Inclusion Criteria

INCLUSION CRITERIA:

DISEASE CHARACTERISTICS:

- Confirmed diagnosis of B-cell non-Hodgkin's lymphoma

- Measurable disease

- Evidence of CD22-positive malignancy by the following criteria,

- > 30% of malignant cells from a disease site CD22+ by FACS analysis or,

- > 15% of malignant cells from a disease site must react with anti-CD22 by
immunohistochemistry

- Patients with indolent subtypes of CD22+ B-cell non-Hodgkin's lymphoma, including,
but not limited to mantle cell lymphoma, follicular lymphoma and Waldenström's
macroglobulinemia, are eligible if stage III-IV.

- Patients must have failed at least two or more courses of prior standard chemotherapy
and/or biologic therapy (e.g. Rituxan). Patients with progressive mantle cell
lymphoma may be eligible if they have failed one prior standard therapeutic regimen.

PATIENTS CHARACTERISTICS

Performance Status

- ECOG 0-2

Life Expectancy

- Life expectancy of less than 6 months, as assessed by the principal investigator

Other

- Patients with other cancers who meet eligibility criteria and have less than 5 years
of disease free survival will be considered on a case-by-case basis

- Must be able to understand and sign informed consent

- Female and male patients must agree to use an approved method of contraception during
the study

Exclusion Criteria:

- History of bone marrow transplant

- Documented and ongoing central nervous system involvement with their malignant
disease (history of CNS involvement is not an exclusion criterion)

- Pregnant or breast-feeding females

- Patients whose plasma contains either a significant level of antibody to CAT-8015 as
measured by ELISA, or antibody that neutralizes the binding of CAT-8015 to CD22 as
measured by a competition ELISA.

- HIV positive serology (due to increased risk of severe infection and unknown
interaction of CAT-8015 with antiretroviral drugs)

- Hepatitis B surface antigen positive

- Uncontrolled, symptomatic, intercurrent illness including but not limited to:
infections requiring systemic antibiotics, congestive heart failure, unstable angina
pectoris, cardiac arrhythmia, psychiatric illness, or social situations that would
limit compliance with study requirements

Hepatic function: serum transaminases (either ALT or AST) or bilirubin

- ≥ Grade 2, unless bilirubin is due to Gilbert's disease

Renal function: Serum creatinine clearance ≤ 60mL/min as estimated by Cockroft-Gault
formula

Hematologic function:

- The ANC < 1000/cmm, or platelet count <50,000/cmm, if these cytopenias are not judged
by the investigator to be due to underlying disease (i.e. potentially reversible with
anti-neoplastic therapy).

- A patient will not be excluded because of pancytopenia ≥ Grade 3, or erythropoietin
dependence, if it is due to disease, based on the results of bone marrow studies

- Baseline coagulopathy > Grade 3 unless due to anticoagulant therapy.

Pulmonary function:

- Patients with < 50% of predicted forced expiratory volume (FEV1) or <50% of predicted
diffusing capacity for carbon monoxide (DLCO), corrected for hemoglobin concentration
and alveolar volume. Note: Patient with no prior history of pulmonary illness are
not required to have PFTs. FEV1 will be assessed after bronchodilator therapy.

Recent prior therapy:

- Cytotoxic chemotherapy, corticosteroids (except stable doses of prednisone), whole
body electron beam radiation therapy, hormonal, biologic or other standard or any
investigational therapy of the malignancy for 3 weeks prior to entry into the trial

- Less than or equal < 3 months prior monoclonal antibody therapy (i.e. rituximab)

- Patients who are receiving or have received radiation therapy less than 3 weeks prior
to study entry will be not be excluded providing the volume of bone marrow treated is
less than 10% and also the patient has measurable disease outside the radiation port

- Any history of prior pseudomonas-exotoxin immunotoxin (PE) administration.