A Study of the Efficacy and Safety of Etrolizumab Treatment in Maintenance of Disease Remission in Ulcerative Colitis (UC) Participants Who Are Naive to Tumor Necrosis Factor (TNF) Inhibitors

Inclusion Criteria:

- Moderately to severely active UC as determined by an MCS of 6-12 with an endoscopic
subscore greater than or equal to (>=) 2 as determined by the central reading
procedure (endoscopy to be performed 4-16 days prior to Day 1), a rectal bleeding
subscore >=1, and a stool frequency subscore >= 1 during the screening period (prior
to Day 1)

- Evidence of UC extending a minimum of 20 centimeters (cm) from the anal verge as
determined by baseline endoscopy (flexible sigmoidoscopy or colonoscopy) performed
during screening, 4-16 days prior to Day 1

- Naive to treatment with any anti-TNF therapy

- Participants must have had an inadequate response, loss of response, or intolerance to
prior corticosteroid and/or immunosuppressant treatment

- Background regimen for UC may include oral 5-aminosalicylate (5-ASA), oral
corticosteroids, budesonide multi-matrix system (MMX), probiotics, azathioprine (AZA),
6-mercaptopurine (6-MP), or methotrexate (MTX) if doses have been stable during the
screening period

- Use of highly effective contraception

- Must have received a colonoscopy within the past year or be willing to undergo a
colonoscopy in lieu of a flexible sigmoidoscopy at screening

Exclusion Criteria:

- A history of or current conditions and diseases affecting the digestive tract, such as
indeterminate colitis, Crohn's disease, fistulas or abdominal abscesses, colonic
mucosal dysplasia, intestinal obstruction, toxic megacolon, or unremoved adenomatous
colonic polyps

- Prior or planned surgery for UC

- Past or present ileostomy or colostomy

- Have received non-permitted inflammatory bowel disease (IBD) therapies (including
natalizumab, vedolizumab, and efalizumab) as stated in the protocol

- Prior treatment with anti-adhesion molecules (such as mucosal addressin cell adhesion
molecule [MAdCAM-1])

- Chronic hepatitis B or C infection, human immunodeficiency virus (HIV), or
tuberculosis (active or latent)