L. Rehman, W. Song, A. Rehman, K. Singh, S. G. Rawat, F. Darbaniyan, C. C. Le, F. M. Aletti, J. Weng, J. Liu, X. Cheng, Y. Tang, S. Patchva, M. D. Richard, F. Chu, J. Cao, C. R. Flowers, E. J. Shpall, M. R. Tanner, J. Fahrmann, E. Elinav, C. K. Stein-Thoeringer, M. D. Jain, R. R. Jenq, A. Jain, S. S. Neelapu, Y. Zheng, N. Y. Saini
Anaerobe-depleting antibiotic exposure is associated with inferior progression-free survival after CD19 CAR T-cell therapy in large B-cell lymphoma, yet the cellular mechanisms linking gut dysbiosis to the CAR T-cell product and whether this imprint is reversible have remained undefined. In two independent CAR-T candidate cohorts, low stool valerate at the time of CAR-T eligibility identified a multi-metabolite-deficient dysbiotic gut microbiome state marked by depletion of fiber-fermenting commensals and loss of carbohydrate-fermentation, SCFA-biosynthesis, and amino-acid metabolism pathways. Reanalysis of single-cell RNA sequencing from 42 lymphoma patients stratified by piperacillin-tazobactam/imipenem/meropenem (PIM) exposure revealed that PIM-exposed CAR T-cell products were CD4-skewed, with significantly elevated AP-1/immediate-early gene (IEG) and cellular activation signatures that together predicted inferior progression-free survival. Ex vivo conditioning of CAR T-cells with valerate produced a chromatin and transcription factor program distinct from butyrate or propionate, characterized by KLF/SP/EGR family engagement, KLF4 promoter opening, and broad induction of AP-1/IEG and MHC class II transcripts, whereas butyrate drove broader chromatin remodeling with TBX21/EOMES/NF-{kappa}B gains and KLF2 promoter closure, and propionate induced an NFY-centered program with preferential commitment to low-mitochondrial-content states. Untargeted metabolomics confirmed valerate uptake and mitochondrial {beta}-oxidation in CAR T-cells, while dietary sodium valerate supplementation in meropenem-treated mice bearing A20 lymphoma significantly reduced tumor burden and extended survival compared with CAR T-cells alone. These findings identify stool valerate as a bedside-deployable biomarker of dysbiosis-imprinted CAR T-cell dysfunction and support ex vivo or dietary valerate supplementation as a clinically tractable strategy to improve CAR-T anti-tumor function in patients with disrupted gut microbiomes.