Colon to Rectum
Am J Gastroenterol. 2025;120(7):1605-1614
A phase 2, multicentric, randomized, double-blind, placebo-controlled, proof of concept study of efficacy and safety of rifamycin SV-MMX 600 mg tablets administered three or two times daily to patients with diarrhea-predominant irritable bowel syndrome
Introduction: Treatment with nonresorbable antibiotics is effective in diarrhea-predominant irritable bowel syndrome (IBS-D). Multimatrix (MMX) formulations ensure targeted drug delivery to the mid-distal small bowel and colon-traditionally considered the origin of IBS symptoms. To assess the efficacy of rifamycin SV-MMX for the treatment of IBS-D.
Methods: Randomized controlled trial in patients with IBS-D (Rome IV). Patients received rifamycin SV-MMX 600 mg (b.i.d = 1200 mg/day or t.i.d = 1800 mg/day) or placebo for 2 weeks. Primary end point was responder rate in the first treatment week on the full analysis set (FAS). Response was defined as decrease in average abdominal pain ≥ 30% and ≥ 50% reduction of days with stool type 6 or 7 based on daily reporting.
Results: A total of 279 patients were randomized (= intention-to-treat [ITT]), and 264 of were included in the FAS. More patients with rifamycin SV-MMX b.i.d (22/88, 25.00%) met the primary end point than t.i.d (10/81, 12.35%) or placebo (9/95, 9.47%) in both FAS and ITT. Adjusted odds ratio (AOR) for b.i.d. versus placebo was 3.26 (95% confidence interval [CI]: 1.39–7.67; p = 0.007) and for t.i.d. versus b.i.d. 0.40 (95% CI: 0.17–0.92; p = 0.031). After treatment, the percentage of monthly global responders was higher in the b.i.d. group versus placebo in the first month (64.2% vs. 46.6%, AOR = 2.14; 95% CI: 1.15–4.00; p = 0.0173) and first 2 months.
Discussion: Rifamycin SV-MMX 600 mg b.i.d. was more effective than placebo and t.i.d. dosing in the first week of treatment. Two months after treatment, rifamycin SV-MMX 600 mg b.i.d. provided more global symptom relief than placebo.