Influence of the microbiota on immune checkpoint inhibitor therapy

In recent years, new approaches to tumor immunotherapy - the use of drugs aimed at inducing or enhancing the anti-tumor immune response - have been actively studied. Monoclonal antibodies targeting co-inhibitory immune checkpoints have demonstrated clinical efficacy in the therapy of many malignant neoplasms. However, there are limitations in the use of these drugs: the occurrence of adverse events related to the involvement of the immune system and difficulty in predicting the results of therapy. In recent years, the microbiome of the tumor and gastrointestinal microenvironment and its metabolites have been considered as predictors and factors influencing immune therapies for cancer. In our review we discuss preclinical and clinical studies analyzing the microbial composition of the gut and tumor microenvironment as a biomarker of immune therapy response and toxicity, ways to influence the microbial composition of human biotopes to modulate immune therapy, identify specific microflora representatives as favorable and unfavorable factors in immune checkpoint inhibitor therapy, identify several limitations in microflora research and future prospects in this area.