DISEASE CHARACTERISTICS:

• Pathologically confirmed acute myeloid leukemia or acute lymphoblastic leukemia

  • Relapsed ≥ 1 time OR refractory disease

    • Patients who fail primary induction therapy or who relapse after achieving complete remission are eligible if they have received ≤ 3 prior courses of induction/reinduction therapy
• No acute promyelocytic leukemia (M3)
• No hyperleukocytosis with > 50,000 blasts/mm^3
• No active CNS leukemia

PATIENT CHARACTERISTICS:

• ECOG performance status 0-2
• AST and ALT ≤ 5 times upper limit normal (ULN)
• Alkaline phosphatase ≤ 5 times ULN
• Bilirubin ≤ 2.0 mg/dL
• Creatinine ≤ 2.0 mg/dL
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• LVEF ≥ 45% by MUGA or ECHO
• No active, uncontrolled infection
• No other life-threatening illness
• No mental deficits and/or psychiatric history that would preclude study compliance
• No active graft-vs-host disease

PRIOR CONCURRENT THERAPY:

• Recovered from all prior therapies
• At least 24 hours since prior hydroxyurea, steroids, imatinib mesylate, arsenic trioxide, interferon, or leukapheresis for blast count control
• At least 4 weeks since prior stem cell transplantation (autologous or allogeneic)
• At least 4 days since prior growth factors
• At least 3 weeks since prior chemotherapy, except for non-aplasia producing treatments (e.g., low-dose cyclophosphamide, hydroxyurea, interferon, imatinib mesylate, mercaptopurine, thalidomide, azacitidine, or decitabine)
• No prior flavopiridol
• No other concurrent chemotherapy, radiotherapy, or immunotherapy