Structural Basis of Nanomolar Inhibition of Tumor-Associated Carbonic Anhydrase IX: X-Ray Crystallographic and Inhibition Study of Lipophilic Inhibitors with Acetazolamide Backbone

Sulfonamide-Bearing Pyrazolone Derivatives as Multitarget Therapeutic Agents: Design, Synthesis, Characterization, Biological Evaluation, In Silico ADME/T Profiling and Molecular Docking Study

The research and design of new inhibitors for the treatment of diseases such as Alzheimer's disease and glaucoma through inhibition of cholinesterases (ChEs; acetylcholinesterase, AChE and butyrylcholinesterase, BChE) and carbonic anhydrase enzymes are among the important targets. Here, a series of novel sulfonamide-bearing pyrazolone derivatives (1a-f and 2a-f) were successfully synthesized and characterized by using spectroscopic and analytical methods. The inhibitory activities of these newly synthesized compounds were evaluated both in vitro and in silico for their effect on carbonic anhydrases (hCA I and hCA II isoenzymes) and ChEs. The in vitro studies showed that these novel compounds demonstrated potential inhibitory activity, with KI values covering the following ranges: 18.03 ± 2.86-75.54 ± 4.91 nM for hCA I, 24.84 ± 1.57-85.42 ± 6.60 nM for hCA II, 7.45 ± 0.98-16.04 ± 1.60 nM for AChE, and 34.78 ± 5.88-135.70 ± 17.39 nM for BChE. Additionally, many of these compounds showed promising inhibitory activity, and some showed higher potency than reference compounds. While the in silico studies have also identified the potential binding positions of these compounds, using the crystal structures of hCA I, II, AChE and BChE receptors. The varying affinities demonstrated by these designed compounds for ChEs and hCA isoenzymes show that these compounds could hold promise as potential alternative agents for selectively inhibiting ChEs and hCAs in the treatment of diseases such as Alzheimer's disease and glaucoma.

Investigating the Anti-Inflammatory Potential of SLC-0111: A Carbonic Anhydrase Inhibitor Targeting Cyclooxygenase-Mediated Inflammatory Pathways in a Carrageenan-Induced Rat Model

Inflammation is a fundamental physiological reaction that leads to the development of many diseases, including tissue damage, asthma, diabetes, atherosclerosis, inflammatory bowel disease, and cancer. The enzyme COX is a vital mediator in inflammatory processes. Interestingly, the COX enzyme possesses multiple structural similarities to the carbonic anhydrase enzyme. SLC-0111, a molecule known for its potent and selective inhibition of carbonic anhydrase, has not yet been studied for its potential effects on acute inflammation, proinflammatory cytokine levels, or oxidative stress parameters. Our study seeks to assess the binding affinity of SLC-0111 to the COX enzyme, as well as its possible anti-inflammatory properties. We treated rats SLC-0111 at dosages of 50, 100, and 200 mg/kg for 3 days before generating inflammation with carrageenan (CAR). Following CAR delivery, paw thickness was evaluated at 4-h intervals to assess inflammatory levels. Additionally, protein extravasation in paw tissue has been examined using Evans Blue (EB) dye. MDA and glutathione (GSH) levels in paw tissue were measured to assess oxidative stress. Carrageenan enhanced edema, protein extravasation, and proinflammatory cytokines TNF-α, IL-1β, IL-6, IL-4, and IL-13. SLC-0111 decreased all of these, except for IL-4. Similarly, the histological findings of our research indicated that SLC-0111 had an anti-inflammatory effect at a dose of 200 mg/kg. However, SLC-0111 had no significant effect on MDA or GSH levels. These data represent that SLC-0111 may have anti-inflammatory properties and could be used as a treatment for inflammation-related disorders.

Multiple Binding Modes of Inhibitors to Human Carbonic Anhydrases: An Update on the Design of Isoform-Specific Modulators of Activity

Human carbonic anhydrases (hCAs) are widespread zinc enzymes that catalyze the hydration of CO2 to bicarbonate and a proton. Currently, 15 isoforms have been identified, of which only 12 are catalytically active. Given their involvement in numerous physiological and pathological processes, hCAs are recognized therapeutic targets for the development of inhibitors with biomedical applications. However, despite massive development efforts, very few of the presently available hCA inhibitors show selectivity for a specific isoform. X-ray crystallography is a very useful tool for the rational drug design of enzyme inhibitors. In 2012 we published in Chemical Reviews a highly cited review on hCA family (Alterio, V. et al. Chem Rev. 2012, 112, 4421-4468), analyzing about 300 crystallographic structures of hCA/inhibitor complexes and describing the different CA inhibition mechanisms existing up to that date. However, in the period 2012-2023, almost 700 new hCA/inhibitor complex structures have been deposited in the PDB and a large number of new inhibitor classes have been discovered. Based on these considerations, the aim of this Review is to give a comprehensive update of the structural aspects of hCA/inhibitor interactions covering the period 2012-2023 and to recapitulate how this information can be used for the rational design of more selective versions of such inhibitors.

