Anti-CD19 and Anti-CD22 Immunotoxins in Treating Patients With Refractory or Relapsed B-Cell Acute Lymphoblastic Leukemia

OBJECTIVES:

- Determine the maximum tolerated dose of deglycosylated ricin A chain-conjugated
anti-CD19 and anti-CD22 immunotoxins (Combotox) in patients with refractory or relapsed
B-cell acute lymphoblastic leukemia.

- Determine the toxicity of Combotox in these patients.

- Determine the pharmacokinetic (PK) profile of Combotox in these patients.

- Determine any antitumor activity of Combotox, in terms of the percentage of blasts in
bone marrow and peripheral blood.

- Determine the levels of human antimouse and human anti-dgA antibodies in patients
treated with Combotox.

- Determine if there is a correlation between PK parameters and toxicity of Combotox in
these patients.

- Determine if the expression of the CD19 and CD22 cell surface antigens is affected by
Combotox.

OUTLINE: This is a dose-escalation study.

Patients receive deglycosylated ricin A chain-conjugated anti-CD19 and anti-CD22
immunotoxins (Combotox) IV over 4 hours on days 1, 3, and 5 in the absence of disease
progression or unacceptable toxicity.

Cohorts of patients receive escalating doses of Combotox until the maximum tolerated dose is
determined.

After completion of study treatment, patients are followed periodically.

PROJECTED ACCRUAL: A total of 20 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

- Histologically confirmed adult acute lymphoblastic leukemia

- B-cell lineage

- Refractory or relapsed disease based on a bone marrow/peripheral blood examination,
cytogenetic studies, or polymerase chain reaction amplification

- Disease refractory to conventional therapy and other therapies of higher
priority

- At least 50% of the blasts (in bone marrow or peripheral blood) expressing CD19
and/or CD22 by flow cytometry

PATIENT CHARACTERISTICS:

- ECOG performance status 0-2

- Life expectancy > 2 months

- Creatinine < 1.5 times normal

- Bilirubin < 1.5 times normal

- ALT or AST < 2.5 times normal

PRIOR CONCURRENT THERAPY:

- Prior chemotherapy, biologic therapy, and/or radiotherapy allowed