Heterocoumarins Are Selective Carbonic Anhydrase IX and XII Inhibitors with Cytotoxic Effects against Cancer Cells Lines

Thia- and Seleno-Michael Reactions for the Synthesis of Carbonic Anhydrases Inhibitors

Novel chalcogen-containing amides and esters bearing the benzenesulfonamide moiety have been synthesised upon nucleophilic conjugate addition of thiols and selenols to suitable electron-deficient alkenes. The activity of the synthesised compounds as Carbonic Anhydrases inhibitors has been investigated in vitro and the inhibition mechanism has been elucidated by X-rays studies.

Benzopyrone, a privileged scaffold in drug discovery: An overview of FDA-approved drugs and clinical candidates

Natural products have always served as an important source of drugs for treating various diseases. Among various privileged natural product scaffolds, the benzopyrone class of compounds has a substantial presence among biologically active compounds. One of the pioneering anticoagulant drugs, warfarin approved in 1954 bears a benzo-α-pyrone (coumarin) nucleus. The widely investigated psoriasis drugs, methoxsalen, and trioxsalen, also contain a benzo-α-pyrone nucleus. Benzo-γ-pyrone (chromone) containing drugs, cromoglic acid, and pranlukast were approved as treatments for asthma in 1982 and 2007, respectively. Numerous other small molecules with a benzopyrone core are under clinical investigation. The present review discusses the discovery, absorption, distribution, metabolism, excretion properties, and synthetic approaches for the Food and Drug Administration-approved and clinical-stage benzopyrone class of compounds. The role of the pyrone core in biological activity has also been discussed. The present review unravels the potential of benzopyrone core in medicinal chemistry and drug development.

Iodine/Oxone® oxidative system for the synthesis of selenylindoles bearing a benzenesulfonamide moiety as carbonic anhydrase I, II, IX, and XII inhibitors

A wide range of 3-selenylindoles were synthesized via an eco-friendly approach that uses Oxone® as the oxidant in the presence of a catalytic amount of iodine. This mild and economical protocol showed broad functional group tolerance and operational simplicity. A series of novel selenylindoles bearing a benzenesulfonamide moiety were also synthesized and evaluated as carbonic anhydrase inhibitors of the human (h) isoforms hCa I, II, IX, and XII, which are involved in pathologies such as glaucoma and cancer. Several derivatives showed excellent inhibitory activity towards these isoforms in the nanomolar range, lower than that shown by acetazolamide.

Phthalazine Sulfonamide Derivatives as Carbonic Anhydrase Inhibitors. Synthesis, Biological and in silico Evaluation

Carbonic Anhydrases (CAs) are a large family of zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide involved in several biological processes. They show a wide diversity in tissue distribution and their subcellular localization. Twenty-two novel phthalazine derivatives were designed, synthesized, and evaluated against four human isoforms: hCA I, hCA II, hCA IX, and hCA XII. Compounds appeared to be very active mostly against hCA IX (7) and hCA I (6) isoforms being more potent than reference drug acetazolamide (AAZ). Some compounds appeared to be very selective with a selectivity index up to 13.8. Furthermore, docking was performed for some of these compounds on all isoforms to understand the possible interactions with the active site. Additionally, the most active compounds against hCA IX were subjected to cell viability assay. The anticancer activity of the compounds (3 a-d, 5 d, 5 i, and 5 m) was investigated using two human breast cancer cell lines, i. e. MCF-7 and MDA-MB-231 cells, and the normal counterpart, namely MCF10-A cells.

The dopamine D2 receptors antagonist Veralipride inhibits carbonic anhydrases: solution and crystallographic insights on human isoforms

The inhibitory effects of veralipride, a benzamide-class antipsychotic acting as dopamine D2 receptors antagonist incorporates a primary sulfonamide moiety and was investigated for its interactions with carbonic anhydrase (CA) isoforms. In vitro profiling using the stopped-flow technique revealed that veralipride exhibited potent inhibitory activity across all tested hCA isoforms, with exception of hCA III. Comparative analysis with standard inhibitors, acetazolamide (AAZ), and sulpiride, provided insights for understanding the relative efficacy of veralipride as CA inhibitor. The study reports the X-ray crystal structure analysis of the veralipride adduct with three human (h) isoforms, hCA I, II, and CA XII mimic, allowing the understanding of the molecular interactions rationalizing its inhibitory effects against each isoform. These findings contribute to our understanding of veralipride pharmacological properties and for the design of structural analogs endowed with polypharmacological properties.

