Patients with CML in lymphoid blast crisis (LBC-CML) or advanced Ph+ ALL have an unsatisfactory and only brief response to imatinib mesylate (IM). Moreover, treatment options in pts who failed IM are extremely limited. Dasatinib (BMS-354825) is a novel, oral kinase inhibitor that targets BCR-ABL and SRC kinases, and has shown promising clinical activity in a Phase I dose escalating study in patients with BCR-ABL-positive leukemias. Between January 2005 and June 2005, 77 pts (42 CML-LBC and 35 Ph+ ALL) who had failed IM-based therapy were enrolled in this multinational Phase II study investigating the safety and efficacy of dasatinib. This preliminary analysis summarizes data on the first 28 pts accrued (13 CML-LBC and 15 Ph+ ALL) who were accrued prior to March 20, 2005. Dasatinib was administered orally at 70 mg twice daily (BID) on a continuous daily dosing schedule; dose escalation to 100 mg BID or dose reduction to 50 mg and 40 mg BID were allowed for poor initial response or persistent toxicity, respectively. Complete blood counts were performed weekly and bone marrow evaluation, including cytogenetic analysis, was scheduled every month. Mutation analyses were performed in all pts. 27 pts were IM resistant and 1 was IM intolerant; 17 (61%) pts had received prior IM doses >600 mg/day, 13 (46%) pts received IM for