Inclusion Criteria

DISEASE CHARACTERISTICS:

- Prior morphologic diagnosis of acute lymphoblastic leukemia (ALL)

- No M0, mixed lineage, or L3 (Burkitt's) ALL

- Refractory to a standard induction regimen OR relapsed after successful prior
induction therapy

- Standard induction regimen is defined as any program of treatment that includes
vincristine and prednisone or high-dose cytarabine/mitoxantrone

- Any number of inductions or remissions allowed

- Must have evidence of ALL in bone marrow or peripheral blood

- Immunophenotyping of the blood or bone marrow lymphoblasts must be performed to
determine lineage (B cell, T cell, or mixed B/T cell)

- No extramedullary only disease in the absence of bone marrow or blood
involvement

- Co-expression of myeloid antigens (CD13 and CD33) allowed

- Patients with Philadelphia chromosome-positive (Ph+) ALL or bcr/abl-positive ALL who
were previously eligible for imatinib mesylate treatment must have received imatinib
mesylate either alone or in combination with chemotherapy for ALL and must have
either failed treatment or been unable to tolerate treatment

- No CNS involvement as determined by lumbar puncture (for previous CNS history or
clinical signs or symptoms of CNS) or by clinical exam (if no previous history or
signs/symptoms)

- Must be registered on SWOG-S9910 and SWOG-9007

PATIENT CHARACTERISTICS:

- Zubrod performance status 0-2

- Creatinine ≤ 1.5 times upper limit of normal (ULN)

- AST or ALT ≤ 1.5 times ULN

- Bilirubin ≤ 1.5 times ULN

- No psychiatric disorders that would interfere with study compliance

- No uncontrolled systemic fungal, bacterial, viral, or other infection

- No other severe concurrent disease

- No other serious or poorly controlled medical condition that would preclude study
participation

- No history of serious organ dysfunction or disease involving the heart, kidney,
liver, or other organ system that would preclude study participation

- HIV negative

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No pre-existing motor or sensory neuropathy ≥ grade 2

- No other prior malignancies, except for the following:

- Adequately treated basal cell or squamous cell skin cancer

- In situ cervical cancer

- Adequately treated stage I or II cancer in complete remission

- Any other prior cancer for which the patient has been disease free for ≥ 5 years

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- Recovered from prior therapy

- No prior clofarabine

- More than 2 weeks since prior chemotherapy, major surgery, or other investigational
agents

- More than 6 weeks since prior monoclonal antibodies

- Prior allogeneic or autologous bone marrow transplant allowed provided the following
criteria are met:

- More than 90 days since transplant

- No acute graft-versus-host disease (GVHD) ≥ grade 2 OR moderate or severe
limited chronic GVHD OR extensive chronic GVHD of any severity

- Prior maintenance therapy with steroids, vincristine, and/or anti-metabolite agents,
such as, but not limited to, mercaptopurine, thioguanine, or methotrexate allowed

- Concurrent hydroxyurea allowed