Aryl and heteroaryl sulfonamides (ArSO₂NH₂) are therapeutically used to inhibit the catalytic activity of carbonic anhydrases (CAs). Using a “click-tail” approach a novel class of glycoconjugate benzene sulfonamides have been synthesized that contain diverse carbohydrate−triazole tails. These compounds were assessed for their ability to inhibit three human CA isozymes in vitro: cytosolic hCA I and hCA II and transmembrane, tumor-associated hCA IX. This isozyme has a minimal expression in normal tissue but is overexpressed in hypoxic tumors and its inhibition is a current approach toward new cancer therapies. The qualitative structure−activity for all derivatives demonstrated that the stereochemical diversity present within the carbohydrate tails effectively interrogated the CA active site topology, to generate several inhibitors that were potent and selective toward hCA IX, an important outcome in the quest for potential cancer therapy applications based on CA inhibition.

Carbonic anhydrase IX (CA IX) is an extracellular transmembrane homodimeric zinc metalloenzyme that has been validated as a prognostic marker and therapeutic target for several types of aggressive cancers. CA IX shares a close homology with other CA isoforms, making the design of CA IX isoform selective inhibitors challenging. In this paper, we describe the development of a new class of CA IX inhibitors that comprise a sulfamate as the zinc binding group, a variable linker, and a carbohydrate “tail” moiety. Seven compounds inhibited CA IX with low nM K_i values of 1–2 nM and also exhibited permeability profiles to preferentially target the binding of extracellular CA IX over cytosolic CAs. The crystal structures of two of these compounds in complex with a CA IX-mimic (a variant of CA II, with active site residues that mimic CA IX) and one compound in complex with CA II have been determined to 1.7 Å resolution or better and demonstrate a selective mechanism of binding between the hydrophilic and hydrophobic pockets of CA IX versus CA II. These compounds present promising candidates for anti-CA IX drugs and the treatment for several aggressive cancer types.