A Phase 2b, Randomized, Double-Blind, Placebo-Controlled, Multicenter Study to Assess the Safety, Efficacy, and Pharmacokinetics of RNIB21 in Patients With Irritable Bowel Syndrome With Diarrhea (IBS-D)

What this Trial Is About

Researchers are evaluating the combination of rifaximin and N-acetyl-L-cysteine (NAC) to treat patients with irritable bowel syndrome with diarrhea (IBS-D). This phase 2b, multi-center, randomized, double-blind, placebo-controlled study aims to see if this combination reduces IBS-D symptoms better than rifaximin alone. Rifaximin is an FDA-approved antibiotic for IBS-D, while NAC is a dietary supplement used for other conditions and is not yet approved for IBS-D treatment in combination with rifaximin. Participants will be randomly assigned to one of three groups: rifaximin 66 mg plus NAC 560 mg three times daily, rifaximin 132 mg plus NAC 560 mg three times daily, or a placebo taken three times daily. The study includes a screening phase, a 14-day treatment phase with visits at the start, week 1, and week 2, followed by a 14-week follow-up phase with an end-of-study visit. A subset of patients will provide blood samples to study how the drugs are processed in the body. Participants will report their abdominal pain daily using a pain scale and record stool consistency using the Bristol Stool Scale through a smartphone app and questionnaires. The main outcome is the proportion of patients who experience relief in both abdominal pain and stool consistency during the 4 weeks after treatment. Researchers will monitor safety and symptom changes throughout the study, which lasts approximately 14 weeks for each participant.

Efficacy of Rifaximin With NAC in IBS-D