S1563 Fecal Microbiota vs Standard Medical Therapy in Inducing Histologic Remission in Ulcerative Colitis: A Systematic Review

Introduction: Ulcerative colitis (UC) is a chronic inflammatory bowel disease that often requires long-term immunosuppressive therapy or biologics for disease control. Fecal microbiota transplantation (FMT), which aims to restore intestinal microbial balance, has emerged as a promising therapeutic option in UC. However, evidence regarding its efficacy in inducing histologic remission remains limited. This systematic review aims to evaluate the efficacy of FMT in inducing clinical, endoscopic, and histologic remission in patients with active UC. Methods: Following PRISMA guidelines, a comprehensive literature search was conducted using multiple databases, covering the last 10 years (2015–2025). We included randomized controlled trials (RCTs) and open-label studies assessing clinical, endoscopic, and/or histologic remission in adults with active UC receiving FMT vs standard therapy or placebo. The primary outcome was clinical remission; secondary outcomes included endoscopic and histologic remission. Quality assessment and data extraction were performed independently by 2 reviewers. Results: Five trials evaluated FMT for inducing remission in active UC. In the double-blind LOTUS trial (2022; n = 35), corticosteroid-free clinical and endoscopic remission was achieved in 53% of FMT recipients, compared to 15% in the placebo group (P = 0.027); sustained endoscopic and histologic remission was observed at 56 weeks (100% in the FMT group). In an open-label, factorial RCT (2022; n = 22), clinical remission at 6 weeks occurred in 67% of patients pretreated with antibiotics, compared to 18% of those who were not ( P = 0.065). A smaller RCT (2021; n = 12) reported clinical remission in 33% of patients receiving encapsulated FMT, compared to placebo (P = 0.45). Two open-label capsule studies (2023; n = 21 and n = 22) reported clinical remission rates of 57.1%, with endoscopic remission in 47.6%, and mycobiome shifts (e.g., increased Kazachstania) associated with response. Conclusion: FMT appears to be an effective therapy for inducing clinical, endoscopic, and histologic remission in patients with active ulcerative colitis. While these 5 trials revealed promising results, larger and well-powered randomized trials are required to confirm efficacy, optimize treatment protocols, and identify likely responders.