Suppression of leukemia expressing wild-type or ITD-mutant FLT3 receptor by a fully human anti-FLT3 neutralizing antibody.
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.
Li
Yiwen
Y
Department of Immunology, ImClone Systems, 180 Varick St, New York, NY 10014, USA. yiwen.li@imclone.com
Li
Hongli
H
Wang
Mei-Nai
MN
Lu
Dan
D
Bassi
Rajiv
R
Wu
Yan
Y
Zhang
Haifan
H
Balderes
Paul
P
Ludwig
Dale L
DL
Pytowski
Bronislaw
B
Kussie
Paul
P
Piloto
Obdulio
O
Small
Donald
D
Bohlen
Peter
P
Witte
Larry
L
Zhu
Zhenping
Z
Hicklin
Daniel J
DJ
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
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