Cytosolic Isoforms hCA Research Articles

Synthesis and Carbonic Anhydrase I, II, IX, and XII Inhibition Studies with a Series of Cyclic Sulfonyl Guanidines.

A series of thirteen cyclic sulfonyl guanidines were prepared and evaluated against tumor-associated human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA IX and hCA XII, as well as against off-target cytosolic isoforms hCA I and hCA II. The compounds reported here were generally inactive against both off-target isoforms (KI>100 μM), while all of them moderately inhibited both target isoforms hCA IX and XII in the submicromolar to micromolar ranges in which KI values spanned from 0.57 to 8.4 μM against hCA IX and from 0.34 to 9.7 against hCA XII. Due to the notable selectivity of the title compounds toward isoforms hCA IX and XII, they can be considered as useful scaffolds for further chemical optimization to develop new highly selective antitumor agents.

Isocoumarins incorporating chalcone moieties act as isoform selective tumor-associated carbonic anhydrase inhibitors.

Aim: A series of isocoumarin-chalcone hybrids were prepared and assays for the inhibition of four isoforms of human carbonic anhydrase (hCA; EC 4.2.1.1), hCA I, II, IX and XII. Materials & methods: Isocoumarin-chalcone hybrids were synthesized by condensing acetyl-isocoumarin with aromatic aldehydes. They did not significantly inhibit off-target cytosolic isoforms hCA I and II (KI>100μM) but acted as low micromolar or submicromolar inhibitors for the tumor-associated isoforms hCA IX and XII. Results & conclusion: Our work provides insights into a new and scarcely investigated chemotype which provides interesting tumor-associated CA inhibitors, considering that some such derivatives like sulfonamide SLC-0111 are in advanced clinical trials for the management of metastatic advanced solid tumors.

In-vitro and in-silico investigations of SLC-0111 hydrazinyl analogs as human carbonic anhydrase I, II, IX, and XII inhibitors.

Two novel series of hydrazinyl-based benzenesulfonamides 9a-j and 10a-j were designed and synthesized using SLC-0111 as the lead molecule. The newly synthesized compounds were evaluated for their inhibitory activity against four different human carbonic anhydrase (hCA) isoforms I, II, IX, and XII. Both the series reported here were practically inactive against the off-target isozyme hCA I. Notably, derivative 10a exhibited superior potency (Ki of 10.2 nM) than acetazolamide (AAZ) against the cytosolic isoform hCA II. The hCA IX and XII isoforms implicated in tumor progression were effectively inhibited with Kis in the low nanomolar range of 20.5-176.6 nM and 6.0-127.5 nM, respectively. Compound 9g emerged as the most potent and selective hCA IX and XII inhibitor with Ki of 20.5 nM and SI of 200.1, and Ki of 6.0 nM and SI of 683.7, respectively, over hCA I. Furthermore, six compounds (9a, 9h, 10a, 10g, 10i, and 10j) exhibited significant inhibition toward hCA IX (Kis = 27.0, 41.1, 27.4, 25.9, 40.7, and 30.8 nM) relative to AAZ and SLC-0111 (Kis = 25.0 and 45.0 nM, respectively). These findings underscore the potential of these derivatives as potent and selective inhibitors of hCA IX and XII over the off-target hCA I and II.

Synthesis, carbonic anhydrase inhibition studies and modelling investigations of phthalimide–hydantoin hybrids

A novel series of hydantoins incorporating phthalimides has been synthesised by condensation of activated phthalimides with 1-aminohydantoin and investigated for their inhibitory activity against a panel of human (h) carbonic anhydrase (CA, EC 4.2.1.1): the cytosolic isoforms hCA I, hCA II, and hCA VII, secreted isoform hCA VI, and the transmembrane hCA IX, by a stopped-flow CO2 hydrase assay. Although all newly developed compounds were totally inactive on hCA I and mainly ineffective towards hCA II, they generally exhibited moderate repressing effects on hCA VI, VII, and IX with K Is values in the submicromolar to micromolar ranges. The salts 3a and 3b, followed by derivative 5, displayed the best inhibitory activity of all the evaluated compounds and their binding mode was proposed in silico. These compounds can also be considered interesting starting points for the development of novel pharmacophores for this class of enzyme inhibitors.

Sulfonyl thiourea derivatives from 2-aminodiarylpyrimidines: Invitro and in silico evaluation as potential carbonic anhydrase I, II, IX, and XII inhibitors.

