FLT3/ITD-IN-1 (Compound 1) is a potent FLT3 internal tandem duplications ( FLT3-ITD ) inhibitor with IC 50 values of 38.2 nM and 144.1 nM against FLT3 and FLT3-ITD, respectively. FLT3/ITD-IN-1 displays excellent antiproliferative activities against acute myeloid leukemia cell lines.