Studies in 3,4-diaryl-1,2,5-oxadiazoles and their N-oxides: search for better COX-2 inhibitors.

A series of 3,4-diaryl-1,2,5-oxadiazoles and 3,4-diaryl-1,2,5-oxadiazole N-oxides were prepared and evaluated for COX-2 and COX-1 binding affinity in vitro and for antiinflammatory activity by the rat paw edema method. p-Methoxy (p-OMe) substituted compounds 9, 21, 34, 41, 42 showed COX-2 enzyme inhibition higher than that showed by compounds with other substituents. 3,4-Di(4-methoxyphenyl)-1,2,5-oxadiazole N-oxide (42) showed COX-2 enzyme inhibition of 54% at 22 micromol L(-1) and COX-1 enzyme inhibition of 44% at 88 micromol L(-1) concentrations, but showed very low in vivo anti-inflammatory activity.