pH regulators and their inhibitors in tumor microenvironment

As an important characteristic of tumor, acidic tumor microenvironment (TME) is closely related to immune escape, invasion, migration and drug resistance of tumor. The acidity of the TME mainly comes from the acidic products produced by the high level of tumor metabolism, such as lactic acid and carbon dioxide. pH regulators such as monocarboxylate transporters (MCTs), carbonic anhydrase IX (CA IX), and Na+/H+ exchange 1 (NHE1) expel protons directly or indirectly from the tumor to maintain the pH balance of tumor cells and create an acidic TME. We review the functions of several pH regulators involved in the construction of acidic TME, the structure and structure-activity relationship of pH regulator inhibitors, and provide strategies for the development of small-molecule antitumor inhibitors based on these targets.

Novel Carbonic Anhydrase Inhibitors with Dual-Tail Core Sulfonamide Show Potent and Lasting Effects for Glaucoma Therapy

Glaucoma, a leading cause of irreversible vision loss worldwide, is characterized by elevated intraocular pressure (IOP), a well-established risk factor across all its forms. We present the design and synthesis of 39 novel carbonic anhydrase inhibitors by a dual-tailed approach, strategically crafted to interact with distinct hydrophobic and hydrophilic pockets of CA active sites. The series was investigated against the CA isoforms implicated in glaucoma (hCA II, hCA IV, and hCA XII), and the X-ray crystal structures of compounds 25a, 25f, and 26a with CA II, along with 14b in complex with a hCA XII mimic, were determined. Selected compounds (14a, 25a, and 26a) underwent evaluation for their ability to reduce IOP in rabbits with ocular hypertension. Derivative 26a showed significant potency and sustained IOP-lowering effects, surpassing the efficacy of the drugs dorzolamide and bimatoprost. This positions compound 26a as a promising candidate for the development of a novel anti-glaucoma medication.

Synthetic Approaches to Novel Human Carbonic Anhydrase Isoform Inhibitors Based on Pyrrol-2-one Moiety

New dihydro-pyrrol-2-one compounds, featuring dual sulfonamide groups, were synthesized through a one-pot, three-component approach utilizing trifluoroacetic acid as a catalyst. Computational analysis using density functional theory (DFT) and condensed Fukui function explored the structure-reactivity relationship. Evaluation against human carbonic anhydrase isoforms (hCA I, II, IX, XII) revealed potent inhibition. The widely expressed cytosolic hCA I was inhibited across a range of concentrations (KI 3.9-870.9 nM). hCA II, also cytosolic, exhibited good inhibition as well. Notably, all compounds effectively inhibited tumor-associated hCA IX (KI 1.9-211.2 nM) and hCA XII (low nanomolar). Biological assessments on MCF7 cancer cells highlighted the compounds' ability, in conjunction with doxorubicin, to significantly impact tumor cell viability. These findings underscore the potential therapeutic relevance of the synthesized compounds in cancer treatment.

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.

Photoactivatable Heptamethine-Based Carbonic Anhydrase Inhibitors Leading to New Anti-Antibacterial Agents

With the aim to propose innovative antimicrobial agents able to not only selectively inhibit bacterial carbonic anhydrases (CAs) but also to be photoactivated by specific wavelengths, new heptamethine-based compounds decorated with a sulfonamide moiety were synthesized by means of different spacers. The compounds displayed potent CA inhibition and a slight preference for bacterial isoforms. Furthermore, minimal inhibitory and bactericidal concentrations and the cytotoxicity of the compounds were assessed, thus highlighting a promising effect under irradiation against S. epidermidis. The hemolysis activity test showed that these derivatives were not cytotoxic to human red blood cells, further corroborating their favorable selectivity index. This approach led to the discovery of a valuable scaffold for further investigations.

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.

