The primary objective of this study is to evaluate the efficacy and safety of KHK4827 in subjects with moderate to severe plaque psoriasis randomized in a double-blind manner to receive KHK4827 or placebo for 12 weeks

Inclusion Criteria:

• Subject has had stable moderate to severe plaque psoriasis for at least 6 months
• Subject has involved BSA ≧ 10%, PASI ≧ 12, and sPGA ≧ 3 at screening and at baseline

Exclusion Criteria:

• Subject diagnosed with erythrodermic psoriasis, pustular psoriasis, guttate psoriasis, or a medication-induced psoriasis, or other skin conditions (e.g., eczema) at screening that would interfere with study evaluations
• Subject scheduled to undergo a surgical intervention during the study period
• Subject has any active infection or history of infections as defined in the study protocol
• Subject has known history of Crohn's disease
• Subject has any other significant concurrent medical condition or laboratory abnormalities, as defined in the study protocol
• Subject has not stopped using certain psoriasis therapies as defined in the study protocol
• Subject has previously used any anti-IL-17 biologic therapy
• Subject is pregnant or breast feeding, or planning to become pregnant while enrolled in the study
• Women of child-bearing potential or fertile men who do not agree to use effective contraception from the day of providing consent through 12 weeks after the last dose of investigational product.
• Subject has known history or evidence of suicidal ideation (severity of 4 or 5) or any suicidal behavior based on an assessment with the Columbia-Suicide Severity Rating Scale (C-SSRS) at screening or at baseline
• Subject has severe depression based on a total score of ≥ 15 on the Patient Health Questionnaire-8 (PHQ-8) at screening or at baseline
• Subject has known history or evidence of a psychiatric disorder that, in the opinion of the investigator, would pose a risk to subject safety or interfere with the study evaluation, procedures or completion
• Subject has known history of alcohol and/or substance abuse within the last 12 months"