For efficacy assessment in vivo, we established a patient-derived xenograft (PDX) from an AML patient with FLT3-ITD, DNMT3A, IDH1 and NPM1 mutations in NSG mice. Upon engraftment, mice were randomized to receive vehicle or single agent ABBV-744 at a well-below MTD dose of 9.4 mg/kg for 21 days. The median survival time of mice treated with ABBV-744 (Median survival: 76 days) was significantly higher compared to untreated mice (Median survival: 67.5 days, p=0.007, Fig 1B).