Inclusion Criteria:

• Men or women 18 to 80 years of age at the time of consent
• Previous diagnosis of ulcerative colitis, based on available endoscopic and histopathologic report, at least 3 months before screening
• Mild-to-moderate disease activity based on Modified Mayo Score that should be between 4 and 6 with an endoscopic subscore >1 based on endoscopic evaluation performed during screening phase
• Subjects are permitted to receive a concomitant therapeutic dose of the following IPs: Corticosteroids (≤20 mg/day of prednisone equivalents) at stable dose for at least 2 weeks before screening and mesalazine or other 5-ASA (including salazopyrin) at stable dose for at least 4 weeks before screening
• Ability to provide a written informed consent and to be compliant with the schedule of protocol assessments.

Exclusion Criteria:

• concomitant immunosuppressive therapy, including but not limited to thiopurines, methotrexate, anti-TNFalfas, anti-integrins and anti-IL12/23 or JAK inhibitors. Biological therapies should be stopped at least 8 weeks before baseline, except for ustekinumab which should be stopped for at least 12 weeks before baseline, small molecules agent should be discontinued 5 elimination half-lives within baseline. Patients that have been previously treated with ≥ 2 advanced/biological drugs (even if belonging to the same class) will be excluded.

• Intolerance to topical therapy (enemas)

• Allergy to A. muciniphila or any other component of the IP

• Crohn's disease or inflammatory bowel disease unclassified (IBD-U)

• Subject who received IV/intramuscular corticosteroids within 14 days prior to Screening or during the Screening period.

• Subject who received topical therapy (i.e., enema or suppository of aminosalicylates / corticosteroids) within 14 days prior to Screening or during the Screening period.

• Subject who received fecal microbial transplantation within 3 months prior to Baseline.

• Subjects with the following chronic or active infections:

  • Active, chronic, or recurrent infection that based on the Investigator's clinical assessment makes the subject unsuitable candidate for the study
  • Infection with C. difficile, intestinal pathogen bacteria, intestinal parasites as identified during Screening as per clinical practice,
  • Are infected with human immunodeficiency virus (HIV),
  • Subject who has any condition including any physical, psychological, or psychiatric condition, which in the opinion of the Investigator, would compromise the safety of the subject or the quality of the data and renders the subject an unsuitable candidate for the study.

• Pregnancy and breastfeeding