A NEW LEAD COMPOUND FOR THE DEVELOPMENT OF CARBONIC ANHYDRASE INHIBITORS

Carbonic anhydrases (CAs) are ubiquitous metalloenzymes, which catalyze the reversible hydration of carbon dioxide to bicarbonate ion and proton. These proteins are present in prokaryotes and eukaryotes, and are encoded by six evolutionarily unrelated gene families.[1,2] Human CAs (hCAs) are widely distributed in many tissues and organs. Since at these sites CAs play a crucial role in various physiological processes, they have recently become interesting targets for pharmaceutical research. Indeed, several CA inhibitors (CAIs) incorporating a sulfonamide/sulfamate/sulfamide moieties are currently clinically used for the treatment or prevention of a multitude of diseases such as glaucoma, solid tumors, etc.[1] However, these compounds are generally poorly selective towards the different CA isoforms. For this reason, despite many encouraging results, new zinc binding groups (ZBGs) are continuously tested in order to advance upon the identification of isoform selective CAIs.[1] Here, we report the synthesis, inhibition and structural studies of hydroxylamine-O-sulfonamide, a molecule containing two ZBGs, namely the sulfonamide and hydroxylamine moieties.[3] The inhibitor action of this molecule was tested against all catalytically active hCA isoforms, revealing that it possesses a rather variable behavior against the different human isozymes. To elucidate the binding mode of hydroxylamine-O-sulfonamide to CA active site, an original crystallography-assisted Raman spectroscopy approach was utilized. In particular, the X-ray structures of hydroxylamine-O-sulfonamide in complex with hCA II, the best characterized hCA isoform, showed that hydroxylamine-O-sulfonamide is in part coordinated in the classical manner, as all sulfonamides/sulfamates, binding the catalytic zinc ion through the sulfonamide nitrogen and in part through hydroxylamine moiety in a side-on fashion, which is an unusual inhibition pattern for this family of enzymes. This surprising observation was further proved by Raman microspectroscopy experiments. Altogether our data indicate that the hydroxylamine-O-sulfonamide versatility can be exploited for drug design purposes for obtaining new effective and selective CAIs. References 1. Alterio, V., Di Fiore, A., D'Ambrosio, K., Supuran, C.T., De Simone, G. Chem. Rev., 2012, 112, 4421. 2.De Simone, G., Di Fiore, A., Capasso C., Supuran, C. T. Bioorg. Med. Chem. Lett., 2015, 25, 1385. 3. Di Fiore A, Vergara A, Caterino M, Alterio V, Monti SM, Ombouma J, Dumy P, Vullo D, Supuran CT, Winum JY, De Simone G. Chem. Commun. (Camb.), 2015. In press.