A Phase I/II Study to Determine Safety and Efficacy of Arsenic Trioxide (Trisneox™) in Combination With Imatinib (STI571, Gleevec™) in Patients With Chronic Myelogenous Leukemia in Accelerated or Blastic Phase Disease or Ph+ Acute Lymphoblastic Leukemia

OBJECTIVES: Primary * Determine the maximum tolererated dose of arsenic trioxide when administered with imatinib mesylate in patients with accelerated or blastic phase chronic myelogenous leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia. * Determine the rate of complete morphologic remission in the bone marrow of patients treated with this regimen. OUTLINE: This is a phase I dose-escalation study of arsenic trioxide followed by a phase II study. * Phase I: * Induction therapy: Patients receive oral imatinib mesylate once daily on days 1-35 (weeks 1-5) and arsenic trioxide IV over 1-4 hours on days 1-5, 8-12, 15-19, and 22-26 (weeks 1-4). Patients undergo bone marrow evaluation on week 5. Patients achieving a morphologic remission proceed to consolidation therapy. Patients not achieving morphologic remission receive a second course of imatinib mesylate as above on weeks 6-10 and arsenic trioxide as above on weeks 6-9. Patients are re-evaluated on week 10. Patients achieving morphologic remission proceed to consolidation therapy. Patients not achieving a morphologic remission are removed from study. * Consolidation therapy: Patients receive oral imatinib mesylate as in induction therapy on approximately weeks 6-11 (or weeks 11-16\*) and arsenic trioxide IV over 1-4 hours on days 1, 3, 5, 8, 10, 12, 15, 17, 19, 22, 24, and 26 (approximately weeks 6-9 OR weeks 11-14\*). Patients who remain in morphologic remission receive a second course of imatinib mesylate as in induction therapy on approximately weeks 12-17 (or weeks 17-22\*) and arsenic trioxide as above (in consolidation therapy) on approximately weeks 12-15 (or weeks 17-20\*). NOTE: \*For patients who receive a second course of induction therapy Cohorts of 6 patients receive escalating doses of arsenic trioxide until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 6 patients experience dose-limiting toxicity. * Phase II: Patients receive arsenic trioxide at the MTD and imatinib mesylate as in phase I. Treatment in both phases continues in the absence of unacceptable toxicity or disease progression. After completion of consolidation therapy, patients may continue imatinib mesylate off study at the discretion of the physician. Patients who become candidates for stem cell transplantation at any time during the study are removed from study. PROJECTED ACCRUAL: A total of 6-43 patients (6-12 for phase I and 37 \[including 6 patients from phase I\] for phase II) will be accrued for this study within 2 years.