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Objectives: Recent studies have identified expression of the non‐functional P2X7 (nfP2X7) receptor on various malignant cells including ovarian cancer, but not on normal cells, which makes it a promising tumour‐associated antigen candidate for chimeric antigen receptor (CAR)‐T‐cell immunotherapies. In this study, we assessed the cytotoxic effects of nfP2X7‐CAR‐T cells on ovarian cancer using in vitro and in vivo models. Methods: We evaluated the effects of nfP2X7‐CAR‐T cells on ovarian cancer cell lines (SKOV‐3, OVCAR3, OVCAR5), normal peritoneal cells (LP‐9) and primary serous ovarian cancer cells derived from patient ascites in vitro using monolayer and 3D spheroid assays. We also evaluated the effects of nfP2X7‐CAR‐T cells on patient‐derived tissue explants, which recapitulate an intact tumour microenvironment. In addition, we investigated the effect of nfP2X7‐CAR‐T cells in vivo using the OVCAR‐3 xenograft model in NOD‐scid IL2Rγnull (NSG) mice. Results: Our study found that nfP2X7‐CAR‐T cells were cytotoxic and significantly inhibited survival of OVCAR3, OVCAR5 and primary serous ovarian cancer cells compared with un‐transduced CD3+ T cells in vitro. However, no significant effects of nfP2X7‐CAR‐T cells were observed for SKOV3 or normal peritoneal cells (LP‐9) cells with low P2X7 receptor expression. Treatment with nfP2X7‐CAR‐T cells increased apoptosis compared with un‐transduced T cells in patient‐derived explants and correlated with CD3 positivity. Treatment with nfP2X7‐CAR‐T cells significantly reduced OVCAR3 tumour burden in mice compared with un‐transduced CD3 cells for 7–8 weeks. Conclusion: This study demonstrates that nfP2X7‐CAR‐T cells have great potential to be developed as a novel immunotherapy for ovarian cancer. [ABSTRACT FROM AUTHOR]