Crisaborole is a topically administered, boron-containing, anti-inflammatory compound that inhibits the phosphodiesterase-4 (PDE4) activity and thereby suppresses the cytokine release of TNFalpha, IL-12, IL-23 and other cytokines. PDE4 is an an enzyme that converts the intracellular second messenger 3'5'-cyclic adenosine monophosphate (cAMP) into the active metabolite adenosine monophosphate (AMP). By inhibiting PDE4 and thus increasing levels of cAMP, crisaborole controls inflammation. The use of boron chemistry enabled synthesis of a low-molecular-weight compound (251 daltons), thereby facilitating effective penetration of crisaborole through human skin. Crisaborole is in clinical development for the topical treatment of psoriasis and being pursued for the topical treatment of atopic dermatitis. Preliminary studies in children and adults demonstrated favorable efficacy and safety profiles. Crisaborole may represent an anti-inflammatory option that safely minimizes the symptoms and severity of AD and that can be used for both acute and long-term management.

Roflumilast is a specific phosphodiesterase type (4PDE4) inhibitor indicated for use as a treatment to reduce the risk of COPD exacerbations in patients with severe COPD associated with chronic bronchitis and a history of exacerbations.

APREMILAST, (±)- is a mixture of isomers, one of them is therapeutic active S form (apremilast), an inhibitor of phosphodiesterase 4. This active form is sold under the brand name OTEZLA for the treatment of adult patients with active psoriatic arthritis.