Study to Evaluate Safety and Effectiveness of Oral Apremilast (CC-10004) in Patients With Moderate to Severe Plaque Psoriasis. (ESTEEM 2)

This study will evaluate the effects of an experimental (being tested) study drug called apremilast. Apremilast works by lowering some of the chemicals that affect psoriasis and therefore improves the symptoms of psoriasis. The purpose of this study is to test apremilast and compare its effects to placebo (an inactive substance which contains no medicine but is in the same form as the drug). This study will test efficacy (improvement of signs and symptoms) and safety of apremilast in patients with moderate to severe psoriasis.