Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of AMG 139 in Healthy Subjects and Subjects with Moderate to Severe Psoriasis

Part A – Healthy Volunteers: - Healthy male or female of non-reproductive potential subjects between 18 to 45 years-of-age - Body mass index (BMI) between 18 and 32 kg/m2 - Normal or clinically acceptable physical examination, clinical laboratory values, and ECG - Additional inclusion criteria apply Part B – Psoriasis Subjects: - Male or female of non-reproductive potential subjects with PsO between 18 to 55 years-of-age - Body mass index (BMI) between 18 and 32 kg/m2 - Normal or clinically acceptable physical examination (PE), clinical laboratory values, and ECG; clinically acceptable PE includes evidence of moderate to severe plaque PsO - Diagnosis of plaque PsO for at least 6 months - Moderate to severe plaque PsO defined by: - A minimum PASI score of ≥ 10 - Psoriasis involving ≥ 10% of the Body Surface Area (BSA) - Additional inclusion criteria apply

Parts A – 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 evaluation, procedures or completion; - Recent or on-going infection(s) - Underlying condition(s) that predisposes the subject to infections - History of malignancy of any type, other than in situ cervical cancer or surgically excised non-melanomatous skin cancers in past 5 years - Additional exclusion criteria apply Part B – Psoriasis Subjects: - 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 evaluation, procedures or completion; - Recent or on-going infection(s) - Underlying condition(s) that predisposes the subject to infections - Guttate, pustular, or other non-plaque forms of PsO - Evidence of skin conditions other than PsO (eg, eczema) that would interfere with evaluations of the effect of investigational product on psoriasis - History of malignancy of any type, other than in situ cervical cancer or surgically excised non-melanomatous skin cancers in past 5 years - Additional exclusion criteria apply