Oridonin-induced ferroptosis potentiates cancer immunotherapy

We identify oridonin induces ferroptosis through high throughput screening. • We found oridonin covalently binds to cysteine to block glutathione synthesis via its α, β-unsaturated carbonyl group. • We developed a tumor-targeting and hypoxia-responsive nanoparticle platform to deliver oridonin to achieve specific induction of tumor cells ferroptosis in vivo. • We found oridonin inhibits tumor growth and enhances antitumor immunity in various animal tumor models of colorectal cancer transplants and metastases. Ferroptosis, an iron-dependent form of regulated cell death characterized by the accumulation of lipid peroxidation and iron, has emerged as a compelling vulnerability for cancer therapy. However, the scarcity of potent ferroptosis inducers with favorable pharmacological properties and their limited ability to reshape the immunosuppressive tumor microenvironment (TME) remain significant challenges. Here, we identify Oridonin (Ori), the major active component of the traditional Chinese medicine Rabdosia rubescens , as a novel and potent ferroptosis inducer through high-throughput screening (HTS). Mechanistically, we reveal that Ori covalently binds to cysteine to impair glutathione (GSH) biosynthesis, thereby triggering lipid peroxidation and ferroptosis. Notably, the α, β-unsaturated carbonyl group within Ori is identified as the critical pharmacophore for the ferroptosis-inducing effect. Considering that the therapeutic efficacy of Ori in vivo is greatly limited by its poor water solubility and tumor targeting ability, we engineer a tumor-targeting and hypoxia-responsive nanoparticle platform to deliver Ori (Ori-NP) to enable precise intratumoral release. Our results demonstrate that Ori-NP effectively suppresses tumor progression by inducing tumor cells ferroptosis mediated by ACSL4. Beyond direct cytotoxicity, Ori-NP serves as a potent immunomodulator that remodels the immunosuppressive TME by promoting dendritic cell maturation and enhancing CD8 + T cell infiltration. Consequently, the combination of Ori-NP with anti-PD-1 antibodies yields a potent synergistic antitumor effect. Overall, our research provides a powerful therapeutic strategy to harness ferroptosis for synergistic cancer immunotherapy.