Gilteritinib combined with ruxolitinib has antileukemic activity in vivo. (A) Workflow of PDX experiments. Primary IgH-CRLF2 ALL cells (BALL091) were transferred to irradiated NSG mice, and drug treatment was initiated 30 days later. DMSO, gilteritinib (Gilt) (30 mg/kg), ruxolitinib (Ruxo) (60 mg/kg), or gilteritinib/ruxolitinib combination were administered intraperitoneally daily for 14 days. hCD19+ cells in PB were monitored over time by FACS, and leukemia burden in the spleen was assessed the day after the last drug injection. (B) Proportions of hCD19+ ALL cells in PB were examined by FACS over a 2-week period. Data are represented as means ± SD. Spleen weight (C), ALL cell numbers in spleen (D) and proportions of ALL cells in BM (E) were assessed the day after the last drug injection. Data are represented as individual values with mean ± SD bars. P values were calculated using one-way ANOVA with Tukey’s posttest for multiple comparisons. *P < .05, **P < .01, ***P < .001, ****P < .0001.