We found that oxamate altered the phenotypes of tumor-infiltrating CAR-T cells in GBM mouse model, including increased expressions of immunostimulating IFN-γ, cytotoxic perforin, and granzyme B. Furthermore, we confirmed that oxamate downregulated the levels of ectonucleotidases CD39 and CD73 for regulating immune microenvironment and CCR8 expressed in tumor-infiltrating Treg cells in CAR-T therapy. The gene discussed is PRF1; the disease is glioblastoma.