Exploring structural properties of potent human carbonic anhydrase inhibitors bearing a 4-(cycloalkylamino-1-carbonyl)benzenesulfonamide moiety

Chemistry of heterocycles as carbonic anhydrase inhibitors: A pathway to novel research in medicinal chemistry review

Nowadays, the scientific community has focused on dealing with different kinds of diseases by exploring the chemistry of various heterocycles as novel drugs. In this connection, medicinal chemists identified carbonic anhydrases (CA) as one of the biologically active targets for curing various diseases. The widespread distribution of these enzymes and the high degree of homology shared by the different isoforms offer substantial challenges to discovering potential drugs. Medicinal and synthetic organic chemists have been continuously involved in developing CA inhibitors. This review explored the chemistry of different heterocycles as CA inhibitors using the last 11 years of published research work. It provides a pathway for young researchers to further explore the chemistry of a variety of synthetic as well as natural heterocycles as CA inhibitors.

Discovery of a novel series of potent carbonic anhydrase inhibitors with selective affinity for μ Opioid receptor for Safer and long-lasting analgesia

In this study, we investigated the development of dual-targeted ligands that bind to both μ-opioid receptor (MOR) and carbonic anhydrase (CA) enzymes, using fentanyl structure as a template. We synthesized and evaluated 21 novel compounds with dual-targeted affinity identifying the lead candidate compound 8, showing selective affinity for MOR and potent inhibition of several cytosolic CA isoforms. By means of repeated treatment of 3 daily administrations for 17 days, fentanyl (0.1 mg/kg, subcutaneously) led to tolerance development, pain threshold alterations and withdrawal symptoms in CD-1 mice, as well as astrocyte and microglia activation in the dorsal horn of the lumbar spinal cord. In contrast, compound 8 (0.32 mg/kg s.c.) maintained stable during days its analgesic effect at the higher dose tested with fewer withdrawal symptoms, allodynia development and glial cells activation. Our results suggest that targeting both MOR and CA enzymes can lead to the development of new class of potent analgesic agents with fewer side effects and reduced tolerance development. Further studies are needed to explore the potential mechanisms underlying these effects and to further optimize the therapeutic potential of these compounds.

Novel bis-ureido-substituted sulfaguanidines and sulfisoxazoles as carbonic anhydrase and acetylcholinesterase inhibitors

To discover alternative substances to compounds used to treat many diseases, especially treating Alzheimer's disease (AD) and Parkinson's disease targeting carbonic anhydrase (hCA) and acetylcholinesterase (AChE) enzymes, is important. For this purpose, a series of novel bis-ureido-substituted sulfaguanidine (SG1-4) and sulfisoxazole (SO1-4) derivatives were synthesized, and their inhibitory capacities were screened against hCA isoenzymes (hCA I and II) and AChE. Possible binding mechanisms of inhibitors to the active site were elucidated by in silico studies, and the results were supported by in vitro results. Moreover, the percent radical scavenging capacities of the derivatives were also evaluated. The derivatives (SG1-4 and SO1-4) were more effective against hCAs compared to standard drug acetazolamide (KI values of 98.28-439.17 nM for hCA I and II, respectively) and exhibited the highest inhibition with the KIs in the ranges of 2.54 ± 0.50-41.02 ± 7.52 nM for hCA I, 11.20 ± 2.97-67.14 ± 13.58 nM for hCA II, and 257.60 ± 27.84-442.60 ± 52.13 nM for AChE. Also, compounds SG1 and SO1 also showed ABTS radical scavenging activity at the rate of 70% and 78%, respectively. These results will contribute to the literature for the rational design and synthesis of new potent and selective inhibitors targeting hCAs and AChE with multifunctional effects such as radical scavenging as well as inhibition. This study focused on the synthesis and inhibitory effects of bis-ureido-substituted sulfaguanidine (SG1-4) and sulfisoxazole (SO1-4) derivatives against human hCA I and II isoforms and AChE. In order to test synthesized derivatives' free radical scavenging potentials were the DPPH and ABTS assays. In silico studies elucidated possible binding mechanisms of inhibitors to the active site.

