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.

FDA-approved next-generation sequencing assays based on cell-free DNA offers new opportunities in a molecular-tumor-board context thanks to the noninvasiveness of liquid biopsy, the diversity of analyzed parameters and the short turnaround time. It gives the opportunity to study the heterogeneity of the tumor, to elucidate complex resistance mechanisms and to adapt treatment strategies. However, lowering the limit of detection and increasing the panels’ size raise new questions in terms of detection of incidental germline alterations, occult malignancies and clonal hematopoiesis of indeterminate potential mutations. In this review, after a technological discussion and description of the common problematics encountered, we establish recommendations in properly using these FDA-approved tests in a molecular-tumor-board context.

Next-generation sequencing (NGS) assays based on plasma cell-free DNA (cfDNA) are increasingly used for clinical trials inclusion. Their optimized limit of detection applied to a large number of genes leads to the identification of mutations not confirmed in tissue. It becomes essential to describe the characteristics and consequences of these liquid biopsy-only mutations. In the STING protocol (Gustave Roussy, NCT04932525), 542 patients with advanced solid cancer had cfDNA-based and tissue-based NGS analysis (performed by FoundationOne® Liquid CDx and FoundationOne CDx™, respectively). Mutations identified in the liquid biopsy but not in the paired tissue were considered as liquid biopsy-only mutations irrespective of their variant allelic frequency (VAF). Out of 542 patients, 281 (51.8%) harbored at least one liquid biopsy-only mutation. These patients were significantly older, and more heavily pretreated. Liquid biopsy-only mutations occurring in TP53, and in DDR genes (ATM, CHEK2, ATR, BRCA2, and BRCA1) accounted for 90.8% of all the mutations. The median VAF of these mutations was generally low (0.37% and 0.40% for TP53 and DDR genes respectively). The variant type repartition depended on the gene. Liquid biopsy-only mutations affected hotspot in TP53 codon 273, 125, 195, 176, 237 or 280 and ATM codon 2891 and 3008. In a subset of 37 patients, 75.0%, 53.5% and 83.3% of the liquid biopsy-only mutations occurring respectively in ATM, TP53, and CHEK2 were confirmed in the matching whole blood sample. Although liquid biopsy-only mutations makes the interpretation of liquid biopsy results more complex, they have distinct characteristics making them more easily identifiable.

Although chimeric antigen receptor (CAR) T cells have shown excellent results in treating hematological malignancies, they also cause side effects. Patients treated with CAR T cells experience persistent cytopenia or hematotox. Here, using a fully immunocompetent mouse model, we recapitulated hematotox and demonstrated that a lymphodepleting regimen alone was insufficient to induce hematotox and required CAR T cell injection. Analysis of bone marrow (BM) samples from patients experiencing hematotox revealed a correlation between BM CAR T cells and hematotox severity. CAR T cells exhibited an activated program, leading to intense inflammation. In addition, we observed a high rate of clonal hematopoiesis in our patient cohort and the emergence of distinct hematopoietic clones in the months after CAR T cell injection. Our study provides insights into the pathophysiology of hematotox and highlights the need for long-term follow-up studies to determine the relevance of this intense BM inflammation in clonal selection.

Chimeric antigen receptor (CAR) T-cell therapy is currently approved for the treatment of B-cell non-Hodgkin lymphomas and B-cell acute lymphoblastic leukemia. Prolonged hematological toxicity is a... Plain language summary Chimeric antigen receptor (CAR) T cell is a new type of immunotherapy that was recently validated for the treatment of some types of B-cell lymphoma and leukemia. One of the ...