ERBB2 and cancer: Furthermore, ADCP is one of the cytotoxic mechanisms used by rituximab, ofatumumab, ocaratuzumab, and obinutuzumab, which are human monoclonal antibodies targeting CD20, a B cell surface protein, in chronic lymphocytic leukemia (28), as well as trastuzumab, an anti-HER2 monoclonal antibody that triggers phagocytic cytotoxicity of HER2+ cancer cells both in vitro and in vivo (29).