Study to Evaluate Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of AMG 181.

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