PRIOR CONCURRENT THERAPY: Biologic therapy: At least 48 hours since prior interferon alfa At least 6 weeks since prior hematopoietic stem cell transplantation No concurrent anticancer biologic therapy Chemotherapy: At least 6 weeks since prior busulfan At least 24 hours since prior hydroxyurea At least 2 weeks since prior homoharringtonine At least 1 week since prior low-dose cytarabine (less than 30 mg/m2 every 12-24 hours daily) At least 2 weeks since prior moderate-dose cytarabine (100-200 mg/m2 for 5-7 days) At least 4 weeks since prior high-dose cytarabine (1-3 g/m2 every 12-24 hours for 6-12 doses) At least 3 weeks since prior anthracyclines, mitoxantrone, or etoposide No concurrent anticancer chemotherapy Endocrine therapy: Not specified Radiotherapy: Not specified Surgery: Not specified Other: At least 4 weeks since other prior investigational agents No other concurrent anticancer investigational agents