Safety and Efficacy of an Immune Cell-Specific Chimeric Promoter in Regulating Anti-PD-1 Antibody Expression in CAR T Cells.

T cells modified to co-express cytokine or other factors with chimeric antigen receptor (CAR) can induce substantial and persistent increases in antitumor capacity . However, the uncontrolled expression of cytokines or factors can lead to the overactivation of immune cells, causing severe adverse events such as cytokine release syndrome (CRS) and neurotoxicity by CAR T cells with excessive growth potential. Conventional promoters are unregulated, and their expression is unlimited in T cells. In this study, by connecting the cytomegalovirus (CMV) enhancer, core interferon gamma (IFN-γ) promoter, and a T-lymphotropic virus long terminal repeat sequence (TLTR), we constructed and screened the chimeric promoter CIFT, which was highly expressed in some cell lines secreting IFN-γ and silenced in others. We placed this promoter upstream of the anti-programmed cell death protein 1 (anti-PD-1) antibody gene, and this construct was co-transfected with the CAR construct into T cells. or CAR T cells showed increased secretion of anti-PD-1 antibody under control of the chimeric promoter CIFT. pS-CIFT-αPD-1/CAR T also had similar or lower PD-1 expression, higher levels of T cell activation, more release of IFN-γ, and better antitumor activity specifically against mesothelin-positive and PD-1 ligand 1 (PD-L1)-positive cell lines. The chimeric promoter may be a promising strategy to manipulate the content of immune checkpoint inhibitors or other proteins in future therapeutic approaches for cancer treatment.