To assess the safety and tolerability of multiple subcutaneous doses of AMG 181 in healthy subjects, in subjects with active ulcerative colitis, and in subjects with active Crohn's disease.

Inclusion Criteria:

• Body Mass Index (BMI) between 18 and 34 kg/m2
• Normal physical and neurological examination, clinical laboratory values and ECG
• Ulcerative Colitis Disease Activity Index (UCDAI, aka Mayo score) score of 4 to 10 (inclusive), with a minimum sigmoidoscopy score of 1; (for subjects with ulcerative colitis)
• Crohn's Disease Activity Index (CDAI) score of >150 and < 450 at screening (for subjects with Crohn's disease)
• Additional inclusion criteria apply

Exclusion Criteria:

• 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
• Underlying condition(s) that predisposes the subject to infections
• Disease limited to the rectum, i.e. within 10 cm of the anal verge (for subjects with ulcerative colitis)
• Evidence of severe disease (as evidenced by an Hb concentration less or equal to 10g/dL; toxic megacolon, or an UCDAI score greater than 10) (for subjects with ulcerative colitis)
• Subject has short bowel syndrome (for subjects with Crohn's disease)
• Presence of an ostomy (for subjects with Crohn's disease)
• Presence of a fistula (for subjects with Crohn's disease)
• Additional exclusion criteria apply