FMT to Convert Response to Immunotherapy

In this study the aim is to investigate whether transfer of the microbiota of either responder or non-responder patients via fecal microbiotica transplantation (FMT) can convert the response to immunotherapy in immune checkpoint inhibitors (ICI) refractory metastatic melanoma patients. This is a randomized double-blind intervention phase Ib/IIa trial in ICI refractory metastatic melanoma patients receiving either FMT of an ICI responding or FMT from an ICI non-responding donor, in combination with ICI. Following randomization, patients will receive vancomycin 250 mg, four times daily for 4 days (day -5 up until day -2), and undergo bowel clearance on day -1 (in total 1L MoviPrep). The FMT, either derived from donor group R (who showed a good response on anti-PD-1 therapy) or donor group NR (who showed progression on anti-PD-1 therapy), will be performed by a gastroenterologist using esophagogastroduodenoscopy. A total amount of 198mL (containing a total of 60 gram feces) will be used for transplantation. Anti-PD-1 treatment will be continued according to the patient's regular treatment schedule. Evaluation of safety and response to treatment will be performed.