Microbiome-Supplement for Ulcerative Colitis

Inclusion Criteria: 1. Adults aged 18 to 75 years inclusive at screening. 2. Documented diagnosis of ulcerative colitis established at least 3 months before screening, based on standard clinical, endoscopic, and histologic criteria. 3. Mild-to-moderate active ulcerative colitis defined by a partial Mayo score of 4 to 8 at screening. 4. Rectal bleeding subscore of at least 1 at screening. 5. Objective intestinal inflammation defined by fecal calprotectin of at least 250 micrograms per gram at screening, measured by the central laboratory or by a validated harmonized assay. 6. Eligible disease extent: left-sided colitis or extensive/pancolitis. Proctosigmoiditis is eligible if inflammation extends beyond isolated proctitis and is measurable by study endoscopy. Isolated ulcerative proctitis (E1 only) is eligible only within a prespecified cap not exceeding 10 percent of total enrollment. 7. Either no current ulcerative colitis-directed therapy, or stable oral and/or rectal 5-aminosalicylate (5-ASA, mesalamine) therapy at unchanged dose for at least 8 weeks before randomization, with intent to continue at the same unchanged dose through Week 24 unless rescue therapy is clinically required. 8. Able and willing to provide written informed consent. 9. Able and willing to comply with study visits, stool sampling, endoscopy, medication restrictions, and diary/patient-reported outcome completion. 10. Participants of childbearing potential must agree to use a highly effective method of contraception during dosing and for at least 4 weeks after the last dose, in accordance with EMA/CTFG guidance and local ethics requirements. Exclusion Criteria: 1. Crohn disease, inflammatory bowel disease-unclassified, microscopic colitis, ischemic colitis, infectious colitis, radiation colitis, or any other non-ulcerative-colitis form of colitis. 2. Severe ulcerative colitis, acute severe ulcerative colitis, fulminant colitis, toxic megacolon, or any disease severity requiring immediate hospitalization or treatment escalation in the investigator's judgment. 3. Isolated ulcerative proctitis (E1 only) outside the prespecified 10 percent enrollment cap. 4. Use of biologics, Janus kinase (JAK) inhibitors, sphingosine-1-phosphate (S1P) receptor modulators, or systemic immunosuppressants within 8 weeks before randomization, or planned use of any of these during the trial. 5. Systemic corticosteroids within 4 weeks before randomization. 6. Current budesonide-class therapy at baseline. 7. Rectal or topical corticosteroids unless discontinued at least 2 weeks before randomization. 8. Antibiotic use within 4 weeks before randomization, except topical antibiotics not expected to affect the gut microbiota. 9. Probiotic, prebiotic, synbiotic, postbiotic, fermented microbiome-directed supplement, or other non-study microbiome-directed product within 4 weeks before randomization, or planned use during the trial. 10. Active or recent Clostridioides difficile infection within 12 weeks before screening (screening uses a two-step algorithm: glutamate dehydrogenase plus toxin A/B enzyme immunoassay, with reflex nucleic acid amplification testing for discordant results). 11. Positive stool test for any clinically relevant enteric infection at screening, per local diagnostic standard operating procedures. 12. Prior colectomy, planned colectomy, known dysplasia requiring intervention, or colorectal cancer. 13. Pregnancy, breastfeeding, or planned pregnancy during the trial. 14. Uncontrolled clinically significant comorbidity, including but not limited to uncontrolled diabetes, advanced liver or renal disease, unstable cardiovascular disease, immunodeficiency, active malignancy other than adequately treated non-melanoma skin cancer, or any other condition compromising participant safety or interpretation of study results. 15. Known allergy, intolerance, or contraindication to any component of the investigational product or matching placebo. 16. Participation in another interventional clinical trial within 30 days before screening. 17. Any other condition that, in the investigator's judgment, would make participation unsafe or compromise protocol adherence.