A First-in-Human, Double Blind, Single Dose Study in Healthy Subjects and Subjects With Mild Atopic Asthma.

Inclusion Criteria (All subjects) * Is a current non-smoker, has not used any nicotine or tobacco containing products (including but not limited to: snuff, chewing tobacco, cigars, cigarettes, pipes, or nicotine patches) within the last 6 months, and cumulative smoking history is ≤10 pack years. * Females must be of documented non-reproductive potential (ie, postmenopausal \[see definition below\]; OR history of hysterectomy; OR history of bilateral salpingectomy; OR history of bilateral oophorectomy). * Body mass index (BMI) between ≥ 18.0 and ≤ 32.0 kg/m2 at screening. (Subjects with mild atopic asthma only) * Documented history of mild, stable atopic asthma within 2 years of screening. * Has used only inhaled short-acting β2-agonists (less than twice weekly) to treat asthma. * Pre-bronchodilator forced expiratory volume in 1 second (FEV1) \> 70% predicted at screening. Exclusion Criteria (All subjects) * History or evidence of a clinically significant disorder, condition or disease that, in the opinion of the Principal Investigator or Amgen medical monitor would pose a risk to subject safety or interfere with the study evaluation, procedures, or completion. * Subject has a history of residential exposure to tuberculosis without a documented history of prophylactic treatment of tuberculosis or subject has a positive purified protein derivative (PPD) or QuantiFERON test at screening. Subjects with a documented negative PPD or QuantiFERON test within 4 weeks prior to screening who have no known tuberculosis exposure and have not traveled to an area with tuberculosis do not need to have a test performed at screening. * Has donated or lost ≥ 500 mL of blood or plasma within 8 weeks of administration of the first dose of IP. Other criteria may apply.