The primary objective of this study is to evaluate the effect of abrilumab on induction of remission in adults with moderate to severe ulcerative colitis after 8 weeks of treatment as assessed by a total Mayo Score ≤ 2 points, with no individual subscore > 1 point.

The study consisted of a 24-week double-blind, placebo-controlled treatment period followed by an open-label period of approximately 108 weeks. Participants were eligible to enter the open-label period of the study early if they did not achieve a response at week 8 and had an inadequate response at week 12 or later or if they experienced disease worsening after achieving response and/or remission at week 8. Failure to achieve response at week 8 was defined as failure to achieve a decrease from baseline in total Mayo Score ≥ 3 points and ≥ 30% decrease from baseline. Inadequate response at week 12 or later was defined as failure to achieve a 2-point decrease and 25% improvement in partial Mayo Score compared with screening and minimum partial Mayo Score ≥ 5 points. Disease worsening was defined as an increase in partial Mayo Score ≥ 3 points from the week 8 value and minimum partial Mayo Score ≥ 5 points with recto-sigmoidoscopy sub-score ≥ 2.

Participants were planned to be randomized in a 2:1:2:2:2 ratio to placebo or abrilumab at 7 mg, 21 mg, 70 mg (on day 1, week 2, week 4, and every 4 weeks thereafter until week 24), or 210 mg (on day 1 followed by placebo in weeks 2 and 4 and every 4 weeks thereafter until week 24), respectively. Due to a consistent discrepancy between the investigational product (IP) instruction manual (IPIM) description of vial positions and the actual vial positions in the IP package participants were initially randomized to 3 arms (placebo, 70 mg, and 210 mg) with a randomization ratio of 4:3:2. The study was temporarily paused while this issue was investigated. Once the discrepancy was corrected, Protocol Amendment 3 implemented, and affected participants completed their double-blind treatment period, the study resumed enrollment and randomization per protocol. Neither the randomization nor study blind was compromised and therefore the intent-to-treat principle was maintained.

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)