Hypoxia‐Responsive Nanosystem for Synergistic Cancer Therapy: Enhancing Ferroptosis via a Novel GPX4 Inhibitor and Facilitating Precise Photodynamic Therapy

ABSTRACT The glutathione peroxidase 4 (GPX4) inhibitor RSL3 exhibits limited selectivity, unfavorable pharmacokinetics, and dose‐dependent toxicity, which restrict its therapeutic application. Meanwhile, the efficacy of photodynamic therapy (PDT) is compromised by tumor hypoxia and off‐target phototoxicity. In this study, we synthesized a novel GPX4 inhibitor, RSL3‐ClAc, via a Pictet‐Spengler reaction followed by chloroacetylation. RSL3‐ClAc shows enhanced GPX4 binding affinity and inhibitory activity, resulting in improved ferroptosis induction in tumor cells. RSL3‐ClAc was further co‐assembled with an NTR‐activatable photosensitizer, C2‐NO 2 , through nanoprecipitation to construct a carrier‐free, hypoxia‐responsive nanoplatform (RC/C2‐NO 2 @PEG). The nanoparticles exhibit good colloidal stability and preferential tumor accumulation through the enhanced permeability and retention (EPR) effect. Under hypoxic conditions, nitroreductase‐mediated activation of C2‐NO 2 produces near‐infrared fluorescence for tumor imaging and generates singlet oxygen ( 1 O 2 ) to enable localized PDT. Importantly, PDT‐induced depletion of intracellular NAD(P)H suppresses the FSP1‐CoQ 10 antioxidant pathway, thereby overcoming ferroptosis resistance. By integrating hypoxia‐responsive imaging, GPX4 inhibition, and ferroptosis‐sensitized PDT, this nanoplatform achieves potent antitumor efficacy with favorable biosafety. Overall, this work provides a rational and translatable strategy for precision cancer therapy.