6-phosphogluconate dehydrogenase blockade in T Cells mitigates acute graft-versus-host disease while preserving graft-versus-tumor activity

T cells undergo significant metabolic reprogramming after allogeneic hematopoietic cell transplantation (allo-HCT). However, the influence of metabolic pathway reprogramming on altering the severity and mortality of acute graft-versus-host disease (aGvHD), a critical allo-HCT complication, remains unclear. Through single-cell RNA sequencing (scRNA-seq) of allogeneic T cells isolated from the spleen of GvHD mice, we uncovered that 6-phosphogluconate dehydrogenase (6PGD), the second major rate-limiting enzyme in the oxidative pentose phosphate pathway, is upregulated and activated during allo-HCT. Clinical and histopathological analyses revealed that 6PGD deficiency in donor T cells significantly mitigates aGvHD severity and mortality in murine models of acute GvHD. An in vitro assay using murine and human T cells and an in vivo murine GvHD model showed that in the absence of an intact 6PGD pathway, donor T cell proliferation was reduced. Metabolic analyses confirmed that blocking 6PGD activity shifted T cell metabolism from glycolysis to oxidative phosphorylation (OXPHOS), as evidenced by isotope-labeled metabolic tracing and Seahorse assays. Pharmacological inhibition of 6PGD with 6-aminonicotinamide (6AN) demonstrated similar efficacy as the infusion of donor 6PGD deficient T cells in reducing aGvHD severity in allogeneic aGvHD and humanized xenogeneic GvHD models. Importantly, 6PGD inhibition preserved the graft-versus-tumor (GvT) effect by promoting the generation of a small subset of effector T cells with potent anti-tumor activity. From these findings we propose 6PGD as a promising therapeutic target for alleviating aGVHD the beneficial GvT effects. Splenic donor T cells (CD45+, H2kb+, H2kd-, TCRβ+) were harvested, sorted on day +7 and day +14 and examined for T cell clusters using single cell RNA sequencing (scRNA seq).