Increasing evidence suggests that the gut microbiome may modulate the efficacy of cancer immunotherapy. In a B cell-lymphoma patient cohort from five centers in Germany and the United States (Germany, N=66; US, N=106, Total, N=172), we demonstrate that wide-spectrum antibiotics treatment (‘high-risk antibiotics’) prior to CD19-targeted chimeric antigen receptor (CAR)-T cell therapy is associated with adverse outcomes, but this effect is likely confounded by an increased pre-treatment tumor burden and systemic inflammation in high-risk antibiotics-pre-treated patients. To resolve this confounding effect and gain insights into antibiotics-masked microbiome signals impacting CAR-T efficacy, we focused on the high-risk antibiotics non-exposed patient population. Indeed, in these patients, significant correlations were uncovered between pre-CAR-T-infusion Bifidobacterium longum and microbiome-encoded peptidoglycan biosynthesis, and CAR-T treatment-associated 6-months survival or lymphoma progression. Furthermore, predictive pre-CAR-T treatment microbiome-based machine-learning algorithms trained on the high-risk antibiotics non-exposed German cohort and validated by the respective US cohort robustly segregated long-term responders from non-responders. Bacteroides, Ruminococcus, Eubacterium and Akkermansia were most important in determining CAR-T responsiveness, with Akkermansia also associating with pre-infusion peripheral T cell levels in these patients. Collectively, we uncover conserved microbiome features across clinical and geographical variations, which may enable cross-cohort microbiome-based predictions of outcomes in CAR-T cell immunotherapy.
