A fully humanized monoclonal antibody directed against the CD20 antigen with potential antineoplastic activity. Following binding, veltuzumab triggers complement-dependent cell lysis (CDCL) and antibody-dependent cell-mediated cytotoxicity (ADCC) in cells that overexpress CD20. CD20 antigen is a hydrophobic transmembrane protein located on pre-B and mature B lymphocytes.