Inhibition Studies on Human and Mycobacterial Carbonic Anhydrases with N-((4-Sulfamoylphenyl)carbamothioyl) Amides

A library of structurally diverse N-((4-sulfamoylphenyl)carbamothioyl) amides was synthesized by selective acylation of easily accessible 4-thioureidobenzenesulfonamide with various aliphatic, benzylic, vinylic and aromatic acyl chlorides under mild conditions. Inhibition of three α-class cytosolic human (h) carbonic anhydrases (CAs) (EC 4.2.1.1); that is, hCA I, hCA II and hCA VII and three bacterial β-CAs from Mycobacterium tuberculosis (MtCA1-MtCA3) with these sulfonamides was thereafter investigated in vitro and in silico. Many of the evaluated compounds displayed better inhibition against hCA I (K_I = 13.3-87.6 nM), hCA II (K_I = 5.3-384.3 nM), and hCA VII (K_I = 1.1-13.5 nM) compared with acetazolamide (AAZ) as the control drug (K_I values of 250, 12.5 and 2.5 nM, respectively, against hCA I, hCA II and hCA VII). The mycobacterial enzymes MtCA1 and MtCA2 were also effectively inhibited by these compounds. MtCA3 was, on the other hand, poorly inhibited by the sulfonamides reported here. The most sensitive mycobacterial enzyme to these inhibitors was MtCA2 in which 10 of the 12 evaluated compounds showed K_Is (K_I, the inhibitor constant) in the low nanomolar range.

Recombinant human carbonic anhydrase VII: Purification, characterization, inhibition, and molecular docking studies

Human carbonic anhydrase VII (hCA VII), a cytosolic enzyme, defends against oxidative stress by preventing reactive oxygen species from forming. In our study, first, hCA VII was cloned into Escherichia coli (One Shot Mach1-T1R) strain by using cDNA of the human brain and successfully expressed. The integrity of the plasmid generated by colony PCR was checked, and after, for protein expression, the plasmid was transformed into E. coli BL21 (DE-3) strain. hCA VII expression was observed after 6 h of isopropyl-D-1-thiogalactopyranoside (IPTG) induction. The fusion protein containing hexahistidine (6xHis) was purified with 7.02 EU/mg of specific activity, had 48.07% of purification yield, and approximately 21-folds using a ProbondTM nickel chelating resin affinity column. Then, both molecular mass determination and purity control of the purified recombinant enzyme was done by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). The mass of the SUMO-hCA VII fusion protein was calculated as 46.77 kDa. As a result of Western blot analysis using anti-His G-HRP antibody, the fusion protein was detected as approximately 45 kDa. Furthermore, the characterization assays and in vitro inhibition studies were done for the recombinant enzyme. K_I values of these agents were found between 0.29 μM and 157.6 mM. Finally, molecular docking investigations of these antibiotics were undertaken to understand further the binding interactions on the active site of this recombinant enzyme.

Design, synthesis, biological evaluation and crystal structure determination of dual modulators of carbonic anhydrases and estrogen receptors

Multi-target compounds have become increasingly important for the development of safer and more effective drug candidates. In this work, we devised a combined ligand-based and structure-based multi-target repurposing strategy and applied it to a series of hexahydrocyclopenta[c]quinoline compounds synthesized previously. The in silico analyses identified human Carbonic Anhydrases (hCA) and Estrogen Receptors (ER) as top scoring candidates for dual modulation. hCA isoforms IX and XII, and ER subtypes ER⍺ and/or ERβ are co-expressed in various cancer cell types, including breast and prostate cancer cells. ER⍺ is the primary target of anti-estrogen therapy in breast cancer, and the hCA IX isoform is a therapeutic target in triple-negative breast cancer. ER⍺-mediated transcriptional programs and hCA activity in cancer cells promote favorable microenvironments for cell proliferation. Interestingly, several lines of evidence indicate that the combined modulation of these two targets may provide significant therapeutic benefits. Moving from these first results, two additional hexahydrocyclopenta[c]quinoline derivatives bearing a sulfonamide zinc binding group (hCA) and a phenolic hydroxyl (ER) pharmacophoric group placed at the appropriate locations were designed and synthesized. Interestingly, these compounds were able to directly modulate the activities of both hCA and ER targets. In cell-based assays, they inhibited proliferation of breast and prostate cancer cells with micromolar potency and cell type-selective efficacy. The compounds inhibited hCA activity with nanomolar potency and isoform-selectivity. In transactivation assays, they reduced estrogen-driven ER activity with micro-molar potency. Finally, crystal structures of the synthesized ligands in complex with the two targets revealed that the compounds bind directly to the hCA active site, as well as to the ER ligand-binding domain, providing structural explanation to the observed activity and a rationale for optimization of their dual activity. To the best of our knowledge, this work describes the design, synthesis and biological characterization of the first dual modulators of hCA and ER, laying the ground for the structure-based optimization of their multi-target activity.