Synthesis of Selenoesters via Aldol Condensation and/or Conjugate Reduction and Their Antiviral Activities

A variety of unsaturated selenoesters (including phenolic ones) were produced in good to high yields and with high E/Z ratios using TiCl₄-promoted aldol condensation between Se-phenyl selenoacetate and their respective aldehydes without aqueous workup. A representative phenolic unsaturated selenoester was applied to acylation of tyrosine methyl ester without protection of the phenolic hydroxy groups to furnish the corresponding amino acid conjugate. The conjugate reduction of the unsaturated selenoesters including phenolic ones and selenocoumarin with HSiEt₃ was catalyzed by B(C₆F₅)₃ to afford the corresponding saturated selenoesters in good to high yields. This method was also applicable to the reduction of a saturated selenoester to the corresponding O-silyl hemiselenoacetal in a high yield. Moreover, most acyclic unsaturated selenoesters were found to show good multiple antiviral activities against HIV-1, HBV, and SARS-CoV-2.

First-in-Class Dual Hybrid Carbonic Anhydrase Inhibitors and Transient Receptor Potential Vanilloid 1 Agonists Revert Oxaliplatin-Induced Neuropathy

Here, we report for the first time a series of compounds potentially useful for the management of oxaliplatin-induced neuropathy (OINP) able to modulate the human Carbonic Anhydrases (hCAs) as well as the Transient Receptor Potential Vanilloid 1 (TRPV1). All compounds showed effective in vitro inhibition activity toward the main hCAs involved in such a pathology, whereas selected items reported moderate agonism of TRPV1. X-ray crystallographic experiments assessed the binding modes of the two enantiomers (R)-37a and (S)-37b within the hCA II cleft. Although the tails assumed diverse orientations, no appreciable effects were observed for their hCA II affinity. Similarly, the activity of (R)-39a and (S)-39b on TRPV1 was not influenced by the stereocenters. In vivo evaluation of the most promising derivatives (R)-12a, (R)-37a, and the two enantiomers (R)-39a, (S)-39b revealed antihypersensitivity effects in a mouse model of OINP with potent and persistent effect up to 75 min after administration.

Design, Synthesis and Biological Evaluation of New Carbohydrate-Based Coumarin Derivatives as Selective Carbonic Anhydrase IX Inhibitors via “Click” Reaction

In this work, we designed a series of new carbohydrate-based coumarin carbonic anhydrase IX inhibitors by using 1,2,3-triazoles as linker. Next, these designed compounds were synthesized by the optimized one-pot click chemistry reaction condition. Subsequently, these target compounds were assayed for the inhibition of three carbonic anhydrase isoforms (CA I, CA II and CA IX). Intriguingly, all the compounds showed better CA IX inhibitory activity than initial coumarin fragments. Among them, compound 10a (IC₅₀: 11 nM) possessed the most potent CA IX inhibitory activity, which was more potent than the reference drug acetazolamide (IC₅₀: 30 nM). Notably, compound 10a showed 3018-fold, 1955-fold selectivity relative to CA I and CA II, respectively. Meanwhile, representative compounds could reduce tumor cell viability and the extracellular acidification in HT-29 and MDA-MB-231 cancer cell lines. Even more interestingly, our target compounds had no apparent cytotoxicity toward MCF-10A cell line. In addition, the in vitro stability assays also indicated our developed compounds possessed good liver microsomal metabolic stabilities and plasma stability. Furthermore, representative compounds revealed relatively low hERG cardiac toxicity and acute toxicity. Furthermore, docking studies were carried out to understand the interactions of our target compounds with the protein target CA IX. Collectively, our results suggest that compound 10a, as a selective CA IX inhibitor, could be an important lead compound for further optimization and development as an anticancer agent.

Design, Synthesis and Molecular Docking Study of Novel 3-Phenyl-β-Alanine-Based Oxadiazole Analogues as Potent Carbonic Anhydrase II Inhibitors

Carbonic anhydrase-II (CA-II) is strongly related with gastric, glaucoma, tumors, malignant brain, renal and pancreatic carcinomas and is mainly involved in the regulation of the bicarbonate concentration in the eyes. With an aim to develop novel heterocyclic hybrids as potent enzyme inhibitors, we synthesized a series of twelve novel 3-phenyl-β-alanine 1,3,4-oxadiazole hybrids (4a-l), characterized by ¹H- and ¹³C-NMR with the support of HRESIMS, and evaluated for their inhibitory activity against CA-II. The CA-II inhibition results clearly indicated that the 3-phenyl-β-alanine 1,3,4-oxadiazole derivatives 4a-l exhibited selective inhibition against CA-II. All the compounds (except 4d) exhibited good to moderate CA-II inhibitory activities with IC₅₀ value in range of 12.1 to 53.6 µM. Among all the compounds, 4a (12.1 ± 0.86 µM), 4c (13.8 ± 0.64 µM), 4b (19.1 ± 0.88 µM) and 4h (20.7 ± 1.13 µM) are the most active hybrids against carbonic CA-II. Moreover, molecular docking was performed to understand the putative binding mode of the active compounds. The docking results indicates that these compounds block the biological activity of CA-II by nicely fitting at the entrance of the active site of CA-II. These compounds specifically mediating hydrogen bonding with Thr199, Thr200, Gln92 of CA-II.

