This is a multicenter, randomized, double-blind, placebo-controlled Phase II clinical study to evaluate ICP-488.Efficacy, safety, PK, and PD characteristics in Chinese adults with moderate to severe plaque psoriasis.

Inclusion Criteria:

1. Subjects voluntarily participate in this study and have signed informed consent.
2. Male or female subjects between the ages of 18 and 70 (including the threshold) at the time of signing the ICF.
3. History of plaque psoriasis ≥6 months at baseline.
4. Subjects need to receive systemic therapy and/or phototherapy.
5. The following three criteria were met: a) psoriasis Area and Severity index (PASI) score ≥12; b) Psoriasis affected body surface area (BSA) ≥10%; c) Static physician overall assessment (sPGA) ≥3 scores

Exclusion Criteria:

1. The diagnosis was non-plaque psoriasis.
2. Presence of infection or immune-related disease.
3. Subjects with a history of TB or at risk for TB.
4. Received related treatment within the time window specified in the protocol.
5. An interval of less than 5 half-lives or 28 days (if any available halflife data) from the last dose of a strong CYP1A2 inhibitor or inducer, or a plan to use concurrently medications, dietary supplements or food with strong CYP1A2 inhibitory or inductive effect during study participation.
6. The investigator has determined that there are clinically significant test results and that participation in this trial would pose an unacceptable risk to patients; Or the laboratory values of the subjects in the screening period meet the criteria specified in the protocol.
7. Pregnant or lactating women, or women who plan to become pregnant during study participation.
8. A history of severe drug allergies.
9. Any other conditions in which the investigator considers it unsuitable for the subject to participate in this study.