Key Inclusion Criteria:  Male or female, over the age of 18 Chronic atopic dermatitis (AD) diagnosed at least 1 year. Subject with EASI score ≥16, IGA ≥ 3 (on the 0 to 4 IGA scale, in which 3 is moderate and 4 is severe), ≥ 10% body surface area (BSA) of AD involvement. Subjects with a history of an inadequate response or medically inappropriate use of topical drug treatment within 6 months.  Key Exclusion Criteria:  Inadequate washout period for prior drug therapy (eg. corticosteroids, immunosuppressive/ immunomodulating, biologics, phototherapy, Chinese traditional medicine, anti-infective agents). History of exposure to active TB, and/or history or current evidence of TB infection. Positive serology results at Screening for hepatitis B, hepatitis C or HIV. Any history of vernal keratoconjunctivitis (VKC) or atopic keratoconjunctivitis (AKC) within 6 months before the baseline visit. History of clinical parasite infection, recent or planned travel to an area with endemic parasite infection within 6 months before the Screening visit Any medical or psychiatric condition, laboratory, or ECG parameter which, in the opinion of the Investigator or the Sponsor's medical monitor, would place the subject at risk, interfere with participation in the study, or interfere with the interpretation of study results.