Faecal microbiota transplantation does not improve irritable bowel syndrome symptoms in phase 3 trial
Primary endpointProportion of participants with a reduction of 75 points or more in IBS-SSS score at 90 days after treatment compared with baseline
Where these numbers come from
“119 (40%) participants in the donor faecal microbiota transplantation group and 57 (38%) in the placebo group showed an improvement of at least 75 points on the IBS-SSS at 90 days after treatment.”
“The absolute difference was 1.9 percentage points (95% CI -8.1 to 12.0; p=0.76).”
The publication
A phase 3 trial found that faecal microbiota transplantation did not provide clinical benefit for patients with moderate-to-severe irritable bowel syndrome. At 90 days, 40% of participants receiving donor faeces improved by at least 75 points on the IBS-Severity Scoring System, compared with 38% in the placebo group, a difference that was not statistically significant.
Who the findings apply to
The trial enrolled men and women aged 18 to 65 years with moderate-to-severe irritable bowel syndrome.
Diagnosis was defined by Rome IV criteria and an IBS-Severity Scoring System score of 175 points or higher.
Participants aged 50 years or older required a colonoscopy within five years before enrolment to rule out colorectal cancer.
Participants with IBS with predominantly diarrhoea required negative biopsies to exclude microscopic colitis.
Why this matters
The study aimed to determine if restoring healthy gut microbiota via transplantation could alleviate IBS symptoms, given the potential role of microbiota composition in the condition's pathogenesis. The lack of significant difference between the intervention and placebo groups suggests that microbiota modulation alone is insufficient for symptom improvement in this patient population.
What the study found
The primary endpoint was the proportion of participants with a reduction of 75 points or more in IBS-SSS score at 90 days after treatment compared with baseline.
In the donor faecal microbiota transplantation group, 119 of 299 participants (40%) showed an improvement of at least 75 points on the IBS-SSS at 90 days.
In the placebo group, 57 of 151 participants (38%) showed an improvement of at least 75 points on the IBS-SSS at 90 days.
The absolute difference between groups was 1.9 percentage points (95% CI -8.1 to 12.0; p=0.76), indicating no statistically significant benefit.
What the result does not establish
The trial was conducted at five hospitals in Norway, which may limit the generalizability of the findings to other populations.
The study used a once-only rectal enema for treatment delivery, so results may not apply to other administration methods or repeated dosing schedules.
The authors note that microbiota modulation alone might be insufficient for symptom improvement, suggesting that other pathogenic mechanisms may be involved in IBS.
Authors’ conclusion
“The trial did not show a clinical benefit of faecal microbiota transplantation in patients with IBS. These findings suggest that microbiota modulation alone might be insufficient for symptom improvement in IBS.”
Study and sources
Faecal microbiota transplantation in irritable bowel syndrome (REFIT2): a randomised, double-blind, placebo-controlled, phase 3 trial
Randomised trial · Phase 3 · Lancet · 2026-09-24
Sources and limitations
- PubMed record PMID 42785338 (PubMed / NLM · 2026-09-27)
- Trial registry NCT04691544 (ClinicalTrials.gov · 2026-09-27)
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