A fully human, high-affinity IgG1 monoclonal antibody directed against the B cell CD20 cell surface antigen with potential antineoplastic activity. Ofatumumab binds specifically to CD20 on the surfaces of B cells, triggering complement-dependent cell lysis (CDCL) and antibody-dependent cell-mediated cytotoxicity (ADCC) of B cells overexpressing CD20. The CD20 antigen, found on over 90% of B cells, B cell lymphomas, and other B cells of lymphoid tumors of B cell origin, is a non-glycosylated cell surface phosphoprotein that acts as a calcium ion channel; it is exclusively expressed on B cells during most stages of B cell development. [ ]