Inclusion Criteria:

- Patients must have a histological diagnosis of B cell non-Hodgkin's lymphoma,
including diffuse large B-cell, mantle cell, follicular, small lymphocytic, and
marginal zone lymphoma by the World Health Organization criteria.

- Patients must have an archived paraffin or fresh tumor specimen available for
immunohistologic evaluation of CD40, CD20, & CD79a.

- Patients must have relapsed lymphoma and must have failed frontline chemotherapy.

- Patients who have not received autologous stem cell transplant must have refused or
be ineligible for it.

- Patients must have completed radiotherapy, chemotherapy, and/or treatment with
investigational anti-cancer agents 4 weeks prior to registration. Patients must have
completed any monoclonal antibody treatment, including rituximab, 6 months prior to
registration.

- Patients must have completed autologous bone marrow transplant 4 months prior to
registration.

- Patient must have at least one site of measurable disease defined by unidimensional
lesion ≥ 2 cm by conventional CT scan.

- Patients must have an ECOG performance status ≤ 2 and a life expectancy > 3 months.

- Patients must have the following required baseline laboratory data:

- Platelet count ≥ 75,000/mm3,

- Hemoglobin ≥ 9.0 g/dL,

- Absolute neutrophil count ≥ 1,250/mm3,

- ALT/AST ≤ 2.5 times ULN,

- Total bilirubin ≤ 1.5 times ULN,

- Creatinine < 1.5 mg/dL,

- Females of childbearing potential must have a negative serum β-hCG pregnancy test
result within 3 days prior to the first dose of SGN-40 and must agree to use an
effective contraceptive method during the course of the study and for 6 months
following the last dose of study drug.

- If a deep venous thrombosis or other vascular even has required medical or surgical
intervention in the past year, patients must either be on stable dose of
anticoagulant therapy for at least 3 weeks or have completed anticoagulant therapy at
least 3 months prior to registration with radiographic confirmation that thrombosis
is resolved.

- Patients must be at least 18 years of age.

- Patients must be available for periodic blood sampling, study-related assessments and
management of toxicity at the treating institution.

Exclusion Criteria:

- Patients with history or clinical evidence of leptomeningeal or central nervous
system (CNS) lymphoma.

- Patients with a documented history within 6 months of registration of a cerebral
vascular event, myocardial infarction, deep venous thrombosis or other vascular event
that has required medical or surgical intervention. Patients must have completed
anticoagulant therapy at least 3 months prior to registration. Prophylactic
anticoagulant therapy for indwelling catheters is acceptable.

- Patients who have received an allogeneic stem cell transplant.

- Patients who have had major surgery within 4 weeks prior to registration.

- Patients with a known hypersensitivity to recombinant proteins or any excipient
contained in the drug formulation.

- Patients with a history of another primary malignancy that has not been in remission
for at least 5 years (non-melanoma skin cancer and cervical carcinoma in situ on
biopsy or a squamous intraepithelial lesion on PAP smear are exempt from the five
year limit).

- Patients with any active systemic viral, bacterial, or fungal infection within four
weeks prior to registration.

- Patients with known positivity for HIV, hepatitis B or hepatitis C infection.

- Patients with a history of significant chronic or recurrent infections requiring
treatment.

- Patients with a history of migraines or severe headaches requiring medical therapy
within 12 months of enrollment.

- Patients on systemic steroids who have not been on a stable daily dose (not exceeding
10 mg prednisone or equivalent) during 4 weeks prior to the first dose of SGN 40.

- Patients who are pregnant or breastfeeding.

- Patients with any serious underlying medical condition that would impair their
ability to receive or tolerate the planned treatment.

- Patients with dementia or altered mental status that would preclude the understanding
and/or rendering of informed consent.