Dual potency anti-HER2/neu and anti-EGFR anthracycline immunoconjugates in chemotherapeutic-resistant mammary carcinoma combined with cyclosporin A and verapamil P-glycoprotein inhibition

Abstract

Immunoconjugates of epirubicin were synthesized with monoclonal antibodies against the epidermal growth factor receptors, HER2/neu and EGFR, by creating a sulfhydryl-reactive epirubicin intermediate applying heterobifunctional succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), which was introduced at α-monoamide groups of the epirubicin carbohydrate moiety. In parallel, N-succinimidyl-S-acetylthioacetate (SATA) was used to incorporate a sulfhydryl group into immunoglobulin at the terminal amine position of ϵ-lysine amino acid residues. Eprirubicin–SMCC–SATA–IgG immunoconjugates were produced by reacting epirubicin–SMCC and SATA–IgG at appropriate molar ratios. Epirubicin–(anti-HER2/neu) and epirubicin–(anti-EGFR) had greater potency against chemotherapeutic-resistant SKBr-3 mammary carcinoma than did epirubicin at epirubicin-equivalent concentrations. Epirubicin–(anti-HER2/neu) was more potent than epirubicin–(anti-EGFR), and a synergistic level of antineoplastic activity was detected with an epirubicin immunoconjugate 50/50 combination. Competitive P-glycoprotein inhibition with cyclosporin A or verapamil enhanced the potency of the epirubicin immunoconjugate 50/50 combination. Minor levels of antineoplastic activity were detected only with an immunoglobulin 50/50 combination of anti-HER2/neu and anti-EGFR. The investigations represent a potential strategy for enhancing the selective internalization, intracellular deposition, and antineoplastic potency of chemotherapeutics in multidrug-resistant neoplasias.