A series of synthesized sulfonyl thiourea derivatives (7a-o) of substituted 2-amino-4,6-diarylpyrimidines (4a-o) exhibited the remarkable inhibitory activity against some the human carbonic anhydrases (hCAs), including hCA I, II, IX, and XII isoforms. The inhibitory efficacy of synthesized sulfonyl thiourea derivatives were experimentally validated by invitro enzymatic assays. 7a (KI = 46.14 nM), 7j (KI = 48.92 nM), and 7m (KI = 62.59 nM) (for isoform hCA I); 7f (KI = 42.72 nM), 7i (KI = 40.98 nM), and 7j (KI = 33.40 nM) (for isoform hCA II); 7j (KI = 228.5 nM), 7m (KI = 195.4 nM), and 7n (KI = 210.1 nM) (for isoform hCA IX); 7l (KI = 116.9 nM), 7m (KI = 118.8 nM), and 7n (KI = 147.2 nM) (for isoform hCA XII) in comparison with KI values of 452.1, 327.3, 437.2, and 338.9 nM, respectively, of the standard drug AAZ. These compounds also had significantly more potent inhibitory action against cytosolic isoform hCA I and tumor-associated isoforms hCA IX and hCA XII. Furthermore, the potential inhibitory compounds were subjected to in silico screening for molecular docking and molecular dynamics simulations. The results of invitro and in silico studies revealed that compounds 7a, 7j, and 7m were the most promising derivatives in this series due to their significant effects on studied hCA I, II, IX, and XII isoforms, respectively. The results showed that the sulfonyl thiourea moiety was accommodated deeply in the active site and interacted with the zinc ion in the receptors.

Potent inhibitors of tumor associated carbonic anhydrases endowed with cathepsin B inhibition.

Twenty-one novel extended analogs of acetazolamide were synthesized and screened in vitro for their inhibition efficacy against human carbonic anhydrase (hCA) isoforms I, II, IX, XII, and cathepsin B. The majority of the compounds were found to be effective inhibitors of tumor-associated hCA IX and XII, and poor inhibitors of cytosolic hCA I. Despite the strong to moderate inhibition potential possessed by these compounds toward another cytosolic isoform hCA II, some of them demonstrated better potency against hCA IX and/or XII isoforms as compared to hCA II. Four compounds (11f, 11g, 12c, and 12g) effectively inhibited hCA IX and/or XII isoforms with considerable selectivity over the off-targets hCA I and II. Interestingly, five compounds,including 11f, 11g, 12c, 12d, and 12g, inhibited hCA IX even better than the clinically used acetazolamide. Some of the novel synthesized compounds exhibited higher anti-cathepsin B potential than acetazolamide, with % inhibition of around 50%, at a concentration of 10-7 M. Further, two compounds (12g and 12c) that showed effective and selective inhibition activity profiles against hCA IX and XII were additionally found to be effective inhibitors of cathepsin B.

Potent and selective carbonic anhydrase inhibition activities of pyrazolones bearing benzenesulfonamides

This research introduces a series of fourteen 4-aryl-hydrazonopyrazolone sulfonamide derivatives, denoted as 3(a-g) and 4(a-g), which encompass various aromatic substitutions. The aim was to assess the inhibitory potential of these compounds against four significant isoforms, including the cytosolic isoforms hCA I and II, as well as the tumor-associated membrane-bound isoforms hCA IX and XII. Most of the tested compounds exhibited substantial inhibition against the tumor-associated isoform hCA IX, with Ki values spanning from 1.1 to 158.2 nM. Notably, compounds 3e and 3g showed particularly strong inhibitory activity against the tumor-associated membrane-bound isoforms, hCA IX and XII, while maintaining a high selectivity ratio over cytosolic off-target isoforms hCA I and II. This selectivity is vital due to the potential of hCA IX and hCA XII as drug targets for hypoxic tumors. In an effort to create novel analogs that exhibit enhanced carbonic anhydrase inhibitory activity and specificity, we investigated the structure–activity relationships of these compounds and provided a concise interpretation of our findings. Consequently, these compounds merit consideration for subsequent medicinal and pharmacological research, holding potential for developing novel therapeutic agents targeting specific isoforms in hypoxic tumors.

