The primary objective of the study was to evaluate the efficacy of 611 in Chinese adults with moderate to severe atopic dermatitis.

The maximum study duration was 64 weeks per participants, including a screening period of up to 4 weeks, a 52-week treatment period, and an 8-week follow-up period.

Inclusion Criteria:

1. Subject must be able to understand and comply with the requirements of the study. and must participate voluntarily and sign the written informed consent.
2. Male or female adults ages 18 to 75 years old when signing the informed consent.
3. AD (according to Hanifin-Rajka Criteria) that had been present for at least 1 years before the screening visit.
4. Eczema Area and Severity Index (EASI) score greater than or equal to (>=) 16 at the screening and baseline visits.
5. Investigator's Global Assessment (IGA) score >=3 (on the 0 to 4 IGA scale, in which 3 was moderate and 4 was severe) at the screening and baseline visits.
6. Participants with >=10 percent (%) body surface area (BSA) of AD involvement at the screening and baseline visits.
7. Baseline Pruritus Numerical Rating Scale (NRS) average score for maximum itch intensity >=4.
8. Recent history (within 12 months before the screening visit) of inadequate response to treatment with topical medications or for whom topical treatments were otherwise medically inadvisable (e.g., because of important side effects or safety risks).
9. Have applied a stable dose of topical emollient (moisturizer) twice daily for at least the 7 consecutive days immediately before the baseline visit.
10. Female subjects of reproductive age (and their male partners) and male subjects (and their female partners) must use highly effective contraception throughout the study period and for at least 3 months after the last dose. The subjects had no plans to pregnancy, donate sperm or donate egg during the whole study period and for at least 3 months after the last dose.

Exclusion Criteria:

1. Presence of skin comorbidities that may interfere with study assessments
2. Presence of active endoparasitic infections; or suspected endoparasitic.
3. Any history of vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC).
4. History of malignancy within 5 years before the baseline visit, except completely treated in situ carcinoma of the cervix at least 1 year, completely treated and resolved non-metastatic squamous or basal cell carcinoma of the skin at least 1 year.
5. Active chronic or acute infection requiring treatment with systemic anti-infective therapy within 2 weeks before the baseline visit, or superficial skin infections within 1 week before the baseline visit.
6. Known or suspected history of immunosuppression, including history of invasive opportunistic infections (e.g., histoplasmosis, listeriosis, coccidioidomycosis, pneumocystosis, aspergillosis) despite infection resolution: or unusually frequent infections, per investigator judgment.
7. Active TB, unless that was well documented that the participants had adequately treated.
8. Any medical condition that, in the opinion of the investigator, is serious or unstable and may affect the subject's safety and/or prevent the subject from completing the study
9. Treatment with topical drugs such as corticosteroids, topical calcineurin inhibitors, PDE inhibitors, or Janus kinase (JAK) inhibitors within 2 weeks before baseline;
10. The lab abnormalities at screening or baseline and not suitable for inclusion in the study judged by investigator;
11. Patients who have active Hepatitis B, Hepatitis C or HIV infections as determined by positive results at Screening.
12. History of alcohol or drug abuse within 6 months before baseline.
13. History of hypersensitivity to 611 or their excipients.
14. Have been vaccinated with live (attenuated) vaccine within 2 months before baseline or planned during the study period;
15. Have used any investigational drug/treatment within 12 weeks before baseline;
16. Planned or anticipated major surgical procedure during the patient's participation in this study.
17. Pregnant or lactating women, or subjects with pregnancy or lactation plans during the study period.
18. Any reason which, in the opinion of investigator, would prevent the subject from participating in the study.