In order to minimize systemic toxicity and induce the accumulation of high cytokine concentrations at the tumour site, CAR‐T cells were modified to produce IL‐12, IL‐18, IL‐7, IL‐15 and IL‐21 cytokines, and activation and persistence of CAR‐T cells were, therefore, enhanced in vivo.78 The gene discussed is IL21; the disease is neoplasm.