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2014 Abstracts

Long-Circulating Backbone-Degradable HPMA Copolymer-Gemcitabine Conjugates for the Treatment of Ovarian Carcinoma

Shwan Javdan, University of Utah

Life Sciences

Each year in the United States, over 22,000 new cases of ovarian carcinoma are diagnosed and 14,000 women die from its progressive cancer stages. Anthracyclines, a class of common chemotherapy drugs, have long been the primary treatment for this and many other cancers, but they often leave patients with cardiotoxicity, hepatotoxicity, and other adverse effects. Polymer-drug conjugates using poly[N-(2-hydroxypropyl)methacrylamide] (poly-HPMA) are nanosized, water-soluble constructs that accumulate passively in solid tumors by the enhanced permeability and retention effect as well as actively by cell surface targeting methods. As such, they have exhibited reduced toxicity in the body. The goal of this study was to develop a novel, targeted HPMA copolymer-drug conjugate for the treatment of ovarian carcinoma. To accomplish this, an antibody fragment called Fab’, targeted to ovarian carcinoma cell surface antigen OA3, was bound to an HPMA copolymer-gemcitabine conjugate. Gemcitabine is a nucleoside analog used in chemotherapy that has demonstrated considerable effectiveness in recent years. The copolymer-gemcitabine conjugate was successfully developed following the synthesis of all the requisite components, including Fab’, diblock chain-transfer agent (di-CTA), N-(2-(2-pyridyldithio)ethyl)methacrylamide (PDTEMA), and polymerizable backbone-degradable gemcitabine derivative. Syntheses of di-CTA and PDTEMA were optimized and then characterized by high-performance liquid chromatography, H-NMR, and mass spectrometry. Monomers were combined by reversible addition-fragmentation chain-transfer polymerization, and then the Fab’ fragment was bound to the polymer backbone via a disulfide exchange reaction with PDTEMA. The targeted copolymer-drug conjugate was then verified by fast-protein liquid chromatography as well as ultraviolet-visible spectroscopy. A number of in vitro tests have demonstrated the properties of an efficient drug delivery system. Flow cytometry displayed active accumulation of the copolymer-gemcitabine conjugate to OVCAR3 cell surfaces. Furthermore, IC50 measurement found promising drug efficacy comparable to modern anthracyclines. Future work will involve in vivo evaluation of the conjugate’s therapeutic efficacy in nude mice bearing OVCAR3-xenografts.