Inosine promotes immune checkpoint blockade (ICB) therapy by affecting the adenosine A2A receptor on T cells in addition to the required costimulation, promoting the effect of anti-CTLA4 in reducing tumor size and increasing IFN-γ+CD8+ and IFN-γ+CD4+ T-cell infiltration in mouse models of Msh2LoxP/LoxPVillin-Cre tumors, MB49 bladder tumors, and heterotopic melanoma. Here, CTLA4 is linked to neoplasm.