A Phase 2 Clinical Study of KHK4827

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