA and competes with FL for binding to cell-surface FLT3 receptor. IMC-EB10 treatment inhibits FL-induced phosphorylation of FLT3 in EOL-1 and EM3 leukemia cells and FL-independent constitutive activation of ITD-mutant FLT3 in BaF3-ITD and MV4;11 cells. Activation of the downstream signaling proteins mitogen-activated protein kinase (MAPK) and AKT is also inhibited in these cell lines by antibody treatment. The antibody inhibits FL-stimulated proliferation of EOL-1 cells and ligand-independent proliferation of BaF3-ITD cells. In both EOL-1 xenograft and BaF3-ITD leukemia models, treatment with IMC-EB10 significantly prolongs the survival of leukemia-bearing mice. No overt toxicity is observed with IMC-EB10 treatment. Taken together, these data demonstrate that IMC-EB10 is a specific and potent inhibitor of wild-type and ITD-mutant FLT3 and that it deserves further study for targeted therapy of human AML.
authors.affiliation: Department of Immunology, ImClone Systems, 180 Varick St, New York, NY 10014, USA. yiwen.li@imclone.com
authors.forename: Yiwen
authors.initials: Y
authors.lastname: Li
authors.forename: Hongli
authors.initials: H
authors.lastname: Li
authors.forename: Mei-Nai
authors.initials: MN
authors.lastname: Wang
authors.forename: Dan
authors.initials: D
authors.lastname: Lu
authors.forename: Rajiv
authors.initials: R
authors.lastname: Bassi
authors.forename: Yan
authors.initials: Y
authors.lastname: Wu
authors.forename: Haifan
authors.initials: H
authors.lastname: Zhang
authors.forename: Paul
authors.initials: P
authors.lastname: Balderes
authors.forename: Dale L
authors.initials: DL
authors.lastname: Ludwig
authors.forename: Bronislaw
authors.initials: B
authors.lastname: Pytowski
authors.forename: Paul
authors.initials: P
authors.lastname: Kussie
authors.forename: Obdulio
authors.initials: O
authors.lastname: Piloto
authors.forename: Donald
authors.initials: D
authors.lastname: Small
authors.forename: Peter
authors.initials: P
authors.lastname: Bohlen
authors.forename: Larry
authors.initials: L
authors.lastname: Witte
authors.forename: Zhenping
authors.initials: Z
authors.lastname: Zhu
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Hicklin
mesh_terms: D000818:Animals; D000912:Antibodies, Neoplasm / Q000494:pharmacology* / Q000627:therapeutic use; D001667:Binding, Competitive; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology / Q000627:therapeutic use; D007938:Leukemia / Q000188:drug therapy*; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D016688:Mice, Inbred NOD; D008819:Mice, Nude; D009154:Mutation; D009374:Neoplasms, Experimental / Q000188:drug therapy; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D015398:Signal Transduction / Q000187:drug effects; D015996:Survival Rate; D020080:Tandem Repeat Sequences; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D000912:Antibodies, Neoplasm; D007140:Immunoglobulin Fab Fragments; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; C084881:flt3 ligand protein; C497970:FLT3 protein, human; C497971:Flt3 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3