Cosmo Pharmaceuticals N.V announced the successful outcome of its Phase II Proof of Concept (POC) clinical trial of Rifamycin-MMX 600mg in Irritable Bowel Syndrome with Diarrhea (IBS-D). The drug tested is different from Aemcolo®/Relafalk®, which is already approved for Traveler's Diarrhea: while it shares the same active ingredient (Rifamycin SV) and MMX technology, it contains a higher dose of API (600mg) and different release features. The trial investigated the efficacy and safety of two doses of Rifamycin SV-MMX 600mg against placebo after a 2-week course of treatment followed by a 3 months follow-up. The primary endpoint was the proportion of subjects who achieved success, defined as an adequate relief of both abdominal pain and diarrhea at the end of the first week of treatment (at least 30% decrease in pain score and at least 50% reduction in the number of days per week with diarrhea). Other endpoints included reduction in bloating, improved stool consistency, decreased sense of urgency, and improvement in quality of life as assessed through the IBS QoL questionnaire. The trial was conducted in 25 sites located in 4 countries in Western Europe and recruited 279 patients in the ITT ("Intention to treat") population. The trial was very successful notwithstanding the decision by Cosmo to reduce the envisaged sample size by 20% due to COVID-19 restrictions. Results show the achievement of statistical significance in all the study populations (ITT, FAS, m-FAS and PP) for the composite primary endpoint (substantial pain and diarrhea decrease) [OR 3.26 (1.39 - 7.67); p-value 0.0066] and for most secondary endpoints such as adequate relief of IBS-related symptoms [OR 2.18 (1.12 - 4.26); p-value 0.0227 ] and IBS-related bloating at the end of treatment period [OR 2.13 (1.11 - 4.07); p-value 0.0223].