Diuretics with carbonic anhydrase inhibitory action: a patent and literature review (2005 - 2013)

Inhibition of the β-carbonic anhydrase from the protozoan pathogen Trichomonas vaginalis with sulphonamides

Sulphonamides and their isosteres are classical inhibitors of the carbonic anhydrase (CAs, EC 4.2.1.1) metalloenzymes. The protozoan pathogen Trichomonas vaginalis encodes two such enzymes belonging to the β-class, TvaCA1 and TvaCA2. Here we report the first sulphonamide inhibition study of TvaCA1, with a series of simple aromatic/heterocyclic primary sulphonamides as well as with clinically approved/investigational drugs for a range of pathologies (diuretics, antiglaucoma, antiepileptic, antiobesity, and antitumor drugs). TvaCA1 was effectively inhibited by acetazolamide and ethoxzolamide, with K_Is of 391 and 283 nM, respectively, whereas many other simple or clinically used sulphonamides were micromolar inhibitors or did not efficiently inhibit the enzyme. Finding more effective TvaCA1 inhibitors may constitute an innovative approach for fighting trichomoniasis, a sexually transmitted infection, caused by T. vaginalis.

The effects of cardiac drugs on human erythrocyte carbonic anhydrase I and II isozymes

Cardiovascular diseases are the leading cause of mortality worldwide. In recent years, the relationship between carbonic anhydrase inhibitors and atherosclerosis has attracted attention. In this study, we aimed to determine the in vitro effects of 35 frequently used cardiac drugs on human carbonic anhydrase I (hCA I) and II (hCA II). The inhibitory effects of the drugs on hCA I and hCA II were determined with both the hydratase and esterase methods. The most potent inhibitors observed were propafenone (hCA I: 2.8 µM and hCA II: 3.02 µM) and captopril (hCA I: 1.58 µM and hCA II: 6.25 µM). Isosorbide mononitrate, propranolol, furosemide, and atorvastatin were also potent inhibitors. The inhibitor constant, Ki, value from the Lineweaver-Burk plot for propafenone was 2.38 µM for hCA I and 2.97 µM for hCA II. The tested cardiac drugs showed potent in vitro inhibition of the hCA I and II isozymes. Especially, in patients with atherosclerotic heart disease, these drugs may be preferred primarily due to the beneficial effects of carbonic anhydrase inhibition on atherosclerosis.

Bioorganometallic derivatives of 4-hydrazino-benzenesulphonamide as carbonic anhydrase inhibitors: synthesis, characterisation and biological evaluation

A series of bio-organometallic-hydrazones of the general formula [{(η5-C5H4)-C(R)=N-N(H)-C6H4-4-SO2NH2}]MLn(MLn = Re(CO)3, Mn(CO)3, FeCp; R=H, CH3) were prepared by reaction of formyl/acetyl organometallic precursors with 4-hydrazino-benzenesulphonamide. All compounds were characterized by conventional spectroscopic techniques (infra-red, 1H and 13C NMR, mass spectrometry and elemental analysis). Biological evaluation as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors agents was carried out using four human/h) isoforms, hCA I, II, IX and XII. The cytosolic isoforms hCA I and II were effectively inhibited by almost all derivatives with inhibition constants of 1.7-22.4 nM. Similar effects were observed for the tumour-associated transmembrane isoform hCA XII (KIs of 1.9-24.4 nM). hCA IX was less sensitive to inhibition with these compounds. The presence of bio-organometallic or metallo-carbonyl moieties in the molecules of these CAIs makes them amenable for interesting pharmacologic applications, for example for compounds with CO donating properties.

