Synthesis of new class of non-sulfonamide bis-benzimidazoles as antitumor agents by inhibiting carbonic anhydrase-IX enzyme.

In several types of cancers, the expression of carbonic anhydrase-IX (CA-IX) enzyme is elevated than its normal level which ultimately plays a key role in the tumor growth of epithelial cells in breast and lung cancer by acidifying tumor microenvironment, therefore, inhibition of this target is important in antitumor therapy. We have synthesized bis-benzimidazole derivatives (1-25) by using 3,3'-diaminobenzidine and various aromatic aldehydes and characterized by various spectroscopic methods (UV/Visible, 1HNMR, 13CNMR, and mass spectrometry). Their inhibitory potential for human CA-IX (hCA-IX) was evaluated in-vitro, where several synthesized derivatives showed potent inhibition of hCA-IX (IC50 values in range of 5.23 ± 1.05 to 40.10 ± 1.78 μM) and compounds 3-5, 7-8, 13-16, 21 and 23 showed superior activity than the standard drug "acetazolamide" (IC50 = 18.24 ± 1.43 μM). Furthermore, all these compounds showed no toxicity on human fibroblast cell lines (BJ cell lines). Moreover, molecular docking was carried out to predict their binding modes in the active site of CA-IX and revealed a significant role of imidazole ring of synthesized entities in their effective binding with the specific residues of CA-IX. The obtained results paved the way for further in vivo and other pharmacological studies for the optimization of these molecules as possible anti-cancer agents.