Abrilumab (AMG 181) in Adults With Moderate to Severe Ulcerative Colitis

Inclusion Criteria: * Diagnosis of ulcerative colitis (UC) established ≥ 3 months before baseline by clinical and endoscopic evidence and corroborated by a histopathology report. * Moderate to severe active UC as defined by a total Mayo score of 6 to 12 with a centrally read rectosigmoidoscopy score ≥2 prior to baseline * Inadequate response to, loss of response to, or intolerance to at least one of the following treatments: * Immunomodulators * Anti-TNF agents * Corticosteroids (non-US sites only). * Neurological exam free of clinically significant, unexplained signs or symptoms during screening and no clinically significant change prior to randomization Exclusion Criteria: * Disease limited to the rectum (ie, within 10 cm of the anal verge) * Toxic megacolon * Crohn's Disease * History of subtotal colectomy with ileorectostomy or colectomy with ileoanal pouch, Koch pouch, or ileostomy for UC * Planned bowel surgery within 24 weeks from baseline * Stool positive for C. Difficile toxin at screening * History of gastrointestinal surgery within 8 weeks of baseline * Primary Sclerosing Cholangitis * Any uncontrolled or clinically significant systemic disease * Condition or disease that, in the opinion of the investigator would pose a risk to subject safety or interfere with study evaluation, procedures or completion. * Known to have tested positive for hepatitis B virus surface antigen, hepatitis C virus antibody or human immunodeficiency virus (HIV) * Underlying condition that predisposes subject to infections (eg, uncontrolled diabetes; history of splenectomy) * Known history of drug or alcohol abuse within 1 year of screening * Malignancy (other than resected cutaneous basal or cutaneous squamous cell carcinoma, or treated in situ cervical cancer considered cured) within 5 years of screening visit (if a malignancy occurred \> 5 years ago, subject is eligible with documentation of disease free state since treatment) * Immunosuppressive therapy with either cyclosporine A, tacrolimus, or mycophenolate mofetil, within 1 month prior to baseline * Prior exposure to anti tumor necrosis factor (TNF) agents, within 2 months, or 5 times the respective elimination half life (whichever is longer) prior to baseline * Any prior exposure to vedolizumab, rituximab, efalizumab, natalizumab * Use of topical (rectal) aminosalicylic acid (eg, mesalamine) or topical (rectal) steroids within 2 weeks prior to baseline * Use of intravenous or intramuscular corticosteroids within 2 weeks prior to screening and during screening * Previously treated with AMG 181 * Received any type of live attenuated vaccine \< 1 month prior to baseline or is planning to receive any such live attenuated vaccine over the course of the study * Treatment of infection with intravenous (within 30 days of baseline) or oral (within 14 days prior to baseline) antibiotics, antivirals, or antifungals * Abnormal laboratory results at screening * Any other laboratory abnormality, which, in the opinion of the investigator, will prevent the subject from completing the study or will interfere with the interpretation of the study results * Currently enrolled in another investigational device or drug study, or less than 30 days since ending another investigational device or drug study(s), or receiving other investigational agent(s)