PD166326 prolongs survival in a murine model of imatinib mesylate–resistant CML. Mice with the CML-like disease induced by the imatinib mesylate–resistant Bcr/Abl mutants H396P (A), M351T (B), or T315I (C) were randomly assigned to treatment with PD166326 (25 mg/kg orally twice a day; ▴), imatinib mesylate (100 mg/kg orally twice a day; •), or placebo (▪) and analyzed for survival according to the method of Kaplan and Meier. The number of animals (N) in each cohort is shown at right. Imatinib mesylate did not prolong the survival of any of the groups. PD166326 prolonged the survival of P210/H396P (P < .001) and P210/M351T (P = .03) animals, but not T315I/P210.