Evaluation of 611 in Chinese Children With Moderate to Severe Atopic Dermatitis(AD)

Inclusion Criteria: 1. The participants and their legally acceptable representatives are able to understand and comply with the research procedures, agree to participate in the research, and sign the Informed Consent Form (ICF) ; 2. When signing the informed consent form, the age should be ≥ 2 years old and \< 6 years old for part A, and ≥ 2 years old and \< 12 years old for part B. any gender, with body weight ≥ 15 kg at baseline; 3. During the screening process, patients were diagnosed with atopic dermatitis (AD) according to the Hanifin - Rajka criteria, and their AD medical history was evaluated by researchers to be ≥ 6 months for participants aged ≥2 years to \<6 years, ≥ 3 months for participants aged ≥6 years to \<12 years; 4. At the screening and baseline, the Eczema Area and Severity Index (EASI) score is ≥ 16 points; 5. At the screening and baseline, the Investigator Global Assessment (IGA) score is ≥3 points; 6. At the time of screening and baseline, the affected body surface area (BSA) by atopic dermatitis (AD) is ≥10%; 7. At baseline, the weekly average score of Daily pruritus Numerical Rating Scale (NRS) is ≥ 4 points; 8. Participants should have relevant medical records, other medical visit records, or other evidence within the previous year for researchers to evaluate. The participants have poor efficacy of topical drug treatment; 9. Be willing to use a stable dose of emollient (moisturizer) on the affected areas of atopic dermatitis (AD) twice a day for at least 7 days before randomization and continue to use it throughout the study period; 10. Participants with potential fertility (e.g., females who have experienced menarche or males who have had nocturnal emissions) must agree to avoid sexual activity or use highly effective contraceptive methods throughout the entire study period and for at least 3 months after the last dose of the medication; 11. The participants (if applicable) and their legally acceptable representatives shall be able to understand and complete (either independently or with the assistance of a guardian) the research - related questionnaire filling. Exclusion Criteria: 1. Intolerance to TCS / TCI treatment or contraindications to TCS / TCI; 2. Merge other skin comorbidities that may interfere with the research evaluation; 3. Combined with active parasitic infections (such as helminths) or suspected parasitic infections ; 4. Any history of vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) ; 5. Randomly select patients with any malignant tumor diagnosed within the past 5 years or currently having the disease; 6. The participant had a severe infection requiring intravenous antibiotics and/or hospitalization within 4 weeks before randomization, or had an active infection requiring oral antibiotics within 2 weeks before randomization, and the investigator evaluated that there might be uncontrollable risks for the participant to participate in this study. Or with a skin infection that requires treatment with topical anti-infective agents within 1 week before randomization; 7. A history of known or suspected immunosuppression, including a history of invasive opportunistic infections; or those who, although the infection has resolved, are considered by the investigator to be likely to have frequent recurrences; 8. Active tuberculosis, unless that was well documented that the participants had adequately treated; 9. Any medical condition that, in the opinion of the investigator, is serious or unstable and may affect the safety of the participants during the study and/or prevent the participants from completing the study, including but not limited to cardiovascular, gastrointestinal, liver, kidney, neurological, musculoskeletal, infectious, endocrine, metabolic, hematological, and mental diseases; 10. Participants who have received topical therapies for AD systemic traditional Chinese medicine for AD, systemic glucocorticoids, or other immunosuppressants / immunomodulators, any cell-depleting agents, monoclonal antibodies within a specified period prior to randomization. 11. Received live vaccines or live attenuated vaccines within 4 weeks before randomization; 12. Participants with abnormal laboratory parameters deemed ineligible for enrollment at the Investigator's discretion. ; 13. At the screening, the test results are positive for hepatitis B, positive for hepatitis C virus antibody (HCVAb), positive for human immunodeficiency virus antibody (HIVAb), and positive for serum Treponema pallidum antibody (TPAb); 14. Used any investigational drugs within 8 weeks or 5 half-lives (whichever is longer) before randomization; 15. Had a history of alcohol or drug abuse within 6 months before randomization; 16. Known to be allergic or intolerant to any components of the investigational drug; 17. Planned or were expected to undergo major surgical operations during the study period; 18. According to the investigator's judgment, the participants were not suitable to participate in the study due to other diseases or reasons.