Tumor acidosis and adenosine (ADO) accumulation are key metabolic aberrations that drive T cell exhaustion, suppress cytotoxicity, and confer radioresistance, posing a major obstacle for solid tumor therapy. To address this, we designed pH-responsive layered double hydroxide nanosheets loaded with the CD73 inhibitor PSB-12379 (denoted as LDH@PSB) for concurrent acidosis neutralization and ADO blockade. The nanosheets rapidly degraded under mildly acidic conditions (pH ∼6.5), elevating extracellular pH and releasing PSB-12379 to inhibit radiation-induced CD73 upregulation and ADO production. This dual intervention restored T cell function by increasing cytotoxic mediator expression (e.g., IFN-γ, granzyme B) and reducing exhaustion markers (e.g., PD-1, TIGIT). Meanwhile, Mn2⁺ ions released from LDH@PSB activated the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway, synergizing with radiotherapy-induced immunogenic cell death to boost antitumor immunity. In murine B16F10 melanoma and CT26 colon carcinoma models, LDH@PSB with radiotherapy markedly inhibited tumor growth, prolonged survival, and increased tumor-infiltrating CD8⁺ T cells with enhanced cytotoxicity. Combination with anti-PD-1 therapy further induced systemic immunity to eradicate distant tumors. This strategy simultaneously alleviates tumor acidosis, disrupts ADO-mediated immunosuppression, and activates cGAS-STING signaling, offering a potent approach to enhance radioimmunotherapy.
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