Fecal Microbiota Transplant in Immunotherapy-Resistant Melanoma: What Can We Expect in the Near Future?

Melanoma is a malignancy of melanocytes, melanin-producing cells in the basal layer of the epidermis. Despite representing only 1% of skin cancers, melanoma is responsible for over 80% of skin cancer deaths. Treatment with immune checkpoint inhibitors (ICIs) that target the programmed death 1 (PD-1) protein and the cytotoxic T-lymphocyte antigen 4 (CTLA-4) pathways drastically transformed the management of patients with advanced melanoma. Before the introduction of ICIs, the average life expectancy for a patient with advanced melanoma ranged from six to 12 months, and now, this average survival has increased to over six years. However, despite this outstanding clinical success, most patients with advanced melanoma treated with ICIs will experience disease progression, immediately or after an initial response to treatment. Nowadays, some studies have looked at the mechanism behind the resistance to immunotherapy, with the aim of developing new treatments to overcome it. Emerging data suggest that gut microbiota (GM) influences response to immunotherapy. Importantly, unlike tumor genomics, the GM is changeable; thus, modulation of the GM is an attractive approach to overcome immunotherapy resistance. One of these approaches is the fecal microbiota transplant (FMT), which consists of the exchange of manipulated feces from a donor to a recipient who has a disorder related to intestinal dysbiosis to directly change the recipient's gut microbial composition and confer a health benefit. This review pretends to discuss the clinical benefit of FMT in the treatment of immunotherapy-resistant melanoma and potential adverse effects, including recent and ongoing clinical trials.