Purity >98%. Apremilast is an inhibitor of phosphodiesterase 4 (PDE4) with an IC50 value of 74 nM when tested in U937 cell lysates with 1 mM cAMP. It is orally active, significantly decreasing epidermal thickness and epithelial cell proliferation index in a mouse model of psoriasis. Apremilast reduces both TNF-Alpha and matrix metalloproteinase-3 production in gut lamina propria mononuclear cells from patients with inflammatory bowel disease. It also blocks spontaneous production of TNF-Alpha from human rheumatoid synovial cells and improves clinical score in mouse models of arthritis.