Polyglutamates are highly biocompatible, biodegradable and multifunctional polymers, which have been effectively used as building blocks in Polymer Therapeutics due to their feasible synthesis, versatile architectures with tunable structural properties, and tailored bioresponsiveness [1,2]. Studies reporting single or combination polypeptide-drug conjugates (PDCs) have underscored the importance of the rational design of appropriate linking moieties [1], which can permit the tightly controlled release of the given active agent at the desired site of action.<br/>Self-immolative linkers integrating a disulfide bond represent one of the most powerful means to achieve specific intracellular drug release from PDCs [3]. While multiple studies have sought to explore drug release mechanisms and fine-tune the activity of the disulfide linker [4], the influence of both the drug's structural features (i.e., hydrophobicity, electronegativity) and the linker-associated spacer on release kinetics remains unexplored.<br/>We successfully synthesized and characterized two types of disulfide linkers with four different drugs and studied their drug release kinetics in the presence of dithiothreitol (5 mM), which mimics the reducing environment observed within cells and dithiothreitol (10 µM) as a negative control. We analyzed the intermediate and final metabolites of the release studies by liquid chromatography-mass spectrometry (LC-MS) using positive ionization mode following one mass transition for each molecule. Drug release profiles demonstrated that the disulfide bond cleavage rate depends not only on the type of chemical bond between the linking moiety and the drug but also on the drug's structural features and its ability to form a resonance-stabilized structure.<br/>These findings highlight the importance of rigorous analysis of disulfide linkers in understanding structure-function correlations between linker structure, drug chemistry, and drug release kinetics.<br/>Here, we establish how the exhaustive and systematic characterization of drug release profiles can significantly improve the discovery and selection of the optimal linker composition in the rational design of polyglutamate-drug conjugates with a desired pharmacokinetic profile.

Engineering Polyglutamate-drug self-immolative linkers: Importance of drug chemical nature on release kinetics

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.