Carbonic anhydrase inhibitors. Inhibition of the cytosolic human isozymes I and II, and the transmembrane, tumor-associated isozymes IX and XII with substituted aromatic sulfonamides activatable in hypoxic tumors.

Some 2-mercapto-substituted-benzenesulfonamides and their disulfides/sulfones were prepared and investigated as inhibitors of four isoforms of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), that is, CA I and II (cytosolic enzymes), and the tumor-associated CA IX and XII. Some mercaptans led to a consistent increase of inhibitory power (52.8- to 243-fold) over the corresponding oxidized (S-S type) derivatives, acting as potential hypoxia-activatable drugs.