Biochemically based design of cyclooxygenase-2 (COX-2) inhibitors: Facile conversion of nonsteroidal antiinflammatory drugs to potent and highly selective COX-2 inhibitors

All nonsteroidal antiinflammatory drugs (NSAIDs) inhibit the cyclooxygenase (COX) isozymes to different extents, which accounts for their anti-inflamm atory and analgesic activities and their gastrointestinal side effects. We have exploited biochemical differences between the two COX enzymes to ident ify a strategy for converting carboxylate-containing NSAIDs into selective COX-2 inhibitors. Derivatization of the carboxylate moiety in moderately se lective COX-1 inhibitors, such as 5,8,11,14-eicosatetraynoic acid (ETYA) an d arylacetic and fenamic acid NSAIDs, exemplified by indomethacin and meclo fenamic acid, respectively, generated potent and selective COX-2 inhibitors . In the indomethacin series, esters and primary and secondary amides are s uperior to tertiary amides as selective inhibitors. Only the amide derivati ves of ETYA and meclofenamic acid inhibit COX-2; the esters are either inac tive or nonselective. Inhibition kinetics reveal that indomethacin amides b ehave as slow, tight-binding inhibitors of COX-2 and that selectivity is a function of the time-dependent step. Site-directed mutagenesis of murine CO X-2 indicates that the molecular basis for selectivity differs from the par ent NSAIDs and from diarylheterocycles. Selectivity arises from novel inter actions at the opening and at the apex of the substrate-binding site. Lead compounds in the present study are potent inhibitors of COX-2 activity in c ultured inflammatory cells. Furthermore, indomethacin amides are orally act ive, nonulcerogenic, anti-inflammatory agents in an in vivo model of acute inflammation. Expansion of this approach can be envisioned for the modifica tion of all carboxylic acid-containing NSAIDs into selective COX-2 inhibito rs.