Due to the lack of a clinical efficacy signal in the induction treatment phase, Seres closed the dosing phases of open label and maintenance portions of the study. Patients who had received prior doses were followed for safety data.

A Randomized, Double-Blind, Placebo-Controlled, Multiple Dose, Multicenter Study to Assess Efficacy and Safety of SER-287 in Adults with Active Mild-to-Moderate Ulcerative Colitis

This is a Phase 2B randomized, double-blind, placebo-controlled, multiple dose, multicenter study designed to evaluate the efficacy, safety and microbiome alterations associated with two dose levels of SER-287, after pre-treatment with vancomycin, in adult subjects, age 18-80, with active mild-to-moderate ulcerative colitis (UC).

Inclusion Criteria:

• Documented diagnosis of UC at least three months prior to screening, and with a minimum disease extent of 15 cm from the anal verge
• Active mild-to-moderate UC
• Inadequate response to, loss of response to, or intolerance of, at least one of the following conventional therapies: 5-ASA compounds, corticosteroids, 6-mercaptopurine (6-MP) or azathioprine (AZA), anti-TNFα, anti-integrin or tofacitinib

Exclusion Criteria:

• Known history of Crohn's disease
• No previous history of treatment for UC (treatment-naïve)
• Subjects on steroid medication who are unable to have steroids tapered and be completely off steroids at least two weeks prior to screening
• Unable to stop steroid enemas or suppositories, or 5-ASA enemas or suppositories, at least two weeks prior to screening
• Subjects who have received any investigational or approved biologic therapy within eight weeks or five half-lives prior to screening (whichever is longer)
• Subjects who have received any investigational or approved non-biologic therapy, except for those specifically listed in the Permitted Concomitant Medications, for the treatment of underlying disease, within 30 days or five half-lives prior to screening (whichever is longer)
• Major gastrointestinal surgery (not including appendectomy or cholecystectomy) within two months before screening, or any history of total colectomy