This study is designed to evaluate the efficacy and safety of KHK4827 in subjects with moderate to severe plaque psoriasis in a randomized, double-blind, placebo-controlled, parallel group study. Pharmacokinetics of KHK4827 will also be assessed.

Inclusion Criteria:

• Subject has had stable moderate to severe plaque psoriasis for at least 6 months.
• Subject has received at least one previous phototherapy or systemic psoriasis therapy or has been a candidate to receive phototherapy or systemic psoriasis therapy in the opinion of the investigator.
• Subject has involved BSA ≥ 10% and PASI ≥ 12 at screening and at baseline.

Exclusion Criteria:

• Subject diagnosed with erythrodermic psoriasis, pustular psoriasis, medication-induced, or medication-exacerbated psoriasis.

• Evidence of skin conditions at the time of the screening visit (eg, eczema) that would interfere with evaluations of the effect of investigational product on psoriasis.

• Subject has any active Common Terminology Criteria for Adverse Events (CTCAE) grade 2 or higher infection

• Subject has a significant concurrent medical condition or laboratory abnormalities, as defined in the study protocol.

• Subject has used the following therapies within 14 days of the first dose: topical calcineurin inhibitors including tacrolimus

  , topical vitamin A, activated form D3 or activated form D3 analogue preparations, weak through strong topical steroids (excluding application on the scalp, axillae, and groin)

• Subject has used the following therapies within 28 days of the first dose: any other systemic psoriasis therapy (eg, vitamin A, calcineurin inhibitors, methotrexates, steroids), UVA therapy (with or without psoralen), very strong or strongest topical steroid, tar therapy

• Subject has used the following therapies within 3 months of the first dose: adalimumab, etanercept, infliximab, or live vaccines

• Subject has used ustekinumab within 6 months of the first dose

• Subject has previously used an anti-interleukin-17 biologic therapy