Spectral and crystallographic study of pyridinic analogues of nimesulide: determination of the active form of methanesulfonamides as COX-2 selective inhibitors.

Compound 7, N-(3-phenoxy-4-pyridinyl)trifluoromethanesulfonamide, showed in vitro (whole blood assay) a strong inhibitory activity on the two cyclooxygenase (COX) enzymes (IC(50)(COX-1) = 2.2 microM and IC(50)(COX-2) = 0.4 microM), being more active but less COX-2-selective than nimesulide. Physicochemical studies and structural analyses indicated that the anionic sulfonamidate species seemed to be the active form of methanesulfonamides, which optimally interacted with the COX enzymes' active sites.