To determine the in vivo efficacy of HER2-BsAb, the breast carcinoma cell lines HCC1954 (HER2high), MCF-7 (HER2low) and ovarian carcinoma cell line SKOV3, as well as HER2(+) patient derived breast cancer and gastric cancer xenografts (PDXs) were used in DKO mice xenograft models. Here, ERBB2 is linked to breast carcinoma.