This is a multicenter, randomized, double-blind, parallel, placebo-controlled Phase III clinical study to evaluate the efficacy and safety of JS005 in 702 adult patients with moderate-to-severe chronic plaque psoriasis

The study consisted of four periods: screening period (up to 4 weeks), induction period (12 weeks), maintenance period (40 weeks) and follow-up period (8 weeks). This study planned to recruit 702 subjects, who were randomized into JS005 300mg group (234 subjects), JS005 150mg group (234 subjects) and placebo group (234 subjects) at a ratio of 1:1:1, and were stratified by whether they had previsouly received biologic treatments (continuous biologic treatment for ≥3 months at recommended doses or intolerance for safety reasons) and body weight (≥70 kg or < 70 kg).

Inclusion Criteria:

1. Subjects voluntarily particpate in this clinical study and sign the informed consent form.
2. Male and female patients aged 18-75 years at the time of screening (both inclusive).
3. Fertile female subjects must be willing to use a highly effective contraceptive method during the study period and 20 weeks (expected 5 half-lives) after the last study drug administration and have a negative pregnancy test during the screening period and prior to randomization.

Exclusion Criteria:

1. Pregnant and lactating women.
2. A history of inflammatory bowel disease or other conditions with a high risk of perforation (e.g., severe gastrointestinal ulcers, etc.) or with other active autoimmune diseases (e.g., systemic lupus erythematosus, Sarcoidosis, etc.).
3. Have a type of psoriasis other than chronic plaque psoriasis (e.g., pustular, erythrodermic, and guttate psoriasis), drug-induced psoriasis, or have an active inflammatory skin disease other than psoriasis
4. Use of phototherapy, including but not limited to ultraviolet A phototherapy (with or without psoralens), ultraviolet B phototherapy, or excimer laser within 4 weeks prior to randomization. Subjects are unwilling to avoid excessive sunlight exposure within 4 weeks prior to randomization and during the study period;
5. A (current) history of systemic infection or serious infection requiring hospitalization and/or intravenous anti-infective therapy (e.g., antibiotics, antifungal agents, antiviral agents) within 12 weeks prior to randomization; a history of any active infection, other than common upper respiratory infections, within 2 weeks prior to randomization;

The study uses a double-blind design in which subjects, investigators, and other researchers will remain blind to the allocation of the study drug and placebo.

If serious adverse events occur to subjects during the study, the investigator must be informed of the treatment received by the subjects before appropriate treatment can be given. For safety reasons, the investigator may unblind the subjects urgently after obtaining the consent of the sponsor's medical monitor.