Tinkering under the Hood: Metabolic Optimisation of CAR-T Cell Therapy

Abstract

Chimeric antigen receptor (CAR)-T cells are one of the most exciting areas of immunotherapy to date. Clinically available CAR-T cells are used to treat advanced haematological B-cell malignancies with complete remission achieved at around 30–40%. Unfortunately, CAR-T cell success rates are even less impressive when considering a solid tumour. Reasons for this include the paucity of tumour specific targets and greater degree of co-expression on normal tissues. However, there is accumulating evidence that considerable competition for nutrients such as carbohydrates and amino acids within the tumour microenvironment (TME) coupled with immunosuppression result in mitochondrial dysfunction, exhaustion, and subsequent CAR-T cell depletion. In this review, we will examine research avenues being pursued to dissect the various mechanisms contributing to the immunosuppressive TME and outline in vitro strategies currently under investigation that focus on boosting the metabolic program of CAR-T cells as a mechanism to overcome the immunosuppressive TME. Various in vitro and in vivo techniques boost oxidative phosphorylation and mitochondrial fitness in CAR-T cells, resulting in an enhanced central memory T cell compartment and increased anti-tumoural immunity. These include intracellular metabolic enhancers and extracellular in vitro culture optimisation pre-infusion. It is likely that the next generation of CAR-T products will incorporate these elements of metabolic manipulation in CAR-T cell design and manufacture. Given the importance of immunometabolism and T cell function, it is critical that we identify ways to metabolically armour CAR-T cells to overcome the hostile TME and increase clinical efficacy.

CAR-T Cell Performance: How to Improve Their Persistence?

“…The metabolic requirements of T cells depend on their degree of activation, differentiation, and functionality. For example, cells in a quiescent state, such as T N cells, rely on a catabolic metabolism of low-energy consumption, which uses the oxidation of fatty acids, amino acids, and glucose as energy sources, mainly through oxidative phosphorylation pathways ( 161 ). However, upon cell activation, the metabolism becomes highly glycolytic to generate the intermediate biomolecules required for cell proliferation.…”

“…Specific metabolic and epigenetic changes must occur in cells in order to proliferate and differentiate. As can be seen, metabolism is intimately linked to cell activation, proliferation, migration, and function, and therefore to the very fate of T cells ( 85 , 161 , 162 ).…”

“…In this sense, it is known that the CD28 co-stimulating domain increases the glycolytic metabolism and differentiation of T cells toward the T EM cell subpopulations. In contrast, the 4-1BB co-stimulating domain increases oxidative metabolism and mitochondrial biogenesis, promoting differentiation to the T CM phenotype, characterized by improved cell proliferation and persistence ( 88 , 161 ). Hence, it can be concluded that promoting a low metabolic activity over the CAR-T cell manufacturing process could favor the production of T cells with a less differentiated phenotype, which would have greater longevity and antitumor potential.…”

BOXR1030, an anti-GPC3 CAR with exogenous GOT2 expression, shows enhanced T cell metabolism and improved anti-cell line derived tumor xenograft activity

“…Nutrient starvation and stress encountered in the hostile TME can impact metabolism in tumor infiltrating T cells including CAR+ T cells and indeed, these T cells have been shown to be impaired metabolically (mitochondrial mass, glycolysis) in patients [ 12 – 14 ]. Changes in T cell metabolism including in CAR T cells have been reported to impact T cell exhaustion and persistence [ 15 – 17 ].…”

Influence of Culture Conditions on Ex Vivo Expansion of T Lymphocytes and Their Function for Therapy: Current Insights and Open Questions

“…Fewer data exist on the changes in intracellular metabolism during the initial expansion phase. Further strategies to improve CAR T cell function, differentiation, and/or persistence in culture have been recently reviewed by Jenkins et al (2021) and include, among others, LDH inhibition, and inhibition of cholesterol esterification by the enzyme cholesterol acyltransferase 1 (ACAT1) utilizing the repurposed drug avasimibe (Yang et al, 2016). This may result in an increased number of T memory cells, arginine supplementation or expression of arginine resynthesizing enzymes, and glucose restriction, for example, galactose addition can increase enhanced effector capabilities including IFNg and granzyme B production (Yang et al, 2016).…”