Novel cyclometalated iridium(III) complexes with a π-expansive benzothiophene ligand for enhanced photodynamic therapy against human osteosarcoma by disrupting Iron homeostasis.

Osteosarcoma, a prevalent primary bone malignancy in adolescents, remains a therapeutic challenge owing to its high recurrence rate and resistance to conventional treatments. Integrating photodynamic therapy (PDT) with ferroptosis induction offers a promising anticancer strategy. However, the precise control of cancer-specific inducers remains elusive. In this study, we developed a novel Iridium (III) complex (Ir-X) incorporating a π-expansive 1-(benzo[b]thiophen-2-yl) isoquinoline ligand, which demonstrated exceptional photophysical properties, including a high singlet oxygen quantum yield, prolonged triplet excited state lifetime, and potent nanomolar cytotoxicity against osteosarcoma cells. These properties facilitate efficient generation of reactive oxygen species (ROS) under 525 nm laser irradiation. In vitro studies demonstrated that Ir-X-mediated PDT significantly reduced osteosarcoma cell viability by inducing ferroptosis, evidenced by increased intracellular iron accumulation, elevated lipid peroxidation, glutathione depletion, and mitochondrial dysfunction. Furthermore, the therapeutic potential of Ir-X was substantiated in xenograft models, where it significantly suppressed tumor growth without causing systemic toxicity in the major organs. Mechanistically, RNA sequencing and bioinformatic analyses revealed that Ir-X orchestrates a dual mechanism by upregulating NCOA4 expression and activating autophagy pathways, leading to enhanced ferritin degradation, iron release, and ultimately triggers ferroptosis. Genetic manipulation studies provided compelling evidence for the critical role of NCOA4, as its ablation substantially diminished the antitumor efficacy of Ir-X, whereas its overexpression amplified the therapeutic effects. These findings establish Ir-X as a promising therapeutic agent that synergistically induces ferroptosis through NCOA4-mediated ferritinophagy, establishing a fundamental basis for advancing iridium-based photosensitizers and pioneering therapeutic strategies against ferroptosis-vulnerable cancers.