FLT3 is expressed mainly in hematopoietic progenitors and dendritic cells, and its constitutive activation induces signaling cascades, which suppress normal regulation of apoptosis, differentiation, and proliferation in leukemic cells. FLT3 inhibitors are tyrosine kinase inhibitors that compete for the ATP binding site in the active domain of the kinase, inhibiting the ability of the protein to be phosphorylated, leading to a reduction in levels of that protein.