Suppression of leukemia expressing wild-type or ITD-mutant FLT3 receptor by a fully human anti-FLT3 neutralizing antibody

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

Research output: Contribution to journalArticlepeer-review

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. IMC-E-B10 (immunoglobulin G1[IgG1],κ) 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 down-stream 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.

Original languageEnglish (US)
Pages (from-to)1137-1144
Number of pages8
JournalBlood
Volume104
Issue number4
DOIs
StatePublished - Aug 15 2004
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

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