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Ester and Amide Derivatives of the Nonsteroidal Antiinflammatory Drug, Indomethacin, as Selective Cyclooxygenase-2 Inhibitors

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journal contribution
posted on 08.07.2000 by Amit S. Kalgutkar, Alan B. Marnett, Brenda C. Crews, Rory P. Remmel, Lawrence J. Marnett
Recent studies from our laboratory have shown that derivatization of the carboxylate moiety in substrate analogue inhibitors, such as 5,8,11,14-eicosatetraynoic acid, and in nonsteroidal antiinflammatory drugs (NSAIDs), such as indomethacin and meclofenamic acid, results in the generation of potent and selective cyclooxygenase-2 (COX-2) inhibitors (Kalgutkar et al. Proc. Natl. Acad. Sci. U.S.A. 2000, 97, 925−930). This paper summarizes details of the structure−activity studies involved in the transformation of the arylacetic acid NSAID, indomethacin, into a COX-2-selective inhibitor. Many of the structurally diverse indomethacin esters and amides inhibited purified human COX-2 with IC50 values in the low-nanomolar range but did not inhibit ovine COX-1 activity at concentrations as high as 66 μM. Primary and secondary amide analogues of indomethacin were more potent as COX-2 inhibitors than the corresponding tertiary amides. Replacement of the 4-chlorobenzoyl group in indomethacin esters or amides with the 4-bromobenzyl functionality or hydrogen afforded inactive compounds. Likewise, exchanging the 2-methyl group on the indole ring in the ester and amide series with a hydrogen also generated inactive compounds. Inhibition kinetics revealed that indomethacin amides behave as slow, tight-binding inhibitors of COX-2 and that selectivity is a function of the time-dependent step. Conversion of indomethacin into ester and amide derivatives provides a facile strategy for generating highly selective COX-2 inhibitors and eliminating the gastrointestinal side effects of the parent compound.