Novel benzofuran-based sulphonamides as selective carbonic anhydrases IX and XII inhibitors: synthesis and in vitro biological evaluation

Pursuing on our efforts toward searching for efficient hCA IX and hCA XII inhibitors, herein we report the design and synthesis of new sets of benzofuran-based sulphonamides (4a,b, 5a,b, 9a-c, and 10a-d), featuring the zinc anchoring benzenesulfonamide moiety linked to a benzofuran tail via a hydrazine or hydrazide linker. All the target benzofurans were examined for their inhibitory activities toward isoforms hCA I, II, IX, and XII. The target tumour-associated hCA IX and XII isoforms were efficiently inhibited with KIs spanning in ranges 10.0-97.5 and 10.1-71.8 nM, respectively. Interestingly, arylsulfonehydrazones 9 displayed the best selectivity toward hCA IX and XII over hCA I (SIs: 39.4-250.3 and 26.0-149.9, respectively), and over hCA II (SIs: 19.6-57.1 and 13.0-34.2, respectively). Furthermore, the target benzofurans were assessed for their anti-proliferative activity, according to US-NCI protocol, toward a panel of sixty cancer cell lines. Only benzofurans 5b and 10b possessed selective and moderate growth inhibitory activity toward certain cancer cell lines.

Synthesis and evaluation of 2,4,5-trisubstitutedthiazoles as carbonic anhydrase-III inhibitors

A series of 17 compounds (12-16 b) with 2,4,5-trisubstitutedthiazole scaffold having 5-aryl group, 4-carboxylic acid/ester moiety, and 2-amino/amido/ureido functional groups were synthesised, characterised, and evaluated for their carbonic anhydrase (CA)-III inhibitory activities using the size exclusion Hummel-Dreyer method (HDM) of chromatography. Compound 12a with a free amino group at the 2-position, carboxylic acid moiety at the 4-position, and a phenyl ring at the 5-position of the scaffold was found to be the most potent CA-III inhibitor (Ki = 0.5 μM). The presence of a carboxylic acid group at the 4-position of the scaffold was found to be crucial for the CA-III inhibitory activity. Furthermore, replacement of the free amino group with an amide and urea group resulted in a significant reduction of activity (compounds 13c and 14c, Ki = 174.1 and 186.2 μM, respectively). Thus, compound 12a (2-amino-5-phenylthiazole-4-carboxylic acid) can be considered as the lead molecule for further modification and development of more potent CA-III inhibitors.

Analgesic and Antiallodynic Effects of 4-Fluoro-N-(4-Sulfamoylbenzyl) Benzene Sulfonamide in a Murine Model of Pain

INTRODUCTION

Physical, chemical, thermal injuries along with infectious diseases lead to acute pain with associated inflammation, being the primary cause of hospital visits. Moreover, neuropathic pain associated with diabetes is a serious chronic disease leading to high morbidity and poor quality of life.

OBJECTIVE

Earlier multiple sulphonamides have been reported to have an antinociceptive and antiallodynic profile. 4-Fluoro-N-(4-sulfamoylbenzyl) Benzene Sulfonamide (4-FBS), a synthetic sulfonamide with reported carbonic anhydrase inhibitory activity, was investigated for its potential effects in mice model of acute and diabetic neuropathic pain.

METHODS AND RESULTS

4-FBS was given orally (p.o.) one hour before the test and then mice were screened for antinociceptive activity by using the tail immersion test, which showed significant antinociceptive effect at both 20 and 40 mg/kg doses. To explore the possible mechanisms, thermal analgesia of 4-FBS was reversed by the 5HT3 antagonist ondansetron 1mg/kg intraperitoneally (i.p.) and by the µ receptor antagonist naloxone (1 mg/kg i.p.), implying possible involvement of serotonergic and opioidergic pathways in the analgesic effect of 4-FBS. Diabetes was induced in mice by a single dose of streptozotocin (STZ) 200 mg/kg i.p. After two weeks, animals first became hyperalgesic and progressively allodynic in the fourth week, which was evaluated through behavioral parameters like thermal and mechanical tests. 4-FBS at 20 and 40 mg/kg p.o. significantly reversed diabetes-induced hyperalgesia and allodynia at 30, 60, 90, and 120 minutes.

CONCLUSION

These findings are significant and promising while further studies are warranted to explore the exact molecular mechanism and the potential of 4-FBS in diabetic neuropathic pain.

