ERBB2 and breast adenocarcinoma: Gemcitabine-(C4-amide)-[anti-HER2/neu] and gemcitabine had nearly identical anti-neoplastic cytotoxicity against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) at gemcitabine-equivalent concentrations of 10−10 M and 10−9 M but gemcitabine was much more potent at 10−8 M (85.9%-vs-50.6% residual survival), 10−9 M (4.6%-vs-72.7% residual survival), and 10−6 M (4.7%-vs-58.9% residual survival) respectively (Figure 6).