Many non-steroidal anti-inflammatory drugs (NSAIDs) are potent but non-selective inhibitors of both COX-1 and COX-2 in humans.[1] CAY10404 is one of the most selective inhibitors of COX-2 which has been reported to date, with a selectivity index (SI; SI = IC50 COX-1/IC50 COX-2) of >500,000. (The COX-1 IC50 is >500 mM, and COX-2 IC50 is <1 nM.)[2] As a reference point, the SI of celecoxib is about 400. Thus, CAY10404 has an SI which is several logs greater than the first generation of selective COX-2 inhibitors, and is comparable to the SI of second generation selective COX-2 inhibitors, such as valdecoxib and etoricoxib.[3]

Reference：
[1.] Barnett, J., Chow, J., Ives, D., et al. Purification, characterization and selective inhibition of human prostaglandin G/H synthase 1 and 2 expressed in the baculovirus system. Biochim Biophys. Acta. 1209(1), 130-139 (1994).
[2]. Habeeb, A.G., Rao, P.N.P., and Knaus, E.E. Design and syntheses of diarylisoxazoles: Novel inhibitors of cyclooxygenase-2 (COX-2) with analgesic-antiinflammatory activity. Drug Development Research 51, 273-286 (2000).
[3]. Mardini, I.A., and Fitzgerald, G.A. Selective inhibitors of cyclooxygenase-2: A growing class of anti-inflammatory drugs. Molecular Interventions 1(1), 30-38 (2001).