Structure-guided identification of a selective sulfonamide-based inhibitor targeting the human carbonic anhydrase VA isoform

In recent years, multistep hybrid computational protocols have attracted attention for their application in the drug discovery of enzyme inhibitors. So far, there are large collections of human carbonic anhydrase (hCA) inhibitors, but only a few of them selectively inhibit the mitochondrial isoforms hCA VA and VB as potential therapeutics in obesity treatment. Most sulfonamide-based inhibitors show poor selectivity for inhibiting isoforms of therapeutic interest over ubiquitous hCA I and hCA II. Herein, we propose a combination of ligand- and structure-based approaches to generate pharmacophore models for hCA VA inhibitors. Then, we performed a virtual screening (VS) campaign on a database of commercially available sulfonamides. Finally, the in silico screening followed by docking studies suggested several "hit compounds" that demonstrated to inhibit hCA VA at a low nanomolar concentration in a stopped-flow CO₂ hydrase assay. Notably, the best candidate, 2-(3,4-dihydro-2H-quinolin-1-yl)-N-(4-sulfamoylphenyl)acetamide (code name VAME-28) proved to be a potent hCA VA inhibitor (K_i value of 54.8 nM) and a more selective agent over hCA II when compared to the reference compound topiramate.

Applications of Isosteres of Piperazine in the Design of Biologically Active Compounds: Part 1

Piperazine and homopiperazine are well-studied heterocycles in drug design that have found gainful application as scaffolds and terminal elements and for enhancing the aqueous solubility of a molecule. The optimization of drug candidates that incorporate these heterocycles in an effort to refine potency, selectivity, and developability properties has stimulated the design and evaluation of a wide range of bioisosteres that can offer advantage. In this review, we summarize the design and application of bioisosteres of piperazine and homopiperazine that have almost exclusively been in the drug design arena. While there are ∼100 approved drugs that incorporate a piperazine ring, only a single marketed agricultural product is built on this heterocycle. As part of the review, we discuss some of the potential reasons underlying the relatively low level of importance of this heterocycle to the design of agrochemicals and highlight the potential opportunities for their use in contemporary research programs.

New Sulfamethoxazole Derivatives as Selective Carbonic Anhydrase IX and XII Inhibitors: Design, Synthesis, Cytotoxic Activity and Molecular Modeling

In this study new sulphamethoxazole derivatives (S1-S4, S6-S12, and S14-S22) were designed and synthesized and their structures were fully characterized and validated using NMR, mass, and IR spectroscopy, as well as elemental analyses. All new derivatives (S1-S22) were assayed against human carbonic anhydrase (hCAs IX and XII) for their inhibitory activities. hCAs IX and XII were chosen due to the fact that CAIX expression is recognized as a hypoxia marker with a poor prognosis in breast cancer. When compared to Dorzolamide HCl as a standard reference, derivatives S2, S3, S8, S9, and S15 had the most effective inhibition with low IC₅₀ values. The active compounds were further evaluated against hCAs I and II inhibitory activity and compounds S8, S9 and S15 showed the least inhibitory effect compared to the reference standard, acetazolamide, indicating that their effect in normal cells is the lowest. Cell viability tests for the selected compounds were carried out on MCF7 (normoxia and hypoxia) and on the normal breast cell line (MCF10a) with Staurosporine as a standard. The results showed that compound S15 had a highly potent cytotoxic effect. Furthermore, cell cycle analysis results showed that compound S15 triggered cell cycle arrest and apoptosis in G1/S of MCF7 cancer cells. Finally, molecular docking was performed to point out the possible explanation for the vital structural features and key-interactions exerted by our ligands with hCAs IX and XII that might share additional designs and highlight possible leads for a hopeful anticancer agent. Consequently, sulphamethoxazole Derivative S15 could be the potential lead for emerging selective cytotoxic compounds directing h CAs IX and XII.

