Dual-Drug Polymer Conjugates of Gemcitabine and Hydroxychloroquine for Pancreatic Cancer: The Critical Role of Linker Chemistry

Abstract

Stimuli-responsive polymer–drug conjugates (PDCs) offer a powerful platform to enhance therapeutic precision in cancer treatment by enabling controlled and context-specific drug release. Herein, we report the rational design of dual-drug copolymeric systems incorporating gemcitabine (GEM) and hydroxychloroquine (HCQ), in which linker chemistry is systematically engineered to modulate drug release profiles and therapeutic efficacy. A library of copolymers featuring ester, carbamate, carbonate, and disulfide-containing linkages was synthesized to evaluate the impact of chemical connectivity on drug liberation and cytotoxic performance in pancreatic adenocarcinoma models. Comparative release studies revealed that incorporation of a redox-responsive disulfide–carbamate linker significantly enhances GEM release relative to carbamate alone, while carbonate linkages provide superior release of HCQ compared to ester and carbamate analogues. These findings underscore the critical role of orthogonal linker selection in independently tuning the release kinetics of multiple payloads within a single macromolecular construct. Among the synthesized polymer drug conjugates, P(OEG/HCQ-CB/GEM-SS-C) copolymer exhibited the most promising performance, demonstrating efficient drug release and enhanced cytotoxicity against pancreatic cancer cells, and it was chosen for further evaluation. Biological evaluation demonstrated efficient cellular internalization of this optimized system in both BxPC-3 monolayers and 3D spheroids, as evidenced by time-dependent increases in fluorescence intensity using a BODIPY-labeled analogue. Collectively, this study highlights a modular linker-engineering strategy to achieve spatiotemporally controlled codelivery of synergistic therapeutics and identifies a promising dual-drug PDC candidate for further preclinical development against pancreatic cancer.