• Response rate [ Time Frame: After even cycle numbers (2,4,6,8,10) ] [ Designated as safety issue: No ]
  

• Duration of Response: [Timeframe: Date that a response begins with the date that PD is documented.] [ Time Frame: 30 days after last dose of study drug ] [ Designated as safety issue: No ]
  

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