Biological evaluation of p-toluene sulphonylhydrazone as carbonic anhydrase IX inhibitors: An approach to fight hypoxia-induced tumors.

To find potential inhibitors of human carbonic anhydrase IX (CAIX), we have successfully deigned, synthesized and characterized three p-toluene sulphonylhydrazone derivatives (1-3). Molecular docking studies provided the structural basis of CAIX inhibition and a deeper insight into the protein-ligand interactions. p-Toluene sulphonylhydrazone derivatives show a well organized conformational compatibility with the active site of CAIX. The protein-ligand complex was stabilized by several non-covalent interactions offered by residues present in the active site cavity. The actual binding affinity of synthesized compounds with CAIX was experimentally measured by fluorescence and isothermal titration calorimetry (ITC). Results of both fluorescence binding and ITC measurements show the binding affinity of p-Toluene sulphonylhydrazone derivatives to the CAIX in the μM range. CAIX enzyme inhibition assay showed the IC50 values in nM range. Though all the three compounds (1-3) showed a good binding with CAIX, compound 2 showed the best inhibition of CAIX activity. These compounds were non-toxic on normal cell lines (HEK-293) and significantly inhibit the proliferation of hypoxic cancer cells. All compounds induce apoptosis in the hypoxic cancer cells. These compounds may be further exploited as promising therapeutic agents to control the hypoxia-induced tumors.