Patient treatment and disease course and ex vivo studies of patient-derived leukemia. (A) Clinical treatment course (top axis) and disease burden, as represented by log(proportion of FISH⁺ cells) on the left y-axis and log(proportion of digital droplet polymerase chain reaction [ddPCR]⁺ cells) on the right y-axis, throughout therapy (time on x-axis). Our patient started therapy with sorafenib, followed by concurrent treatment with 3 cycles of intensive chemotherapy with significant disease reduction but persistent MRD, which was eliminated after treatment with single-agent gilteritinib. (B) Results from ex vivo drug screen showed the lower 50% inhibitory concentration (IC₅₀) of type I compared with type II FLT3 inhibitors in this patient’s leukemia samples. C1, C2, C3, cycle 1, cycle 2, cycle 3; Inh, inhibitor.