ERBB2 and neoplasm: However, not all monoclonal antibodies exert equally well all anti-tumor activities, which depend on the specific HER-2 antigenic epitope bound (for example, pertuzumab is much better at inhibiting dimerization than trastuzumab), and on the isotype of the Ig molecule (for example, mouse IgG2a, IgG2b and IgG3 mediate complement-dependent cytotoxicity better than IgG1) [17,18,19,20].