Synthesis and biological evaluation of sulfonamide-based compounds as inhibitors of carbonic anhydrase from Vibrio cholerae

This study reports our continued efforts to identify inhibitors capable of targeting carbonic anhydrases (CAs) expressed in bacteria. Based on previously identified chemotypes, we designed and synthesized new analogs that were screened toward the α, β, and γ classes encoded in Vibrio cholerae (Vch). The K_i values measured in the stopped-flow hydrase assay revealed that very simple structural modifications might induce a relevant impact on the inhibitory effects as well as the selectivity profile over ubiquitous human isozymes (hCA I/II). Unfortunately, the best active VchCA inhibitors demonstrated a dramatic loss of hCA II selectivity when compared to previously reported compounds. Among the new series of sulfonamides, several molecules proved to be about sevenfold more potent against VchCAγ than the reference compound acetazolamide, thus furnishing new insights for further development of inhibitors targeting CAs expressed in bacteria.

Acipimox inhibits human carbonic anhydrases

Acipimox, a nicotinic acid derivative in clinical use for the treatment of hyperlipidaemia, incorporates a free carboxylic acid and an N-oxide moiety, functionalities known to interact with the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) and inhibit its activity. Herein we report that acipimox acts as a low micromolar CA inhibitor (CAI) against most human (h) isoforms possessing catalytic activity, hCA I – XIV. By using computational techniques (docking and molecular dynamics simulations), we propose that acipimox coordinates through its carboxylate group to the zinc ion from the enzyme active site cavity, whereas the N-oxide group is hydrogen-bonded to the proton shuttle His residue in some isoforms (hCA I) or to active site Thr or Gln residues in other isoforms (hCA II, III, IV, VII, etc). As some CA isoforms are involved in lipogenesis, these data may be useful for the design of more effective CAIs with antiobesity activity.

Targeting Metalloenzymes by Boron-Containing Metal-Binding Pharmacophores

Metalloenzymes have critical roles in a wide range of biological processes and are directly involved in many human diseases; hence, they are considered as important targets for therapeutic intervention. The specific characteristics of metal ion(s)-containing active sites make exploitation of metal-binding pharmacophores (MBPs) critical to inhibitor development targeting metalloenzymes. This Perspective focuses on boron-containing MBPs, which display unique binding modes with metalloenzyme active sites, particularly via mimicking native substrates or tetrahedral transition states. The design concepts regarding boron-containing MBPs are highlighted through the case analyses on five distinct classes of clinically relevant nucleophilic metalloenzymes from medicinal chemistry perspectives. The challenges (e.g., selectivity) faced by some boron-containing MBPs and possible strategies (e.g., bioisosteres) for metalloenzyme inhibitor transformation are also discussed.

4-Sulfamoylphenylalkylamides as Inhibitors of Carbonic Anhydrases Expressed in Vibrio cholerae

A current issue of antimicrobial therapy is the resistance to treatment with worldwide consequences. Thus, the identification of innovative targets is an intriguing challenge in the drug and development process aimed at newer antimicrobial agents. The state-of-art of anticholera therapy might comprise the reduction of the expression of cholera toxin, which could be reached through the inhibition of carbonic anhydrases expressed in Vibrio cholerae (VchCAα, VchCAβ, and VchCAγ). Therefore, we focused our interest on the exploitation of sulfonamides as VchCA inhibitors. We planned to design and synthesize new benzenesulfonamides based on our knowledge of the VchCA catalytic site. The synthesized compounds were tested thus collecting useful SAR information. From our investigation, we identified new potent VchCA inhibitors, some of them displayed high affinity toward VchCAγ class, for which few inhibitors are currently reported in literature. The best interesting VchCAγ inhibitor (S)-N-(1-oxo-1-((4-sulfamoylbenzyl)amino)propan-2-yl)furan-2-carboxamide (40) resulted more active and selective inhibitor when compared with acetazolamide (AAZ) as well as previously reported VchCA inhibitors.