Carbonic Anhydrase Inhibitors Targeting Metabolism and Tumor Microenvironment

The tumor microenvironment is crucial for the growth of cancer cells, triggering particular biochemical and physiological changes, which frequently influence the outcome of anticancer therapies. The biochemical rationale behind many of these phenomena resides in the activation of transcription factors such as hypoxia-inducible factor 1 and 2 (HIF-1/2). In turn, the HIF pathway activates a number of genes including those involved in glucose metabolism, angiogenesis, and pH regulation. Several carbonic anhydrase (CA, EC 4.2.1.1) isoforms, such as CA IX and XII, actively participate in these processes and were validated as antitumor/antimetastatic drug targets. Here, we review the field of CA inhibitors (CAIs), which selectively inhibit the cancer-associated CA isoforms. Particular focus was on the identification of lead compounds and various inhibitor classes, and the measurement of CA inhibitory on-/off-target effects. In addition, the preclinical data that resulted in the identification of SLC-0111, a sulfonamide in Phase Ib/II clinical trials for the treatment of hypoxic, advanced solid tumors, are detailed.

Single and combined effects of the drugs salicylic acid and acetazolamide: Adverse changes in physiological parameters of the freshwater macrophyte, Lemna gibba

Pharmaceutical drugs are among the most used chemicals, for human and veterinary medicines, aquaculture and agriculture. Pharmaceuticals are biologically active molecules, having also environmental persistence, thereby exerting biological effects on non-target species. Among the most used pharmaceuticals, one may find salicylic acid (SA), a non-steroid anti-inflammatory drugs (NSAIDs), and acetazolamide (ACZ), a diuretic drug that acts by inhibiting the activity of carbonic anhydrase (CA). In this work, single and combined effects of SA and ACZ were assessed in the aquatic macrophyte Lemna gibba L., focusing on physiological parameters, namely photosynthetic pigments, (chlorophyll a, b and total (Chl a, b and TChl) as well as carotenoids (Car)). In addition, chemical biomarkers, namely, glutathione S-transferases (GSTs), catalase (CAT) and carbonic anhydrase (CA) activities, were also determined. The highest concentrations of ACZ, caused a decrease in the contents of all chlorophylls; this effect was however reverted by SA exposure. Both ACZ and SA levels caused a decrease in CA activity. Nevertheless, when in combination, this inhibition was not observed in plants exposed to the lowest concentration of these drugs. In conclusion, both pharmaceuticals have the capacity to cause alterations in L. gibba enzymatic activity and photosynthetic pigments content. Additionally, SA seems to exert a protective effect on this species against deleterious effects caused by ACZ.

Effect of 4-Fluoro-N-(4-Sulfamoylbenzyl) Benzene Sulfonamide on Acquisition and Expression of Nicotine-Induced Behavioral Sensitization and Striatal Adenosine Levels

Introduction

Behavioral sensitization is a phenomenon that develops from intermittent exposure to nicotine and other psychostimulants, which often leads to heightened locomotor activity and then relapse. Sulfonamides that act as carbonic anhydrase inhibitors have a documented role in enhancing dopaminergic tone and normalizing neuroplasticity by stabilizing glutamate release.

Objective

The aim of the current study was to explore synthetic sulfonamides derivative 4-fluoro-N-(4-sulfamoylbenzyl) benzene-sulfonamide (4-FBS) (with documented carbonic anhydrase inhibitory activity) on acquisition and expression of nicotine-induced behavioral sensitization.

Methods

In the acquisition phase, selected 5 groups of mice were exposed to saline or nicotine 0.5mg/kg intraperitoneal (i.p) for 7 consecutive days. Selected 3 groups were administered with 4-FBS 20, 40, and 60 mg/kg p.o. along with nicotine. After 3 days of the drug-free period, ie, day 11, a challenge dose of nicotine was injected to all groups except saline and locomotor activity was recorded for 30 minutes. In the expression phase, mice were exposed to saline and nicotine only 0.5 mg/kg i.p for 7 consecutive days. After 3 days of the drug-free period, ie, day 11, 4-FBS at 20, 40, and 60 mg/kg were administered to the selected groups, one hour after drug a nicotine challenge dose was administered, and locomotion was recorded. At the end of behavioral experiments, all animals were decapitated and the striatum was excised and screened for changes in adenosine levels, using HPLC-UV.

Results

Taken together, our findings showed that 4-FBS in all 3 doses, in both sets of experiments significantly attenuated nicotine-induced behavioral sensitization in mice. Additionally, 4-FBS at 60mg/kg significantly lowered the adenosine level in the striatum.

