ERBB2 and neoplasm: In the case of 56, the in vivo evaluation in a BT-474 xenograft mice model of HER2+ breast cancer confirmed its efficacy with complete tumor regression in all mice treated only twice at 5 mg/kg, resulting in more efficacy than the ADC ado-trastuzumab emtansine (T-DM1), which only cured three out of eight mice.