Synthesis, biochemical screening and in-silico investigations of arylsulfonamides bearing linear and cyclic tails

A small series of arylsulfonamide derivatives was designed and synthesized to study linear and cyclic inhibitors targeting human Carbonic Anhydrases (hCAs EC 4.2.1.1) as essential enzymes regulating (patho)-physiological processes. Particularly, the synthesis of these ten compounds was inspired to the well-known arylsulfonamides having flexible or constrained linkers able to maintain the two crucial moieties, anchoring zinc group and hydrophobic tail, in the optimized orientation within CA cavities of tumor-expressed isoforms hCA IX and hCA XII. The synthesized imine derivatives and related cyclic 1,3-thiazin-4-ones were screened in a stopped-flow carbon dioxide hydrase assay and proved to be effective inhibitors against hCA IX and hCA XII isoforms with Ki values ranging of 3.7-215.7 nM and 5.7-415.0 nM, respectively. Molecular docking studies of both series of arylsulfonamides were conducted to propose their binding mode within hCA IX and hCA XII active sites thus highlighting their distinct ability to occupy the two catalytic cavities. Moreover, the 4-[(3-cyanophenyl)methylidene]aminobenzene-1-sulfonamide 7 proved to reduce the cell viability of breast carcinoma (MCF-7) and colon rectal carcinoma (HCT-116) human cell lines under the fixed doses of 10 μM. These results encouraged us to continue our efforts in developing potent and efficient arylsulfonamides targeting hCA IX and hCA XII isoforms.

Development and Optimization of a Bromothymol Blue-Based PLA2 Assay Involving POPC-Based Self-Assemblies

Phospholipase A2 (PLA2) is a superfamily of phospholipase enzymes that dock at the water/oil interface of phospholipid assemblies, hydrolyzing the ester bond at the sn-2 position. The enzymatic activity of these enzymes differs based on the nature of the substrate, its supramolecular assemblies (micelle, liposomes), and their composition, reflecting the interfacial nature of the PLA2s and requiring assays able to directly quantify this interaction of the enzyme(s) with these supramolecular assemblies. We developed and optimized a simple, universal assay method employing the pH-sensitive indicator dye bromothymol blue (BTB), in which different POPC (3-palmitoyl-2-oleoyl-sn-glycero-1-phosphocholine) self-assemblies (liposomes or mixed micelles with Triton X-100 at different molar ratios) were used to assess the enzymatic activity. We used this assay to perform a comparative analysis of PLA2 kinetics on these supramolecular assemblies and to determine the kinetic parameters of PLA2 isozymes IB and IIA for each supramolecular POPC assembly. This assay is suitable for assessing the inhibition of PLA2s with great accuracy using UV-VIS spectrophotometry, being thus amenable for screening of PLA2 enzymes and their substrates and inhibitors in conditions very similar to physiologic ones.

Design, synthesis, evaluation of biological activities and molecular docking and dynamic studies of novel acetazolamide analog compounds

Modification of drugs used in the clinic is a frequently used method with regards to medicinal chemistry in the development of new drugs. Acetazolamide is a drug in clinical use as a CA inhibitor. Within the scope of this study, the 'N-(5-sulfamoyl-1,3,4-thiadiazol-2-yl) acetamide' structure, which is acetazolamide residue, was kept constant; various mercaptan substitutions were made from methylene adjacent to the carbonyl group in the structure. Compounds 4c, 4d, 4e, 4 g, 4h, 4i, and 4j exhibited inhibitor activity against CA enzyme with IC50=0.238 ± 0.010, 0.161 ± 0.007, 0.067 ± 0.002, 0.084 ± 0.003, 0.033 ± 0.001, 0.049 ± 0.002 and 0.187 ± 0.008 µM, respectively. The intermolecular interactions of the promising compounds with aromatase enzyme were investigated through the SP docking approach, which revealed significant binding interaction energies associated with these compounds. To measure the stability of the compounds in the enzyme active site, dynamic studies were performed at 100 ns. In addition to the RMSD, RMSF parameters, the interaction ratios of compound 4h with amino acids in the enzyme active site and the interaction histograms were also investigated. The results obtained are quite promising. Continuous interactions were exhibited with Thr199, Glu106, His96, His94 and His119, which are important for the CA enzyme.Communicated by Ramaswamy H. Sarma.

Discovery of novel 1,8-naphthalimide piperazinamide based benzenesulfonamides derivatives as potent carbonic anhydrase IX inhibitors and ferroptosis inducers for the treatment of triple-negative breast cancer

A novel series of 1,8-naphthalimide piperazinamide based benzenesulfonamides derivatives were designed and synthesized as carbonic anhydrase IX (CA IX) inhibitors and ferroptosis inducers for the treatment of triple-negative breast cancer (TNBC). The representative compound 9o exhibited more potent inhibitory activity and selective against CA IX over off-target CA II, compared with positive control SLC-0111. Molecular docking study was also performed to gain insights into the binding interactions of 9o in the binding pocket of CAIX. Moreover, compound 9o exhibited superior antitumor activities against breast cancer cells under hypoxia than that of normoxia conditions. Mechanism studies revealed that compound 9o could act as DNA intercalator and effectively suppressed cell migration, arrested the cell cycle at G1/S phase and induced apoptosis in MDA-MB-231 cells, while inducing ferroptosis accompanied by the dissipation of MMP and the elevation intracellular levels of ROS. Notably, in vivo studies demonstrated that 9o effectively inhibited tumor growth and metastasis in a highly metastatic murine breast cancer 4 T1 xenograft model. Taken together, this study suggests that compound 9o represents a potent and selective CA IX inhibitor and ferroptosis inducer for the treatment of TNBC.