Conclusion

The behavioral and adenosine modulation is promising, and more receptors level studies are warranted to explore the exact mechanism of action of 4-FBS.

The Anticancer Activity for the Bumetanide-Based Analogs via Targeting the Tumor-Associated Membrane-Bound Human Carbonic Anhydrase-IX Enzyme

The membrane-bound human carbonic anhydrase (hCA) IX is widely recognized as a marker of tumor hypoxia and a prognostic factor within several human cancers. Being undetected in most normal tissues, hCA-IX implies the pharmacotherapeutic advent of reduced off-target adverse effects. We assessed the potential anticancer activity of bumetanide-based analogues to inhibit the hCA-IX enzymatic activity and cell proliferation of two solid cancer cell lines, namely kidney carcinoma (A-498) and bladder squamous cell carcinoma (SCaBER). Bumetanide analogues efficiently inhibit the target hCA-IX in low nanomolar activity (IC₅₀ = 4.4–23.7 nM) and have an excellent selectivity profile (SI = 14.5–804) relative to the ubiquitous hCA-II isoform. Additionally, molecular docking studies provided insights into the compounds’ structure–activity relationship and preferential binding of small-sized as well as selective bulky ligands towards the hCA-IX pocket. In particular, 2,4-dihydro-1,2,4-triazole-3-thione derivative 9c displayed pronounced hCA-IX inhibitory activity and impressive antiproliferative activity on oncogenic A-498 kidney carcinoma cells and is being considered as a promising anticancer candidate. Future studies will aim to optimize this compound to fine-tune its anticancer activity as well as explore its potential through in-vivo preclinical studies.

Synthesis, Computational Studies and Assessment of in Vitro Activity of Squalene Derivatives as Carbonic Anhydrase Inhibitors

We report novel molecules incorporating the nontoxic squalene scaffold and different carbonic anhydrase inhibitors (CAIs). Potent inhibitory action, in the low-nanomolar range, was detected against isoforms hCA II for sulfonamide derivatives, which proved to be selective against this isoform over the tumor-associate hCA IX and XII isoforms. On the other hand, coumarin derivatives showed weak potency but high selectivity against the tumor-associated isoform CA IX. These compounds are interesting candidates for preclinical evaluation in glaucoma or various tumors in which the two enzymes are involved. In addition, an in silico study of inhibitor-bound hCA II revealed extensive interactions with the hydrophobic pocket of the active site and provided molecular insights into the binding properties of these new inhibitors.

Evaluation of some thiophene-based sulfonamides as potent inhibitors of carbonic anhydrase I and II isoenzymes isolated from human erythrocytes by kinetic and molecular modelling studies

BACKGROUND

Thiophene(s) are an important group in therapeutic applications, and sulfonamides are the most important class of carbonic anhydrase (CA) inhibitors. In this study, inhibition effects of some thiophene-based sulfonamides on human erythrocytes carbonic anhydrase I and II isoenzymes (hCA-I and hCA-II) were investigated. Thiophene-based sulfonamides used in this study showed potent inhibition effect on both isoenzymes at very small concentrations.

MATERIALS AND METHODS

We report on the purification of the carbonic anhydrase I and II isoenzymes (hCA-I and hCA-II) using affinity chromatography method. The inhibition effect of the thiophene-based sulfonamides was determined by IC₅₀ and K_i parameters. A molecular docking study was performed for each molecule.

RESULTS

Thiophene-based sulfonamides showed IC₅₀ values of in the range of 69 nM to 70 µM against hCA-I, 23.4 nM to 1.405 µM against hCA-II. K_i values were in the range of 66.49 ± 17.15 nM to 234.99 ± 15.44 µM against hCA-I, 74.88 ± 20.65 nM to 38.04 ± 12.97 µM against hCA-II. Thiophene-based sulfonamides studied in this research showed noncompetitive inhibitory properties on both isoenzymes. To elucidate the mechanism of inhibition, a molecular docking study was performed for molecules 1 and 4 exhibiting a strong inhibitory effect on hCA-I and hCA-II. The compounds inhibit the enzymes by interacting out of catalytic active site. The sulfonamide and thiophene moiety played a significant role in the inhibition of the enzymes.

