Identification of Novel and Potent Indole-Based Benzenesulfonamides as Selective Human Carbonic Anhydrase II Inhibitors: Design, Synthesis, In Vitro, and In Silico Studies

Abstract

In recent decades, human carbonic anhydrase inhibitors (hCAIs) have emerged as an important therapeutic class with various applications including antiglaucoma, anticonvulsants, and anticancer agents. Herein, a novel series of indole-based benzenesulfonamides were designed, synthesized, and biologically evaluated as potential hCAIs. A regioisomerism of the sulfonamide moiety was carried out to afford a total of fifteen indole-based benzenesulfonamides possessing different amide linkers that enable the ligands to be flexible and develop potential H-bond interaction(s) with the target protein. The activity of the synthesized compounds was evaluated against four hCA isoforms (I, II, IX and, XII). Compounds 2b, 2c, 2d, 2f, 2h and 2o exhibited potent and selective profiles over the hCA II isoform with Ki values of 7.3, 9.0, 7.1, 16.0, 8.6 and 7.5 nM, respectively. Among all, compound 2a demonstrated the most potent inhibition against the hCA II isoform with an inhibitory constant (Ki) of 5.9 nM, with 13-, 34-, and 9-fold selectivity for hCA II over I, IX and XII isoforms, respectively. Structure–activity relationship data attained for various substitutions were rationalized. Furthermore, a molecular docking study gave insights into both inhibitory activity and selectivity of the target compounds. Accordingly, this report presents a successful scaffold hoping approach that reveals compound 2a as a highly potent and selective indole-based hCA II inhibitor worthy of further investigation.

Suppression of Tumor Growth and Cell Migration by Indole-Based Benzenesulfonamides and Their Synergistic Effects in Combination with Doxorubicin

“…Therefore, compounds A1 , A6 , and A15 were chosen to determine their IC 50 values on these breast cancer cells. These findings agree with our previous report, in which higher inhibitory activities are observed against the human CA IX isoform by A1 , A4 , A6 , and A15 [ 20 ]. Although A1 , A6 , and A15 exhibited similar cytotoxic patterns in three types of breast cancer cells, the IC 50 values of A1 and A6 on MDA-MB-231 cells were determined to be over 100 µM ( Figure 3 ).…”

“…The indole-based benzenesulfonamides were originally designed and synthesized as potential human CA inhibitors [ 20 ]. Prior to the identification of CA isoform(s) mediating the cytotoxic effects of A6 and A15 , we first examined the protein levels of several CA isoforms, including ubiquitously expressed cytosolic CA I and II and cancer-associated transmembrane CA IX and XII, in the presence or absence of CoCl 2 in MCF-7 and SK-BR-3 cells using western blotting.…”

“…As previously described ( Figure 4 A), CoCl 2 significantly induced CA II expression in MCF-7 cells. Moreover, compounds A6 and A15 were reported to potently inhibit the CA II isoform, with K i values of 16.0 and 7.5 nM, respectively [ 20 ]. These findings prompted us to examine whether CA II played any role in the cytotoxic effects of A6 and A15 on MCF-7 and SK-BR-3 cells.…”

“…The expression of CA IX was upregulated by CoCl 2 treatment in both MCF-7 and SK-BR-3 cells ( Figure 4 ). Although several compounds, including our compounds ( A6 and A15 ), have been reported to potently inhibit the human CA II isoform with Ki values of around 10 nM, compounds A4 , A6 , and A15 were also shown to inhibit CA IX with Ki values of 165.5, 165.1, and 169.6 nM, respectively [ 20 ]. Consistent with this report, the present study demonstrates that A6 and A15 strongly suppress the CoCl 2 -induced CA IX expression in both cell types ( Figure 5 ).…”

“…A series of novel indole-based benzenesulfonamides were synthesized and biologically evaluated as potential CA inhibitors by measuring the inhibitory constant ( K i ) against four human CA isoforms (CA I, II, IX, and XII). Among these derivatives, compounds 2a −d , 2f , 2h , and 2o were reported to exhibit potent and selective inhibition of the CA II isoform, with compound 2a being the most potent [ 20 ]. In the present study, these compounds ( 2a −2o ) were sequentially renamed ( A1 −A15 , Figure 1 ) and evaluated for their anticancer activities against various cancer cell lines.…”