A Phase 2 Study of HS-20118 to Evaluate the Efficacy and Safety in Participant With Moderate-to-Severe Plaque Psoriasis

Inclusion Criteria:

1. Participants voluntarily agree to comply with all study procedures and scheduled follow-up assessments, and to cooperate with the collection of lesion photographs and other protocol-specified requirements;
2. Diagnosis of plaque psoriasis, with or without PsA, established for at least 26 weeks prior to the first administration of study intervention. If previously diagnosed with psoriasis, participants must have a documented history of psoriasis for at least 26 weeks and must be confirmed by the investigator during screening to have plaque psoriasis;
3. At screening and baseline, participants must be confirmed by the investigator to have stable moderate-to-severe plaque psoriasis, as defined by meeting all of the following four criteria:

1) No morphological changes or significant disease flares during the 4 weeks preceding screening, as assessed by the investigator; 2) BSA≥10%； 3) PASI≥12； 4) IGA≥3； 4. Be a candidate for phototherapy or systemic treatment for plaque psoriasis; 5. Participants must have no plans for pregnancy or sperm/egg donation during the study period. If of childbearing age, women must not be pregnant or breastfeeding, and must have a negative blood pregnancy test within 7 days before randomization. Participants and their partners must voluntarily use highly effective contraception during the study period and for at least 3 months after the last dose.

Exclusion Criteria:

1. Known allergy, hypersensitivity, or intolerance to biologics, study drugs, or their excipients.
2. Non-plaque psoriasis (e.g., guttate, erythrodermic, pustular, or drug-induced psoriasis) at screening or randomization.
3. Other skin lesions or systemic autoimmune diseases (e.g., systemic lupus erythematosus, Sjögren's syndrome, scleroderma) that may affect the safety and efficacy assessment of the study drug.
4. Other skin lesions or systemic autoimmune diseases (e.g., systemic lupus erythematosus, Sjögren's syndrome, scleroderma) that may affect the safety and efficacy assessment of the study drug.
5. Severe, progressive, or poorly controlled renal, hepatic, cardiac, vascular, pulmonary, gastrointestinal, endocrine, neurological, hematologic, rheumatologic, psychiatric, or metabolic disorders; or current signs or symptoms related to these conditions.
6. History of malignancy within 5 years before screening (except for adequately treated skin basal cell carcinoma, in situ skin cancer, or in situ cervical cancer with no recurrence for at least 12 weeks before the first dose).
7. History of lymphoproliferative disorders (e.g., lymphoma), unexplained monoclonal gammopathy, or signs and symptoms suggestive of lymphoproliferative disorders (e.g., splenomegaly or severe lymphadenopathy).
8. Any other condition deemed by the investigator as unsuitable for participation in the clinical study.