To define the parameters for dose-dependent engraftment of MET-2 commensal bacteria for the treatment of mild to moderate ulcerative colitis

This study will deliver MET-2 at two different doses via an oral capsule in patients with active mucosal inflammation and observe its safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD) and clinical efficacy as compared to placebo. The goal is to define the parameters for dose-dependent engraftment of MET-2 commensal bacteria for the treatment of mild to moderate ulcerative colitis not fully responsive to conventional therapy.

Inclusion Criteria:

1. Mild to Moderate UC.

2. ≥ 18 years old.

3. Able to provide informed consent, or have a caregiver able to provide consent.

4. Subjects must have a documented diagnosis (radiologic or endoscopic with histology) of UC for >3 months before screening. The following must be available in each subject's source documentation:

   • A biopsy report to confirm the histological diagnosis
   • A report documenting disease duration and medication history prior to study colonoscopy

5. Subjects receiving any treatment(s) forUC are eligible provided they are anticipated to be on a stable dose for the duration of the study period and have been on therapy prior to the randomization visit for the following amount of time:

   Prednisone - 4 weeks; Budesonide - 4 weeks; 5-aminosalicylic acid (5-ASA) containing products - 4 weeks; Thiopurine analogs (azathioprine, 6-mercaptopurine) - 12 weeks; Biologic therapy (infliximab, adalimumab, vedolizumab) - 12 weeks; Tofacitinib - 8 weeks.

   No change in dose is permitted for the following time period prior to the randomization visit:

   Prednisone - 2 weeks; Budesonide - 4 weeks; 5-ASA containing products - 4 weeks; Thiopurine analogs (azathioprine, 6-mercaptopurine) - 6 weeks; Biologic therapy (infliximab, adalimumab, vedolizumab) - 6 weeks; Tofacitinib - 4 weeks.

6. Subjects are males or nonpregnant, nonlactating females who, if sexually active, agree to comply with the contraceptive requirements of the protocol, or females of nonchildbearing potential. Males and females of reproductive potential who are sexually active must agree to use acceptable contraception for the duration of the study.

7. Willing to participate in follow up as part of the study.

Exclusion Criteria:

1. Ulcerative colitis with disease limited to only the distal rectum (<5cm from dentate line).
2. Subjects with indeterminate colitis, microscopic colitis, ischemic colitis, infectious colitis, or clinical/histologic findings suggestive of Crohn's disease will be excluded.
3. Subjects with colonic dysplasia or neoplasia. (Subjects with prior history of adenomatous polyps will be eligible if the polyps have been completely removed).
4. Subjects with toxic megacolon or hospitalized for ulcerative colitis.
5. Subjects with colonic stricture, past medical history of colonic resection, a history of bowel surgery within 6 months before screening, or who are likely to require surgery for UC during the treatment period.
6. Use of antibiotics within 6 weeks of randomization visit.
7. Allergy to vancomycin.
8. Elective surgery that will require preoperative antibiotics planned within 3 months of enrolment.
9. Pregnant or planning to get pregnant in the next 6 months.
10. Any condition for which, in the opinion of the investigator, the subject should be excluded from the study.

The assessor will be blinded as to which dosing arm the subjects are assigned.