The goal of this clinical trial is to evaluate the safety, local tolerability, and pharmacokinetic (PK) profile of YR001 Topical Ointment in healthy Chinese participants. This is a first-in-China, Phase I study designed to assess the drug's systemic absorption and disposition following single and multiple topical applications.

The main questions it aims to answer are:

What is the safety and local tolerability profile of YR001 Topical Ointment after single-dose and multiple-dose administration in healthy Chinese participants?

What are the pharmacokinetic characteristics (e.g., plasma drug concentrations) of YR001 Topical Ointment after single and multiple topical applications?

Researchers will compare participants receiving YR001 Topical Ointment with participants receiving vehicle (placebo) to determine whether the safety profile and local tolerability of YR001 are comparable to placebo.

Participants will:

Receive topical application of either YR001 Topical Ointment or matching placebo (vehicle) on approximately 10% or 20% of their body surface area, depending on the assigned group

Undergo serial blood sampling for pharmacokinetic assessments at specified time points before and after drug administration

Complete safety evaluations including physical examinations, vital signs, laboratory tests (hematology, biochemistry, coagulation, thyroid function, urinalysis), 12-lead ECGs, and local tolerability assessments at the application site

Remain in the clinical unit for specified periods during the dosing and follow-up phases, with total study participation duration up to approximately 30 days per participant

Inclusion Criteria:

• Voluntarily sign the informed consent form to participate in the study.

Male or female, aged 18 to 65 years (inclusive).

Body weight ≥ 50 kg and body mass index (BMI) between 18 and 30 kg/m² (inclusive).

Skin at the intended application area is intact without ulceration, injury, sunburn, redness, rash, or other abnormalities at screening and prior to dosing.

Female participants of childbearing potential and all male participants must agree to use effective contraceptive methods during the study and for 3 months after the last dose.

No clinically relevant diseases, including dermatological conditions, as determined by medical history, physical examination, safety laboratory tests, and other assessments, that could adversely affect participant safety or study integrity or interfere with study results.

Willing and able to comply with scheduled study visits, treatment administration, laboratory tests, and other study procedures.

Exclusion Criteria:

• Current or history of clinically significant medical conditions or other disorders that may interfere with the assessment of safety, tolerability, or PK of YR001 Ointment, or place the participant at increased risk.

Pregnant or breastfeeding women, or participants with a positive pregnancy test.

Tattoos, scars, cuts, bruises, or other skin injuries (including excessive UV exposure) at the intended application site that, in the investigator's judgment, may affect drug absorption, distribution, metabolism, excretion, or trial safety.

Dermatological diseases or infections (e.g., acne, impetigo) or skin conditions at the intended application area that may interfere with study assessments, or that the investigator considers may affect drug absorption or skin observation.

Unwilling to refrain from using depilatory creams or wax on the intended application area for 2 weeks prior to dosing and throughout the study.

Positive test results at screening for hepatitis B surface antigen (HBsAg), hepatitis C virus IgG antibody (Anti-HCV), Treponema pallidum antibody (Anti-TP), or human immunodeficiency virus antibody (Anti-HIV).

Existing renal impairment as judged by the investigator.

Existing hepatic impairment as judged by the investigator.

Participation in another interventional clinical trial (e.g., investigational drug, biologic, or device) within 90 days prior to baseline, or currently in the follow-up period of another study, or prior participation in this clinical trial.

Use of any over-the-counter (OTC) or prescription medications (including probiotics/prebiotics, vitamins, herbal supplements, and nutraceuticals, with the exception of acetaminophen/paracetamol) within 14 days prior to baseline, or receipt of vaccination within this period.

Currently diagnosed with acute or chronic inflammatory diseases (limited to autoimmune diseases and infectious diseases, e.g., tuberculosis). Participants whose disease symptoms have resolved for ≥ 12 months without any treatment may be considered in remission and eligible for enrollment.

Use of topical skin products (including emollients) at the intended application site within 48 hours prior to baseline; use of topical products on non-application sites is permitted.

Clinically significant cardiac conduction abnormalities on electrocardiogram (ECG) as judged by the study physician.

Known allergy to the active substance or any excipient of the ointment.

Any major surgery within 6 months prior to the screening period.

Diagnosis of malignancy within 5 years prior to screening, with the exception of successfully treated basal cell carcinoma, squamous cell carcinoma of the skin, or carcinoma in situ of the cervix.

Employees of the sponsor, clinical service organization, or clinical research site.

History of drug abuse or substance use disorder within the past year; history of alcoholism within the past 6 months (as judged by the investigator); smoking > 5 cigarettes per day within the past 3 months, or inability to refrain from smoking during the study.

Any other condition that, in the investigator's opinion, makes the participant unsuitable for participation in the clinical trial.