A stool transplant turned three melanoma patients into responders

Physicians at Sheba Medical Center in Israel suspected the patients' gut bacteria were part of the problem, since mouse studies had linked the microbiome to how tumors react to anti-PD-1 drugs. They ran a small phase 1 trial to test whether changing that microbiome could restart the response.

Each patient received a fecal microbiota transplant from a patient whose melanoma had responded well to anti-PD-1 therapy, then went back on the same immunotherapy that had stopped working for them. Three of the ten patients responded: two partially, one completely.

Biopsies showed immune cell activity shifted after the transplant in both the gut lining and the tumors themselves, not just the bacteria living there. The trial was a phase 1 safety and feasibility study with ten patients, run at one hospital, and three responders is a small number to build on. Larger trials testing the same approach in refractory melanoma are now underway.

Someone else's gut bacteria restarted a stalled treatment.