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.

Neisseria gonorrhoeae carbonic anhydrase inhibition

Carbonic anhydrases (CAs) are ubiquitous enzymes that are found in all kingdoms of life. Though different classes of CAs vary in their roles and structures, their primary function is to catalyze the reaction between carbon dioxide and water to produce bicarbonate and a proton. Neisseria gonorrhoeae encodes for three distinct CAs (NgCAs) from three different families: an α-, a β-, and a γ-isoform. This chapter details the differences between the three NgCAs, summarizing their subcellular locations, roles, essentiality, structures, and enzyme kinetics. These bacterial enzymes have the potential to be drug targets; thus, previous studies have investigated the inhibition of NgCAs-primarily the α-isoform. Therefore, the classes of inhibitors that have been shown to bind to the NgCAs will be discussed as well. These classes include traditional CA inhibitors, such as sulfonamides, phenols, and coumarins, as well as non-traditional inhibitors including anions and thiocarbamates.

Exploring the potency of diazo-coumarin containing hybrid molecules: Selective inhibition of tumor-associated carbonic anhydrase isoforms IX and XII

This study introduces a series of ten hybrid molecules DK(1-10), which combine diazo and coumarin moieties along with diverse aromatic substitutions. The primary objective was to evaluate the inhibitory capabilities of these compounds against four prominent isoforms: the cytosolic hCA I and II, as well as the tumor-associated membrane-bound hCA IX and XII. Impressively, the majority of the tested compounds exhibited significant inhibition activity against the tumor-associated isoforms hCA IX and XII, with KI values ranging from 29.2 to 293.3 nM. Notably, compound DK-8 displayed particularly robust inhibitory activity against the tumor-associated membrane-bound isoforms, hCA IX and XII, yielding KI values of 32.5 and 29.2 nM, respectively. Additionally, another derivative, DK-9, containing a primary sulfonamide, exhibited notable inhibition against hCA XII with a KI value of 36.4 nM. This investigation aimed to explore the structure-activity relationships within these compounds, shedding light on how various substitutions and structural components influence their inhibitory potential. As a result, these compounds present promising candidates for further exploration in medicinal and pharmacological research. Their ability to selectively inhibit specific isoforms, particularly those associated with hypoxic tumors, suggests their potential as foundational compounds for the development of novel therapeutic agents.

Design and Synthesis of Pyrazole Carboxamide Derivatives as Selective Cholinesterase and Carbonic Anhydrase Inhibitors: Molecular Docking and Biological Evaluation

The present study focused on the synthesis and characterization of novel pyrazole carboxamide derivatives (SA1-12). The inhibitory effect of the compounds on cholinesterases (ChEs; AChE and BChE) and carbonic anhydrases (hCAs; hCA I and hCA II) isoenzymes were screened as in vitro. These series compounds have been identified as potential inhibitors with a KI values in the range of 10.69±1.27-70.87±8.11 nM for hCA I, 20.01±3.48-56.63±6.41 nM for hCA II, 6.60±0.62-14.15±1.09 nM for acetylcholinesterase (AChE) and 54.87±7.76-137.20 ±9.61 nM for butyrylcholinesterase (BChE). These compounds have a more effective inhibition effect when compared to the reference compounds. In addition, the potential binding positions of the compounds with high affinity for ChE and hCAs were demonstrated by in silico methods. The results of in silico and in vitro studies support each other. As a result of the present study, the compounds with high inhibitory activity for metabolic enzymes, such as ChE and hCA were designed. The compounds may be potential alternative agents used as selective ChE and hCA inhibitors in the treatment of Alzheimer's disease and glaucoma.

1,3-Diaryl Triazenes Incorporating Disulfonamides Show Both Antiproliferative Activity and Effective Inhibition of Tumor-associated Carbonic Anhydrases IX and XII

AIM

The aim of this study was to synthesize a library of novel di-sulfa drugs containing 1,3- diaryltriazene derivatives TS (1-13) by conjugation of diazonium salts of primary sulfonamides with sulfa drugs to investigate the cytotoxic effect of these new compounds in different cancer types and to determine their inhibitory activity against tumor-associated carbonic anhydrases IX and XII.

