Importantly, MX69-114b had minimal or no inhibitory effect on normal human hematopoiesis in vitro and was very well tolerated in vivo in animal models. Based on the strong inhibitory and apoptotic activity against MDM2-overexpressing ALL, along with minimal or no toxicity to normal cells/tissues, MX69-114b is a candidate for further development as a novel MDM2-targeted therapeutic drug for refractory ALL.