CPX delays tumor growth in mouse models of leukemia. Sublethally irradiated NOD/SCID mice were injected intraperitoneally with (A) MDAY-D2 murine leukemia cells (n = 30; 15 per group), or subcutaneously with (B) K562 cells (n = 30; 15 per group) or (C) OCI-AML2 human leukemia cells (n = 24; 12 per group). After implantation, mice were treated with CPX (25 mg/kg) or vehicle control by oral gavage daily. After 8 (MDAY-D2), 30 (K562), and 16 (OCI-AML2) days, mice were killed and tumors were excised, measured, and weighed. The mean weight and volume ± SD are shown. Means were compared by the Student t test. ***P < .001, **P < .01 (Student t test). One of at least 2 representative experiments is shown. (D) Primary cells from one patient with AML and normal cytogenetics were injected intrafemorally into the right femur of female sublethally irradiated nude/NOD/SCID mice. Four weeks after injection, mice were treated by oral gavage once daily with vehicle (n = 3) or CPX (20 mg/kg; n = 3) for 4 weeks. After treatment, human leukemia cell engraftment in the injected right femur was measured by flow cytometry for human CD45. Data represent the mean ± SD of engrafted human cells from all mice. *P < .05 (Student t test).