In vitro assays for cyclooxygenase activity and inhibitor characterization.

Cyclooxygenases (COX), or Prostaglandin H Synthases (PGHS), are the target enzymes for nonsteroidal anti-inflammatory drugs (NSAIDS). The identification of two isoforms of COX nearly 20 years ago stimulated a flurry of research activity to identify novel, selective inhibitors that could provide potential benefit over existing nonselective NSAIDS. An important contribution to this discovery effort was the development of various in vitro and in vivo assays to support rapid screening of chemical libraries, characterization of inhibitory mechanism, and determination of potency and efficacy to guide follow-up medicinal chemistry efforts. Several assay methods for the in vitro evaluation of COX activity and mechanism of inhibition by test compounds will be reviewed. Each of these methods has inherent advantages and disadvantages with regard to application and the mechanistic detail provided.