Safety and Tolerability Study of COVA322 in Patients With Stable Chronic Moderate-to-severe Plaque Psoriasis

Inclusion Criteria: * Male or female subjects of any ethnic origin; women must be of non-childbearing potential * Aged between 18 to 65 yrs inclusive * Body weight of ≥ 40 kg and body mass index between 19 - 32 kg/m2 inclusive * Established diagnosis of moderate to severe plaque psoriasis for at least 6 months prior to screening. The patients must meet all of the following criteria: * Psoriasis involving ≥ 10% of body surface area * Requirement of phototherapy or systemic therapy * Psoriasis Area and Severity Index (PASI) score of ≥ 10 * Physician"s Global Assessment (PGA) score of ≥ 3 * stable disease Exclusion Criteria: * History of clinically relevant allergies or idiosyncrasies to COVA322 * Any history of clinically significant drug hypersensitivity following any therapy with a therapeutical biologic, or asthma, urticaria, or other allergic diathesis * Clinically significant flare of psoriasis during the 12 weeks before randomization * Current evidence of non-plaque forms of psoriasis * Currently evidence of drug-induced psoriasis * Evidence of any serious systemic or local infection within 3 months before screening * Evidence of subclinical/latent tuberculosis infection * History or any signs of lymphoproliferative disease, or a known malignancy or a history of malignancy within the previous 5 years * History or current evidence of autoimmune diseases other than psoriasis * Women of child-bearing potential * Recent previous exposure to systemic psoriasis treatments, including anti-TNF-α therapies, immunosuppressive agents such as cyclosporine, mycophenolate, or tacrolimus, and other medications affecting the immune function * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) level ≥ 2.5 times the upper limit of normal (ULN) at screening * Serum creatinine level ≥ 1.5 times the ULN at screening * Positive results in any of the virology tests for HIV-Ab, hepatitis C-virus antibody (HCV-Ab) and hepatitis B-virus surface antigen (HBsAg) or hepatitis B core antibody (HBc-Ab)