HPP737 in Adult Patients With Moderate-to-severe Plaque Psoriasis.

Inclusion Criteria: * Subjects voluntarily sign the informed consent form before initiation of any study-related procedures, are able to communicate effectively with investigators, and understand and comply with all requirements of this study; * Age at signing informed consent: age ≥18 years, regardless of gender; * Diagnosed with a history of chronic plaque psoriasis (Psoriasis vulgaris) and disease stability for ≥6 months prior to screening; * Diagnosed with moderate to severe plaque psoriasis (Psoriasis vulgaris), and at screening meets the following requirements: 1) PASI (Psoriasis Area and Severity Index) score ≥ 12; and 2) Static Physician Global Assessment (sPGA) score ≥ 3; and 3) Body Surface Area (BSA) involvement ≥ 10%; * Body Mass Index (BMI): 18 kg/m2 ≤ BMI ≤ 35 kg/m2 Exclusion Criteria: * At screening, diagnosis of psoriasis types other than chronic plaque psoriasis (Psoriasis vulgaris), e.g., pustular psoriasis (Psoriasis pustulosa), erythrodermic psoriasis (Psoriasis erythrodermica), and guttate psoriasis (Psoriasis guttata); * Patients with drug-induced psoriasis (including but not limited to new-onset or exacerbation of psoriasis caused by β-blockers \[beta-blockers\], calcium channel inhibitors \[calcium channel blockers\], or lithium preparations \[lithium salts\]); * Subjects have other skin diseases that may interfere with clinical assessment (e.g., bacterial, fungal, or viral skin infections, seborrheic dermatitis), chronic diarrhea, severe digestive diseases (such as active gastric ulcer, gastrointestinal tract disorders), or history of inflammatory bowel disease (Crohn's disease, ulcerative colitis), or other active autoimmune inflammatory diseases (mixed connective tissue disease, idiopathic inflammatory myopathy); Note: Chronic diarrhea is defined as disease course \>4 weeks, or recurrent diarrhea in a 2-4 week interval. Diarrhea refers to defecation significantly exceeding usual frequency (\>3 times/day), stool consistency is loose, water content (\>85%), and stool may contain mucus, pus, blood, or undigested food. * History of congenital or acquired immunodeficiency; * Severe infection or systemic infection within 4 weeks prior to randomization requiring oral and/or intravenous antimicrobial treatment, or hospitalization due to infection; * At screening, subject's history, symptoms, and examination results indicate active tuberculosis; * History of moderate-to-severe heart failure (New York Heart Association \[NYHA\] functional classification ≥ Class 3), or occurrence of cardiovascular or cerebrovascular events or severe events within 3 months prior to randomization, such that investigators consider these subjects unsuitable for participation in this clinical trial; * History of malignancy in any organ system within 5 years prior to randomization, except for malignancies with low risk of metastasis and mortality, such as adequately treated carcinoma in situ, basal cell carcinoma, or squamous cell carcinoma of the skin; * Subjects with a history of depression and/or, as assessed by the Columbia-Suicide Severity Rating Scale (C-SSRS) during the screening and baseline period, with ideation or any behavior (see Appendix 6). Subjects who answer "yes" to any question on the C-SSRS questionnaire, or those deemed at risk by the investigator's clinical judgment, will be excluded; * Presence of clinically significant, progressive, or uncontrolled disease during the screening period, including but not limited to respiratory, cardiovascular, endocrine, hematologic, skeletal, or neurologic systems, as assessed by the investigator to pose unacceptable risk for participation or interfere with data interpretation; * Prior to screening, use of the following psoriasis treatment modalities/drugs: 1) Received topical treatment for psoriasis within 2 weeks prior to randomization, such as glucocorticoids, vitamin D3 derivatives, retinoids, etc.; however, the subject is permitted to use the following topical treatments: non-medicated shampoos and emollients (i.e., those not containing glucocorticoids or vitamin D3 derivatives); Received phototherapy/photochemotherapy (including but not limited to psoralen plus ultraviolet A \[PUVA\] therapy, ultraviolet B \[UVB\]), or non-biological systemic therapy (including but not limited to systemic glucocorticoids, leflunomide, cyclophosphamide, azathioprine, methotrexate, cyclosporine, retinoids, mycophenolate mofetil, traditional Chinese medicine for the treatment of psoriasis, or other small-molecule targeted agents for the treatment of psoriasis) within 4 weeks prior to randomization; Tumor necrosis factor-alpha (TNF-α) antagonist: (1) The patient has used at least one TNF-α antagonist within the specified time period prior to randomization (for example, adalimumab, infliximab, golimumab, etanercept, or certolizumab pegol within 12 weeks prior to randomization); (2) or the patient has used two or more TNF-α antagonists prior to randomization; 4) Used other biologic agents within 24 weeks prior to randomization, including but not limited to anti-interleukin-17 (anti-IL-17) inhibitors, anti-interleukin-23 (anti-IL-23) inhibitors, anti-interleukin-12/interleukin-23 (anti-IL-12/23) inhibitors, and related agents; * Receipt of live attenuated vaccines within 12 weeks prior to randomization, or planned vaccination with live attenuated vaccines during the study period; * Subjects who have previously used other PDE4 inhibitors (such as apremilast, Hemay005, etc.);