More generally, these studies with TF-1 cells suggest that Flt3-ITD is the primary inhibitor target for A-419259 in Flt3-ITD+ AML, although the presence of Hck and Fgr may modulate Flt3-ITD inhibitor sensitivity especially in the presence of Flt3-ITD kinase domain mutations. This evidence concerns the gene HCK and acute myeloid leukemia.