Fecal microbiota transplant is a therapeutic strategy that involves transfer of feces from a donor to a recipient. The goal of fecal transplant is to restore the microbial balance in the gut of the recipient as a means to improve health. A new study demonstrates that fecal microbiota transplant improves the response to immunotherapy among melanoma patients.

Immunotherapy exploits the immune system to treat cancer. One type of immunotherapy, anti–programmed cell death protein 1 (PD-1) therapy is beneficial in treating patients with advanced melanoma. However, gut microbial composition influences anti–PD-1 efficacy in preclinical models and cancer patients. About 40 percent of melanoma cancer patients do not respond to immunotherapy.

The authors of the study performed fecal microbiota transplants and anti-PD-1 immunotherapy (a drug called pembrolizumab) in melanoma patients who had not responded to all other therapies, including anti-PD-1. The fecal microbiota donors were people who demonstrated robust responses to anti-PD-1 immunotherapy.

More than one-third of the patients who received the transplants responded favorably to the anti-PD-1 immunotherapy despite having not responded before the transplant. The types of gut microbes associated with response to anti–PD-1 increased, as did activation of CD8+ T cells. The number of interleukin-8–expressing myeloid cells (which are involved in immunosuppression) decreased. These findings suggest that fecal microbial transplant is a viable option for improving the response to immunotherapy among melanoma patients and underscore the need for greater understanding of the role the gut microbiota play in immune function.

• Link to study abstract.