Glyco-Coated CdSe/ZnS Quantum Dots as Nanoprobes for Carbonic Anhydrase IX Imaging in Cancer Cells

The bioimaging of cancer cells by the specific targeting of overexpressed biomarkers is an approach that holds great promise in the identification of selective diagnostic tools. Tumor-associated human carbonic anhydrase (hCA) isoforms IX and XII have been considered so far as well-defined biomarkers, with their expression correlating with cancer progression and aggressiveness. Therefore, the availability of highly performant fluorescent tools tailored for their targeting and able to efficiently visualize such key targets is in high demand. We report here on the design and synthesis of a kind of quantum dot (QD)-based fluorescent glyconanoprobe coated with a binary mixture of ligands, which, according to the structure of the terminal domains, impart specific property sets to the fluorescent probe. Specifically, monosaccharide residues ensured the dispersibility in the biological medium, CA inhibitor residues provided specific targeting of membrane-anchored hCA IX overexpressed on bladder cancer cells, and the quantum dots imparted the optical/fluorescence properties.

Chalcogenides-incorporating carbonic anhydrase inhibitors concomitantly reverted oxaliplatin-induced neuropathy and enhanced antiproliferative action

Platinum-based chemotherapy is widely used for the treatment of different tumors but is associated with serious side effects, among which neuropathic pain. Carbonic anhydrase (CA, EC 4.2.1.1) inhibitors have recently been validated as therapeutic agents in neuropathic pain and as antitumor agents. We report the synthesis of new organochalcogenides bearing the benzensulfonamide moiety acting as potent inhibitors of several human CA isoforms and, in particular, against hCA II and VII endowed with potent neuropathic pain attenuating effects. Moreover, in combination with cisplatin or doxorubicin, some of the new CA inhibitors enhanced the effects of the anticancer drugs capability in counteracting breast cancer MCF7 cell viability. The concomitant anti-neuropathic pain and antiproliferative effects of the new chalcogenide-based CA inhibitors represent an innovative approach for the counteraction and management of side effects associated with clinically platinum drugs as antitumor agents.

Screening carbonic anhydrase IX inhibitors in traditional Chinese medicine based on electrophoretically mediated microanalysis

An electrophoretically mediated microanalysis (EMMA) method for the screening of carbonic anhydrase IX inhibitors in traditional Chinese medicine (TCM) was developed. This method combines transverse diffusion of laminar flow profiles (TDLFP) and rapid polarity switching technology to achieve rapid mixing of different reactants. Different electromigration rates of different substances make it possible that incubation, separation and detection are carried out continuously in a same fused-silica capillary. In this experiment, p-nitrophenyl acetate (pNPA) was used as the substrate for the enzyme reaction, which solved the problem that capillary electrophoresis could not detect carbonate, carbon dioxide, etc., the conventional substrates of carbonic anhydrase IX. After optimizing the enzyme reaction and separation conditions, the separation of substrate and product can be finished by baseline within 4 min. The Michaelis constant of carbonic anhydrase IX was measured to be 1.2 mM. A known inhibitor acetazolamide was used to evaluate the feasibility of this method for screening carbonic anhydrase IX inhibitors, and the half-maximal inhibitory concentration (IC₅₀) was calculated to be 1.26 μM. Finally, 4 natural compounds of 15 traditional Chinese medicine standards were discovered to exhibit enzyme inhibitory activity, including polydatin, matrine, dauricine and cepharanthine, proving that the EMMA method is an effective means for screening carbonic anhydrase IX inhibitors. The results were supported by molecular docking study.