Design, synthesis and biochemical evaluation of novel carbonic anhydrase inhibitors triggered by structural knowledge on hCA VII

To tackle the challenge of isoform selectivity, we explored the entrance of the cavity for selected druggable human Carbonic Anhydrases (hCAs). Based on X-ray crystallographic studies on the 4-(4-(2-chlorobenzoyl)piperazine-1-carbonyl)benzenesulfonamide in complex with the brain expressed hCA VII (PDB code: 7NC4), a series of 4-(4(hetero)aroylpiperazine-1-carbonyl)benzene-1-sulfonamides has been developed. To evaluate their capability to fit the hCA VII catalytic cavity, the newer benzenesulfonamides were preliminary investigated by means of docking simulations. Then, this series of thirteen benzenesulfonamides was synthesized and tested against selected druggable hCAs. Among them, the 4-(4-(furan-2-carbonyl)piperazine-1-carbonyl)benzenesulfonamide showed remarkable affinity towards hCA VII (Ki: 4.3 nM) and good selectivity over the physiologically widespread hCA I when compared to Topiramate (TPM).

LigTMap: ligand and structure-based target identification and activity prediction for small molecular compounds

Target prediction is a crucial step in modern drug discovery. However, existing experimental approaches to target prediction are time-consuming and costly. Here, we introduce LigTMap, an online server with a fully automated workflow that can identify protein targets of chemical compounds among 17 classes of therapeutic proteins extracted from the PDBbind database. It combines ligand similarity search with docking and binding similarity analysis to predict putative targets. In the validation experiment of 1251 compounds, targets were successfully predicted for more than 70% of the compounds within the top-10 list. The performance of LigTMap is comparable to the current best servers SwissTargetPrediction and SEA. When testing with our newly compiled compounds from recent literature, we get improved top 10 success rate (66% ours vs. 60% SwissTargetPrediction and 64% SEA) and similar top 1 success rate (45% ours vs. 51% SwissTargetPrediction and 41% SEA). LigTMap directly provides ligand docking structures in PDB format, so that the results are ready for further structural studies in computer-aided drug design and drug repurposing projects. The LigTMap web server is freely accessible at https://cbbio.online/LigTMap. The source code is released on GitHub (https://github.com/ShirleyWISiu/LigTMap) under the BSD 3-Clause License to encourage re-use and further developments.

Developments of small molecules as inhibitors for carbonic anhydrase isoforms

Carbonic anhydrases are ubiquitous, and their role in the hydration of carbon dioxide is essential for the survival of many tissues and organs. However, their association with many pathological diseases, especially in glaucoma, Alzheimer's, obesity, epilepsy, and tumorigenesis, has prompted the design and synthesis of novel carbonic anhydrase inhibitors (CAIs). Herein we describe (1) approaches used in the design of CAIs and (2) synthesis of small molecules as CAIs within the last five years. Despite the active research in this area, there are still more avenues to explore, especially selective inhibition of CA I, CA IX, and XII. These isoforms would continue to open up a diversity of carbonic anhydrase inhibitors containing 1,2,3-triazoles, imidazolone, pyrrolidone, thiadiazole, isatin, and glycoconjugates as part of their molecular frameworks.