MATERIALS AND METHODS

A carbonic anhydrase inhibitory activity of the obtained compounds was evaluated against four selected human carbonic anhydrase isoforms (hCA I, hCA II, hCA IX and hCA XII) by a stoppedflow CO2 hydrase assay. In addition, in vitro, cytotoxicity studies were applied by using A549 (lung cancer), BEAS-2B (normal lung), MCF-7 (breast cancer), MDA-MB-231 (breast cancer), CRL-4010 (normal breast epithelium), HT-29 (colon cancer), and HCT -116 (colon cancer) cell lines.

RESULTS

As a result of the inhibition data, the 4-aminobenzenesulfonamide derivatives were more active than their 3-aminobenzenesulfonamide counterparts. More specifically, compounds TS-1 and TS-2, both of which have primary sulfonamides on both sides of the triazene linker, showed the best inhibitory activity against hCA IX with Ki values of 19.5 and 13.7 nM and also against hCA XII with Ki values of 6.6 and 8.3 nM, respectively. In addition, in vitro cytotoxic activity on the human breast cancer cell line MCF-7 showed that some derivatives of di-sulfa triazenes, such as TS-5 and TS-13, were more active than SLC-0111.

CONCLUSION

With the aim of developing more potent and isoform-selective CA inhibitors, these novel hybrid molecules containing sulfa drugs, triazene linkers, and the classical primary sulfonamide chemotype may be considered an interesting example of effective enzyme inhibitors and important anticancer agents.

Design, synthesis, and biological activity studies of carbonic anhydrase inhibitors

Carbonic anhydrase (CA) enzymes are a common catalytic enzyme in many organisms. Vertebrates and invertebrates have different CA isoforms. Sixteen different isozymes of the α-CA isoform found in vertebrates have been identified so far. The main task of this enzyme is to catalyze the reversible conversion of carbon dioxide into bicarbonate and hydrogen ions in the body. It is widely distributed in many organs and tissues. They are involved in important physiological processes such as pH and CO2 homeostasis, biosynthetic reactions such as gluconeogenesis, lipogenesis, ureagenesis, bone resorption, calcification, tumorigenicity, and electrolyte secretion. As a result of the literature research, it has been determined that the most effective inhibitor of the carbonic anhydrase enzyme is sulfonamides. The R group in the general molecular structure of R-SO2-NH2 generally consists of aromatic or heteroaromatic ring systems. The sulfonamides interact strongly with the Zn2+ ions in the active site of the enzyme. In this study, 10 sulfonamide derivatives were synthesized. Analyses of the obtained compounds are evaluated by using 1H NMR, 13C NMR and HRMS spectroscopic methods. The inhibition effect of the obtained compounds on the carbonic anhydrase enzyme was investigated by means of in vitro kit method. For the selected compounds, docking studies were performed and the enzyme active sites and binding points were determined. It was revealed that the strongest interaction with CA enzymes (CA-I, CA-II, CA-IX, CA-XII) active sites was observed with the compound 2e.

Screening Campaign and Docking Investigations in Identifying New Hit Compounds as Inhibitors of Human Carbonic Anhydrases Expressed In Tumour Cells

The tumor-expressed human carbonic anhydrase (hCA) isoforms hCA IX and hCA XII have been extensively studied to develop anticancer agents targeting solid tumors in combined therapy. These CA  isoforms are considered key factors in controlling tumor microenvironment (TME) of cancer lines that develop high metastatic activity. Herein, we report the discovery of potent hCA IX/hCA XII inhibitors that were disclosed through a screening campaign on an in-house collection of arylsulfonamides preliminary tested toward other hCAs. Among them, the N-(4-sulfamoylphenyl)naphthalene-2-carboxamide (12) and N-(4-sulfamoylphenyl)-3,4-dihydroisoquinoline-2(1H)-carbothioamide (15) proved to be the most intriguing hCA IX/hCA XII inhibitors displaying favourable selectivity ratios over widespread hCA I and hCA II isoforms. To explore their binding mode, we conducted docking studies that described the poses of the best inhibitors in the catalytic site of hCA IX and hCA XII, thus suggesting the privileged pattern of interactions. These structural findings might further improve the knowledge for a successful identification of new sulfonamides as adjuvant agents in cancer management.

Synthesis and Characterization of Novel 1,3-Diaryltriazene-Substituted Sulfaguanidine Derivatives as Selective Carbonic Anhydrase Inhibitors: Biological Evaluation, in Silico ADME/T and Molecular Docking Study

Sulfonamide compounds known as human carbonic anhydrase (hCA) inhibitors are used in the treatment of many diseases such as epilepsy, antibacterial, glaucoma, various diseases. 1,3-diaryl-substituted triazenes and sulfaguanidine are used for therapeutic purposes in many drug structures. Based on these two groups, the synthesis of new compounds is important. In the present study, the novel 1,3-diaryltriazene-substituted sulfaguanidine derivatives (SG1-13) were synthesized and fully characterized by spectroscopic and analytic methods. Inhibitory effect of these compounds on the hCA I and hCA II was screened as in vitro. All the series of synthesized compounds have been identified as potential hCA isoenzymes inhibitory with KI values in the range of 6.44±0.74-86.85±7.01 nM for hCA I and with KI values in the range of 8.16±0.40-77.29±9.56 nM for hCA II. Moreover, the new series of compounds showed a more effective inhibition effect than the acetazolamide used as a reference. The possible binding positions of the compounds with a binding affinity to the hCA I and hCA II was demonstrated by in silico studies. In conclusion, compounds with varying degrees of affinity for hCA isoenzymes have been designed and as selective hCA inhibitors. These compounds may be potential alternative agents that can be used to treat or prevent diseases associated with glaucoma and hCA inhibition.

