Given the limited predictive power of cellular in vitro and ex vivo models as well as cell-line derived mouse model, future preclinical work will need to demonstrate efficacy in genetically heterogeneous models of FLT3-ITD + AML with realistic (sub-)clonal architectures such as FLT3-ITD + PDX cells in NSG mice. Here, FLT3 is linked to acute myeloid leukemia.