Inclusion Criteria

• Has a clinical diagnosis of Ulcerative Colitis (UC) at least 3 months before screening
• Has moderately to severely active UC, defined as a baseline (week 0) Mayo score of 6 to 12, including a screening endoscopy subscore of the Mayo score  ≥ 2 as determined by a central reading of the video endoscopy
• Has failed biologic therapy
  • Has received treatment with 1 or more tumour necrosis factor (TNF) antagonists or vedolizumab at a dose approved for the treatment of UC and failed to respond to or tolerate such treatment
  • Is naïve to biologic therapy (TNF antagonists or vedolizumab) 
  • Has received biologic therapy but has not demonstrated a history of failure to respond to, or tolerate, a biologic therapy and has a prior or current UC medication history that includes at least 1 of the following
    • Inadequate response to or failure to tolerate current treatment with oral corticosteroids or immunomodulators (6-mercaptopurine [6-MP] or azathioprine [AZA]) 
    • History of failure to respond to, or tolerate, at least 1 of the following therapies
      • Oral or IV corticosteroids 
      • Immunomodulators (6-MP or AZA) 
    • History of corticosteroid dependence 
      • An inability to successfully taper corticosteroids without a return of the symptoms of UC
• Before the first administration of study agent vedolizumab must have been discontinued for at least 4 months and anti-tumor necrosis factors (TNFs) for at least 8 weeks

Exclusion Criteria

• Has severe extensive colitis and is at imminent risk of colectomy
• Has UC limited to the rectum only or to < 20 centimeters (cm) of the colon
• Presence of a stoma or history of a fistula
• History of extensive colonic resection (for example, less than 30 cm of colon remaining) that would prevent adequate evaluation of the effect of study agent on clinical disease activity
• History of colonic mucosal dysplasia
  • No exclusion from the study because of a pathology finding of "indefinite dysplasia with reactive atypia''