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: Yiwen Li, Hongli Li, Mei-Nai Wang, Dan Lu, Rajiv Bassi, Yan Wu, Haifan Zhang, Paul Balderes, Dale L Ludwig, Bronislaw Pytowski, Paul Kussie, Obdulio Piloto, Donald Small, Peter Bohlen, Larry Witte, Zhenping Zhu, Daniel J Hicklin
• Journal: Blood (Blood) Vol. 104 Issue 4 Pg. 1137-44 (Aug 15 2004) ISSN: 0006-4971 [Print] United States
• PMID: 15105287 (Publication Type: Journal Article)

Chemical References

• Antibodies, Neoplasm
• Immunoglobulin Fab Fragments
• Membrane Proteins
• Proto-Oncogene Proteins
• flt3 ligand protein
• FLT3 protein, human
• Flt3 protein, mouse
• Receptor Protein-Tyrosine Kinases
• fms-Like Tyrosine Kinase 3

Topics

• Animals
• Antibodies, Neoplasm (pharmacology, therapeutic use)
• Binding, Competitive
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Female
• Humans
• Immunoglobulin Fab Fragments (pharmacology, therapeutic use)
• Leukemia (drug therapy)
• Male
• Membrane Proteins
• Mice
• Mice, Inbred NOD
• Mice, Nude
• Mutation
• Neoplasms, Experimental (drug therapy)
• Proto-Oncogene Proteins (antagonists & inhibitors, genetics, immunology)
• Receptor Protein-Tyrosine Kinases (antagonists & inhibitors, genetics, immunology)
• Signal Transduction (drug effects)
• Survival Rate
• Tandem Repeat Sequences
• fms-Like Tyrosine Kinase 3