Discovery of novel benzenesulfonamides incorporating 1,2,3-triazole scaffold as carbonic anhydrase I, II, IX, and XII inhibitors

Sulfonamides are among the most promising potential inhibitors for carbonic anhydrases (CAs), which are pharmaceutically relevant targets for treating several disease conditions. Herein, a series of benzenesulfonamides bearing 1,2,3-triazole moiety as inhibitors of human (h) α-CAs (hCAs) were designed using the tail approach. The design method combines a benzenesulfonamide moiety with a tail of oxime and a zinc-binding group on a 1,2,3-triazole scaffold. Among the synthesized derivatives, the naphthyl (6m, KI of 68.6 nM, SI of 10.3), and methyl (6a, KI of 56.3 nM, SI of 11.7) derivatives (over hCA IX) and propyl (6c, KI of 95.6 nM, SI of 2.7), and pentyl (6d, KI of 51.1 nM, SI of 6.6) derivatives (over hCA XII) displayed a noticeable selectivity for isoforms hCA I and II, respectively. Meanwhile, derivative 6e displayed a potent inhibitory effect versus the cytosolic isoform hCA I (KI of 47.8 nM) and tumor-associated isoforms hCA IX and XII (KIs of 195.9 and 116.9 nM, respectively) compared with the reference drug acetazolamide (AAZ, KIs of 451.8, 437.2, and 338.9 nM, respectively). Derivative 6b showed higher potency (KI of 33.2 nM) than AAZ (KI of 327.3 nM) towards another cytosolic isoform hCA II. Nevertheless, substituting the lipophilic large naphthyl tail to the 1,2,3-triazole linked benzenesulfonamides (6a-n) raised inhibitory effect versus hCA I and XII and selectivity towards hCA I and II isoforms over hCA IX. Evaluation of the cytotoxic potential of the synthesized derivatives was conducted in L929, MCF-7, and Hep-3B cell lines. Several compounds in the series demonstrated significant antiproliferative activity and minimal cytotoxicity. In the molecular docking study, the sulfonamide moiety interacted with the zinc-ion and neatly fit into the hCAs active sites. The extension of the tail was found to participate in diverse hydrophilic and hydrophobic interactions with adjacent amino acids, ultimately influencing the effectiveness and specificity of the derivatives.

Synthesis, Biological and In Silico Studies of Griseofulvin and Usnic Acid Sulfonamide Derivatives as Fungal, Bacterial and Human Carbonic Anhydrase Inhibitors.

Carbonic anhydrases (CAs, EC 4.2.1.1) catalyze the essential reaction of CO2 hydration in all living organisms, being actively involved in the regulation of a plethora of patho-/physiological conditions. A series of griseofulvin and usnic acid sulfonamides were synthesized and tested as possible CA inhibitors. Since β- and γ- classes are expressed in microorganisms in addition to the α- class, showing substantial structural differences to the human isoforms they are also interesting as new antiinfective targets with a different mechanism of action for fighting the emerging problem of extensive drug resistance afflicting most countries worldwide. Griseofulvin and usnic acid sulfonamides were synthesized using methods of organic chemistry. Their inhibitory activity, assessed against the cytosolic human isoforms hCA I and hCA II, the transmembrane hCA IX as well as β- and γ-CAs from different bacterial and fungal strains, was evaluated by a stopped-flow CO2 hydrase assay. Several of the investigated derivatives showed interesting inhibition activity towards the cytosolic associate isoforms hCA I and hCA II, as well as the three γ-CAs and Malassezia globosa (MgCA) enzyme. Six compounds (1b-1d, 1h, 1i and 1j) were more potent than AAZ against hCA I while five (1d, 1h, 1i, 1j and 4a) showed better activity than AAZ against the hCA II isoform. Moreover, all compounds appeared to be very potent against MgCA with a Ki lower than that of the reference drug. Furthermore, computational procedures were used to investigate the binding mode of this class of compounds within the active site of human CAs.

Tail approach synthesis of triazolylthiazolotriazole bearing benzenesulfonamides as carbonic anhydrase inhibitors capable of inducing apoptosis.

