PRIOR CONCURRENT THERAPY: Biologic therapy: At least 48 hours since prior interferon alfa Prior hematopoietic stem cell transplantation allowed if blood counts have recovered No concurrent biologic therapy Chemotherapy: At least 14 days since prior homoharringtonine At least 24 hours since prior hydroxyurea At least 7 days since prior low dose cytarabine (less than 30 mg/m2 every 12-24 hours daily) At least 14 days since prior moderate dose cytarabine (100-200 mg/m2 for 5-7 days) At least 28 days since prior high dose cytarabine (1-3 g/m2 every 12-24 hours for 6-12 doses) At least 21 days since prior anthracyclines, mitoxantrone, etoposide, methotrexate, or cyclophosphamide At least 6 weeks since prior busulfan No concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: Not specified Surgery: Not specified Other: At least 28 days since prior other investigational agents No concurrent other investigational agents