Identification of the metabolites produced following Iris tectorum Maxim oral administration and a network pharmacology-based analysis of their potential pharmacological properties

1. Iris tectorum Maxim is a traditional herbal medicine that has been used to treat cancer, abdominal distension, hepatic cirrhosis, and inflammatory diseases. How I. tectorum Maxim is metabolised and the mechanistic basis for its pharmacological activity remain to be defined.2. This study was designed to clarify the metabolism of I. tectorum Maxim and to explore the mechanistic basis for its pharmacological activity.3. In the present study, 51 metabolites were identified via mass spectrometry in samples of bile, urine, and faeces from Wistar rats. Metabolites were mainly formed by glucuronidation, sulphation, methylation, and amino acid conjugation.4. Tectoridin, tectorigenin, irigenin, iristectorigenin A, iristectorigenin B, and 6-hydroxygenistein were identified as potentially be bioactive candidate metabolites for which 36 putative targets and 90 interactions were detected through a network pharmacology analysis. Gene set enrichment analyses and compound-disease networks revealed the targets of these metabolites to regulate important proteins associated with cancer as well as cardiovascular, urogenital, and digestive system diseases.5. Molecular docking confirmed the interactions of these six candidate bioactive metabolites with carbonic anhydrase IV, VII, and XII.6. Overall, these data offer new insights into the metabolism and pharmacological activity of I. tectorum Maxim in vivo.

Identification of N-phenyl-2-(phenylsulfonyl)acetamides/propanamides as new SLC-0111 analogues: Synthesis and evaluation of the carbonic anhydrase inhibitory activities

As a front-runner selective CA IX inhibitor currently in Phase Ib/II clinical trials, SLC-0111 has been herein exploited as a lead molecule for development of new different sets of N-phenyl-2-(phenylsulfonyl)acetamides/propanamides incorporating different functionalities; primary sulfonamide (5a-f), free carboxylic (8a, 8d), ethyl ester (8b, 8e), acetyl (8c, 8f) and nitro (10a, 10b), as potential carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. All the prepared analogues have been examined for their CA inhibitory activities towards four human (h) isoenzymes, hCA I, II, IX and XII. Interestingly, replacement of SLC-0111 ureido linker with the flexible sulfonyl acetamide linker, as well as linker branching and elongation strategies successfully enhanced the inhibitory action toward hCA IX isoform, such as in sulfones 5a-d and 5f which displayed better activity than SLC-0111. Furthermore, sulfonamide-based sulfone (5f) and carboxylic acid-based sulfones (8a and 8d) demonstrated interesting selectivity toward the tumor-related hCA IX isoform over both hCA I and hCA II, which suggests them as promising candidates for further development as potential anticancer candidates. Thereafter, the anti-proliferative action for sulfones 5f, 8a and 8d was examined against breast (MCF-7) and colon (HCT-116) cancer cell lines. Also, sulfone 5f was further assessed for its impact on the cell cycle progression and apoptosis in HCT-116 cells.

The crystal structures of 2-(4-benzhydrylpiperazin-1-yl)-N-(4-sulfamoylphenyl)acetamide in complex with human carbonic anhydrase II and VII provide insights into selective CA inhibitor development

Our studies suggest that the acetamide linker and long tails are suitable structural features to design selective CA inhibitors.

Computer-aided identification of human carbonic anhydrase isoenzyme VII inhibitors as potential antiepileptic agents

Human carbonic anhydrase (hCA) belongs to a superfamily of metalloenzymes that reversibly catalyse the hydration of carbon dioxide to give bicarbonate (HCO₃^-) and proton (H⁺). As HCO₃^- ions play an important role in neuronal signalling hence, hCA enzymes are an attractive target for antiepileptic drugs. Out of all the isoforms, hCA VII is predominantly expressed in the brain cortex and hippocampus region, which are the most affected area during seizure activity. Hence, we have identified some hCA VII inhibitors employing computational tools like atom-based 3D quantitative structure-activity relationship (QSAR), auto-QSAR, pharmacophore-based virtual screening, molecular docking, and molecular dynamics (MD) simulations. Atom-based 3D QSAR modelling outperformed auto-QSAR with an R² and Q² value of 0.9634 and 0.9646, respectively. A four-feature pharmacophore model (AADR_1) was developed and a focussed library of around 3,00,000 compounds was screened. Compounds with a phase screen score >2.40 were selected for docking studies. The activity of the selected hits was predicted employing the developed 3D QSAR model. Finally, three compounds were taken up for the MD simulation studies which also suggest that the identified hits might form a stable complex with hCA VII enzyme. A comparative docking study was also done with other hCA isoforms like I, II, IV, IX, and XII to examine the selectivity of the identified hits towards hCA VII. Based on these studies, three hits have been identified as potential hCA VII inhibitor which is drug-like molecules. Further, in vitro studies are required to develop leads from these identified hits.Communicated by Ramaswamy H. Sarma.

