PDE4 inhibitors: sustained patenting activity as leading drugs near the market

The search for novel PDE4 inhibitors remains a highly active field for the pharmaceutical industry with 55 applications published in 1999. These efforts remain concentrated on the identification of compounds based upon catechol or phthalazine derivatives. Several applications suggest such compounds have utility for new indications such as leukaemia and pruritus. Clinical development of a number of compounds, led by cilomilast and roflumilast, is progressing steadily for indications that include COPD, asthma, psoriasis and dermatitis. This review highlights the novel structural classes of PDE4 inhibitors disclosed in the past year's patent applications and the clinical developments with PDE4 inhibitors.