ROS-responsive self-immolative polymeric prodrug for nitrosative stress-mediated cancer therapy

Nitric oxide (NO) has emerged as a promising redox-regulating agent for cancer therapy. However, the clinical applications of conventional NO donors have been limited by their short biological half-lives and poor tumor-specific generation of NO. To address these issues, we have developed reactive oxygen species (ROS)-responsive, self-immolative polymeric prodrug (G-g-PSIP) which undergoes intracellular head-to-tail depolymerization within the tumor microenvironment, resulting in the release of a quinone methide derivative as a glutathione scavenger and a guanidine derivative as an NO donor. Under in vitro conditions, G-g-PSIP exhibited dose-dependent cytotoxicity against CT26 cancer cell line, while exhibiting minimal toxicity toward L929 normal cell line. This tumor-specific cytotoxicity of G-g-PSIP was ascribed to the intracellular depletion of glutathione (GSH) and the generation of NO by responding to elevated levels of ROS. Notably, the cascade-amplified depolymerization of G-g-PSIP led to increased intracellular levels of peroxynitrite, formed via the reaction of NO with superoxide. Furthermore, the synergistic effects of GSH depletion and peroxynitrite accumulation intensified nitrosative stress, thereby inducing ferroptosis-like cell death. As a result, systemic administration of G-g-PSIP in CT26 tumor-bearing mice demonstrated remarkable antitumor efficacy, highlighting its potential as a redox-responsive therapeutic platform for targeted cancer treatment.