Diet-driven microbial ecology underpins associations between cancer immunotherapy outcomes and the gut microbiome.

The gut microbiota shapes the response to immune checkpoint inhibitors (ICIs) in cancer, however dietary and geographic influences have not been well-studied in prospective trials. To address this, we prospectively profiled baseline gut (fecal) microbiota signatures and dietary patterns of 103 trial patients from Australia and the Netherlands treated with neoadjuvant ICIs for high risk resectable metastatic melanoma and performed an integrated analysis with data from 115 patients with melanoma treated with ICIs in the United States. We observed geographically distinct microbial signatures of response and immune-related adverse events (irAEs). Overall, response rates were higher in Ruminococcaceae-dominated microbiomes than in Bacteroidaceae-dominated microbiomes. Poor response was associated with lower fiber and omega 3 fatty acid consumption and elevated levels of C-reactive protein in the peripheral circulation at baseline. Together, these data provide insight into the relevance of native gut microbiota signatures, dietary intake and systemic inflammation in shaping the response to and toxicity from ICIs, prompting the need for further studies in this area.

Distinct Immune Cell Populations Define Response to Anti-PD-1 Monotherapy and Anti-PD-1/Anti-CTLA-4 Combined Therapy.

Cancer immunotherapies provide survival benefits in responding patients, but many patients fail to respond. Identifying the biology of treatment response and resistance are a priority to optimize drug selection and improve patient outcomes. We performed transcriptomic and immune profiling on 158 tumor biopsies from melanoma patients treated with anti-PD-1 monotherapy (n = 63) or combined anti-PD-1 and anti-CTLA-4 (n = 57). These data identified activated T cell signatures and T cell populations in responders to both treatments. Further mass cytometry analysis identified an EOMES+CD69+CD45RO+ effector memory T cell phenotype that was significantly more abundant in responders to combined immunotherapy compared with non-responders (n = 18). The gene expression profile of this population was associated with longer progression-free survival in patients treated with single agent and greater tumor shrinkage in both treatments.