CPM-3 Reactive Oxygen Species (ROS)-Triggered Carbon Monoxide (CO) Prodrugs for Targeted Delivery
Abstract
Carbon monoxide (CO), an established endogenous signaling molecule, shows huge potential as a gaseous therapeutic, with demonstrated ability to slow inflammation, defend tissues from oxidative stress, and protect against various disease pathologies. However, making CO-based therapeutics available in the clinical setting is hampered by the inherent challenges associated with the controlled and targeted delivery of a gaseous drug. Currently, there is no targeted CO delivery approach for diseased states such as osteoarthritis characterized by high levels of reactive oxygen species (ROS), specifically hypochlorite. The goal of this study is to design a chemical strategy wherein the CO prodrug is stable during storage and under normal conditions but would release CO in response to elevated ROS levels in a biological system. In our design, we leverage the reactivity of pyrrole rings to ROS. Installing an alkyne arm proximal to an ROS-sensitive pyrrole ring primes the system for a cascade of intramolecular Diels-Alder followed by retro-Diels Alder leading to the cheletropic release of CO. The synthesis of the prodrugs was achieved via a carbodiimide conjugation strategy. Five CO prodrugs of varying electronic properties and linker lengths were successfully synthesized (25 - 80% yield). The prodrugs were purified using column chromatography and partially characterized using 1H NMR. To study the utility of the designed chemical strategy, preliminary NMR studies of hypochlorite-mediated oxidation of the pyrrole ring were complicated with solubility issues of the prodrugs and hypochlorite in CD3CN/D2O. Alternatively, fluorescent carbon monoxide probes have been synthesized and characterized. Both test tube- and cell-based fluorescence assays are currently on-going. The optimized one-step synthetic approach was key in growing our compound library of potential CO prodrugs. However, NMR-based assays for structure-activity (CO release) relationship studies have been challenging because of solubility issues. The pivot to fluorescence-based assay is expected to eliminate solubility problems, and therefore provide a definitive measure of CO release from the synthesized prodrugs. Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number P20GM103499. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Keywords
Carbon Monoxide, Carbon Monoxide Prodrug, Drug Delivery, Targeted Drug Delivery, ROS
CPM-3 Reactive Oxygen Species (ROS)-Triggered Carbon Monoxide (CO) Prodrugs for Targeted Delivery
University Readiness Center Greatroom
Carbon monoxide (CO), an established endogenous signaling molecule, shows huge potential as a gaseous therapeutic, with demonstrated ability to slow inflammation, defend tissues from oxidative stress, and protect against various disease pathologies. However, making CO-based therapeutics available in the clinical setting is hampered by the inherent challenges associated with the controlled and targeted delivery of a gaseous drug. Currently, there is no targeted CO delivery approach for diseased states such as osteoarthritis characterized by high levels of reactive oxygen species (ROS), specifically hypochlorite. The goal of this study is to design a chemical strategy wherein the CO prodrug is stable during storage and under normal conditions but would release CO in response to elevated ROS levels in a biological system. In our design, we leverage the reactivity of pyrrole rings to ROS. Installing an alkyne arm proximal to an ROS-sensitive pyrrole ring primes the system for a cascade of intramolecular Diels-Alder followed by retro-Diels Alder leading to the cheletropic release of CO. The synthesis of the prodrugs was achieved via a carbodiimide conjugation strategy. Five CO prodrugs of varying electronic properties and linker lengths were successfully synthesized (25 - 80% yield). The prodrugs were purified using column chromatography and partially characterized using 1H NMR. To study the utility of the designed chemical strategy, preliminary NMR studies of hypochlorite-mediated oxidation of the pyrrole ring were complicated with solubility issues of the prodrugs and hypochlorite in CD3CN/D2O. Alternatively, fluorescent carbon monoxide probes have been synthesized and characterized. Both test tube- and cell-based fluorescence assays are currently on-going. The optimized one-step synthetic approach was key in growing our compound library of potential CO prodrugs. However, NMR-based assays for structure-activity (CO release) relationship studies have been challenging because of solubility issues. The pivot to fluorescence-based assay is expected to eliminate solubility problems, and therefore provide a definitive measure of CO release from the synthesized prodrugs. Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number P20GM103499. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.