ERBB2 and neoplasm: The significantly disparate EC50 values (S4xTrastuzumab: 28.4 nM, S4xInotuzumab: 184 nM, and S4xαB7-H3: n.d.)of the three constructs, in addition to the values of the normalized AUC in the internalization assays facilitate a more comprehensive interpretation of the significance of individual mechanistic steps, particularly in conjunction with subsequent tumor cell-specific cytosol penetration assays in Ramos (CD22+), HeLa (B7-H3+), and SKBR-3 (HER2+, B7-H3+) (Figure 6).