Transfer of FRozen Encapsulated multi-donor Stool filtrate for active ulcerative Colitis (FRESCO): study protocol for a prospective, multicenter, double-blind, randomized, controlled trial.

Background: Ulcerative colitis (UC) is a chronic inflammatory bowel disease with significant morbidity and mortality. Although the precise cause remains unknown, disturbances in the intestinal microbial community have been linked to its pathogenesis. Randomized controlled trials in UC and relapsing Clostridioides difficile infection (CDI) have established fecal microbiota (FM) transfer (FMT) as an effective therapy. In this context, preliminary results indicated that the transfer of sterile fecal microbiota filtrates (<0.2 μm; FMF, FMFT) of donor stool also drives gastrointestinal microbiota changes and eliminates symptoms in CDI patients. However, along with the success of FMT, regulatory agencies issued safety alerts following reports of serious adverse events due to transmission of enteric pathogens through FMT. To reduce this risk, we established an extensive test protocol for our donors and quarantine regulations for the produced capsules, but alternative concepts are desirable.

Methods: Our project is a randomized, controlled, longitudinal, prospective, three-arm, multicenter, double-blind study to determine the safety and efficacy of repeated long-term, multi-donor FM or FMF transfers compared to placebo using oral, frozen capsules in 174 randomized patients with mild to moderate active UC. The primary outcome will be clinical remission at week 12.

Discussion: This proposal aims to examine (a) the efficacy of encapsulated transfer of FM and FMF as a therapy for mild to moderate UC, (b) the short- and long-term safety of FMT and FMFT in patients with UC, and (c) the microbial and immunologic changes that occur after FMT and FMFT to help understand how and why it affects inflammatory bowel disease.

Trial Registration: ClinicalTrials.gov NCT03843385 . DRKS (Deutsches Register für Klinische Studien) DRKS00020471.