In tumor cell growth assays, the BsAb effectively inhibited the proliferation of HER2-overexpressing BT474 cells at an IC50 (the antibody concentration inhibiting 50% of cell proliferation) of 0.59 nM on par with that of trastuzumab whose IC50 was 0.5 nM (Fig. 3a). Here, ERBB2 is linked to neoplasm.