Gelsectan® in the Treatment of Patients With Diarrhoea-predominant Irritable Bowel Syndrome

Inclusion criteria: 1. Male or female, age ≥18 years and ≤ 65 years. 2. Positive diagnosis of IBS, according to Rome IV diagnostic criteria, namely recurrent abdominal pain, on average, at least 1 day/week in the last 3 months associated with two or more of the following criteria: * related to defecation * associated with a change in frequency stool * associated with a change in form (appearance) of stool The above criteria must be fulfilled for the last 3 months with symptom onset at least 6 months before diagnosis. 3. Positive diagnosis of IBS-D subtype based on Rome IV diagnostic criteria, i.e., more than 25% of bowel movements with a consistency of type 6 or type 7 (loose or watery stools) on the BSFS, and less than 25% of bowel movements with BSFS types 1 or 2 (hard or lumpy stools), on days with at least one abnormal bowel movement. 4. Negative results to any relevant additional tests or exams whenever deemed appropriate by the Investigator to exclude other disorders or causes of IBS symptoms. 5. At least one type 6 or type 7 bowel movement based on the BSFS on at least 4 days within the last week prior to randomization. 6. Weekly average score of 24-hours worst abdominal pain score ≥ 3 on NRS-11 in the last week prior to randomization. 7. Electronic diary (e-diary) completed on at least 11 of 14 days (≥ 75%) during the screening period (i.e., 2 weeks prior to randomization). 8. Willingness and capability to fulfil all tasks foreseen by the Clinical Investigation Plan (CIP). 9. Signed written informed consent. 10. Females of childbearing potential must have a negative urine pregnancy test (dipstick) at randomization and currently use or agree to use consistently and correctly (i.e., perfect use) a highly effective or acceptable effective contraceptive method for the individual subject and her partner(s) throughout the study treatment period and for at least one full contraceptive cycle (when applicable). Exclusion criteria: 1. Presence of any relevant organic, systemic or metabolic disease (particularly significant history of cardiovascular, renal, neurological, endocrine, metabolic or hepatic disease) that would preclude participation in this study in the opinion of the Investigator, or abnormal laboratory values that will be deemed clinically significant on the basis of predefined values. 2. Known perforation and/or gastrointestinal obstruction. 3. Ascertained organic gastrointestinal diseases, including celiac disease, bile acid malabsorption or inflammatory bowel diseases (Crohn's disease, ulcerative colitis, diverticular disease, infectious colitis, ischemic colitis, microscopic colitis). 4. Presence of other intestinal motility disorders, such as biliary dyskinesia, gastroparesis, intestinal pseudo-obstruction, and narcotic bowel syndrome. 5. Previous major abdominal surgery (uncomplicated appendectomy, cholecystectomy, polypectomy, inguinal hernia surgery, or caesarean section are allowed unless within six months prior to screening). 6. Active malignancy of any type (except for non-invasive basal or squamous cell carcinoma of the skin), or history of a malignancy other than non-invasive basal or squamous cell carcinoma of the skin. Patients with a history of malignancies that have been surgically removed with no evidence of recurrence for at least five years and no treatment prior to screening are allowed to participate in the study. 7. History of allergy or hypersensitivity to any of the investigational product ingredients or excipients. 8. Current use of Gelsectan®. 9. Use of loperamide or antispasmodics (i.e., direct smooth muscle relaxants, anticholinergic agents and calcium channel blockers) in the 14 days prior to randomization. 10. Concomitant use (starting from screening) of weak and potent opioids, 5-HT3 antagonists, such as alosetron and ondansetron, bile acid sequestrants, eluxadoline or any other drug/supplement known to significantly interfere with abdominal pain, stool frequency and consistency and/or intestinal permeability (except for those allowed as rescue therapy starting from randomization), including but not limited to corticosteroids, aminosalicylates, immunosuppressants and biologicals. 11. Prior and concomitant use of probiotics/prebiotics/synbiotics or rifaximin starting from 28 days prior to randomization. Other oral antibiotics and topical antibiotics are allowed. 12. Any major psychiatric unstable disorder, including eating disorders, and use of antidepressant or anxiolytic agents, unless used at a stable dose for at least 6 weeks prior to randomization. 13. History or current evidence of laxative abuse within 5 years prior to screening. 14. Recent history (within 12 months prior to screening) or suspicion of alcohol abuse or drug addiction. 15. Treatment with any investigational drug or medical device within 30 days prior to randomization, or current participation in other clinical trials or investigations. 16. Pregnancy or breastfeeding or intention to look for pregnancy throughout the whole study duration.