OBJECTIVES: Primary * Determine the response rate in patients with cladribine-resistant hairy cell leukemia treated with BL22 immunotoxin. Secondary * Determine the response duration in patients treated with this drug. * Determine the safety of this drug in these patients. * Determine the pharmacokinetics of this drug in these patients. * Correlate BL22 blood levels and toxicity of this drug with the development of neutralizing antibodies in these patients. OUTLINE: Patients receive BL22 immunotoxin IV over 30 minutes on days 1, 3, and 5 followed by rest. Patients are then evaluated at 8 weeks. Patients achieving complete hematologic remission are followed. All other patients continue to receive BL22 immunotoxin as above on days 1, 3, and 5. Treatment repeats every 4 weeks for up to a total of 16 courses in the absence of disease progression or unacceptable toxicity. Patients achieving CR without minimal residual disease (MRD) receive 2 courses beyond CR. Patients achieving CR with MRD receive 4 courses beyond CR. Patients are followed every 4 months for 1 year, every 6 months for 1 year, and then annually thereafter. PROJECTED ACCRUAL: A total of 36 patients will be accrued for this study within 3 years.
DISEASE CHARACTERISTICS: * Histologically confirmed hairy cell leukemia * CD22-positive disease by fluorescence-activated cell sorting with anti-CD22 antibody * Meets at least 1 of the following indications for treatment: * Absolute neutrophil count less than 1,000/mm\^3 * Hemoglobin less than 10 g/dL * Platelet count less than 100,000/mm\^3 * Absolute lymphocyte count greater than 20,000/mm\^3 * Symptomatic splenomegaly * Meets 1 of the following response criteria: * No response * Complete response (CR) or partial response (PR) less than 2 years in duration after the last course of prior cladribine * CR or PR less than 4 years in duration after a second or later course of prior cladribine PATIENT CHARACTERISTICS: Age * 18 and over Performance status * ECOG 0-2 Life expectancy * Not specified Hematopoietic * See Disease Characteristics Hepatic * AST and ALT no greater than 2.5 times upper limit of normal (ULN) * Bilirubin no greater than 2.2 mg/dL * Albumin at least 3.0 g/dL Renal * Creatinine no greater than 1.4 mg/dL OR * Creatinine clearance at least 50 mL/min Cardiovascular * No symptomatic congestive heart failure * No unstable angina pectoris * No cardiac arrhythmia Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No serum that neutralizes more than 75% of the activity of 1 µg/mL of BL22 immunotoxin using a bioassay * No ongoing or active infection * No psychiatric illness or social situation that would preclude study compliance * No other concurrent uncontrolled illness that would preclude study participation * Understand and give informed consent PRIOR CONCURRENT THERAPY: Biologic therapy * No prior BL22 immunotoxin * More than 12 weeks since prior monoclonal antibody therapy Chemotherapy * See Disease Characteristics * More than 4 weeks since prior systemic cytotoxic chemotherapy Endocrine therapy * More than 4 weeks since prior systemic steroids (except stable doses of prednisone no greater than 20 mg/day) Radiotherapy * Not specified Surgery * Not specified Other * No other concurrent investigational agents
is designated in this study