Phase II Trial of JYP0066 Cream in Mild-to-Moderate Atopic Dermatitis

• Participant is ≥12 and ≤75 years of age at the time of signing informed consent; male or female.

Note: Participants who are ≥12 and \<18 years of age at screening and baseline will be classified as adolescents throughout the study.

Body weight ≥40 kg. Meets Williams diagnostic criteria for atopic dermatitis (AD) at screening and baseline, with AD onset at least 6 months before screening.

Williams criteria - Major criterion: itchy skin. Minor criteria: (a) history of flexural dermatitis (elbow/antecubital, popliteal, anterior ankle, neck; in children \<10 y, cheek rash); (b) history of asthma or allergic rhinitis (or atopic disease in first-degree relatives for children \<4 y); (c) generalized dry skin in recent years; (d) flexural eczema (in children \<4 y: cheek/forehead/extensor eczema); (e) onset before age 2 (for patients ≥4 y). Diagnosis = major criterion + ≥3 minor criteria.

vIGA-AD score of 2 (mild) or 3 (moderate) at both screening and baseline. Total AD lesion area of 3%-20% body surface area (BSA) at screening and baseline.

Note: Lesions on scalp, face, and genital area are excluded from BSA calculation at screening and baseline.

Females of childbearing potential must have a negative serum pregnancy test at screening. All participants of childbearing potential (and their partners) must agree to use highly effective contraception from informed consent through 1 month after last study drug administration and must not donate sperm/ova during this period.

Note: Applies also to post-menarchal female adolescents and post-semenarche male adolescents.

Adults: able to understand the purpose and procedures of the study, voluntarily provide written informed consent, and comply with visits/requirements. Adolescents: participant and parent/legal guardian (as applicable) voluntarily provide written informed consent/assent and can communicate with investigator and attend scheduled visits.

Exclusion Criteria:

• Presence of other skin diseases or skin infections that may interfere with AD assessment at screening/baseline, or large tattoos, birthmarks, or scars over AD lesions at screening/baseline.

Unstable AD, or continuously requiring potent topical corticosteroids to control signs/symptoms.

AD lesions located only or mainly on hands, feet, scalp, face, or genitals with no history of classic flexural involvement.

Known/suspected allergy to any component of study cream or its vehicle, or moderate-to-severe allergic disease at IC signing (e.g., food/drug/detergent allergy; AD-related allergy allowed); or history of moderate-to-severe allergic disease.

Use of any of the following prior to study drug:

Any systemic or topical JAK inhibitor before study entry; Biologics affecting AD (e.g., anti-IL-4, IL-5, IL-12/23, IL-13, IL-31, CD20, TNF-α, IgE) within 12 weeks or 5 half-lives (whichever longer) before study drug; Systemic immunosuppressants/immunomodulators (cyclosporine, MTX, azathioprine, MMF), oral/systemic corticosteroids, PDE4 inhibitors within 4 weeks or 5 half-lives (whichever longer); Systemic herbal/Chinese medicine for AD or other autoimmune-inflammatory diseases within 4 weeks; Phototherapy (NBUVB, UVB, UVA1, PUVA), tanning bed, or other light-emitting device within 4 weeks; Any topical AD treatment (except non-medicated emollient) or antihistamines within 1 week (stable-dose antihistamine before screening allowed); Participation in another clinical trial within 4 weeks or 5 half-lives of investigational product (whichever longer); Any vaccination within 4 weeks, BCG within 1 year, or planned live/attenuated vaccine during study; Long-acting anticoagulants (warfarin, dabigatran) within 4 weeks or need for continuous anticoagulation (aspirin ≤100 mg/day allowed); Strong CYP3A4 inhibitors/inducers (rifampin, fluconazole, itraconazole, ketoconazole, posaconazole, voriconazole, nefazodone) within 2 weeks or 5 half-lives; Allergen-specific immunotherapy within 6 months. Major surgical procedure within 12 weeks before screening. Serious infectious disease within 6 months; history of zoster or disseminated zoster; any infection requiring antibiotics within 2 weeks before screening; or active acute/chronic/local infection at screening; or infection judged by investigator likely to worsen with participation.

Active tuberculosis, untreated latent TB, or incompletely cured TB (by history, symptoms, labs, IGRA, imaging).

Conditions negatively affecting immune response (e.g., organ transplant), or known immunodeficiency (acquired, genetic, or drug-induced).

NYHA Class III/IV heart failure; unstable angina; stroke/TIA; MI; CABG/PCI history; uncontrolled hypertension (SBP >160 or DBP >100 mmHg); hypotension (SBP \<90 or DBP \<60); clinically significant electrolyte disorder; or other unstable disease affecting safety.

History of thromboembolic event (DVT, pulmonary embolism, CVA) or known genetic hypercoagulable state.

Clinically relevant severe pulmonary disease (e.g., pulmonary hypertension, acute COPD exacerbation, pneumothorax).

Severe GI disease (peptic ulcer, obstruction) or condition affecting drug absorption (e.g., gastrectomy).

Severe hematologic disease (moderate/severe anemia, proliferative bone marrow disease, thrombocytopenia, hemoglobinopathy), severe coagulation abnormality, or high thrombotic risk.

Malignant tumor or lymphoproliferative disease within past 10 years, except adequately treated non-melanoma skin cancer or cervical intraepithelial neoplasia.

Screening 12-lead ECG with prolonged QTcF (>450 ms male, >470 ms female), family history of long QT, or chronic use of QT-prolonging drugs.