Organic Carbon Monoxide Prodrugs Activated by Endogenous Reactive Oxygen Species for Targeted Delivery

Carbon monoxide (CO) has demonstrated therapeutic benefits in reactive oxygen species (ROS)-rich environments, such as inflammation and cancer. However, the targeted delivery of CO remains challenging, limiting its clinical application and necessitating the development of improved CO-prodrugs. Herein, we report a radical-activated, metal-free, CO-prodrug designed to address delivery limitations and avoid metal-associated toxicity. This tertiary aldehyde-based prodrug is stable under physiological conditions and, upon activation by a radical trigger, releases CO, 2-ethyl-1-butene, and a nontoxic thiol carrier. The stability of the CO-prodrug building block allows for its incorporation into synthetic peptides via solid-phase peptide synthesis and site-specific bioconjugation to therapeutic antibodies. We synthesized trastuzumab conjugates with a CO-prodrug-to-antibody ratio of 23 and demonstrated efficient, tumor-specific CO release in HER2-high-expressing cells. These findings open new avenues for investigating the therapeutic effects of CO. We anticipate that our metal-free CO-prodrug strategy will be broadly applicable to a wide range of synthetic peptide- and protein-based therapeutics.