Synthetic Approaches to Selenoesters

Selenoesters are compounds of great synthetic relevance since they can be used in several types of chemical transformations and mainly due to their great capacity in the formation of acyl radicals. Therefore, the scientific community has been developing several methods for the synthesis of this class of molecules. This review will address the synthesis of these compounds from different starting materials, such as carboxylic acids derivatives (acid chlorides and anhydrides), aldehydes, selenoacetylenes and miscellaneous methods.

Oxidative formation of bis-N-methylquinolinone from anti-head-to-head N-methylquinolinone cyclodimer

The light-driven formation and cleavage of cyclobutane structural motifs resulting from [2 + 2]-pericyclic reactions, as found in thymine and coumarin-type systems, is an important and intensively studied photochemical reaction. Various applications are reported utilizing these systems, among others, in cross-linked polymers, light-triggered drug release, or other technical applications. Herein coumarin is most frequently used as the photoactive group. Quite often, a poor quantum yield for dimerization and cyclobutane-cleavage and a lack of reversibility are described. In this work, we present the identification of a heterogeneous pathway of dimer cleavage found in a rarely studied coumarin analog molecule, the N-methyl-quinolinone (NMQ). The monomer was irradiated in a tube flow-reactor and the reaction process was monitored using online HPLC measurements. We found the formation of a pseudo-equilibrium between monomeric and dimeric NMQ and a continuous rise of a side product via oxidative dimer splitting and proton elimination which was identified as 3,3'-bis-NMQ. Oxidative conversion by singlet oxygen was identified to be the cause of this non-conventional cyclobutane cleavage. The addition of antioxidants suppressing singlet oxygen enables achieving a 100% photochemical conversion from NMQ to the anti-head-to-head-NMQ-dimer. Using dissolved oxygen upon light activation to singlet oxygen limits the reversibility of the photochemical [2 + 2]-cycloaddition and cycloreversion of NMQ and most likely comparable systems. Based on these findings, the development of highly efficient cycloaddition-cycloreversion systems should be enabled.

Coumarin carbonic anhydrase inhibitors from natural sources

Coumarins constitute a relatively new class of inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), possessing a unique inhibition mechanism, acting as "prodrug inhibitors." They undergo the hydrolysis of the lactone ring mediated by the esterase activity of CA. The formed 2-hydroxy-cinnamic acids thereafter bind within a very particular part of the enzyme active site, at its entrance, where a high variability of amino acid residues among the different mammalian CA isoforms is present, and where other inhibitors classes were not seen bound earlier. This explains why coumarins are among the most isoform-selective CA inhibitors known to date among the many chemotypes endowed with such biological activity. As coumarins are widespread secondary metabolites in some bacteria, plants, fungi, and ascidians, many such compounds from various natural sources have been investigated for their CA inhibitory properties and for possible biomedical applications, mainly as anticancer agents targeting hypoxic tumours.

Biological evaluation, radiosensitizing activity and structural insights of novel halogenated quinazoline-sulfonamide conjugates as selective human carbonic anhydrases IX/XII inhibitors

A library of iodoquinazolinones endowed with benzenesulfonamide moiety was designed and synthesized as human carbonic anhydrase (hCA) inhibitors. Compounds 4-17 showed generally poor activity against the cytosolic hCA I and hCA II isoforms. Contrarily they were more potent and showed a variable spectrum of selectivity against the tumor-specific isoforms hCA IX and hCA XII. The 4-iodophenyl derivative 12 and the 4-pyridinyl derivative 15 were the most active and selective in this series against hCA IX and hCA XII isoforms with K_I of 18 and 9 nM, respectively. Compounds 12 and 15 were further screened for their cytotoxicity against MCF-7, HepG-2 and HCT-116 cancer cell lines besides WI38 and MCF-10A normal cell lines to determine their selectivity towards cancer cells. Compound 12 was selective towards HepG-2 and HCT-116 cell lines but less selective towards MCF-7. While compound 15 showed higher selectivity towards HepG-2 than HCT-116 and MCF-7 cell lines. The ability of compounds 12 and 15 to sensitize the cells against gamma irradiation's effect proved their potential radiosensitizing activity. Molecular docking analysis was carried out to discover the possible binding mode of the compounds within the active site of isoform hCA IX and XII. Compounds 12 and 15 revealed the probable fundamental interactions explaining the good activity and selectivity towards the tumor-specific isoforms.

