The purpose of this study is to evaluate the efficacy and safety of vedolizumab intravenous (IV) treatment compared to adalimumab subcutaneous (SC) treatment over a 52-week treatment period.

The drug being tested in this study is called vedolizumab. Vedolizumab is being tested to treat people who have ulcerative colitis. This study will look at the stool frequency, rectal bleeding and findings on endoscopy of people who take vedolizumab compared to those who take adalimumab.

The study will enroll approximately 658 participants. Participants will be randomly assigned (by chance, like flipping a coin) to one of the two treatment groups-which will remain undisclosed to the patient and study doctor during the study (unless there is an urgent medical need):

• Vedolizumab 300 mg IV
• Adalimumab 160 mg on Day 1 followed by 80 mg on Week 2 then 40 mg every 2 weeks SC

All participants will receive 1 intravenous infusion on Day 1 and Weeks 2, 6, 14, 22, 30, 38, and 46. All participants will also receive 4 SC injections on Day 1 or 2 SC injections each on Days 1 and 2, followed by 2 SC injections in 1 day on Week 2 and then 1 SC injection every 2 weeks for up to Week 50. All participants will be asked to record the symptoms of ulcerative colitis in a daily diary.

This multi-center trial will be conducted worldwide. The overall time to participate in this study is 79 weeks. Participants will make approximately 11 visits to the clinic, and will be contacted by telephone 6 months after last dose of study drug for a follow-up assessment.

Inclusion Criteria:

1. Has a diagnosis of ulcerative colitis established at least 3 months prior to screening by clinical and endoscopic evidence and corroborated by a histopathology report.

2. Has moderately to severely active ulcerative colitis as determined by a Mayo score of 6 to 12 with an endoscopic subscore greater than or equal to >=2 within 14 days prior to the randomization.

3. Has evidence of ulcerative colitis proximal to the rectum (>=15 centimeter [cm] of involved colon).

4. With extensive colitis (up to the hepatic flexure) or pancolitis of >8 years duration or left-sided colitis of >12 years duration must have documented evidence that a surveillance colonoscopy was performed within 12 months of the initial screening visit (may be performed during the Screening Period).

5. The participant:

   1. Has had previous treatment with tumor necrosis factor- alpha (TNF-alpha) antagonists without documented clinical response to treatment (example, due to lack of response [primary nonresponders], loss of response, or intolerance [secondary nonresponders]), or
   2. Has previously used a TNF-alpha antagonists (except adalimumab), and discontinued its use due to reasons other than safety, or
   3. Is naïve to TNF-alpha antagonist therapy but is failing current treatment (example, corticosteroids, 5-aminosalicylate [5-ASA], or immunomodulators).

Exclusion Criteria:

1. Clinical evidence of abdominal abscess or toxic megacolon at Screening.

2. Has had an extensive colonic resection, subtotal or total colectomy.

3. Has had ileostomy, colostomy, or known fixed symptomatic stenosis of the intestine.

4. Has a diagnosis of Crohn's colitis or indeterminate colitis, ischemic colitis, radiation colitis, diverticular disease associated with colitis, or microscopic colitis.

5. Has received any of the following for the treatment of underlying disease within 30 days of randomization:

   1. Non-biologic therapies (example, cyclosporine, tacrolimus, thalidomide) other than those specifically listed in Section Permitted Medications For Treatment of UC.
   2. An approved non-biologic therapy in an investigational protocol.

6. Has received any investigational or approved biologic or biosimilar agent within 60 days or 5 half lives prior to the screening (whichever is longer).

7. Has previously received natalizumab, efalizumab, adalimumab, AMG-181, anti-mucosal addressin cell adhesion molecule-1 antibodies, or rituximab.

8. Has previously received vedolizumab.

9. Has history or evidence of adenomatous colonic polyps that have not been removed, or colonic mucosal dysplasia.

10. Evidence of an active infection during Screening.

11. Evidence of, or treatment for, Clostridium difficile (C. difficile) or other intestinal pathogen within 28 days prior to the 1st dose of study drug.

12. Has chronic hepatitis B virus (HBV) infection* or chronic hepatitis C virus (HCV) infection (* HBV immune participants, ie, being hepatitis B surface antigen [HBsAg], may participate).

13. Has active or latent TB, regardless of treatment history.

14. Has used a topical (rectal) treatment with (5-ASA) or corticosteroid enemas/suppositories within 2 weeks of the administration of the 1st dose of study drug.

15. Has a positive progressive multifocal leukoencephalopathy (PML) subjective symptom checklist prior to the administration of the first dose of study drug.

Takeda makes patient-level, de-identified data sets and associated documents available for all interventional studies after applicable marketing approvals and commercial availability have been received (or program is completely terminated), an opportunity for the primary publication of the research and final report development has been allowed, and other criteria have been met as set forth in Takeda's Data Sharing Policy (see www.TakedaClinicalTrials.com for details). To obtain access, researchers must submit a legitimate academic research proposal for adjudication by an independent review panel, who will review the scientific merit of the research and the requestor's qualifications and conflict of interest that can result in potential bias. Once approved, qualified researchers who sign a data sharing agreement are provided access to these data in a secure research environment.