The purpose of this study is to determine whether ublituximab is safe and effective in patients with relapsed or refractory B-cell lymphoma who were previously treated with rituximab.

Inclusion Criteria:

• Relapsed or Refractory B-cell Lymphoma
• Measurable or Evaluable Disease
• Previously treated with at least one line of rituximab or a rituximab based therapy
• Patients ineligible for high dose or combination chemotherapy + stem cell transplant
• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0, 1 or 2
• No active or chronic infection of Hepatitis B or C and no history of HIV based on negative serology

Exclusion Criteria:

• Prior chemotherapy, investigational therapy or radiotherapy within 3 weeks of study entry
• Prior autologous or allogeneic stem cell transplantation within 3 months of study entry
• History of severe hypersensitivity or anaphylaxis to prior rituximab
• Uncontrolled inter-current illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, brain metastasis, or psychiatric illness that would limit compliance with study requirements
• Pregnant women