Gut Microbiota Modulation for Immunotherapy Resensitization in Advanced Renal Cell Carcinoma

The combination of immune checkpoint inhibitors (ICIs) and tyrosine kinase inhibitors (TKIs) has significantly improved clinical outcomes in patients with advanced renal cell carcinoma (RCC). However, 40%-60% of patients still develop primary or acquired resistance. For those with resistant disease, current immune rechallenge strategies have yet to demonstrate clear clinical benefit. Emerging evidence indicates that the gut microbiota plays a critical role in modulating responses to immunotherapy. Microbiota-modulating approaches, including fecal microbiota transplantation (FMT) and live bacterial formulations such as CBM588, have shown preliminary potential to enhance sensitivity to immunotherapy and improve patient outcomes. Nevertheless, whether gut microbiota modulation can resensitize advanced RCC to immunotherapy remains to be investigated. The REMEDY-RCC trial is an investigator-initiated, prospective, open-label, phase II, parallel two-cohort exploratory study primarily designed to investigate whether gut microbiota modulation can restore sensitivity to immunotherapy in patients with advanced RCC. Given the substantial differences in the tumor immune microenvironment and response to ICIs between clear cell RCC (ccRCC) and non-clear cell RCC (nccRCC), this study employs a parallel two-cohort design to stratify these two patient populations: a primary cohort consisting of patients with metastatic ccRCC, and an exploratory cohort consisting of patients with metastatic nccRCC. The primary and secondary endpoints will be analyzed in the primary cohort, whereas the exploratory cohort will be used solely for exploratory and descriptive analyses. The study plans to enroll approximately 33 adult patients with advanced or metastatic RCC, including 27 with metastatic ccRCC and 6 with metastatic nccRCC. Eligible patients will receive the following sequential interventions: bowel decontamination with amoxicillin-clavulanate potassium followed by polyethylene glycol (PEG