COX-1, COX-2, and COX-3 and the future treatment of chronic inflammatory disease.

A new generation of non-steroidal anti-inflammatory drugs has been described that selectively targets the inducible isoform of cyclo-oxygenase, cyclo-oxygenase 2 (COX-2). This isoform is expressed at sites of inflammation, which has led to the speculation that its inhibition could provide all the benefits of current nonsteroidal anti-inflammatory drugs, but without their major side-effects on the gastrointestinal system (which are due to inhibition of COX-1). We have shown that COX-2 (identified by use of specific antibodies) is induced during the resolution of an inflammatory response, inhibition of COX-2 resulting in persistence of the inflammation due to the prevention of the synthesis of a range of anti-inflammatory prostanoids. We propose that there is a third isoform of this enzyme family, COX-3, a proposal that will have implication for the prescription of both existing and new generation anti-inflammatory drugs, and might represent a new therapeutic target.