RATIONALE: Drugs used in chemotherapy, such as cytarabine and clofarabine, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Giving more than one drug (combination chemotherapy) may kill more cancer cells.

PURPOSE: This phase I trial is studying the side effects and best dose of clofarabine when given together with cytarabine and to see how well they work in treating patients with refractory or relapsed acute myeloid leukemia or acute lymphoblastic leukemia.

OBJECTIVES:

• Determine the response rate in adult patients with relapsed or refractory acute myeloid leukemia or acute lymphoblastic leukemia treated with high-dose cytarabine followed by clofarabine.
• Document the safety profile and tolerability of this regimen in these patients.
• Phase I: Patients receive high-dose cytarabine IV over 3 hours followed by clofarabine IV over 2 hours on days 1-5. Treatment repeats for up to 4 courses (1-2 induction courses, 2-3 post-remission courses) in the absence of disease progression or unacceptable toxicity.

A cohort of 3-6 patients receives the starting dose of clofarabine. If 1 of 6 patients experiences dose-limiting toxicity (DLT), a subsequent cohort of patients receives clofarabine at the next higher dose. If ≥ 2 of 6 patients experience DLT, the dose of cytarabine is reduced and subsequent cohorts of patients receive cytarabine at reduced doses and clofarabine as per the dose-escalation scheme above.

PROJECTED ACCRUAL: A total of 9 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Pathologic confirmation of acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL)

  • No M3 AML

• Meets 1 of the following criteria:

  • In first relapse
  • In second relapse after a second complete remission (CR) that lasted ≥ 3 months
  • Refractory to initial induction therapy

• No symptomatic CNS involvement

PATIENT CHARACTERISTICS:

• ECOG performance status ≤ 2
• Creatinine < 2 mg/dL
• Bilirubin ≤ 2 mg/dL
• AST and ALT ≤ 4 times upper limit of normal
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 2 weeks after completing study treatment
• Ejection fraction ≥ 45% by echocardiogram
• No active, uncontrolled systemic infection considered opportunistic, life-threatening, or clinically significant
• No psychiatric disorders that would interfere with giving consent, study participation, or follow-up procedures
• No other severe concurrent disease that would preclude study treatment

PRIOR CONCURRENT THERAPY:

• At least 1 week since prior therapy and recovered

• No other concurrent chemotherapy

  • Hydroxyurea to control WBC count before starting study treatment allowed

• No concurrent corticosteroids unless used for diseases other than leukemia

• No concurrent palliative radiotherapy

• No concurrent growth factors (e.g., epoetin alfa, filgrastim [G-CSF], or sargramostim [GM-CSF]) in patients with AML