This is a multi-centre, randomised controlled trial comparing fecal microbiota transplantation to placebo in an expanded ulcerative colitis population: a feasibility study (FRONTIER-UC) to determine whether a full-scale randomized controlled trial (RCT) to investigate fecal microbiota transplantation (FMT) in ulcerative colitis (UC) is feasible.

This is a randomized, double blind, placebo-controlled trial for UC patients with active disease.

Participants will be grouped into one of two categories

1. Add to current therapy (i.e., adjunct therapy)

   or

2. Initiate or switch to a new advanced agent (i.e., co-administration)

The study will recruit 85 outpatients at 3 Canadian healthcare centres

Inclusion Criteria:

1. 18 years of age or older
2. Able to provide informed consent
3. Established UC diagnosis through standard endoscopic and histologic criteria
4. Active UC
5. Use of effective contraception method for women of childbearing potential for at least 4 weeks prior to receiving study treatment and for the duration of the trial
6. Willing and able to comply with all required study procedures

Exclusion Criteria:

1. Severe UC requiring hospitalization
2. Crohn's disease or indeterminate colitis
3. Irritable bowel syndrome
4. Intestinal infection within 4 weeks of enrollment
5. Evidence of toxic megacolon or gastrointestinal perforation on imaging
6. Planned colectomy
7. Abdominal surgery within 60 days of enrollment
8. Neutropenia with absolute neutrophil count <0.5 x 109/L
9. Peripheral white blood cell count > 35.0 x 109/L and fever (>38C)
10. Planned or actively taking another investigational product
11. Uncontrolled medical conditions such as psychiatric disorders or substance abuse
12. Severe underlying disease such that the patient is not expected to survive for at least 30 days
13. Pregnancy or breastfeeding
14. Unwilling to discontinue non-dietary probiotic
15. Antibiotic use 30 days prior to enrollment or anticipated need for systemic antibiotic use during study
16. FMT for any reason within 6 months of enrollment
17. Investigator's judgement that enrolment is not in the best interest of the patient