For instance, AC220 (Quizartinib), a second-generation class III tyrosine kinase inhibitor (TKI), which has been used to treat FLT3-ITD+ AML in clinical trials, is a more potent and specific FLT3-ITD inhibitor than other TKIs [22,24]; however, prolonged exposure to AC220 could generate FLT3-ITD+ cells that are resistant to AC220 [25]. This evidence concerns the gene FLT3 and acute myeloid leukemia.