Rituximab Plus CAMPATH in Patients With Relapsed/Refractory Low-Grade or Follicular, CD20-positive, B-cell NHL

Inclusion Criteria: For the Phase I portion of the study, patients must have pathologically confirmed diagnosis of low-grade or follicular, CD20-positive, B-cell, non-Hodgkin's lymphoma that has relapsed or is refractory. For the Phase II portion of the study, patients must have a pathologically confirmed diagnosis of low-grade or follicular, CD20-positive, B-cell, non-Hodgkin's lymphoma (Follicular, predominantly small cleaved or follicular, mixed small cleaved and large cell, International Working Formulation classification B or C or REAL classification follicular center grade 1,2) that has relapsed or is refractory. Previously treated with at least one anti-cancer regimen for NHL Measurable disease (lesions that can be accurately measured in 2 dimensions by CT scan with a greatest transverse diameter of >/= to 2cm or palpable lesions with both diameters of 2cm or more) Life expectancy of at least 12 weeks WHO performance status or 0 or 1 Adequate marrow and organ function (as defined in the protocol) Completed major surgery, radiotherapy, chemotherapy, immunotherapy or biotherapy/targeted therapies at least 4 weeks prior to study entry (6 weeks if treated with a nitrosourea or mitomycin). Patients must have recovered from all prior treatment toxicity to Grade 1 or less, exclusive of alopecia. Exclusion Criteria: Prior combination therapy with rituximab and CAMPATH; prior therapy with either agent alone is permitted A history of a T-cell lymphoma Known AIDS-related HIV-positive lymphoma For the Phase II portion of the study (once MTD has been determined), bulky disease, ie, any single mass >10cm or circulating malignant cells of 25,000/uL or more Prior autologous bone marrow or stem cell transplant within 6 months of study entry Prior allogeneic bone marrow transplant or organ transplant Prior radiotherapy to the only site of measurable disease Medical condition requiring chronic use of oral, high-dose corticosteroids Use of investigational agents within 30 days of study enrollment Past history of anaphylaxis following exposure to humanized monoclonal antibodies Known, active, infection, including HIV positive Diagnosis of another malignancy within the previous five (5) years, unless the probability of recurrence of the prior malignancy is < 5%. Patients with curatively treated early stage squamous cell carcinoma of the skin, basal cell carcinoma of the skin, cervical intraepithelial neoplasia (CIN), and patients with a history of malignant tumor in the past that have been disease-free for at least 5 years Active central nervous system (CNS) involvement with lymphoma Pregnant or nursing women Any significant concurrent disease or illness that would, in the opinion of the investigator, compromise patient safety or compliance, or interfere with the interpretation of study results Active hepatitis or a history of prior viral hepatitis B or C, or positive hepatitis B serologies without prior immunization