In vivo efficacy of AT9283 in primary samples. Nonlethally irradiated NOD/SCID mice were intravenously inoculated with cells taken from patients with CML harboring BCR-ABL E255K (A) or BCR-ABL T315I (B). Either 6.25 mg/kg AT9283 (gray) or vehicle (black) controlled was administered twice daily (A) on the indicated schedules (- - -). We administered 15 mg/kg AT9283 (gray), 10 mg/kg At9283 (black dot), or vehicle (black) controlled once daily (B) on the indicated schedules (- - -). Kaplan-Meier survival curves show that treatment with 6.25 mg/kg AT9283 twice daily resulted in a significant survival advantage (P = .008) over vehicle-treated animals of 17 days in the E255K model. Similarly, in the T315I model 10 mg/kg per day or 15 mg/kg per day AT9283 resulted in a marked survival advantage (P = .002).