Structure-Affinity and Selectivity of Aryl-Sulfamates as Inhibitors of Carbonic Anhydrase IX.

Sulfamates inhibit carbonic anhydrases (CA), but are less investigated than sulfonamides, which comprise most CA inhibitors used as pharmaceuticals, except sulfamate topiramate, used clinically to treat epilepsy and migraine. To investigate structure-affinity relationships of sulfamates, we designed and synthesized a series of ortho- and meta-substituted sulfamates and determined their binding affinities by thermal shift assay, enzyme inhibition, and a live-cell competition assay targeting CA IX, an isozyme overexpressed in hypoxic solid tumors. The most promising compounds had Kd values of 0.5 nM. The X-ray crystal structures of sulfamates bound to CA isozymes revealed functional groups responsible for high affinity and selectivity. The pH-dependent affinity measurements revealed the mechanism of sulfamate binding to Zn(II) via the deprotonated, negatively charged amino group. Together with the stability against hydrolysis study, these findings provide insight into the molecular determinants of sulfamate binding and highlight opportunities and limitations of sulfamates for CA-targeted drug development.