Tumor-site directed A1R expression enhances CAR T cell function and improves efficacy against solid tumors

Abstract The efficacy of Chimeric Antigen Receptor (CAR) T cells against solid tumors is limited by immunosuppressive factors in the tumor microenvironment (TME) including adenosine, which suppresses CAR T cells through activation of the A2A receptor (A2AR). To overcome this, CAR T cells were engineered to express A1R, a receptor that signals inversely to A2AR. Using murine and human CAR T cells, constitutive A1R overexpression was demonstrated to significantly enhance CAR T cell effector function albeit at the expense of CAR T cell persistence. Through a novel CRISPR/Cas9 “knock-in” approach we demonstrated that CAR T cells engineered to express A1R in a tumor-localized manner, led to enhanced anti-tumor efficacy dependent on the transcription factor IRF8. This data provides a novel approach for enhancing CAR T cell efficacy in solid tumors and provides proof of principle for site-directed expression of factors that promote effector T cell differentiation.