Crohn's disease is a chronic and complex inflammatory bowel disease affecting the gastrointestinal tract, causing symptoms like abdominal pain, diarrhea, and fatigue. While its exact cause is unclear, it involves genetic, environmental, and immunological factors. Crohn's disease can lead to nutrient deficiencies and has unpredictable flare-ups and remission periods. During the remission phases, irritable bowel syndrome (IBS)-like symptoms can persist in 50% of patients, for which no satisfactory treatment is available yet.

Chitin-glucan is prebiotic, obtained by extraction, isolation and purification from a fungal resource: the mycelium of Aspergillus niger (a microscopic fungus of the Ascomycetes family) of which it composes the cell walls. The biopolymer consists essentially of two types of polysaccharide chains: chitin (poly-N-acetyl-D-glucosamine) and beta-(1,3)-D-glucan (D-glucose units linked essentially via beta-1,3 bonds). Because of its beta bond, human intestinal enzymes cannot digest it, as a result, the majority of chitin-glucan can reach the colon where it can be fermented by the microbiota.

By modulating the composition and/or activity of the intestinal microbiota, fermentation of chitin-glucan could have beneficial effects on health.

The aim of the RELIEVE study is to assess if BK003 could improve the relief of global symptoms, individual symptoms, stool consistency and frequency of evacuations, quality of life, anxiety, and depression in patients with Crohn's disease in remission without treatment or with stable maintenance therapy and having IBS-like symptoms and to confirm the product's safety.

Inclusion Criteria:

• Male and female patients aged from 18 years to 75 years,
• Long standing (>3 months prior to V1) steroid-free clinical remission Crohn's disease according to clinical and biochemical assessments,
• Clinical remission (according to the investigator),
• Absence of inflammatory markers at V1,
• Presence of IBS-like symptoms according to Rome IV criteria,
• Likert scale ≥ 3 for abdominal pain at V0,
• Patient with correct and complete reporting of the study questionnaires and scores during the run-in period (≥ 75% completion),
• To continue all medication used in the last month before inclusion at the same dosage,
• Anti-spasmodic, hypomotility agents, probiotics, prebiotics, bile-acid chelators, and anti-depressants are authorized if consumed for longer than 1 month before inclusion and maintained at a stable dosage for the entire study duration,
• Agreeing to maintain their lifestyle behaviours during the participation in the study,
• Patient has read, understood, and signed the informed consent form (ICF),
• Patients capable of communicating with the investigator, replying to the questionnaires, and understanding the requirements and constraints of the study protocol,
• Possession of a digital device (i.e., smartphone or tablet),
• Patient willing to adhere to the study visit schedule and able to understand and comply with protocol requirements and product administration,
• Male or female patient of childbearing potential who agrees to use acceptable methods of birth control (oral, transdermal, systemic contraception, intrauterine device, condom) for the duration of the study,
• Patient can read and write in French.

Exclusion Criteria:

• Patients with other concomitant organic gastrointestinal abnormalities besides Crohn's disease: ano-perineal lesions, extra-intestinal manifestations of Crohn's disease, colorectal history of cancer or abdominal radiotherapy, symptomatic intestinal stenosis, substance dependence history,
• Patients with significant comorbidities: instable cardiovascular diseases, complicated diabetes, instable thyroid function,
• Patients receiving non-steroidal anti-inflammatory drugs, steroids, opioids, or narcotic analgesics in the last month before V0,
• Patients beginning a diet or a specific treatment for functional symptoms (probiotics, prebiotics, anti spasmodic, chelators, anti-depressants, etc.) within one month before V1,
• Ongoing antibiotics or antibiotics prescribed in the last 2 weeks before V1.
• Excessive alcohol consumption (>30 g/day [i.e., 3 units/day] for men and >20 g/day [i.e., 2 units/day] for women) and/or drug abuse,
• Pregnancy and lactation, or plan to become pregnant during the study period,
• Participation in other studies involving investigational or marketed products concomitantly or less than 3 months prior to V0,
• Known hypersensitivity to any of the ingredients or excipients of the study products,
• Patient who has forfeited their freedom by administrative or legal award, or who is under guardianship or under limited judicial protection.

At V1, all enrolled patients will be randomly allocated to either BK003 or placebo using computerised block-randomisation with a 1:1 ratio. The randomisation list has been generated before study product packaging and each product has a number which will be consecutively allocated to patients in the eCRF.