Apremilast, chemically N-(2-(1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfonyl)ethyl)-1,3-dioxoisoindolin-4-yl)acetamide, is a selective phosphodiesterase 4 (PDE4) inhibitor used in the treatment of moderate to severe plaque psoriasis and active psoriatic arthritis. It works by increasing cyclic AMP (cAMP) levels in immune cells, thereby suppressing the production of pro-inflammatory cytokines such as TNF-α, IL-17, and IL-23. This compound is also explored in research for other inflammatory and autoimmune conditions, including rheumatoid arthritis. Its sulfone and acetamide functionalities are key to its stability, selectivity, and interaction with the PDE4 enzyme.