Evaluation of cytotoxic, antifungal, and larvicidal activities of different bis-sulfonamide Schiff base compounds

Schiff bases (imines or azomethines) are versatile ligands synthesized from the condensation of amino compounds with active carbonyl groups and used for many pharmaceutical and medicinal applications. In our study, we aimed to determine the cytotoxic, antifungal and larvicidal activities of biologically potent bis-sulfonamide Schiff base derivatives that were re-synthesized by us. For this aim, 16 compounds were re-synthesized and tested for their cytotoxic, antifungal and larvicidal properties. Among this series, compounds A1B2, A1B4, A4B2, A4B3, and A4B4 were shown to have cytotoxic activity against tested cancer lung cell line (A549). The most potent antifungal activity was observed in compounds A2B1 and A2B2 against all fungi. A1B1 showed the strongest larvicidal effect at all concentrations at the 72nd h (100% mortality). These obtained results demonstrate that these type of bis-substituted compounds might be used as biologically potent pharmacophores against different types of diseases.

Expression Dynamics of CA IX Epitope in Cancer Cells under Intermittent Hypoxia Correlates with Extracellular pH Drop and Cell Killing by Ureido-Sulfonamide CA IX Inhibitors

Carbonic anhydrase IX (CA IX) is a membrane-bound CA isozyme over-expressed in many hypoxic tumor cells, where it ensures pH homeostasis and has been implicated in tumor survival, metastasis and resistance to chemotherapy and radiotherapy. Given the functional importance of CA IX in tumor biochemistry, we investigated the expression dynamics of CA IX in normoxia, hypoxia and intermittent hypoxia, which are typical conditions experienced by tumor cells in aggressive carcinomas. We correlated the CA IX epitope expression dynamics with extracellular pH acidification and with viability of CA IX-expressing cancer cells upon treatment with CA IX inhibitors (CAIs) in colon HT-29, breast MDA-MB-231 and ovarian SKOV-3 tumor cell models. We observed that the CA IX epitope expressed under hypoxia by these cancer cells is retained in a significant amount upon reoxygenation, probably to preserve their proliferation ability. The extracellular pH drop correlated well with the level of CA IX expression, with the intermittent hypoxic cells showing a similar pH drop to fully hypoxic ones. All cancer cells showed higher sensitivity to CA IX inhibitors (CAIs) under hypoxia as compared to normoxia. The tumor cell sensitivity to CAIs under hypoxia and intermittent hypoxia were similar and higher than in normoxia and appeared to be correlated with the lipophilicity of the CAI.

Tail-Approach-Based Design and Synthesis of Coumarin-Monoterpenes as Carbonic Anhydrase Inhibitors and Anticancer Agents

In this study, sixty novel coumarin-monoterpene compounds were synthesized in two series [thirty-two compounds (12-43) bearing a triazole ring in the first series, and twenty-eight compounds (44-71) bearing an alkyl chain in the second one]. Their inhibitory effects on the human carbonic anhydrase (hCA) isoforms I, II, IX, and XII and anticancer potentials were determined. All synthesized molecules selectively inhibited CA IX and XII. 23 and 42 were found to be the strongest inhibitors, with K _i values of 1.9 nM against hCA IX. Also, 70 showed the highest inhibitory activity with a K _i value of 4.9 nM against hCA XII. Moreover, their cytotoxic effects on colon adenocarcinoma (HT-29), prostate adenocarcinoma (PC-3), and breast adenocarcinoma (MCF-7) cell lines were evaluated. According to the cytotoxicity results, 14 (IC₅₀ = 2.48 μM) and 63 (IC₅₀ = 3.91 μM) exhibited the highest cytotoxicity on the MCF-7 cells, while 23 showed the strongest cytotoxic effect on both PC-3 (IC₅₀ = 9.40 μM) and HT-29 (IC₅₀ = 12.10 μM) cell lines. 14, 23, and 66 decreased CA IX and CA XII protein expression in HT-29 cells, while 23 and 66 showed the strongest reduction of both CA IX and CA XII in MCF-7 cells. All of the selected compounds increased total apoptosis in a concentration-dependent manner in HT-29 and MCF-7 cells. 14 has the strongest apoptotic effect in MCF-7 cells. 23 increased early apoptosis primarily, while 14 and 66 increased total apoptosis in HT-29. In addition, PI/Hoechst staining proves that apoptotic cells are increased in HT-29 with an effect of 14, 23, and 66. As a result of the modeling studies, it has been shown that only the open coumarin form of the compounds can interact directly with the active-site Zn²⁺ ion. It has been shown that coumarin-monoterpene structures with different alkyl and monoterpene groups both specifically inhibit CA IX and XII and exhibit specific cytotoxicity in different cell lines.

