The adoptive transfer of T cells that have been genetically modified to express a CD19-specific chimeric antigen receptor (CAR) is effective for treating human B cell malignancies. However, the persistence of functional CD19 CAR T cells causes sustained depletion of endogenous CD19⁺ B cells and hypogammaglobulinemia. Thus, there is a need for a mechanism to ablate transferred T cells after tumor eradication is complete to allow recovery of normal B cells. Previously, we developed a truncated version of the epidermal growth factor receptor (EGFRt) that is coexpressed with the CAR on the T cell surface. Here, we show that targeting EGFRt with the IgG1 monoclonal antibody cetuximab eliminates CD19 CAR T cells both early and late after adoptive transfer in mice, resulting in complete and permanent recovery of normal functional B cells, without tumor relapse. EGFRt can be incorporated into many clinical applications to regulate the survival of gene-engineered cells. These results support the concept that EGFRt represents a promising approach to improve safety of cell-based therapies.

Cancer-specific TCF1⁺ stem-like CD8⁺ T cells can drive protective anticancer immunity through expansion and effector cell differentiation^1–4; however, this response is dysfunctional in tumours. Current cancer immunotherapies^2,5–9 can promote anticancer responses through TCF1⁺ stem-like CD8⁺ T cells in some but not all patients. This variation points towards currently ill-defined mechanisms that limit TCF1⁺CD8⁺ T cell-mediated anticancer immunity. Here we demonstrate that tumour-derived prostaglandin E2 (PGE₂) restricts the proliferative expansion and effector differentiation of TCF1⁺CD8⁺ T cells within tumours, which promotes cancer immune escape. PGE₂ does not affect the priming of TCF1⁺CD8⁺ T cells in draining lymph nodes. PGE₂ acts through EP₂ and EP₄ (EP₂/EP₄) receptor signalling in CD8⁺ T cells to limit the intratumoural generation of early and late effector T cell populations that originate from TCF1⁺ tumour-infiltrating CD8⁺ T lymphocytes (TILs). Ablation of EP₂/EP₄ signalling in cancer-specific CD8⁺ T cells rescues their expansion and effector differentiation within tumours and leads to tumour elimination in multiple mouse cancer models. Mechanistically, suppression of the interleukin-2 (IL-2) signalling pathway underlies the PGE₂-mediated inhibition of TCF1⁺ TIL responses. Altogether, we uncover a key mechanism that restricts the IL-2 responsiveness of TCF1⁺ TILs and prevents anticancer T cell responses that originate from these cells. This study identifies the PGE₂–EP₂/EP₄ axis as a molecular target to restore IL-2 responsiveness in anticancer TILs to achieve cancer immune control.