What Is the Role of Fecal Microbiota Transplantation in Immunotherapy Trials? Current Perspectives and Future Directions.

Immune checkpoint inhibitors (ICIs) are rapidly transforming the treatment landscape of genitourinary and other immunogenic malignancies. Despite these advances, biomarkers for the prediction of ICI response remain to be established. The gut microbiome has been identified as a modulator of immune regulation and a potential regulator of response to ICIs. Fecal microbiota transplantation (FMT) has emerged as a potential novel therapeutic tool to enhance ICI response, as demonstrated in several trials, spanning across genitourinary malignancies as well as others. While safety and clinical potential of FMT have been demonstrated, FMT parameters including optimal treatment regimens, bowel preparation protocols, patient selection, and donor-host compatibility need to be defined. Furthermore, targeted interventions including probiotic supplementation represent promising therapeutic avenues meriting further study.