Each of the qualities and properties discussed for the selective “targeted” chemotherapeutic delivery and additive or synergistic interactions that can be evoked by gemcitabine-(C4-amide)-[anti-EGFR] and gemcitabine-(C4-amide)-[anti-HER2/neu] collectively serve to explain how the dual-combination of these two covalent immunochemotherapeutics produced additive levels of anti-neoplastic cytotoxicity measured in chemotherapeutic-resistant mammary-adenocarcinoma (SKBr-3) populations functioning as an ex-vivo model for neoplastic disease (Figure 8). The gene discussed is ERBB2; the disease is breast adenocarcinoma.