Apremilast, a small molecule specific inhibitor of phosphodiesterase 4, works intracellularly to modulate pro-inflammatory and anti-inflammatory mediator production.Assess apremilast efficacy and safety in moderate to severe plaque psoriasis.Phase II, 12-week, multicenter, double-blind, placebo-controlled, parallel-group, dose-comparison study of 259 subjects randomized 1 : 1 : 1 to placebo, apremilast 20 mg QD or apremilast 20 mg BID.More subjects receiving apremilast 20 mg BID achieved ≥ 75% reduction in Psoriasis Area and Severity Index (PASI-75) vs. placebo (24.4% vs. 10.3%; P = 0.023)