Coumarins were recently shown to constitute a novel class of mechanism-based carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. We demonstrate that sulfocoumarins (1,2-benzoxathiine 2,2-dioxides) possess a similar mechanism of action, acting as effective CA inhibitors. The sulfocoumarins were hydrolyzed by the esterase CA activity to 2-hydroxyphenyl-vinylsulfonic acids, which thereafter bind to the enzyme in a region rarely occupied by other classes of inhibitors. The X-ray structure of one of these compounds in adduct with a modified CA II enzyme possessing two amino acid residues from the CA IX active site, allowed us to decipher the inhibition mechanism. The sulfonic acid was observed anchored to the zinc-coordinated water molecule, making favorable interactions with Thr200 and Pro201. Some other sulfocoumarins incorporating substituted-1,2,3-triazole moieties were prepared by using click chemistry and showed low nanomolar inhibitory action against the tumor-associated isoforms CA IX and XII, being less effective against the cytosolic CA I and II.

6-Substituted sulfocoumarins bearing the carboxamido, trimethylammonium as well as the cyano and methoxy moieties with interesting inhibitory activity/selectivity against the tumor associated carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA IX and XII are reported. Moieties leading to the best inhibition were tert-butylcarboxamido, phenylcarboxamido, and 4-pyridylcarboxamido, with K(I) values of 2.1-8.1 nM. No inhibition of the off-target hCA II and I was observed. A number of these compounds were evaluated against HT-29 colon cancer cell lines ex vivo. Compounds 9c and 9e revealed effective cytotoxic effects after 72 h of incubation in both normoxic and hypoxic conditions, unlike sulfonamide CA inhibitors that show such effects only in hypoxia. These results may be of particular importance for the choice of future drug candidates targeting hypoxic tumors and metastases, considering the fact that a sulfonamide CA IX inhibitor (SLC-0111) is presently in phase I clinical trials.

No abstract

No abstract

No abstract