FLT3 and acute myeloid leukemia: Therefore, to compare the inhibitory profiles of each compound for Fes and Flt3 directly, we performed in vitro kinase assays using recombinant purified full-length Fes and three Flt3 kinase domains (wild-type plus the AML-associated mutants, Flt3-ITD and Flt3-D835Y).