Inhibition of human carbonic anhydrase (hCA) isoform IX with concurrent induction of apoptosis is a promising approach for targeting cancer in humans. Prompted by the scope, novel benzenesulfonamides containing the 1,2,3-triazolylthiazolotriazole tail were synthesized and screened as inhibitors of hCA isoforms I, II, IV, and IX. The tumor-associated isoform hCA IX was strongly inhibited by the sulfonamides reported here with KI values ranging from 45 nM to 1.882 μM. Overall, nine compounds showed hCA IX inhibition with KI < 250 nM. The glaucoma-associated isoform hCA II was moderately inhibited while the cytosolic isoform hCA I and membrane-bound isoform hCA IV were weakly inhibited by the synthesized sulfonamides. Compound 6Ac (KI = 3.6 nM) was found to be an almost three times more potent inhibitor of hCA II as compared to the standard drug acetazolamide (KI = 12.1 nM). The selective hCA IX inhibitors were further studied for their apoptotic efficacy in goat ovarian cells and showed better results as compared to the control. A comparative study of previously synthesized compounds and molecular docking study of representative compounds revealed some important generalizations that could prove beneficial in further investigations of isoform-selective hCA inhibitors.

4-Cyanamidobenzenesulfonamide derivatives: a novel class of human and bacterial carbonic anhydrase inhibitors

A one-pot two-step protocol was developed for the synthesis of a series of novel 4-cyanamidobenzenesulfonamides from easily accessible methyl (4-sulfamoylphenyl)-carbamimidothioate. The new sulphonamides were investigated as inhibitors of the enzyme carbonic anhydrase (CA, EC 4.2.1.1), the human (h) cytosolic isoforms hCA I, II, VII, and XIII, as well as three bacterial enzymes belonging to the β-CA class, MscCA from Mammaliicoccus (Staphylococcus) sciuri and StCA1 and StCA2, from Salmonella enterica (serovar Typhimurium). The human isoforms were generally effectively inhibited by these compounds, with a clear structure-activity relationship privileging long aliphatic chains (C6, C7 and C18) as substituents at the cyanamide functionality. The bacterial CAs were also inhibited by these compounds, but not as effective as the hCAs. The most sensitive enzyme to these inhibitors was StCA1 (KIs of 50.7 − 91.1 nM) whereas SscCA was inhibited in the micromolar range (KIs of 0.86–9.59 µM).

New Pyridinium Salt Derivatives of 2-(Hydrazinocarbonyl)-3-phenyl-1H-indole-5- sulfonamide as Selective Inhibitors of Tumour-Related Human Carbonic Anhydrase Isoforms IX and XII.

The positively charged membrane impermeant sulfonamides were evaluated as a remarkable class of carbonic anhydrase inhibitors (CAIs) previously. Without affecting the human carbonic anhydrase (hCA), cytosolic isoforms hCA I and II, inhibition of two membrane-associated isoforms hCA IX and XII especially overexpressed in hypoxic tumour cells, makes the pyridinium salt derivatives potent promising therapeutic agents. A novel series of tri, tetra, and cyclo-substituted pyridinium salt derivatives of the lead compound 2- (hydrazinocarbonyl)-3-phenyl-1H-indole-5-sulfonamide has been prepared by using sixteen different pyrylium salts, for the search of selective inhibitors of transmembrane tumour-associated human carbonic anhydrase hCA IX and XII. Molecular modeling studies were carried out to understand and rationalize the in vitro enzyme inhibition data. Six of the new compounds showed good inhibitory profiles with low nanomolar range (< 100 nM) against hCA IX/XII, and compound 5 showed excellent potency with Ki values lower than 10 nM. In addition, molecular modelling studies have presented the possible binding modes of the ligands. Most of the compounds displayed potent inhibitory activity against the tumor-associated hCA IX and XII in the low nanomolar range and selectivity over the off-targeted isoforms hCA I and II. Due to their cationic structure and membrane-impermeant behavior, it is also expected to maximize the selectivity over cytosolic isoforms hCA I/II while inhibiting tumor overexpressed isoforms hCA XI/XII of new compounds in in vivo conditions.

