Lab‐in‐Cell: A Covalent Photosensitizer Reverses Hypoxia and Evokes Ferroptosis and Pyroptosis for Enhanced Anti‐Tumor Immunity

Abstract Photodynamic immunotherapy presents a non‐invasive strategy characterized by spatiotemporal control and minimal side effects to induce immunogenic cell death (ICD). This approach significantly enhances the release of tumor‐associated antigens and damage‐associated molecular patterns, thereby improving cancer immunotherapy outcomes. However, hypoxia and antioxidant defenses at tumor sites considerably diminish the efficacy of photodynamic immunotherapy. In this work, a covalent warhead, alkyneamide, is introduced into an AIE photosensitizer to develop a novel covalent photosensitizer, MBTP‐PA, which targets redox systems and facilitates ferroptosis‐ and pyroptosis‐mediated photodynamic immunotherapy by thiol‐yne click reactions. The covalent photosensitizer interacts with intracellular thiol compounds such as cysteine and glutathione, disrupting the intracellular antioxidant system and alleviating hypoxia. This results in enhanced photodynamic therapy (PDT) efficacy compared to the non‐covalent photosensitizer MBTP‐A. Furthermore, in conjunction with PDT, this reaction therapy can activate ICD through ferroptosis and pyroptosis, thereby enhancing anti‐tumor immunity. Notably, in vivo injection of MBTP‐PA nanoparticles at the tumor site led to the elimination of primary tumors, inhibiting distal tumors and exhibiting minimal side effects. Therefore, this work not only integrates the thiol‐yne click reactions into cellular systems, significantly enhancing the efficacy of photodynamic immunotherapy but also paves the way for developing novel photosensitizers.