CONCLUSION

We hope that this study will contribute to the design of novel thiophene-based sulfonamide derived therapeutic agents that may be carbonic anhydrase inhibitors in inhibitor design studies.

New Dihydrothiazole Benzensulfonamides: Looking for Selectivity toward Carbonic Anhydrase Isoforms I, II, IX, and XII

In the present study we investigated the structure-activity relationships of a new series of 4-[(3-ethyl-4-aryl-2,3-dihydro-1,3-thiazol-2-ylidene)amino]benzene-1-sulfonamides (EMAC10101a-m). All synthesized compounds, with the exception of compound EMAC10101k, preferentially inhibit off-target hCA II isoform. Within the series, compound EMAC10101d, bearing a 2,4-dichorophenyl substituent in position 4 of the dihydrothiazole ring, was the most potent and selective toward hCA II with an inhibitory activity in the low nanomolar range.

Benzofuran-Based Carboxylic Acids as Carbonic Anhydrase Inhibitors and Antiproliferative Agents against Breast Cancer

Pursuing our effort for developing effective inhibitors of the cancer-related hCA IX isoform, here we describe the synthesis of novel benzofuran-based carboxylic acid derivatives, featuring the benzoic (9a-f) or hippuric (11a,b) acid moieties linked to 2-methylbenzofuran or 5-bromobenzofuran tails via an ureido linker. The target carboxylic acids were evaluated for the potential inhibitory action against hCAs I, II, IX, and XII. Superiorly, benzofuran-containing carboxylic acid derivatives 9b, 9e, and 9f acted as submicromolar hCA IX inhibitors with KIs = 0.91, 0.79, and 0.56 μM, respectively, with selective inhibitory profile against the target hCA IX over the off-target isoforms hCA I and II (SIs: 2 to >63 and 4-47, respectively). Compounds 9b, 9e, and 9f were examined for their antiproliferative action against human breast cancer (MCF-7 and MDA-MB-231) cell lines. In particular, 9e displayed promising antiproliferative (IC50 = 2.52 ± 0.39 μM), cell cycle disturbance, and pro-apoptotic actions in MDA-MB-231 cells.

Synthesis and selective inhibitory effects of some 2-oxindole benzenesulfonamide conjugates on human carbonic anhydrase isoforms CA I, CA II, CA IX and CAXII

Three series of 2-oxindole benzenesulfonamide conjugates with different linkers were prepared by the condensation reaction of isatin derivatives 1a-e with different benzenesulfonamides. They were screened for their ability to inhibit human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA I, hCA II, hCA IX and hCA XII. Many compounds revealed promising activity and selectivity toward CAI, CAII and CAIX compared to acetazolamide (AAZ) especially compounds 2b (KI = 97.6, 8.0 nM against hCA I, hCA II, respectively) and 3a (KI = 90.2, 6.5 and 21.4 nM against hCA I, hCA II and hCA IX, respectively) relative to AAZ (KI = 250, 12 and 25 nM). Additionally, compound 4a revealed the highest activity against hCA II and hCA IX with KI of 3.0 and 13.9 nM, respectively. Docking of 2b, 3a and 4a into the active site of CA I, II, IX and XII revealed binding mode comparable to AAZ confirming the inhibition results.

Pyrrolo and pyrrolopyrimidine sulfonamides act as cytotoxic agents in hypoxia via inhibition of transmembrane carbonic anhydrases

A series of novel sulfonamide derivatives bearing pyrrole and pyrrolopyrimidine scaffolds were synthesized and screened as carbonic anhydrase inhibitors. The inhibition activity of the synthesized compounds was evaluated against the cytosolic human carbonic anhydrase isoforms I and II and the transmembranal isoforms IX and XII. Several candidates showed potent inhibitory activity against IX and XII isoforms. Furthermore, ex vivo screening of cytotoxic selectivity and activity of the most potent derivatives were carried out against normal cells (WI38) and cervical cancer cell line (HeLa) under normal and hypoxic conditions using acetazolamide as reference drug. Compound 11b potency was nearly three folds higher in hypoxic than normoxic condition whereas that of compound 11f was nearly four folds higher in hypoxic vs. normoxic HeLa cells. All the screened derivatives exhibited less potency on normal cells (WI38). Molecular docking was carried out to discover the possible binding mode of compounds within the active site of isoform CA IX.