In Silico-Guided Identification of New Potent Inhibitors of Carbonic Anhydrases Expressed in Vibrio cholerae

Carbonic anhydrases from Vibrio cholerae (VchCAs) play a significant role in bacterial pathophysiological processes. Therefore, their inhibition leads to a reduction of gene expression virulence and bacterial growth impairment. Herein, we report the first ligand-based pharmacophore model as a computational tool to study selective inhibitors of the β-class of VchCA. By a virtual screening on a collection of sulfonamides, we retrieved 9 compounds that were synthesized and evaluated for their inhibitory effects against VchCAβ as well as α- and γ-classes of VchCAs and selectivity over human ubiquitous isoforms hCA I and II. Notably, all tested compounds were active inhibitors of VchCAs. The N-(4-sulfamoylbenzyl)-[1,1'-biphenyl]-4-carboxamide (20e) stood out as the most exciting inhibitor toward the β-class (K _i = 95.6 nM), also showing a low affinity against the tested human isoforms. By applying docking procedures, we described the binding mode of the inhibitor 20e within the catalytic cavity of the modeled open conformation of VchCAβ.

N-Quinary heterocycle-4-sulphamoylbenzamides exert anti-hypoxic effects as dual inhibitors of carbonic anhydrases I/II

Acute mountain sickness (AMS) affects approximately 25-50% of newcomers to high altitudes. Two human carbonic anhydrase isoforms, hCA I and II, play key roles in developing high altitude illnesses. However, the only FDA-approved drug for AMS is acetazolamide (AAZ), which has a nearly 100 times weaker inhibitory activity against hCA I (K_i = 1237.10 nM) than hCA II (K_i = 13.22 nM). Hence, developing potent dual hCA I/II inhibitors for AMS prevention and treatment is a critical medical need. Here we identified N-quinary heterocycle-4-sulphamoylbenzamides as potent hCA I/II inhibitors. The newly designed compounds 2b, 5b, 5f, 6d, and 6f possessed the desired inhibitory activities (hCA I: Ki = 16.95-52.71 nM; hCA II: K_i = 8.61-18.64 nM). Their hCA I inhibitory capacity was 22- to 76-fold stronger than that of AAZ. Relative to the control group for survival in a mouse model of hypoxia, 2b and 6d prolonged the survival time of mice by 21.7% and 29.3%, respectively, which was longer than those of AAZ (6.5%). These compounds did not display any apparent toxicity in vitro and in vivo. In addition, docking simulations suggested that the quinary aromatic heterocycle groups stabilised the interaction between hCA I/II and the inhibitors, which could be further exploited in structure optimization studies. Hence, future functional studies may confirm 2b and 6d as potential clinical candidate compounds with anti-hypoxic activity against AMS.

Looking toward the Rim of the Active Site Cavity of Druggable Human Carbonic Anhydrase Isoforms

We report the synthesis and biochemical evaluation of a series of substituted 4-(4-aroylpiperazine-1-carbonyl)benzenesulfonamides (5a-s) developed as inhibitors of druggable carbonic anhydrase (CA) isoforms, as tools for the identification of new therapeutics. X-ray crystallography confirmed that this class of benzenesulfonamides binds CAs through the canonical anchoring of the benzenesulfonamide moiety to the metal ion and a tail-mediated recognition of the middle/top area of the active site cavity. Compound 5e (R = 2-Cl) demonstrated relevant selectivity toward brain-expressed hCA VII. The best balancing in binding affinity and selectivity toward tumor-expressed hCA IX/hCA XII over ubiquitous hCA I/hCA II was found for inhibitor 5o (R = 3-NO₂). Notably 5b (R = 2-F) proved to be the most efficacious inhibitor of hCA XII for which computational studies elucidated the CA recognition process.

