Evaluation of 611 in Chinese Adult Patients With Moderate-to-Severe Atopic Dermatitis

Inclusion Criteria: * Male or female, 18 years or older who has AD (according to Williams Criteria) at the screening visit. * AD that had been present for at least 1 year before the baseline visit. * Body mass index (BMI) was 19-32 kg/m\^2 (including boundary values), male subjects weighed ≥50.0kg, female subjects weighed ≥45.0kg. * Eczema Area and Severity Index (EASI) score greater than or equal to (\>=) 16. * Investigator's Global Assessment (IGA) score \>=3 (on the 0 to 4 IGA scale, in which 3 was moderate and 4 was severe). * Participants with \>=10 percent (%) body surface area (BSA) of AD involvement. * Baseline Pruritus Numerical Rating Scale (NRS) average score for maximum itch intensity \>=4. * Recent history (within 6 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). * Have applied a stable dose of topical emollient (moisturizer) twice daily for at least the 7 consecutive days before the baseline visit. * Subject must be able to understand and complete the study related questionnaires and sign the written informed consent (ICF). Exclusion Criteria: * Presence of any one of the following lab abnormalities at screening: Hemoglobin ≤ the lower limit of normal (LLN); White blood cell count below LLN; Neutrophil count below LLN; Blood platelet count below LLN; Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥ 2 times the upper limit of normal (ULN); Total bilirubin ≥ 1.5 × ULN; Serum creatinine (Cr) ≥ 1.5×ULN; * History of treatment with dupilumab, anti-interleukin (IL)-4 or IL13 agents. * Patients who have received any of the following treatments within 4 weeks before baseline: Treatment with immunosuppressive/immunomodulating substances (e.g., systemic corticosteroids, cyclosporine, mycophenolate mofetil, interferon-gamma \[IFN-γ\], oral JAK inhibitors, compound glycyrrhizin, azathioprine, or methotrexate); Treatment with phototherapy (narrow band ultraviolet B \[NBUVB\], ultraviolet B \[UVB\], ultraviolet A1 \[UVA1\], psoralen + ultraviolet A \[PUVA\]), sunbed or any other light emitting device (LED) therapy; * Treatment with topical drugs such as corticosteroids, topical calcineurin inhibitors, phosphodiesterase (PDE) inhibitors, or Janus kinase (JAK) inhibitors within 1 weeks before baseline; * Treatment with systemic traditional Chinese medicine (TCM) within 4 weeks before baseline or treatment with topical TCM within 1 weeks before baseline; * Patients who have received any of the following biological agents: Treatment with cell depletion agents (e.g., rituximab) within 6 months before baseline. Treatment with other biological agents within 3 months before baseline or 5 drug half-lives (if known), whichever is longer; * Have undergone bleaching baths ≥ twice within 2 weeks before baseline; * Planned or anticipated use of any banned drugs or any prohibited therapeutic procedures during the study. * Have been vaccinated with live (attenuated) vaccine within 8 weeks before baseline or planned during the study period or within 12 months after the study; * History of hypersensitivity to any biological agents. History of hypersensitivity to 611 or their excipients. * Participants who had donated blood (≥200 ml) within 8 weeks before enrollment or had severe blood loss of ≥200 ml, received a blood transfusion within 8 weeks, or planned to donate blood during the course of the study. * 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. * Known or suspected history of immunosuppression, including history of invasive opportunistic infections (e.g., tuberculosis \[TB\], histoplasmosis, listeriosis, coccidioidomycosis, pneumocystosis, aspergillosis). * Any history of vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC). * History of alcohol within 6 months before baseline. * Smoking more than 5 cigarettes per day within 3 months before the screening visit, or unable to stop using any tobacco products during the trial; * History of drug abuse or urine drug screening was positive. * Hepatitis B surface Antigen (HBsAg)-positive, or Hepatitis B core Antibody (HbcAb) was positive and Hepatitis B surface Antibody (HBsAb) was negative, or Hepatitis C Virus Antibodie (HCV Ab)-positive, Human Immunodeficiency Virus Antibody (HIV Ab) positive; * Presence of skin comorbidities that may interfere with study assessments. * History of malignancy within 5 years before the screening visit, except completely treated in situ carcinoma of the cervix, completely treated and resolved non-metastatic squamous or basal cell carcinoma of the skin. * History of parasitic infections within 6 months before baseline. * 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. * Any other medical or psychological condition that was judged by the investigator to be ineligible for enrollment. * Planned or anticipated major surgical procedure during the patient's participation in this study. * Pregnant or lactating women, or subjects with pregnancy or lactation plans during the study period. Women/men unwilling or unable to use highly effective contraception throughout the study period until at least 6 months after the last dose of study drug, and Women of Childbearing Potential (WOCBP) who had a positive pregnancy test and/or were unwilling or unable to undergo a pregnancy test * Other conditions were deemed by the investigator to be inappropriate for trial participation.