Iodoquinazolinones bearing benzenesulfonamide as human carbonic anhydrase I, II, IX and XII inhibitors: Synthesis, biological evaluation and radiosensitizing activity

In the present work, we report the design and synthesis of a set of iodinated quinazolinones carrying benzenesulfonamide moiety as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. The target compounds showed promising inhibitory activity against the four examined human (h) CA isoforms; I, II, IX and XII. Compounds 4-18 displayed variable inhibition constants, ranging as follows: 7.6-782.8 nM for hCA I, 34.4-412.1 nM for hCA II, 29.1-2225.3 nM for hCA IX and 8.8-429.4 nM for hCA XII. Compound 9, the most potent against the tumor-specific CA IX/CA XII (KI = 29.1 and 8.8 nM) gives the possibility to evaluate its cytotoxicity and selectivity in vitro against HepG-2, HCT-116 and MCF-7 cancer cell lines. Compound 9 showed significant cytotoxicity against the tumor cell lines (IC50 = 1.78, 1.94 and 3.07 μM, respectively) and relatively lower toxicity against WI38 normal cell line. The radiosensitizing activity of compound 9 was evaluated and displayed an increase in the radiation-induced cell death in cancer cells after receiving a single dose of 8 Gy gamma radiation. Thus, radiation was able to enhance the antiproliferative activity of compound 9. Molecular docking of 9 into the active site of CA IX and XII revealed the key interactions that could explain its potent activity and selectivity towards these isoforms.

New coumarin/sulfocoumarin linked phenylacrylamides as selective transmembrane carbonic anhydrase inhibitors: Synthesis and in-vitro biological evaluation

Two novel series of phenylacrylamide linked coumarins and sulfocoumarins (6a-p, 8a-i, and 14a-g) were synthesized and evaluated against four physiologically relevant human carbonic anhydrases (hCAs, EC 4.2.1.1), isoforms hCA I, hCA II, hCA IX and hCA XII for their inhibitory action. All new compounds when screened for carbonic anhydrase inhibitory activity have shown selective inhibition towards the tumor associated isoforms hCA IX and XII over CA I and II, with inhibition constants in the submicromolar to low nanomolar range. Compound 6b and 14g exhibited significant inhibition with low nanomolar potency against hCA IX, whereas 6k was effective against hCA XII. Compounds 6b, 14g and 6k may be considered as lead molecules for future development of cancer therapeutics based on a novel mechanism of action.

Benzoxepinones: A new isoform-selective class of tumor associated carbonic anhydrase inhibitors

Benzoxepinones ("homocoumarins") are identified as a new class of selective inhibitors for tumor associated human carbonic anhydrases (hCA, EC 4.2.1.1) isoforms IX and XII. Similar to coumarins, they do not inhibit or poorly inhibit cytosolic human (h) isoforms hCA I and II, but act as nanomolar inhibitors of the trans-membrane, tumor associated isoforms hCA IX and XII.

Exploring the multiple binding modes of inhibitors to carbonic anhydrases for novel drug discovery

INTRODUCTION

The spacious active site cavity of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) shows a great versatility for a variety of binding modes for modulators of activity, inhibitors, and activators, some of which are clinically used drugs.

AREAS COVERED

There are at least four well-documented CA inhibition mechanisms and the same number of binding modes for CA inhibitors (CAIs), one of which superposes with the binding of activators (CAAs). They include (i) coordination to the catalytic metal ion; (ii) anchoring to the water molecule coordinated to the metal ion; (iii) occlusion of the active site entrance; and (iv) binding outside the active site. A large number of chemical classes of CAIs show these binding modes explored in detail by kinetic, crystallographic, and other techniques. The tail approach was applied to all of them and allowed many classes of highly isoform-selective inhibitors. This is the subject of our review.

EXPERT OPINION

All active site regions of CAs accommodate inhibitors to bind, which is reflected in very different inhibition profiles for such compounds and the possibility to design drugs with effective action and new applications, such as for the management of hypoxic tumors, neuropathic pain, cerebral ischemia, arthritis, and degenerative disorders.

Selenolesterase enzyme activity of carbonic anhydrases

Carbonic anhydrases (CAs, E.C. 4.2.1.1) are metalloenzymes expressed on a variety of cell types. Their overexpression leads to serious pathologies, including cancer. The discovery of a series of selenolesters with high structural diversity as novel CA inhibitors is reported here. These compounds show remarkable in vitro inhibition against a panel of human CA isoforms such as hCA I, II, IX and XII. We observed that they undergo a CA mediated hydrolysis, releasing different active selenol fragments, which act as CA inhibitors. Notably, to the best of our knowledge, this is the first example of an enzyme with selenolesterase activity. In addition, X-ray crystallographic data support the proposed mechanism, proving selenolesters as novel pro-drug inhibitors with potential pharmacological applications.

