A Study Comparing the Efficacy and Safety of Etrolizumab With Adalimumab and Placebo in Participants With Moderate to Severe Ulcerative Colitis (UC) in Participants Naive to Tumor Necrosis Factor (TNF) Inhibitors (Study #1)

Inclusion Criteria:

- Diagnosis of UC established at least 3 months prior to randomization (Day 1)

- Moderately to severely active UC as determined by the MCS

- Naive to treatment with TNF inhibitor therapy

- An inadequate response, loss of response, or intolerance to prior corticosteroid
and/or immunosuppressant treatment

- Background UC therapy may include oral 5-aminosalisylate (ASA), oral corticosteroids,
budesonide, probiotics, azathioprine (AZA), 6-mercaptopurine (MP), or methotrexate
(MTX) if doses have been stable for the 8 weeks immediately prior to randomization

- Use of highly effective contraception method as defined by the protocol

- 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, suspicion of ischemic, radiation or microscopic colitis,
Crohn's disease, fistulas or abdominal abscesses, colonic mucosal dysplasia, stricture
(stenosis) of the colon, 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) anti-integrin therapies
(including natalizumab, vedolizumab, and efalizumab) as stated in the protocol

- Any prior treatment with anti-adhesion molecules (e.g., anti-mucosal addressin cell
adhesion molecule-1 [anti-MAdCAM-1])

- Congenital or acquired immune deficiency, chronic hepatitis B or C infection, HIV
positive

- Evidence of or treatment for Clostridium difficile within 60 days prior to
randomization or other intestinal pathogens within 30 days prior to randomization

- History of active or latent tuberculosis (TB), recurrent opportunistic infections,
severe disseminated viral infections and organ transplant

- Any major episode of infection requiring treatment with intravenous (IV) antibiotics
within 8 weeks prior to screening or oral antibiotics within 4 weeks prior to
screening

- Received a live attenuated vaccine within 4 weeks prior to randomization