Asciminib is undergoing clinical development testing in patients with CML and Philadelphia chromosome-positive acute lymphoblastic leukaemia. Single doses of 7.5, 15 and 30 mg/kg ABL001, administered to mice bearing KCL- 22 xenografts, inhibits pSTAT5 (Tyr694), which return to baseline at 10, 12 and 16-20h after administration of the dose, respectively. In mice implanted with KCL-22 tumors, the minimum dose of asciminib required for complete regression is 7.5 mg/kg twice a day (BID) or 30 mg/kg once a day (QD), and is tolerated at doses up to 250 mg/kg BID. Similarly, in xenografts derived from patients, treatment with 7.5 and 30 mg/kg asciminib leads to regressions that are maintained during dosing.