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

Abstract

T cells modified to co-express cytokine or other factors with chimeric antigen receptor (CAR) can induce substantial and persistent increases in antitumor capacity in vivo . 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. In vitro or in vivo, 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.

Chimeric antigen receptor T cells engineered to secrete CD40 agonist antibodies enhance antitumor efficacy

“…1 f), which was potentially attributed to the blocking effect of the anti-CD40 antibody in the culture medium. This result was consistent with those of recent studies showing that CAR-T secreting antibodies could bind to the target antigen expressed in T cells [ 21 , 28 ].…”

“…To further ensure that the antibodies secreted by CAR-T cells induce fewer systemic toxicities, this potential safety concern is worthy of investigation. Encouragingly, we recently successfully designed a T cell-specific and highly active artificial chimeric promoter to control the secretion of anti-PD-1 antibodies at the tumor site [ 28 ]. Studies using this chimeric promoter to control the secretion of anti-CD40 antibodies from CAR-T cells in a syngeneic immunocompetent mouse model are currently underway to explore the potential applicability of anti-CD40 antibody-secreting CAR-T cells and thus further improve the antitumor activity of this therapy for solid tumors.…”

Emerging Novel Combined CAR-T Cell Therapies

“…These investigators co-transfected a promoter construct upstream of the anti-PD-1 antibody gene and the CAR construct into T cells. These anti-PD-1 CAR-T cells had lower PD-1 expression, higher levels of T cell activation, and better anti-tumor activity, specifically against MSLNand PD-L1-positive tumor cells both in vitro and in vivo [40].…”

CAR-T cell potency: from structural elements to vector backbone components

“…Successful gene therapy with CAR-expressing T cells relies on the ability of T cells to maintain adequate receptor expression for a long time. The EF1a promoter is a strong promoter frequently used for CAR expression, as it often drives a strong and stable expression regardless of tissue specificity or the T cell activation state [ 169 , 198 ]. Milone et al evaluated several promoters, including EF1α, CMV, PGK, and UbiC, to identify the one that can drive the highest stable expression of a transgene in primary CD4 and CD8 T cells [ 169 ].…”