Synthesis of a new series of quinoline/pyridine indole-3-sulfonamide hybrids as selective carbonic anhydrase IX inhibitors

In this manuscript, design, rational, synthesisand carbonic anhydrases (CAs) inhibitory profile of the quinoline/pyridine linked indole-3-sulfonamide derivatives were reported. The library of 29newly quinoline/pyridine indole-3-sulfonamide derivatives have been generated and examined against the panel of four physiological relevant human CA isoforms, namely, the cytosolic isoforms hCA I and hCA II and the transmembrane tumor associated isoforms hCA IX and hCA XII. Pyridine indole-3-sulfonamide hybrids are selective inhibit transmembrane tumor associated isoforms hCA IX and hCA XII. However, all synthesized quinoline indole-3-sulfonamide hybrids have inhibitory effect on hCA IX isoforms, whereas few have shown inhibitory activity against hCA II and hCA XII as well. However, among all synthesized compound 6q and6p having good inhibitory activity against hCA IX with Ki 1.47 µM and 1.57 µM respectively.These quinoline/pyridine indole-3-sulfonamide conjugatesmay be regarded as potential leads for hCA IXselective inhibitors as anti-cancer agents.

Pyrazolo[4,3-c]pyridine Sulfonamides as Carbonic Anhydrase Inhibitors: Synthesis, Biological and In Silico Studies.

Carbonic anhydrases (CAs, EC 4.2.1.1) catalyze the essential reaction of CO2 hydration in all living organisms, being actively involved in the regulation of a plethora of patho-/physiological conditions. A series of chromene-based sulfonamides were synthesized and tested as possible CA inhibitors. On the other hand, in microorganisms, the β- and γ- classes are expressed in addition to the α- class, showing substantial structural differences to the human isoforms. In this scenario, not only human but also bacterial CAs are of particular interest as new antibacterial agents with an alternative mechanism of action for fighting the emerging problem of extensive drug resistance afflicting most countries worldwide. Pyrazolo[4,3-c]pyridine sulfonamides were synthesized using methods of organic chemistry. Their inhibitory activity, assessed against the cytosolic human isoforms hCA I and hCA II, the transmembrane hCA IX and XII, and β- and γ-CAs from three different bacterial strains, was evaluated by a stopped-flow CO2 hydrase assay. Several of the investigated derivatives showed interesting inhibition activity towards the cytosolic associate isoforms hCA I and hCA II, as well as the 3β- and 3γ-CAs. Furthermore, computational procedures were used to investigate the binding mode of this class of compounds within the active site of hCA IX. Four compounds (1f, 1g, 1h and 1k) were more potent than AAZ against hCA I. Furthermore, compound 1f also showed better activity than AAZ against the hCA II isoform. Moreover, ten compounds out of eleven appeared to be very potent against the γ-CA from E.coli, with a Ki much lower than that of the reference drug. Most of the compounds showed better activity than AAZ against hCA I as well as the γ-CA from E.coli and the β-CA from Burkholderia pseudomallei (BpsCAβ). Compounds 1f and 1k showed a good selectivity index against hCA I and hCA XII, while 1b was selective against all 3β-CA isoforms from E.coli, BpsCA, and VhCA and all 3γ-CA isoforms from E.coli, BpsCA and PgiCA.

Coumarins inhibit η-class carbonic anhydrase from Plasmodium falciparum

Coumarins were discovered to act as inhibitors of α-carbonic anhydrases (CAs, EC 4.2.1.1) after undergoing hydrolysis mediated by the esterase activity of the enzyme to the corresponding 2-hydroxycinnamic acids. Other classes of CAs among the eight currently known do not possess esterase activity or this activity was poorly investigated. Hence, we decided to look at the potential of coumarins as inhibitors of the η-CA from the malaria-producing protozoan Plasmodium falciparum, PfaCA. A panel of simple coumarins incorporating hydroxyl, amino, ketone or carboxylic acid ester moieties in various positions of the ring system acted as low to medium micromolar PfaCA inhibitors, whereas their affinities for the cytosolic off-target human isoforms hCA I and II were in a much higher range. Thus, we confirm that η-CAs possess esterase activity and that coumarins effectively inhibit this enzyme. Elaboration of the simple coumarin scaffolds investigated here may probably lead to more effective PfaCA inhibitors.

Chromene-Containing Aromatic Sulfonamides with Carbonic Anhydrase Inhibitory Properties.

Carbonic anhydrases (CAs, EC 4.2.1.1) catalyze the essential reaction of CO2 hydration in all living organisms, being actively involved in the regulation of a plethora of patho/physiological conditions. A series of chromene-based sulfonamides were synthesized and tested as possible CA inhibitors. Their inhibitory activity was assessed against the cytosolic human isoforms hCA I, hCA II and the transmembrane hCA IX and XII. Several of the investigated derivatives showed interesting inhibition activity towards the tumor associate isoforms hCA IX and hCA XII. Furthermore, computational procedures were used to investigate the binding mode of this class of compounds, within the active site of hCA IX.

