A monoclonal antibody being studied in the treatment of certain types of B-cell cancers including chronic lymphocytic leukemia (CLL) and follicular non-Hodgkin lymphoma. Monoclonal antibodies are made in the laboratory and can locate and bind to substances in the body, including cancer cells. Ofatumumab binds to CD20, a protein on the surface of normal B cells and most B-cell tumors. Also called HuMax-CD20.