A randomized, double-blind, placebo-controlled pilot study in patients with IBS-D according to Rome IV criteria evaluating the clinical efficacy and safety of oral administration of 2g G-PUR® tid compared to placebo in a cohort of 30 patients over an active treatment period of 12 weeks.

Inclusion Criteria:

1. Age 18-75 years

2. Recurrent abdominal pain, at least one day/week in the last 3 months (with symptom onset at least 6 months before diagnosis), associated with two or more of the following criteria (Rome IV criteria)

   1. Related to defecation
   2. Associated with a change in frequency of stool
   3. Associated with a change in form (appearance) of stool.

3. Moderate to severe abdominal pain as defined with an IBS Symptoms Severity Scale (IBS-SSS) score > 175

4. Patient reports that abnormal bowel movements are usually diarrhea with more than one-fourth (25%) of bowel movements with Bristol stool form types 6 or 7 and less than one-fourth (25%) of bowel movements with Bristol stool form types 1 or 2. Starting during the screening/run-in phase, all patients will keep diaries of stool frequency and consistency. Stool consistency will be assessed according to the Bristol Stool Form scale (Lewis and Heaton, 1997)

5. Stable eating habits, within one month before randomization

6. In patients > 50 years colonoscopy performed during the past 5 years demonstrates no pathology associated with the symptoms reported for IBS

7. Ability to understand trial instructions and to comply with treatment

8. Patient agree to be compliant for study interactive web - response system schedule confirmed at time of randomization

9. Written informed consent prior to enrolment

Exclusion Criteria:

1. Patient has exclusively constipation-predominant IBS (IBS-C) that is characterized by < 3 bowel movements/week or hard and lumpy stools (e.g. Bristol stool form types 1 or 2)
2. Patient has irritable bowel syndrome with mixed bowel habits (IBS-M) with varying symptoms of constipation and diarrhea
3. Calprotectin stool value > 200mg/kg stool
4. Known hypersensitivity to the IMD (known aluminium and/or silicon hypersensitivity)
5. Patient has failed to record >50% of daily diary entries during run-in period
6. Rectal bleeding in the absence of documented bleeding hemorrhoids or anal fissures assessed by fecal occult blood test
7. History of major gastric, hepatic, pancreatic or intestinal surgery or perforation with exception of appendectomy, cholecystectomy and inguinal hernia
8. Patients with a history of positive tests for ova, parasites or clostridium difficile must undergo repeat testing, which must be negative, during the screening period
9. Use of the following prohibited medications: any antibiotics including rifaximin within the past 2 months or during treatment period, use of cholestyramine during entire study period, during run-in phase and during the treatment period any use of concomitant medication effecting the gastrointestinal movement and/or function (e.g. anticholinergic drugs, 5-HT3 receptor antagonists, prokinetic agents, intestinal flora regulating drugs, parasympathetic inhibitors, opioids or eluxadoline)
10. Use of immunosuppressive drugs within the last 6 months or planned use of immunosuppressive drugs during the study
11. Patients treated with tricyclic antidepressants
12. Serotonin re-uptake inhibitors are allowed if the patient is at stable dose for at least 8 weeks prior to signing informed consent and the dose will remain stable throughout the duration of the study.
13. History of inflammatory or immune-mediated gastrointestinal (GI) disorders including inflammatory bowel disease (i.e., Crohn's disease, ulcerative colitis) and celiac disease (by anamnesis and assessed by tTGA levels)
14. Active infection, or abnormalities in laboratory testing, vital signs, or physical examination at screening
15. Participation in any other interventional clinical trial within 4 weeks before study participation
16. Alcohol or drug abuse (History of alcohol abuse or heavy alcohol use as binge drinking on 5 or more days per month within the 12 months prior to screening. Known medication and drug abuse)
17. Pregnant or breastfeeding (for all females, negative pregnancy test at screening and at each treatment visit will be performed).
18. History of cancer (except non-melanoma skin cancer, or carcinoma in situ of cervix) within the previous 12 months or treatment with anticancer therapy (chemotherapy, immunotherapy, radiotherapy, hormone therapy for cancer treatment, targeted therapy or gene therapy) within 12 months before the first administration of investigational product or at any time during the study
19. Patients with known familial colorectal cancer syndromes, where colorectal cancer has not been excluded by colonoscopy
20. Other severe comorbid condition, concurrent medication, or other issue that renders the patient unsuitable for participation in the study, including but not limited to: comorbid condition with an estimated life expectancy of ≤ 12 months, patients with uncontrolled hypothyroidism, uncontrolled hyperthyroidism, patients on dialysis, patients with severe pulmonary (requiring home oxygen, uncontrolled COPD Gold III/ IV) or cardiovascular conditions (heart failure NYHA III and IV, uncontrolled hypertension systolic BP by repeated measurement > 180 mmHg; patient with uncontrolled diabetes with an Hba1c >6.5%)
21. Concomitant psychotherapy is allowed if the patient started therapy for at least 8 weeks prior to signing informed consent and the schedule will remain stable throughout the duration of the study.
22. Known severe psychiatric disorders or mental condition rendering the patient unable to understand the nature, scope and possible consequences of the study;
23. Presence of any condition that impacts compliance with the study procedures
24. Employee at the study site, spouse/partner or relative of any study staff (e.g. investigator, sub-investigators, or study nurse) or relationship to the sponsor)