Carbonic anhydrase inhibitors: Synthesis and inhibition of the human cytosolic isozymes I and II and transmembrane isozymes IX, XII (cancer-associated) and XIV with 4-substituted 3-pyridinesulfonamides

A series of novel 4-substituted-3-pyridinesulfonamides (2-27 and 31-33) have been synthesized and investigated as inhibitors of five isoforms of zinc enzyme carbonic anhydrase (CA, EC 42 11), that is, the cytosolic, ubiquitous isozymes CA I and II, and transmembrane isozymes CA IX, XII (cancer-associated) and XIV. Against the human isozymes hCA I, the new compounds showed inhibition constants in the range of 0.078-11.7 mu M, against hCA II in the range of 9.9-140 nM, against hCA IX in the range of 4.6-313 nM, against hCA XII in the range of 3.4-21.6 nM, and against hCA XIV in the range of 50.9-160 nM, respectively. Compounds 4, 6, 7, 9, 11-14, 19, 20, 22-24, 26, 27, 31 and 32 showed excellent hCA IX inhibitory efficacy, with inhibition constants of 4.6-12 0 nM, being much more effective as compared to the clinically used sulfonamides AAZ, MZA, EZA, DCP and IND 4-[N'-(6-Chloro-7-cyano-1,1-dioxo-1,4,2-benzodithiazin-3-yl)hydrazino]-3-pyridinesulfonamide (31) is the prominent of the compounds due to its remarkable inhibitory activity toward hCA I (K(I)s = 0.078 mu M), hCA IX (K(I)s = 7.2 nM) and hCA XII (K(I)s = 3.4 nM).