Disinhibition of Early CAR-T cell activation via CD5 Knock Out Enhances the Anti-Tumor Activity of Adoptive T Cell Therapies against Cancer

The majority of patients treated with currently approved adoptive T-cell therapies (ACT) and, specifically, chimeric antigen receptor (CAR) T cells will eventually fail treatment. Furthermore, ACT has not been successful against solid cancers and several hematological malignancies, including T-cell lymphomas which have extremely poor prognosis. One of the main barriers to the effective activity of adoptively transferred T cells is their inhibition when they reach the tumor bed. In this study, we discover that CD5 inhibits CAR T activation and that the knockout (KO) of CD5 using CRISPR-Cas9 enhances the anti-tumor effect of CAR and TCR T cells in multiple hematological and solid cancer models. As a consequence, CD5 KO T cells display increased in vivo expansion and persistence. Despite this increased activity, no clear increased toxicity was observed in preclinical models. These findings support the development of CD5 KO adoptive T-cell therapies in early-phase clinical trials for relapsed and refractory cancer. Overall design: Membrane protein CD5 was CRISPR Cas9 knocked out of primary human T cells to compare to an electroporated Mock control.