Study of HXN6005 in Healthy Participants and Patients With Moderate-to-Severe Atopic Dermatitis

Part A (Single Ascending Dose, SAD) is a randomized, double-blind, placebo-controlled, single-dose escalation design conducted in healthy participants. It includes two sequential dose cohorts. A total of 16 healthy participants are planned, with 8 participants per cohort (6 receiving HXN6005 and 2 receiving placebo). Participants receive a single subcutaneous injection of HXN6005 or placebo. All participants are followed for safety, PK, PD, and anti-drug antibody (ADA) assessments.

Part B (Multiple Ascending Dose, MAD) is a randomized, double-blind, placebo-controlled study conducted in patients with moderate-to-severe AD. Part B enrolls 16 patients across two dose cohorts, with 8 patients per cohort (6 receiving HXN6005 and 2 receiving placebo). Patients receive multiple subcutaneous injections of HXN6005 or placebo according to the study schedule.

Part C is a multicenter, randomized, double-blind, placebo-controlled study conducted in patients with moderate-to-severe AD. A total of 35 patients are planned to be randomized into two HXN6005 dose groups and one placebo group, receiving multiple subcutaneous doses according to the study schedule. Regular follow-up visits are conducted to collect efficacy data, safety data, and blood samples for assessment of systemic exposure, immunogenicity, and biomarkers.

• HXN6005 (Drug): Participants will be enrolled sequentially into one of two ascending dose cohorts and will receive a single subcutaneous dose of HXN6005.
• Placebo (Drug): Participants will be enrolled sequentially into one of two ascending dose cohorts and will receive a single subcutaneous dose of placebo.
• HXN6005 (Drug): Participants will be enrolled sequentially into one of two ascending dose cohorts and will receive multiple subcutaneous doses of HXN6005.
• Placebo (Drug): Participants will be enrolled sequentially into one of two ascending dose cohorts and will receive multiple subcutaneous doses of placebo.
• HXN6005 (Drug): Participants will be enrolled in parallel into one of two dose cohorts and will receive multiple subcutaneous doses of HXN6005.
• Placebo (Drug): Participants will be enrolled in a single cohort and will receive multiple subcutaneous doses of placebo.

Primary outcomes

• Part A Adverse events [Up to day 141]: Incidence, severity, and causal relationship of Adverse Events (AEs)
• Part B Adverse Events [Up to day 197]: Incidence, severity, and causal relationship of Adverse Events (AEs)
• Part C Efficacy [Up to day 113]: Change from baseline to Week 16 in the Eczema Area and Severity Index (EASI; range 0-72; higher scores indicate more severe disease) total score among AD participants

Secondary outcomes

• Maximum Observed Plasma Concentration (Cmax) [Up to day 197]: The maximum (peak) observed drug concentration in plasma after administration
• Area Under the Plasma Concentration-Time Curve from Time 0 to the Last Quantifiable Concentration (AUC0-t) [Up to day 197]: Area under the plasma concentration-time curve from time 0 (pre-dose) to the time of the last measurable (quantifiable) plasma concentration
• Incidence of antidrug antibodies (ADA) against HXN6005 [Up to day 197]: The incidence of treatment-emergent ADA against HXN6005 was assessed in serum samples

Sex: All, ages: 18 Years to 70 Years, accepts healthy volunteers

Inclusion Criteria:

1. Participants must be able to understand and comply with the study requirements and voluntarily sign the informed consent form (ICF).
2. (Healthy Participants) Male or female participants aged 18 to 55 years (inclusive) at the time of signing the ICF.
3. (Healthy Participants) Male participants weighing ≥ 50.0 kg and female participants weighing ≥ 45.0 kg, with a body mass index (BMI) between 18.0 and 28.0 kg/m² (inclusive).
4. (Patients with AD) Male or female participants aged 18 to 70 years (inclusive) .
5. (Patients with AD) Participants must have documented AD history, moderate-to-severe disease, and inadequate response to topical therapy at screening.

Exclusion Criteria:

1. Presence of any clinically significant disease at randomization, as judged by the investigator.
2. Known or suspected allergy or intolerance to any component or excipient of HXN6005 injection or placebo.
3. History of severe drug allergy or systemic anaphylactic reactions, such as anaphylactic shock, laryngeal edema, etc.
4. Known or suspected history of immunosuppression, or history of invasive opportunistic infections, including infections that are unusually frequent, recurrent, or prolonged in duration as judged by the investigator, even after resolution of the infection.
5. History of malignancy or malignant disease, with the exception of surgically excised cutaneous squamous cell carcinoma in situ, basal cell carcinoma, and cervical carcinoma in situ that have been in complete remission for more than 5 years without any evidence of recurrence.