A Study for HSK44459 in Participants With Atopic Dermatitis

Inclusion Criteria: * Written informed consent must be obtained * Male or female, ≥18 years old and ≤75 years old * Willing and able to comply with study-specific procedures and the requirements of this study protocol. * Atopic dermatitis has been present for at least 1 year and subject meets Hanifin and Rajka criteria * EASI score≥16 at the screening and baseline visits * IGA score≥3 at the screening and baseline visits * ≥10% body surface area (BSA) of AD involvement at the screening and baseline visits * Baseline WI-NRS≥4 * History of inadequate response to TCS of medium to higher potency (with or without topical calcineurin inhibitors \[TCI\]) or systemic treatment for AD within 6 months prior to screening * Have applied a stable dose of topical emollient (moisturizer) twice daily for at least 7 days before the baseline visit Exclusion Criteria: * Subjects have used AD treatments within the time frame specified in protocol prior to the baseline visit * Prior exposure to any PDE4 inhibitor systemic treatment * Systemic use of known strong CYP3A inhibitors or strong CYP3A inducers within 4 weeks or 5 half-lives prior to randomization or during the course of the study * Participation in other clinical studies within 4 weeks or 5 half-lives prior to randomization * Subjects have laboratory values meeting the criteria in protocol * Presence of skin comorbidities that may interfere with study assessments * Concurrent conditions and history of other diseases as described in protocol