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3451 Mitochondrial Isocitrate Dehydrogenase Inhibition Enhances CAR T-Cell Function By Restraining Antioxidant Metabolism and Histone Acetylation

Program: Oral and Poster Abstracts
Session: 703. Cellular Immunotherapies: Basic and Translational: Poster II
Hematology Disease Topics & Pathways:
Research, Translational Research
Sunday, December 10, 2023, 6:00 PM-8:00 PM

Xiaohui Si, PhD1*, Mi Shao2*, Xinyi Teng2*, Yue Huang3*, Tianning Gu4*, Gang Xiao, PhD5* and He Huang6*

1The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, AL, China
2Bone Marrow Transplantation Center, The First Affiliated Hospital, School of Med, Hangzhou, CHN
3The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
4Bone Marrow Transplantation Center, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
5School of Medicine, Zhejiang University, Hangzhou, China
6The First Affiliated Hospital, College of Medicine, Zhejiang University, Hematology, Hangzhou, AL, China

Introduction: The efficacy of chimeric antigen receptor (CAR) T-cell therapy is hampered by relapse in hematologic malignancies and by hyporesponsiveness in solid tumors. Mitochondria are vital for the regulation of memory T-cell formation or exhaustion. A mitochondria-related compound screening was performed and we found that the FDA-approved isocitrate dehydrogenase 2 (IDH2) inhibitor enasidenib enhances long-lived memory CAR T-cell formation, and improves tumor clearance in vivo. IDH2 as the key component of the tricarboxylic acid (TCA) cycle, we hypothesized that IDH2 inhibition might promote CAR T-cell persistence by reprogramming the metabolism. The study aims to systematically evaluate the role and the mechanism of IDH2 inhibition on CAR T cells, and explore the application of enasidenib in CAR T-cell therapy.

Methods and Results: To identify mitochondrial components that affect the long-term efficacy of CAR T-cells, we performed an in vitro screening using a mitochondria-related compound library based on the enrichment of the CD62L+ CAR T-cell subset, which mainly contains T memory stem cells (TSCM) and central memory T cells (TCM). Among several candidate compounds that promoted memory CAR T-cell formation, enasidenib (ENA), an inhibitor of both wild-type and mutant IDH2 enzymes, was the most effective one. The proportion of CD62L has increased by over 20%. To determine the effect of ENA on exhaustion induced by tonic CAR signaling and tumor antigen stimulation, we measured the expression of inhibitory receptors PD-1, TIM-3, and LAG-3 and the level of apoptosis in freshly expanded CAR T cells and B-ALL encountered CAR T cells. CAR T cells treated with ENA exhibited reduced surface levels of those inhibitory receptors. We measured the production of granzyme B and IFNγ, and tumor rechallenge assay in CAR T cells after ENA treatment to assess the effector function, ENA treated CAR T cells exerted enhanced and sustained cytotoxicity in a tumor rechallenge assay at an extreme E:T ratio of 1:10. These results were observed not only in CD19-41BBζ CAR T cells, but also in CD19-28ζ and GD2-28ζ CAR T cells. CAR T cells expanded in the presence of ENA significantly prolonged survival of recipients after Nalm-6 infusion (p < 0.0001), extended in vivo ENA treatment further enhanced CAR T-cell expansion and tumor suppression. The median survival was extended from 45 to 67.5 days. Consistent with the effect of ENA treatment, IDH2 knockdown increased the proportions of the Tscm/Tn and Tcm subsets, and alleviated CAR T-cell exhaustion. IDH2-knockdown CAR T cells had sustained cytotoxicity and higher CD62L expression after rounds of killing B-ALL cells in vitro.

To systematically explore the effects of IDH2 inhibition on the metabolism of CAR T cells, relative metabolite amounts was measured using mass spectrometry (MS). IDH2-inhibited CAR T cells exhibited a substantial reduction of metabolites in the TCA cycle, including succinate, fumarate, and malate, and in the glycolysis pathway, including lactate, phosphoenolpyruvate. Mechanistically, IDH2 inhibition reprogram central carbon metabolism of CAR T cells by redirects glucose carbon utilization from glycolysis to the pentose phosphate pathway. In addition, IDH2 limits cytosolic acetyl-CoA level to prevent histone acetylation that promotes memory cell formation.

Significance: Our study indicates that metabolic intervention in CAR T cells with the FDA-approved IDH2 inhibitor enasidenib can advance current treatment, with better tumor eradication and CAR T-cell persistence.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH