The purpose of this study is to assess the efficacy and safety of HSK44459 in adults with Atopic Dermatitis

This is a multicenter, randomized, double-blind, parallel group, placebo controlled phase 2 study to assess the efficacy and safety of HSK44459 in adult 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