Metabolic engineering against the arginine microenvironment enhances CAR-T cell proliferation and therapeutic activity.

Haematological and solid cancers catabolise the semi-essential amino acid arginine to drive cell proliferation. However, the resulting low arginine microenvironment also impairs chimeric antigen receptor T cells (CAR-T) cell proliferation, limiting their efficacy in clinical trials against haematological and solid malignancies. T cells are susceptible to the low arginine microenvironment due to the low expression of the arginine re-synthesis enzymes argininosuccinate synthase (ASS) and ornithine transcarbamylase (OTC). We demonstrate T cells can be re-engineered to express functional ASS or OTC enzymes, in concert with different chimeric antigen receptors. Enzyme modifications increase CAR-T cell proliferation, with no loss of CAR cytotoxicity or increased exhaustion. In vivo, enzyme-modified CAR-T cells lead to enhanced clearance of leukaemia or solid tumour burden, providing the first metabolic modification to enhance CAR-T cell therapies.