This study investigates the clinical relevance of the gut microbiome at taxonomic and metabolic levels in anti-CD19 chimeric antigen receptor (CAR) T-cell therapy, both in patients and in a preclinical syngeneic tumor model. Patients with B-cell lymphoma treated with CD19 CAR T cells exhibited profound intestinal dysbiosis, exacerbated after CAR T-cell infusion. This dysbiosis was characterized by low bacterial richness, low soluble MAdCAM-1, and loss of Akkermansia species, associated with resistance to therapy. Mechanistically, oral Akkermansia massiliensis supplementation increased CAR T-cell infiltration into the bone marrow, inverted the CD4/CD8 CAR T-cell ratio, favored Tc1 CD8+ T-cell polarization, and promoted the release of tryptophan-derived indole metabolites, leading to better tumor control. The clinical benefit of Akkermansia spp. supplementation was abolished when CAR T cells were genetically deficient in the indole receptor, aryl hydrocarbon receptor (AhR). AhR-agonistic indoles alone failed to replicate the bacterium’s anticancer effects. These findings suggest that Akkermansia supplementation could improve CAR T-cell potency in patients with intestinal Akkermansia deficiency. Significance: B-cell lymphoma patients treated with CAR T cells harbor major gut microbiota perturbations and related metabolism that restrain CAR T-cell therapy. Reprogramming the gut microbiota ecosystem by oral A. massiliensis supplementation induces CAR T-cell niching and Tc1 differentiation in the bone marrow, promoting tumor control in an AhR-dependent manner.

Hypomethylating agent (HMA) plus venetoclax (VEN) regimens are standard of care in patients with acute myeloid leukemia (AML) ineligible for intensive chemotherapy. While the VEN label recommends continuous 28-day cycles, shortened VEN durations may induce similar response rates and improve tolerability. It is unknown how a VEN exposure reduced to 7 days during cycles compares to standard HMA + VEN. We retrospectively compared newly diagnosed AML patients treated with azacitidine (AZA) x 7 days plus VEN x 7 days (“7 + 7” regimen) from the first cycle (n = 82) vs patients treated with standard dose HMA + VEN (std-HMA/VEN) (n = 166). Composite complete remission rate was similar between cohorts (72% vs 72%; p = 0.95) and a median number of cycles to best response was 2 with “7 + 7” vs 1 with std-HMA/VEN (p = 0.03). Concerning toxicity, platelet transfusion rates during cycle 1 as well as early mortality at 8-weeks (6% vs 16%; p = 0.03) were lower in “7 + 7” cohort. Finally, the median OS was 11.2 months (2-year 28%) with “7 + 7” vs 10.3 months (2-year 34%) with “std-HMA/VEN” (p = 0.75). In summary, acknowledging limitations of a retrospective comparison, a shortened course of VEN used for 7 days every 28 days resulted in similar response rates and survival when compared to standard VEN exposure.