Seeking new approach for therapeutic treatment of cholera disease via inhibition of bacterial carbonic anhydrases: experimental and theoretical studies for sixteen benzenesulfonamide derivatives

A series of sixteen benzenesulfonamide derivatives has been synthesised and tested as inhibitors of Vibrio cholerae carbonic anhydrase (CA) enzymes, belonging to α-CA, β-CA, and γ-CA classes (VchCAα, VchCAβ, and VchCAγ). The determined Ki values were compared to those of selected human CA isoforms (hCA I and hCA II). Structure-affinity relationship analysis highlighted that all tested compounds proved to be active inhibitors of VchCAα at nanomolar concentration. The VchCAβ activity was lower to respect inhibitory efficacy toward VchCAα, whereas, these benzenesulfonamide derivatives failed to inhibit VchCAγ. Interestingly, compound 7e combined the best activity toward VchCAα and VchCAβ. In order to obtain a model for binding mode of our inhibitors toward bacterial CAs, we carried out docking simulations by using the available crystal structures of VchCAβ.

Sulfonamides incorporating piperazine bioisosteres as potent human carbonic anhydrase I, II, IV and IX inhibitors

Starting from the molecular simplification of (R) 4-(3,4-dibenzylpiperazine-1-carbonyl)benzenesulfonamide 9a, a compound endowed with selectivity for human Carbonic Anhydrase (hCA) IV, a series of piperazines and 4-aminopiperidines carrying a 4-sulfamoylbenzamide moiety as Zn-binding group have been designed and tested on human isoforms hCA I, II, IV and IX, using a stopped flow CO₂ hydrase assay. The aim of the work was to derive structure-activity relationships useful for designing isoform selective compounds. These structural modifications changed the selectivity profile of the analogues from hCA IV to hCA I and II, and improved potency. Several of the new compounds showed subnanomolar activity on hCA II. X-ray crystallography of ligand-hCAII complexes was used to compare the binding modes of the new piperazines and the previously synthesized 2-benzyl-piperazine analogues, explaining the inhibition profiles.

Application of hydrazino and hydrazido linkers to connect benzenesulfonamides with hydrophilic/phobic tails for targeting the middle region of human carbonic anhydrases active site: Selective inhibitors of hCA IX

Herein we report the design and synthesis of three different sets of novel benzenesulfonamides (5a-e, 7a-e and 10a-d) incorporating hydrophilic/hydrophobic tails by hydrazido or hydrazino linkers. The newly synthesized benzenesulfonamides were examined in vitro for their inhibitory activity towards four human (h) carbonic anhydrase (hCA, EC 4.2.1.1) isoforms, hCA I, II, IX and XII using a stopped-flow CO₂ hydrase assay. All these isoforms were inhibited by the sulfonamides (5a-e, 7a-e and 10a-d) with variable degrees in the following K_I ranges: 76.8-357.4 nM for hCA I, 8.2-94.6 nM for hCA II, 2.0-46.3 nM for hCA XI, and 8.3-88.3 nM for hCA XII. The sulfonamide 7d exhibited potent anti-proliferative activity against breast MCF-7 cancer cell line under both normoxic and hypoxic conditions with IC₅₀ values equal 3.32 ± 0.06 and 8.53 ± 0.32 μM, respectively, which are comparable to the reference drug doxorubicin (IC₅₀ = 2.36 ± 0.04 and 8.39 ± 0.25 μM, respectively). Furthermore, 7d was screened for cell cycle disturbance and apoptosis induction in MCF-7 cells. It was found to persuade cell cycle arrest at G2-M stage as well as to alter the Sub-G1 phase, also, 7d resulted in a significant increase in the percent of annexinV-FITC positive apoptotic cells from 1.03 to 18.54%. Molecular docking study was carried out for 7d within the hCA IX and hCA XII active sites to rationalize the obtained inhibition results.