The purpose of this study is to determine the optimal dose of Campath for patients with relapsing or refractory (failed standard therapy) non-Hodgkin's lymphoma. The study will also evaluate the safety of the drug and whether it is effective in treating these patients.

This study is being conducted in 2 parts with the primary objective of part 1 being to determine the maximum tolerated dose (MTD) of CAMPATH (alemtuzumab, MABCAMPATH, CAMPATH) administered intravenously (IV) once a week as treatment for relapsing or refractory non-Hodgkin's lymphoma (NHL). The primary objective of part 2 is to determine the overall response rate (complete response, CR/unconfirmed , plus partial response) of weekly IV CAMPATH in the treatment of relapsing or refractory NHL. This is a Phase I/II study, open-label, multicenter study to evaluate the efficacy and safety of weekly IV CAMPATH as therapy for patients with relapsing or refractory non-Hodgkin's lymphoma.

Inclusion Criteria: Patients must have:

• Pathologically confirmed diagnosis of relapsing or refractory non-Hodgkin's lymphoma that has failed conventional therapy.
• Measurable disease (lesions that can be accurately measured by CT scan and a greatest transverse diameter larger or equal to 1 cm or palpable lesions that both diameters larger or equal to 2 cm).
• Life expectancy of at least 12 weeks. - World Health Organization (WHO) performance status (PS) of 0, 1, or 2.
• Adequate marrow and organ function (details are listed in the protocol).
• Female patients with childbearing potential must have a negative serum pregnancy test within 2 weeks prior to enrollment. Male and female patients must agree to use an effective contraceptive method while on study treatment, if appropriate, and for a minimum of 6 months following study therapy.
• Signed, written informed consent.

Exclusion Criteria: Patients must not have:

• Prior autologous bone marrow or stem cell transplant within 6 months of study entry.
• A history of prior allogeneic bone marrow transplant or organ transplant.
• Previously untreated non-Hodgkin's lymphoma.
• Previously treated with CAMPATH.
• Patients with bulky disease, ie any single mass > 7.5cm.
• Prior radiotherapy to the only site of measurable disease.
• Medical condition requiring chronic use of oral, high-dose corticosteroids.
• Autoimmune thrombocytopenia.
• Use of investigational agents within previous 30 days or any anti-cancer therapy within the previous 3 weeks. Patients must have recovered from all acute toxicities of any prior therapy.
• Past history of anaphylaxis following exposure to humanized monoclonal antibodies.
• Active, uncontrolled infection, including human immunodeficiency virus (HIV) positive.
• Active secondary malignancy.
• Active central nervous system (CNS) involvement with NHL.
• Pregnant or lactating women. Male or female patients who do not agree to use effective contraceptive method(s) during the study.
• 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.