Carbonic anhydrase activation profile of indole-based derivatives

Carbonic Anhydrase Activators (CAAs) could represent a novel approach for the treatment of Alzheimer’s disease, ageing, and other conditions that require remedial achievement of spatial learning and memory therapy. Within a research project aimed at developing novel CAAs selective for certain isoforms, three series of indole-based derivatives were investigated. Enzyme activation assay on human CA I, II, VA, and VII isoforms revealed several effective micromolar activators, with promising selectivity profiles towards the brain-associated cytosolic isoform hCA VII. Molecular modelling studies suggested a theoretical model of the complex between hCA VII and the new activators and provide a possible explanation for their modulating as well as selectivity properties. Preliminary biological evaluations demonstrated that one of the most potent CAA 7 is not cytotoxic and is able to increase the release of the brain-derived neurotrophic factor (BDNF) from human microglial cells, highlighting its possible application in the treatment of CNS-related disorders.

Development of oxathiino[6,5-b]pyridine 2,2-dioxide derivatives as selective inhibitors of tumor-related carbonic anhydrases IX and XII

Oxathiino[6,5-b]pyridine 2,2-dioxides are identified as a new class of isoform-selective nanomolar inhibitors of tumor associated human carbonic anhydrases (hCA) IX and XII. At the same time they do not inhibit or poorly inhibit cytosolic isoforms hCA I and II. Oxathiino[6,5-b]pyridine 2,2-dioxides exhibited good antiproliferative properties on tumor cell lines MCF-7 (Human breast adenocarcinoma), A549 (human lung (alveolar) adenocarcinoma) and HeLa (epithelioid cervix carcinoma).

Synthesis and Biological Evaluation of Imidazo[2 ,1-b]Thiazole based Sulfonyl Piperazines as Novel Carbonic Anhydrase II Inhibitors.

A novel series of imidazo[2,1-b]thiazole-sulfonyl piperazine conjugates (9aa-ee) has been synthesized and evaluated for carbonic anhydrase (CA, EC 4.2.1.1) inhibitory potency against four isoforms: The cytosolic isozyme hCA I, II and trans-membrane tumor-associated isoform hCA IX and hCA XII, taking acetazolamide (AAZ) as standard drug, using a stopped flow CO2 hydrase assay. The results revealed that most of the compounds showed selective activity against hCA II whereas none of them were active against hCA I, IX, XII (Ki > 100 µM). The physiologically dominant cytosolic isoform hCA II was inhibited by these molecules with inhibition constants in the range of 57.7–98.2 µM. This new derivative, thus, selectively inhibits hCA II over the hCA I, IX, XII isoforms, which may be used for further understanding the physiological roles of some of these isoforms in various pathologies.

New thiopyrimidine-benzenesulfonamide conjugates as selective carbonic anhydrase II inhibitors: synthesis, in vitro biological evaluation, and molecular docking studies

In the present work, a new series of thiopyrimidine-benzenesulfonamide conjugates was designed, synthesized and tested as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. Our design strategy was based on the molecular hybridization of the benzenesulfonamide moiety as a zinc binding group (ZBG), an alkylated thiopyrimidine moiety as a spacer and (un)substituted phenyl moieties with various electronic and hydrophobic environments as a tail. The designed and synthesized compounds were evaluated against four human (h) CA isoforms hCA I, hCA II, hCA IX and hCA XII. Series 6 showed promising activity and selectivity toward the cytosolic isoforms hCA I and hCA II versus the membrane bound isoforms hCA IX and hCA XII. Compounds 6e and 6f showed Ki of 0.04 µM against hCA II with a selectivity of 15.8- to 980-fold towards hCA II over hCA I, hCA IX, hCA XII isoforms. Molecular docking in the hCA II active site attributed the promising inhibitory activity of series 6 to the interaction of their sulfonamide moiety with the active site Zn2+ ion as well as its hydrogen bonding with the key amino acids Thr199 and Thr200. Through hydrophobic interaction, the benzenesulfonamide and the thiopyrimidine moieties interact with the hydrophobic side chains of the amino acids Val121/Leu198 and Ile91/Phe131, respectively. These results indicated that the designed and synthesized series is an interesting scaffold that can be further optimized for the development of selective antiglaucoma drugs.