{
  "id": 5345363,
  "title": "Microbial valerate is associated with CAR T dysbiosis and its supplementation enhances CAR T function in B-cell lymphoma",
  "url": "https://urgent.news/2026/09/03/microbial-valerate-is-associated-with-car-t-dysbiosis-and-its",
  "topic": "science",
  "section": "Science",
  "published": "2026-09-03T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.09.01.748711v1?rss=1"
  },
  "original_language": "en",
  "account": "Microbial valerate has been linked to a condition known as CAR T dysbiosis, which negatively impacts the effectiveness of CAR T-cell therapy in treating B-cell lymphoma. This discovery stems from two separate studies conducted on CAR-T candidate cohorts. The research found that lower levels of valerate in stool samples were associated with a dysbiotic gut microbiome, characterized by a decline in fiber-fermenting commensals and an absence of carbohydrate-fermentation, SCFA-biosynthesis, and amino-acid metabolism pathways.\n\nFurther analysis of single-cell RNA sequencing data from 42 lymphoma patients, taking into account their exposure to piperacillin-tazobactam/imipenem/meropenem (PIM), revealed that CAR T-cell products exposed to PIM exhibited a CD4-skewed profile. This CD4-skewed CAR T-cell product showed significantly elevated AP-1/immediate-early gene (IEG) and cellular activation signatures, which were directly linked to a poorer progression-free survival rate.\n\nEx vivo conditioning of CAR T-cells with valerate led to a unique chromatin and transcription factor program, distinct from that induced by butyrate or propionate. This valerate-driven program was characterized by the engagement of the KLF/SP/EGR family, the opening of the KLF4 promoter, and the broad induction of AP-1/IEG and MHC class II transcripts. Conversely, butyrate induced a broader chromatin remodeling, with gains in TBX21/EOMES/NF-{kappa}B and a closure of the KLF2 promoter. Propionate, on the other hand, triggered an NFY-centered program, favoring low-mitochondrial-content states.\n\nUntargeted metabolomics confirmed the uptake and mitochondrial {beta}-oxidation of valerate in CAR T-cells. Dietary sodium valerate supplementation in mice bearing A20 lymphoma, after receiving meropenem treatment, significantly reduced tumor burden and extended survival compared to CAR T-cells alone. These findings suggest that stool valerate can serve as a bedside-deployable biomarker for dysbiosis-imprinted CAR T-cell dysfunction, and that ex vivo or dietary valerate supplementation can be a clinically feasible approach to enhance CAR-T anti-tumor function in patients with disrupted gut microbiomes.",
  "summary": "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…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}