Phase 3b Safety and Efficacy Study of Apremilast to Treat Moderate to Severe Plaque-plaque Psoriasis

This study will test the clinical effectiveness and safety of apremilast compared with placebo as well as etanercept compared with placebo in the same group of patients with moderate to severe plaque psoriasis.

This is a phase 3b, multicenter, randomized, placebo-controlled, double-blind, double-dummy, study of the efficacy and safety of apremilast, etanercept, and placebo, in adults with moderate to severe plaque psoriasis. 250 participants will be randomized 1:1:1 to the three treatment groups. All subjects will receive both tablets and injections through Week 16. The study will consist of four phases: * Screening Phase - up to 35 days * Double-blind Placebo-controlled Phase - Weeks 0-16 * Apremilast Extension Phase - Weeks 16-104 * Post-treatment Observational Follow-up Phase During the double-blind, placebo-controlled phase, subjects will receive treatment with one of the following: * apremilast (APR) 30 mg tablets orally twice a day (BID) plus once weekly (QW) evaluator/subject-blinded subcutaneous (SC) saline (placebo) injections (1 mL x 2 injections SC), or * etanercept (ETN) 50 mg evaluator/subject-blinded subcutaneous (SC) once weekly (QW) injections (2 x 25 mg) plus placebo tablets orally twice a day (BID), or * placebo tablets and evaluator/subject-blinded subcutaneous (SC) saline (placebo) injections. All subjects will be asked to participate in a 4-week Post-treatment Observational Follow-up Phase either upon completion of the study or upon discontinuation of investigational product for those subjects who terminate the study early.