Structural Characterization of Thiadiazolesulfonamide Inhibitors Bound to Neisseria gonorrhoeae α-Carbonic Anhydrase

Drug-resistant Neisseria gonorrhoeae is a critical threat to public health, and bacterial carbonic anhydrases expressed by N. gonorrhoeae are potential new therapeutic targets to combat this pathogen. To further expand upon our recent reports of bacterial carbonic anhydrase inhibitors for the treatment of N. gonorrhoeae, our team has solved ligand-bound crystal structures of the FDA-approved carbonic anhydrase inhibitor acetazolamide, along with three analogs, in complex with the essential α-carbonic anhydrase isoform from N. gonorrhoeae. The structural data for the analogs presented bound to N. gonorrhoeae α-carbonic anhydrase supports the observed structure-activity relationship for in vitro inhibition with this scaffold against the enzyme. Moreover, the ligand-bound structures indicate differences in binding poses compared to those traditionally observed with the close human ortholog carbonic anhydrase II. These results present key differences in inhibitor binding between N. gonorrhoeae α-carbonic anhydrase and the human carbonic anhydrase II isoform.

Adamantane-Substituted Purine Nucleosides: Synthesis, Host-Guest Complexes with β-Cyclodextrin and Biological Activity

Purine nucleosides represent an interesting group of nitrogen heterocycles, showing a wide range of biological effects. In this study, we designed and synthesized a series of 6,9-disubstituted and 2,6,9-trisubstituted purine ribonucleosides via consecutive nucleophilic aromatic substitution, glycosylation, and deprotection of the ribofuranose unit. We prepared eight new purine nucleosides bearing unique adamantylated aromatic amines at position 6. Additionally, the ability of the synthesized purine nucleosides to form stable host-guest complexes with β-cyclodextrin (β-CD) was confirmed using nuclear magnetic resonance (NMR) and mass spectrometry (ESI-MS) experiments. The in vitro antiproliferative activity of purine nucleosides and their equimolar mixtures with β-CD was tested against two types of human tumor cell line. Six adamantane-based purine nucleosides showed an antiproliferative activity in the micromolar range. Moreover, their effect was only slightly suppressed by the presence of β-CD, which was probably due to the competitive binding of the corresponding purine nucleoside inside the β-CD cavity.

Copper-based theranostic nanocatalysts for synergetic photothermal-chemodynamic therapy

Chemodynamic therapy (CDT) has aroused extensive attention as a potent therapeutic modality. However, its practical application is severely restricted by the strong acidity requirement for Fenton reaction and upregulated antioxidant defense within metastatic breast cancer. Herein, a copper-based single-site nanocatalyst functionalized with carbonic anhydrase inhibitor (CAI) was constructed for magnetic resonance/photoacoustic imaging (MRI/PA)-guided synergetic photothermal therapy (PTT) and CDT. Once reaching tumor sites, the nanocatalyst can be recognized by tumor cell membranes-overexpressed carbonic anhydrase IX (CA IX). Subsequently, the single-site Cu^II can be reduced to Cu^I by the tumor-overexpressed glutathione (GSH), which simultaneously impaired the tumor antioxidant defense system and triggered CAI release for inducing intracellular H⁺ accumulation. Further, the decreased intracellular pH can accelerate the nanocatalyst biodegradation to release more Cu^II and CAI to participate in next-cycle GSH-depletion and cytoplasm acidification, respectively, thereby continuously supplying Cu^I and H⁺ for self-cyclically amplified CDT. Upon laser irradiation, the nanocatalyst can generate local heat, which not only permits PTT but also enhances the nanocatalyst-mediated CDT. Moreover, the suppression of CA IX can hinder the tumor extracellular matrix degradation to prevent tumor metastasis. Overall, this work highlighted the great application prospect in enhancing CDT via tumor acidic/redox microenvironment remodeling, and provides an insightful paradigm for inhibiting breast cancer metastasis. STATEMENT OF SIGNIFICANCE: The practical application of chemodynamic therapy (CDT) is severely restricted by the strong acidity requirement for Fenton reaction and upregulated antioxidant defense within cancer. Herein, we developed a carbonic anhydrase inhibitor (CAI)-functionalized Cu-based nanocatalyst. Once reaching tumor sites, the Cu^II can be reduced to Cu^I by the tumor-overexpressed glutathione (GSH), which simultaneously impaired the tumor antioxidant system and triggered CAI release for inducing intracellular H⁺ accumulation. Further, the decreased intracellular pH can accelerate the nanocatalyst biodegradation to release more Cu^II and CAI to participate in next-cycle GSH-depletion and cytoplasm acidification, respectively, thus continuously supplying Cu^I and H⁺ for self-cyclically amplified CDT. Upon laser irradiation, the nanocatalyst not only permits PTT but also enhances the CDT.

