To assess the safety and tolerability of single subcutaneous (SC) and intravenous (IV) doses of AMG 181 in healthy subjects and of a single SC dose in subjects with mild to moderate ulcerative colitis (UC)

Inclusion Criteria: Healthy Volunteers

• Healthy male or female subjects of non-reproductive potential between 18 to 45 year-of -age
• Body Mass Index (BMI) between 18 and 34 kg/m2
• Normal physical and neurological examination, clinical laboratory values and ECG
• Additional inclusion criteria apply

Inclusion Criteria: Subjects with Mild to Moderate Ulcerative Colitis

• Male or female subjects between 18 to 55 year-of -age
• Body Mass Index (BMI) between 18 and 34 kg/m2
• Diagnosis of Ulcerative Colitis for at least 2 months
• Active, mild to moderate disease as defined by an Ulcerative Colitis Disease Activity Index (UCDAI, aka Mayo score) score of 4 to 9 (inclusive), with a minimum sigmoidoscopy score of 1
• Additional inclusion criteria apply

Exclusion criteria: Healthy Volunteers

• History or evidence of a clinically significant disorder (including psychiatric), condition or disease that would pose a risk to subject safety or interfere with the study evaluations, procedures or completion
• History of malignancy of any type, other than in situ cervical cancer or surgically excised non-melanomatous skin cancers within the past 5 years
• Recent or on-going infection(s)
• Underlying condition(s) that predisposes the subject to infections
• Additional exclusion criteria apply

Exclusion criteria: Subjects with Mild to Moderate Ulcerative Colitis

• Disease limited to the rectum, i.e. within 20 cm of the anal verge
• Any prior gastrointestinal surgery
• Evidence of severe disease (as evidenced by an Hb concentration <11g/dL; toxic megacolon, or an UCDAI score≥10)
• Immunosuppressive therapy with either azathioprine, methotrexate, or mercaptopurine, within the past 3 months
• Prior exposure to a biologic agent or cyclosporine A
• Use of antibiotics within the past 2 weeks of screening and during screening period
• Use of topical (e.g. suppository or enema) mesalamine or steroids within two weeks prior to day 1
• Additional exclusion criteria apply