Vedolizumab Intravenous (IV) Dose Optimization in Ulcerative Colitis

Inclusion Criteria: 1. Has a diagnosis of UC established at least 1 month prior to Screening by clinical and endoscopic evidence and corroborated by a histopathology report. 2. Has moderately to severely active UC as determined by a complete Mayo score of 6 to 12 with an endoscopic subscore ≥2 within 28 days prior to enrollment. 3. Has evidence of UC proximal to the rectum (≥15 cm of involved colon) prior to start of vedolizumab IV dosing. 4. Has been determined to be suitable for vedolizumab IV for routine management of UC by their physician. 5. Has a family history of colorectal cancer, personal history of increased colorectal cancer risk, age \>50 years, or other known risk factor must be up-to-date on colorectal cancer surveillance (may be performed during screening). 6. Has demonstrated an inadequate response with, lost response to, or intolerance of at least 1 of the following agents: immunomodulators, corticosteroids, or tumor necrosis factor-alpha (TNF-α) antagonists. Subject who are naive to TNF-α antagonist therapy or who have previously failed TNF-α antagonist therapy (including primary and secondary non-responders or intolerant) may be included. Week 6 Randomized Treatment Period Inclusion Criteria 7. Following Lead-in Period, the subject is assessed as having high vedolizumab drug clearance based on a predefined Week 5 serum vedolizumab concentration threshold (\<50 microg/mL). 8. Following Lead-in Period, the subject is a non-responder based on partial Mayo score at Week 6. Exclusion Criteria: 1. Has clinical evidence of abdominal abscess or toxic megacolon at the Screening Visit. 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 screening: 1. Non-biologic therapies (eg. cyclosporine, tacrolimus, thalidomide) 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 screening (whichever is longer). 7. Has previously had prior exposure to approved or investigational anti-integrin antibodies (e.g. natalizumab, efalizumab, etrolizumab, AMG-181, anti-MAdCAM-1 antibodies or rituximab). 8. Has previously received approved or investigational vedolizumab. 9. The subject currently requires or is anticipated to require surgical intervention for UC during the study. 10. Has history or evidence of adenomatous colonic polyps that have not been removed, or colonic mucosal dysplasia. 11. Has any evidence of an active infection during Screening (eg, sepsis, cytomegalovirus, or listeriosis). 12. Has a clinically significant infection (eg, pneumonia, pyelonephritis) within 30 days prior to screening, or ongoing chronic infection. 13. Has evidence of active C. difficile as evidenced by positive C. difficile toxin or is having treatment for C. difficile infection or other intestinal pathogens during Screening. 14. Has a known history of infection with human immunodeficiency virus (HIV), hepatitis B (HBV), or chronic HBV (HBV immune subjects (ie, being hepatitis B surface antigen \[HBsAg\] negative and hepatitis B antibody positive) may, however, be included), or hepatitis C virus (HCV) infection. Subjects with documented successful treatment of HCV with sustained virological response (SVR) at 26 weeks can be enrolled. 15. Has active or latent tuberculosis (TB), as evidenced by the following: a. A diagnostic TB test performed within 30 days of screening or during the Screening Period that is positive, defined as: i. Positive QuantiFERON test or 2 successive indeterminate QuantiFERON tests, OR ii. A TB skin test reaction ≥ 5 mm OR, b. Chest X-ray within 3 months of screening that is suspicious for pulmonary TB, and a positive or 2 successive indeterminate QuantiFERON tests within 30 days prior to Screening or during the Screening Period. 16. Has any identified congenital or acquired immunodeficiency (eg, common variable immunodeficiency, HIV infection, organ transplantation). 17. Has any live vaccination within 30 days prior to Screening or is planning to receive any live vaccination during participation in the study. 18. Has used a topical (rectal) treatment with (5-ASA) or corticosteroid enemas/suppositories within 2 weeks prior to Screening. 19. Has a history of hypersensitivity or allergies to vedolizumab IV or its components. 20. Has received total parenteral nutrition (TPN) or albumin in the last 30 days prior to screening. 21. Has any unstable or uncontrolled cardiovascular disorder, heart failure moderate to severe (New York Class Association III or IV), any pulmonary, hepatic, renal, GI, genitourinary, hematological, coagulation, immunological, endocrine/metabolic, or other medical disorder that, in the opinion of the investigator, would confound the study results or compromise subject safety. 22. Has had a surgical procedure requiring general anesthesia within 30 days prior to screening or is planning to undergo major surgery during the study period. 23. Has a history of malignancy, except for the following: adequately-treated non-metastatic basal cell skin cancer; squamous cell skin cancer that has been adequately treated and that has not recurred for at least 1 year prior to Screening; and history of cervical carcinoma in situ that has been adequately treated and that has not recurred for at least 3 years prior to screening. Subjects with remote history of malignancy (eg, \>10 years since completion of curative therapy without recurrence) will be considered based on the nature of the malignancy and the therapy received and must be discussed with the sponsor on a case by-case basis prior to Screening. 24. Has a history of any major neurological disorders, including stroke, multiple sclerosis, brain tumor, demyelinating, or neurodegenerative disease. 25. Has a positive progressive multifocal leukoencephalopathy (PML) subjective symptom checklist during Screening or prior to the administration of the first dose of study drug on Day 1. 26. Has a history of drug abuse (defined as any illicit drug use) or a history of alcohol abuse within 1 year prior to the Screening Visit.