Antiproliferative effects of sulphonamide carbonic anhydrase inhibitors C18, SLC-0111 and acetazolamide on bladder, glioblastoma and pancreatic cancer cell lines

Carbonic anhydrase IX/XII (CA IX/XII), are cell-surface enzymes typically expressed by cancer cells as a form of adaptation to hypoxia and acidosis. It has been widely reported that these proteins play pivotal roles in cancer progression fostering cell migration, aggressiveness and resistance to first line chemo- and radiotherapies. CA IX has emerged as a promising target in cancer therapy and several approaches and families of compounds were characterised in the attempt to find optimal targeting by inhibiting of the high catalytic activity of the enzyme. In the present work, different cell lines representing glioblastoma, bladder and pancreatic cancer have been exploited to compare the inhibitory and antiproliferative effect of primary sulphonamide acetazolamide (AAZ), the Phase Ib/II clinical grade sulphonamide SLC-0111, and a membrane-impermeant positively charged, pyridinium-derivative (C18). New hints regarding the possibility to exploit CA inhibitors in these cancer types are proposed.

Adamantane-Substituted Purines and Their β-Cyclodextrin Complexes: Synthesis and Biological Activity

Cyclin-dependent kinases (CDKs) play an important role in the cell-division cycle. Synthetic inhibitors of CDKs are based on 2,6,9-trisubstituted purines and are developed as potential anticancer drugs; however, they have low solubility in water. In this study, we proved that the pharmaco-chemical properties of purine-based inhibitors can be improved by appropriate substitution with the adamantane moiety. We prepared ten new purine derivatives with adamantane skeletons that were linked at position 6 using phenylene spacers of variable geometry and polarity. We demonstrated that the adamantane skeleton does not compromise the biological activity, and some of the new purines displayed even higher inhibition activity towards CDK2/cyclin E than the parental compounds. These findings were supported by a docking study, which showed an adamantane scaffold inside the binding pocket participating in the complex stabilisation with non-polar interactions. In addition, we demonstrated that β-cyclodextrin (CD) increases the drug’s solubility in water, although this is at the cost of reducing the biochemical and cellular effect. Most likely, the drug concentration, which is necessary for target engagement, was decreased by competitive drug binding within the complex with β-CD.

Carbonic Anhydrases as Potential Targets Against Neurovascular Unit Dysfunction in Alzheimer’s Disease and Stroke

The Neurovascular Unit (NVU) is an important multicellular structure of the central nervous system (CNS), which participates in the regulation of cerebral blood flow (CBF), delivery of oxygen and nutrients, immunological surveillance, clearance, barrier functions, and CNS homeostasis. Stroke and Alzheimer Disease (AD) are two pathologies with extensive NVU dysfunction. The cell types of the NVU change in both structure and function following an ischemic insult and during the development of AD pathology. Stroke and AD share common risk factors such as cardiovascular disease, and also share similarities at a molecular level. In both diseases, disruption of metabolic support, mitochondrial dysfunction, increase in oxidative stress, release of inflammatory signaling molecules, and blood brain barrier disruption result in NVU dysfunction, leading to cell death and neurodegeneration. Improved therapeutic strategies for both AD and stroke are needed. Carbonic anhydrases (CAs) are well-known targets for other diseases and are being recently investigated for their function in the development of cerebrovascular pathology. CAs catalyze the hydration of CO₂ to produce bicarbonate and a proton. This reaction is important for pH homeostasis, overturn of cerebrospinal fluid, regulation of CBF, and other physiological functions. Humans express 15 CA isoforms with different distribution patterns. Recent studies provide evidence that CA inhibition is protective to NVU cells in vitro and in vivo, in models of stroke and AD pathology. CA inhibitors are FDA-approved for treatment of glaucoma, high-altitude sickness, and other indications. Most FDA-approved CA inhibitors are pan-CA inhibitors; however, specific CA isoforms are likely to modulate the NVU function. This review will summarize the literature regarding the use of pan-CA and specific CA inhibitors along with genetic manipulation of specific CA isoforms in stroke and AD models, to bring light into the functions of CAs in the NVU. Although pan-CA inhibitors are protective and safe, we hypothesize that targeting specific CA isoforms will increase the efficacy of CA inhibition and reduce side effects. More studies to further determine specific CA isoforms functions and changes in disease states are essential to the development of novel therapies for cerebrovascular pathology, occurring in both stroke and AD.

Reconsidering anion inhibitors in the general context of drug design studies of modulators of activity of the classical enzyme carbonic anhydrase

Inorganic anions inhibit the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) generally by coordinating to the active site metal ion. Cyanate was reported as a non-coordinating CA inhibitor but those erroneous results were subsequently corrected by another group. We review the anion CA inhibitors (CAIs) in the more general context of drug design studies and the discovery of a large number of inhibitor classes and inhibition mechanisms, including zinc binders (sulphonamides and isosteres, dithiocabamates and isosteres, thiols, selenols, benzoxaboroles, ninhydrins, etc.); inhibitors anchoring to the zinc-coordinated water molecule (phenols, polyamines, sulfocoumarins, thioxocoumarins, catechols); CAIs occluding the entrance to the active site (coumarins and derivatives, lacosamide), as well as compounds that bind outside the active site. All these new chemotypes integrated with a general procedure for obtaining isoform-selective compounds (the tail approach) has resulted, through the guidance of rigorous X-ray crystallography experiments, in the development of highly selective CAIs for all human CA isoforms with many pharmacological applications.

