This study is a multicenter, randomized, double-blind, placebo-controlled Phase II clinical trial, aiming to evaluate the efficacy, safety, and tolerability of CMS-D001 in participants with moderate to severe atopic dermatitis, as well as to assess the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of CMS-D001 and its major metabolites (as applicable) in participants with moderate to severe atopic dermatitis, so as to provide a basis for the dosage of the Phase III confirmatory clinical trial.

Approximately 160 participants with moderate to severe atopic dermatitis are planned to be enrolled and randomly assigned to four groups in a 1:1:1:1 ratio. Stratification will be performed based on participants' baseline IGA scores (3 or 4) at the time of randomization.

Each participant will receive study treatment once daily (QD) for 12 consecutive weeks. The dosage and frequency for each group are as follows:

Trial Group 1: CMS-D001 50 mg, QD; Trial Group 2: CMS-D001 100 mg, QD; Trial Group 3: CMS-D001 200 mg, QD; Control Group: Placebo, QD. The study is divided into three phases: a Screening Period (up to 4 weeks), a Treatment Period (12 weeks), and a Safety Follow-up Period (4 weeks after the last dose).

During the study, all participants must adhere to the study visit schedule to undergo efficacy and safety assessments. They will also be required to complete blood sample collections for Pharmacokinetic (PK) and Pharmacodynamic (PD) evaluations, and information regarding Adverse Events (AEs) and concomitant medications will be collected.

Inclusion Criteria:

• Aged 18-75 years, willing to sign the ICF
• Clinical diagnosis of AD (Hanifin & Rajka criteria) for ≥1 year
• At screening and baseline, EASI score ≥ 16 points, IGA ≥ 3, BSA ≥ 10%, Itch NRS ≥ 4
• Documented history of inadequate response to topical corticosteroids (TCS) or -topical calcineurin inhibitors (TCI).
• Subject has applied a topical emollient (moisturizer) daily for at least 7 days prior to the Baseline Visit.

Exclusion Criteria:

• Other active skin conditions that may interfere with AD assessment.
• History of a serious bacterial, fungal, or viral infection requiring hospitalization or intravenous antimicrobial therapy within 3 months prior to the first dose.
• History of a bacterial, fungal, or viral infection requiring oral antimicrobial therapy within 4 weeks prior to the first dose.
• Active infection or acute illness within 7 days prior to the first dose.
• Chronic or recurrent infectious diseases at screening or baseline that may increase safety risks.
• Evidence of active TB. Patients with evidence of latent tuberculosis may enter the trial after sufficient treatment had initiated and maintained according to protocol.
• History of a major or unstable clinical condition within 6 months prior to the first dose, which would compromise participation.
• History of malignant tumour within 5 years before screening.
• Previous or current autoimmune diseases.
• Positive results of confirmatory test for hepatitis B, hepatitis C, human
• immunodeficiency virus (HIV) or syphilis.
• Allergic to any component of the investigational drug.