In studies of both single-agent gilteritinib (62, 63) and single-agent crenolanib (64) resistance in patients with R/R FLT3-mutated AML, only 12% of patients receiving gilteritinib, and 11% of patients receiving crenolanib developed F691L mutations at the time of resistance. This evidence concerns the gene FLT3 and acute myeloid leukemia.