Selective phosphodiesterase 4 inhibitors in the treatment of allergy and inflammation.

Phosphodiesterase (PDE)4 inhibitors are a novel class of drugs in development for the treatment of inflammatory airways diseases, including asthma, allergic rhinitis and chronic obstructive pulmonary disease. PDE4 inhibitors are potent anti-inflammatory agents both in vitro and in vivo, but few have successfully proceeded to phase II and III clinical trials, as a result of insufficient clinical efficacy and unacceptable side effects, including nausea and emesis, which have hampered their progression. A greater understanding of the molecular biology of PDE4 has led to the development of efficacious compounds with fewer side effects. This review focuses on how selective PDE4 inhibitors can advance the treatment of airways diseases and deal with the challenges that lie ahead.