This is a single-center, randomized, double-blind, placebo-controlled Phase I clinical study, which comprises two parts: Single Ascending Dose (SAD) and Multiple Ascending Dose (MAD) in healthy subjects.Three dose groups are pre-scheduled for the SAD part. After the safety and tolerability of subjects in the second SAD dose group are confirmed, the MAD part will be initiated upon evaluation by the Safety Review Committee (SRC). Four dose groups are tentatively planned for the MAD part.Each dose group will enroll 8 subjects, who will be randomized at a 6:2 ratio to receive either ETD-001 gel or placebo.

Inclusion Criteria:

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Subjects meeting any of the following exclusion criteria will be excluded from this trial:

1. Fully understand the purpose, nature and methodology of the trial, as well as potential adverse reactions, and voluntarily sign the informed consent form.
2. Healthy male or female Chinese subjects aged between 18 and 60 years inclusive (age determined on the date of signing the informed consent form).
3. Body Mass Index (BMI) ranging from 19 to 26 kg/m² inclusive; male subjects shall weigh no less than 50 kg, and female subjects no less than 45 kg.
4. No skin rupture, lesions (including skin lesions caused by dermatoses), redness, rash, pigmentation, tattoos, excessive hair or abnormal warmth at the intended application site.
5. Subjects are deemed to be in good general health by the investigator based on medical history, physical examination, vital signs, 12-lead electrocardiogram, laboratory tests (blood routine, urine routine, blood biochemistry) and viral serology results (all findings are normal or abnormalities are clinically insignificant).
6. Female subjects must be non-pregnant and non-lactating. All subjects, regardless of gender, must agree to use medically approved effective contraception from the screening period until 6 months after the last dose. They shall not donate sperm or ova during the study period and within 6 months after the last dose.

Exclusion Criteria:

1. Subjects who are allergic to the investigational drug or any of its excipients; those with allergic diathesis (e.g., allergy to two or more types of drugs, foods or pollen); or those with severe systemic allergic diseases (e.g., severe asthma, allergic rhinitis, etc.).
2. Subjects with clinically significant abnormal medical conditions or factors, including but not limited to metabolic, hepatic, renal, hematological, pulmonary, cardiovascular, gastrointestinal, urological, endocrine, neurological and psychiatric diseases, or other conditions deemed inappropriate for participation in this study by the investigator.
3. Subjects who have taken or are expected to take any prescription drugs, over-the-counter medications, vitamin products, health supplements or traditional 4.Chinese medicinal preparations within 14 days prior to the first dose, or within 5 half-lives of the study drug (whichever is longer); or those who have consumed foods or beverages that may induce or inhibit hepatic metabolic enzymes (e.g., grapefruit) within 7 days before dosing.

Subjects with abnormal liver or renal function:

1. Total Bilirubin (TBIL) > 1.5 × ULN;

2. AST or ALT ≥ 1.5 × ULN;

3. Blood Urea Nitrogen (BUN) and Creatinine (CRE) > 1.5 × ULN. 5.Subjects with confirmed positive test results for hepatitis B, hepatitis C, Human Immunodeficiency Virus (HIV) or syphilis at screening.

   6.Subjects with a history of drug abuse within the past five years, those who have used illicit drugs within 3 months prior to screening, or those with a positive drug abuse screening result at baseline.

   7.Subjects consuming more than 14 units of alcohol per week within 3 months prior to screening (1 alcohol unit = 360 mL beer, or 45 mL spirits with 40% alcohol content, or 150 mL wine); those who have consumed alcoholic products within 48 hours before receiving the investigational drug; or those with a positive breath alcohol test at baseline.

   8.Subjects smoking more than 5 cigarettes per day or habitually using nicotine-containing products within 3 months prior to screening.

   9.Subjects who have ingested any foods or beverages containing caffeine or xanthine or their metabolites (e.g., coffee, tea, chocolate) within 48 hours prior to the first dose.

   10.Subjects who have received blood or blood products, or donated/lost more than 400 mL of blood within 3 months prior to the first dose; or those who plan to donate blood during the trial and within 3 months after trial completion.

   11.Subjects who have participated in another clinical trial and taken other investigational products within 30 days prior to the first dose, or within 5 half-lives of the study drug (whichever is longer).

   12.Subjects who have suffered from clinically significant severe illnesses or undergone major surgery within 28 days prior to the first dose, or who are expected to receive major surgery during the trial.

   13.Subjects with difficult venous access or a history of needle phobia or hemophobia.

   14.Female subjects with a positive pregnancy test at screening or baseline, who are breastfeeding or planning to become pregnant.

   15.Subjects with a history of chronic skin diseases (e.g., eczema, psoriasis, etc.).

   16.Any other conditions that, in the investigator's judgment, may prevent the subject from giving informed consent or complying with the trial protocol, or may compromise trial results or the subject's personal safety if the subject participates in the trial.