Evaluation of 611 in Chinese Children and Adolescents With Moderate to Severe Atopic Dermatitis

Inclusion Criteria: * Subjects or their legal guardians must be able to understand and comply with the study procedures. and must participate voluntarily and sign the written informed consent. * When signing the informed consent form (ICF), Part 1: 12 years old ≤ age \< 18 years old, weight ≥ 30kg; Part 2: 6 years old ≤ age \< 12 years old, weight ≥ 15kg. * AD (according to Hanifin-Rajka Criteria) that had been present for at least 1 years before the screening visit. * (Investigator's Global Assessment) IGA ≥ 3 at screening and baseline visits. * (Eczema Area and Severity Index) EASI ≥16 at screening and baseline visits. * Participants with \>=10 percent (%) body surface area (BSA) of AD involvement at screening and baseline visits. * Baseline peak pruritus Numerical Rating Scale (NRS) average score for maximum itch intensity ≥4. * With documented recent history (within 1 year before the baseline visit) of inadequate response to topical AD medication(s) or for whom topical treatments is medically inadvisable. * Willing apply a stable dose of topical emollient (moisturizer) twice daily for at least the 7 consecutive days immediately before the baseline visit and continue for the duration of the study. * Potentially fertile subjects (such as women who have had their first period or men who have had sperm implantation) must use highly effective contraception throughout the study period and for at least 3 months after the last dose. * Patient, either alone or with help of parent…