Synthesis carbonic anhydrase enzyme inhibition and antioxidant activity of novel benzothiazole derivatives incorporating glycine, methionine, alanine, and phenylalanine moieties

Thirteen novel benzothiazole derivatives incorporating glycine, methionine, alanine, and phenylalanine were synthesised by facile acylation reactions through benzotriazole or DCC mediated reactions and their structures were identified by 1H-NMR, 13C-NMR, and FT-IR spectroscopic techniques and elemental analysis. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was assessed against four human (h) isoforms, hCA I, hCA II, hCA V, and hCA XIII. Some of the synthesised compounds showed good in vitro carbonic anhydrase inhibitory properties, with inhibition constants in the micromolar level. The new amino acid benzothiazole conjugates found to be more effective against hCA V and hCA II inhibition. In vitro antioxidant activities of the novel compounds were determined by DPPH method. Most of the synthesised compounds showed moderate to low antioxidant activities compared to the control antioxidant compounds (BHA and α-tocopherol).

Synthesis of novel tellurides bearing benzensulfonamide moiety as carbonic anhydrase inhibitors with antitumor activity

We have synthetized a novel series of β-hydroxy tellurides bearing the benzenesulfonamide group as potent inhibitors of carbonic anhydrase enzymes. In a one pot procedure, we discovered both the ring opening reaction of the three-membered ring and the cleavage of the sulfonamide protecting moiety at the same time. Moreover, the first X-ray co-crystallographic structure of a β-hydroxy telluride derivative with hCA II is reported. The potent effects of these compounds against the tumor-associated hCA IX with low nanomolar constant inhibition values give the possibility to evaluate their activity in vitro using a breast cancer cell line (MDA-MB-231). Compounds 7e and 7g induced significant toxic effects against tumor cells after 48 h incubation in normoxic conditions killing over 50% of tumor cells at 3 μM, but their efficacy decreased in hypoxic conditions reaching the 50% of the tumor cell viability only at 30 μM. These unusual features make them interesting lead compounds to act as antitumor agents, not only as Carbonic Anhydrase IX inhibitors, but reasonably in different pathways, where hCA IX is not overexpressed.

Syntesis of thio- and seleno-acetamides bearing benzenesulfonamide as potent inhibitors of human carbonic anhydrase II and XII

A novel series of thio- and seleno-acetamides bearing benzenesulfonamide were synthetized and tested as human carbonic anhydrase inhibitors. These compounds were tested for the inhibition of four human (h) isoforms, hCA I, II, IX, and XII, involved in pathologies such as glaucoma (CA II and XII) or cancer (CA IX/XII). Several derivatives showed potent inhibition activity in low nanomolar range such as 3a, 4a, 7a and 8a. Furthermore, based on the tail approach we explain the interesting and selective inhibition profile of compound such as 5a and 9a, which were more selective for hCA I, 9b which was selective for hCA II, 3f selective for hCA IX and finally, 3e and 4b selective for hCA XII, over the other three isoforms. They are interesting leads for the development of more effective and isoform-selective inhibitors.

Benzensulfonamides bearing spyrohydantoin moieties act as potent inhibitors of human carbonic anhydrases II and VII and show neuropathic pain attenuating effects

Carbonic Anhydrases have been recently validated as novel therapeutic targets in neuropathic pain. In this study, we combine the anticonvulsant propriety of spyrohydantoin and the CA inhibitor moiety of benzenesulfonamide to synthesize a novel series of spyrohydantoin bearing sulfonamides with strong activity against hCA II and VII. These isoforms are present in the nervous system and largely expressed both at the central as well as at peripheral level and can be modulated for pain relief. The crystal structures of hCA II in complex with selected compounds 5a-c demonstrate the importance of the tail in the binding modes within the isoform. Finally, in vivo, in an animal model of oxaliplatin induced neuropathy, compounds with organoselenium tails (8b-c) showed potent neuropathic pain attenuating effects. Taken together, these data strongly suggest the translational utility of these inhibitors as novel pain relievers.