Simultaneous Dual Selective Targeted Delivery of Two Covalent Gemcitabine Immunochemotherapeutics and Complementary Anti-Neoplastic Potency of [Se]-Methylselenocysteine

Abstract

The anti-metabolite chemotherapeutic, gemcitabine is relatively effective for a spectrum of neoplastic conditions that include various forms of leukemia and adenocarcinoma/carcinoma. Rapid systemic deamination of gemcitabine accounts for a brief plasma half-life but its sustained administration is often curtailed by sequelae and chemotherapeutic-resistance. A molecular strategy that diminishes these limitations is the molecular design and synthetic production of covalent gemcitabine immunoche- motherapeutics that possess properties of selective “targeted” delivery. The simultaneous dual selective “targeted” delivery of gemcitabine at two separate sites on the external surface membrane of a single cancer cell types represents a therapeutic approach that can increase cytosol chemotherapeutic deposition; prolong chemotherapeutic plasma half-life (reduces administration frequency); minimize innocent exposure of normal tissues and healthy organ systems; and ultimately enhance more rapid and thorough resolution of neoplastic cell populations. Materials and Methods: A light-reactive gemcitabine intermediate synthesized utilizing succinimidyl 4,4-azipentanoate was covalently bound to anti-EGFR or anti-HER2/ neu IgG by exposure to UV light (354-nm) resulting in the synthesis of covalent immunoche- motherapeutics, gemcitabine-(C 4 - amide )-[anti-EGFR] and gemcitabine-(C 4 - amide )-[anti-HER2/ neu ]. Cytotoxic anti-neoplastic potency of gemcitabine-(C 4 - amide )-[anti-EGFR] and gemcitabine-(C 4 - amide )-[anti-HER2/ neu ] between gemcitabine-equivalent concentrations of 10 -12 M and 10 -6 M was determined utilizing chemotherapeutic-resistant mammary adenocarcinoma (SKRr-3). The organoselenium compound, [Se]-methylselenocysteine was evaluated to determine if it complemented the anti-neoplastic potency of the covalent gemcitabine immunoche- motherapeutics. Results: Gemcitabine-(C 4 - amide )-[anti-EGFR], gemcitabine-(C 4 - amide )-[anti-HER2/ neu ] and the dual simultaneous combination of gemcitabine-(C 4 - amide )-[anti-EGFR] with gemcitabine-(C 4 - amide )-[anti-HER2/ neu ] all had anti-neoplastic cytotoxic potency against mammary adenocarcinoma. Gemcitabine-(C 4 - amide )-[anti-EGFR] and gemcitabine-(C 4 - amide )-[anti-HER2/ neu ] produced progressive increases in anti-neoplastic cytotoxicity that were greatest between gemcitabine-equivalent concentrations of 10 -9 M and 10 -6 M. Dual simultaneous combinations of gemcitabine-(C 4 - amide )-[anti-EGFR] with gemcitabine-(C 4 - amide )-[anti-HER2/ neu ] produced levels of anti-neoplastic cytotoxicity intermediate between each of the individual covalent gemcitabine immunochemotherapeutics. Total anti-neoplastic cytotoxicity of the dual simultaneous combination of gemcitabine-(C 4 - amide )-[anti-EGFR] and gemcitabine-(C 4 - amide )-[anti-HER2/ neu ] against chemothe-rapeutic-resistant mammary adenocarcinoma (SKBr-3) was substantially higher when formulated with [Se]-methylsele-no-cysteine.