A substance being studied in the treatment of certain types of non-Hodgkin lymphoma (NHL) and acute lymphoblastic leukemia (ALL). It is also being studied in the treatment of an autoimmune disease called systemic lupus erythematosus (SLE). Epratuzumab binds to a protein called CD22, which is found on B cells (a type of white blood cell) and some types of cancer cells. This may help suppress the body’s immune response and it may help kill cancer cells. Epratuzumab is a type of monoclonal antibody.