Synthesis, Molecular Docking Analysis and Biological Evaluations of Saccharide-Modified Thiadiazole Sulfonamide Derivatives

A series of saccharide-modified thiadiazole sulfonamide derivatives has been designed and synthesized by the “tail approach” and evaluated for inhibitory activity against carbonic anhydrases II, IX, and XII. Most of the compounds showed high topological polar surface area (TPSA) values and excellent enzyme inhibitory activity. The impacts of some compounds on the viability of HT-29, MDA-MB-231, and MG-63 human cancer cell lines were examined under both normoxic and hypoxic conditions, and they showed certain inhibitory effects on cell viability. Moreover, it was found that the series of compounds had the ability to raise the pH of the tumor cell microenvironment. All the results proved that saccharide-modified thiadiazole sulfonamides have important research prospects for the development of CA IX inhibitors.

Inhibitors of CA IX Enzyme Based on Polyhedral Boron Compounds

This review describes recent progress in the design and development of inhibitors of human carbonic anhydrase IX (CA IX) based on space-filling carborane and cobalt bis(dicarbollide) clusters. CA IX enzyme is known to play a crucial role in cancer cell proliferation and metastases. The new class of potent and selective CA IX inhibitors combines the structural motif of a bulky inorganic cluster with an alkylsulfamido or alkylsulfonamido anchor group for Zn²⁺ ion in the enzyme active site. Detailed structure-activity relationship (SAR) studies of a large series containing 50 compounds uncovered structural features of the cluster-containing inhibitors that are important for efficient and selective inhibition of CA IX activity. Preclinical evaluation of selected compounds revealed low toxicity, favorable pharmacokinetics and ability to reduce tumor growth. Cluster-containing inhibitors of CA IX can thus be considered as promising candidates for drug development and/or for combination therapy in boron neutron capture therapy (BNCT).

PEG Linker Length Strongly Affects Tumor Cell Killing by PEGylated Carbonic Anhydrase Inhibitors in Hypoxic Carcinomas Expressing Carbonic Anhydrase IX

Hypoxic tumors overexpress membrane-bound isozymes of carbonic anhydrase (CA) CA IX and CA XII, which play key roles in tumor pH homeostasis under hypoxia. Selective inhibition of these CA isozymes has the potential to generate pH imbalances that can lead to tumor cell death. Since these isozymes are dimeric, we designed a series of bifunctional PEGylated CA inhibitors (CAIs) through the attachment of our preoptimized CAI warhead 1,3,4-thiadiazole-2-sulfonamide to polyethylene glycol (PEG) backbones with lengths ranging from 1 KDa to 20 KDa via a succinyl linker. A detailed structure−thermal properties and structure–biological activity relationship study was conducted via differential scanning calorimetry (DSC) and via viability testing in 2D and 3D (tumor spheroids) cancer cell models, either CA IX positive (HT-29 colon cancer, MDA-MB 231 breast cancer, and SKOV-3 ovarian cancer) or CA IX negative (NCI-H23 lung cancer). We identified PEGylated CAIs DTP1K 28, DTP2K 23, and DTP3.4K 29, bearing short and medium PEG backbones, as the most efficient conjugates under both normoxic and hypoxic conditions, and in the tumor spheroid models. PEGylated CAIs did not affect the cell viability of CA IX-negative NCI-H23 tumor spheroids, thus confirming a CA IX-mediated cell killing for these potential anticancer agents.

Experimental Carbonic Anhydrase Inhibitors for the Treatment of Hypoxic Tumors

Carbonic anhydrase (CA, EC 4.2.1.1) isoforms IX and XII are overexpressed in many hypoxic tumors as a consequence of the hypoxia inducible factor (HIF) activation cascade, being present in limited amounts in normal tissues. These enzymes together with many others are involved in the pH regulation and metabolism of hypoxic cancer cells, and were validated as antitumor targets recently. A multitude of targeting strategies against these enzymes have been proposed and are reviewed in this article. The small molecule inhibitors, small molecule drug conjugates (SMDCs), antibody-drug conjugates (ADACs) or cytokine-drug conjugates but not the monoclonal antibodies against CA IX/XII will be discussed. Relevant synthetic chemistry efforts, coupled with a multitude of preclinical studies, demonstrated that CA IX/XII inhibition leads to the inhibition of growth of primary tumors and metastases and depletes cancer stem cell populations, all factors highly relevant in clinical settings. One small molecule inhibitor, sulfonamide SLC-0111, is the most advanced candidate, having completed Phase I and being now in Phase Ib/II clinical trials for the treatment of advanced hypoxic solid tumors.