The goal of this clinical trial is to evaluate the safety, tolerability, pharmacokinetic characteristics and pharmacodynamics of HXN6005 in Healthy Participants.

Researchers will compare HXN6005 to a placebo (a look-alike substance that contains no drug).

Participants will take a single dose of HXN6005 or placebo on Day 1, and visit the clinic for followup and tests per the protocol scheme.

This study consists of 4 Cohorts, including three sequential ascending-dose cohorts (Cohort 1,2 and 4), and one paralleled cohorts (Cohort 3).

The investigator and participants will be blinded to treatment assignment. Participants in different dose groups will be enrolled from the low-dose group to the high-dose group.

Eight healthy participants will be randomly enrolled per cohort. In cohort 1,2 and 4 there will be a sentinel group comprising two participants who will be randomized in a 1:1 ratio to receive either HXN6005 or placebo. In Cohort 3, eight participants will be randomized in a 6:2 ratio to receive HXN6005 or placebo.

Following dosing on Day 1, blood samples will be collected according to the protocol. Participants in Cohorts 1-4 will be followed up to Day 141. The final follow-up visit will be determined based on the safety and PK data derived from the previous single ascending dose (SAD) cohorts, which may be earlier or later than Day 141 (±7 days).

Inclusion Criteria:

1. Participants must sign an Institutional Review Board (IRB) approved informed consent form before any study specific procedure.
2. Male and female participants aged between 18 to 55 years, inclusive.
3. Participants must have a body mass index between 18 to 35 kg/m2, inclusive.
4. Healthy participants, in the opinion of the Investigator and as determined by medical history, with normal or clinically acceptable physical examination, clinical laboratory tests and ECG results at Screening and before randomization.
5. Female participants must be postmenopausal, surgically sterile, or, if of childbearing potential, agree to use highly effective contraception combined with a condom from screening until 180 days post-dose, and refrain from egg donation or in vitro fertilization during this period.
6. Male participants, with their female partner of childbearing potential, agree to use a condom as well as highly effective contraception, and refrain from sperm donation and in vitro fertilization until 180 days after the dosing of the study drug.
7. Participants must be willing to understand and comply with all research procedures and restrictions, and able to communicate effectively with researchers.

Exclusion Criteria:

1. Females who are pregnant, planning to become pregnant, or lactating during the trial;
2. History of febrile illness or evidence of any active or suspected infection within 30 days before randomization;
3. Participant at risk for tuberculosis;
4. History of malignancy within 5 years before randomization, except for non-melanoma skin cancers (e.g., basal cell carcinoma, squamous cell carcinoma) that have been successfully treated/excised for more than 12 months;
5. Have known type I/II diabetes;
6. Positive for human immunodeficiency virus antibodies, syphilis antibodies, hepatitis B surface antigen, or hepatitis C antibodies;
7. Positive for drugs use before randomization;
8. Have used nicotine or tobacco containing products within 3 months prior to dosing, or unwilling to abstain from the use of tobacco or nicotine containing products during confinement in the CRU;
9. Have a history of alcohol abuse (alcohol consumption in excess of 14 units per week (1 unit contains 14g alcohol, such as 360 mL beer or 45 mL spirits with 40% alcohol or 150 mL wine) in the past one year before randomization, or unwilling to abstain from alcohol for 48 hours prior to admission to the CRU;
10. Have received an experimental agent (vaccine, drug, biologic, device, blood product or medication) within 30 days or 5 half-lives before randomization, or plan to receive another experimental agent during the trial;
11. Known exposure to any type of antibody or anti-TSLP therapy within 5 half-lives before randomization;
12. Have donated blood (excluding plasma donations) of approximately 1 pint (500 mL) or more within 30 days before randomization, or those who plan to donate blood during the trial or within 30 days after the end of the study;
13. Use of prescription or over-the-counter drugs or dietary or herbal supplements within 7 days or 5 half-lives (whichever is longer) before randomization;
14. Recent exposure to live vaccines within 30 days, or non-live vaccines (including mRNA COVID/flu) within 2 weeks before randomization, or plan to receive vaccines during the trial;
15. Participants with herpes zoster reactivation or cytomegalovirus that resolved within 60 days before randomization;
16. Have clinically significant interventional therapies (surgery, paracentesis, etc.) within 6 months before randomization, or plan to have any surgeries during the trial;
17. History of clinically significant hypersensitivity reactions to biologic agents, therapeutic proteins, or to specific excipients relevant to the study drug formulation.
18. Have any other conditions that would, in the opinion of the investigator, put the participants at increased risk for participation in this trial.