Abstract IA025: Targeting the gut microbiome for cancer immunotherapy

Abstract

Abstract Growing evidence suggests that the gut microbiota modulates the efficacy and toxicity of cancer therapy, most notably immunotherapy and its immune-related adverse effects. The impaired response to immunotherapy in patients treated with antibiotics supports this role of the microbiota. Until recently, results pertaining to the identification of the microbial species responsible for these effects were incongruent, and relatively few studies analyzed the underlying mechanisms. Gut microbial communities (microbiotypes) with non-uniform geographic distribution were associated with favorable and unfavorable outcomes, contributing to discrepancies between cohorts Now, a better understanding of the taxonomy of the species involved and of their mechanisms of action has been achieved. Defined bacterial species have been shown to promote a response to immune checkpoint inhibitors through the production of different products or metabolites, although a suppressive effect of Gram(-) bacteria may be dominant in some unresponsive patients. Machine learning approaches trained on patients’ microbiota composition can predict the ability of patients to respond to immunotherapy with some accuracy. Thus, the interest in modulating the microbiota composition to improve patients’ responsiveness to therapy has been mounting. Our data of a fecal microbiota transfer clinical trial in anti-PD1 refractory melanoma patients has provided clinical proof of concept of the possibility to target the gut microbiota composition in cancer therapy. Also, both in clinical studies and in experimental animals, diets rich in fibers improve the response to immunotherapy by modifying the gut microbiome suggesting the possibility of dietary approaches to target the microbiota composition in cancer therapy. However, while many early clinical studies have analyzed the association of the microbiota composition with the response to anti-PD-1 in cancer patients, emerging evidence suggests that the association may be context dependent and different types of mono or combination immunotherapies may be differentially regulated by the microbiota, Thus, a more personalized approach depending original gut microbiota composition of the patients and the type of immunotherapy protocol selected may be necessary for optimal clinical results. Citation Format: Giorgio Trinchieri. Targeting the gut microbiome for cancer immunotherapy [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr IA025.