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Blood, 15 April 2007, Vol. 109, No. 8, pp. 3400-3408. Prepublished online as a Blood First Edition Paper on January 5, 2007; DOI 10.1182/blood-2006-06-029579.
NEOPLASIA ABT-869, a multitargeted receptor tyrosine kinase inhibitor: inhibition of FLT3 phosphorylation and signaling in acute myeloid leukemia1 Division of Hematology/Oncology, Department of Pediatrics, Gwynne Hazen Cherry Memorial Laboratories, and Mattel Children's Hospital Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at the University of California at Los Angeles (UCLA); 2 Cancer Research, R47J-AP9, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL; 3 Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA; 4 Molecular Biology Institute, UCLA; 5 Division of Biology, California Institute of Technology, Pasadena, CA; 6 Division of Hematology-Oncology, Department of Medicine, University of California at San Francisco In 15% to 30% of patients with acute myeloid leukemia (AML), aberrant proliferation is a consequence of a juxtamembrane mutation in the FLT3 gene (FMS-like tyrosine kinase 3internal tandem duplication [FLT3-ITD]), causing constitutive kinase activity. ABT-869 (a multitargeted receptor tyrosine kinase inhibitor) inhibited the phosphorylation of FLT3, STAT5, and ERK, as well as Pim-1 expression in MV-4-11 and MOLM-13 cells (IC50 approximately 1-10 nM) harboring the FLT3-ITD. ABT-869 inhibited the proliferation of these cells (IC50 = 4 and 6 nM, respectively) through the induction of apoptosis (increased sub-G0/G1 phase, caspase activation, and PARP cleavage), whereas cells harboring wild-type (wt)FLT3 were less sensitive. In normal human blood spiked with AML cells, ABT-869 inhibited phosphorylation of FLT3 (IC50 approximately 100 nM), STAT5, and ERK, and decreased Pim-1 expression. In methylcellulose-based colony-forming assays, ABT-869 had no significant effect up to 1000 nM on normal hematopoietic progenitor cells, whereas in AML patient samples harboring both FLT3-ITD and wt-FLT3, ABT-869 inhibited colony formation (IC50 = 100 and 1000 nM, respectively). ABT-869 dose-dependently inhibited MV-4-11 and MOLM-13 flank tumor growth, prevented tumor formation, regressed established MV-4-11 xenografts, and increased survival by 20 weeks in an MV-4-11 engraftment model. In tumors, ABT-869 inhibited FLT3 phosphorylation, induced apoptosis (transferase-mediated dUTP nick-end labeling [TUNEL]) and decreased proliferation (Ki67). ABT-869 is under clinical development for AML.
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