Organoruthenium(II) complexes of acetazolamide potently inhibit human carbonic anhydrase isoforms I, II, IX and XII

Two acetazolamide (AAZ) complexes with ruthenium(II) η6-p-cymene chloride were synthesised, characterised and tested for their inhibitory effects on several carbonic anhydrase (CA, EC 4.2.1.1) isoforms with pharmacological applications. Against human (h) isoform hCA I, the two complexes showed inhibition constants in the range of 8.5-23.4 nM (AAZ has a KI of 250 nM), against hCA II of 0.48-4.2 nM, whereas against hCA IX of 0.63-3.8 nM and against hCA XII of 0.04-0.52 nM, respectively. These highly effective ruthenium acetazolamide derivatives against the tumour-associated CA isoforms IX and XII warrant further in vivo studies, in hypoxic tumours overexpressing these enzymes.

Synthesis and biological evaluation of novel 3-(quinolin-4-ylamino)benzenesulfonamidesAQ3 as carbonic anhydrase isoforms I and II inhibitors

Carbonic anhydrases (CAs, EC 4.2.1.1) are crucial metalloenzymes that are involved in diverse bioprocesses. We report the synthesis and biological evaluation of novel series of benzenesulfonamides incorporating un/substituted ethyl quinoline-3-carboxylate moieties. The newly synthesised compounds were in vitro evaluated as inhibitors of the cytosolic human (h) isoforms hCA I and II. Both isoforms hCA I and II were inhibited by the quinolines reported here in variable degrees: hCA I was inhibited with KIs in the range of 0.966-9.091 μM, whereas hCA II in the range of 0.083-3.594 μM. The primary 7-chloro-6-flouro substituted sulphfonamide derivative 6e (KI = 0.083 μM) proved to be the most active quinoline in inhibiting hCA II, whereas, its secondary sulfonamide analog failed to inhibit the hCA II up to 10 μM, confirming the crucial role of the primary sulphfonamide group, as a zinc-binding group for CA inhibitory activity.

Inhibition of bacterial α-, β- and γ-class carbonic anhydrases with selenazoles incorporating benzenesulfonamide moieties

A series of benzenesulfonamides incorporating selenazoles with diverse substitution patterns were investigated as inhibitors of six bacterial carbonic anhydrases (CAs, EC 4.2.1.1) from bacterial pathogens, such as Helicobacter pylori (hpCAα was the investigated enzyme), Vibrio cholerae (all the three CAs from this pathogen were considered, VchCAα, VchCAβ and VchCAγ) and Burkholderia pseudomallei (with its two CAs, BpsCAβ and BpsCAγ). All these sulfonamides were effective CA inhibitors, with potencies in the low micromolar or submicromolar range, making them attractive as lead compounds for designing antibacterials with a novel mechanism of action, which could counteract the extensive resistance problem observed with many clinically used antibiotics.

Optimization, thermodynamic characteristics and solubility predictions of natural deep eutectic solvents used for sulfonamide dissolution

The limited water solubility of sulfonamides provokes a search for new solvents offering not only increased solubility but also environmental and health safety. Therefore, six sulfonamides were studied in a series of natural deep eutectic solvents (NADES) comprising choline chloride with multi-hydroxyl compounds. Experimental screening aimed at finding the optimized NADES composition revealed that unimolar proportion of choline chloride and glycerol offers the highest solubility advantage, equal up to 43 times compared with water at 37 °C. Besides, quantum chemistry computations based on the COSMO-RS protocol were conducted in order to gain an insight into the thermodynamic characteristics of the systems and to explain the origin of the observed solubility increase. It was found that the factor responsible for the solubility gain in NADES are the interactions between choline chloride and sulfonamide drug molecules, having the highest affinities expressed in terms of Gibbs free energy of corresponding reactions. Finally, utilizing the obtained results together with artificial neural networks led to a perfect match between experimental and predicted solubility, documented by the mean absolute percentage error value below 2.5%. The developed protocol seems to be so general and accurate that screening of potential new API-NADES systems can be significantly simplified.

State of the Art on Carbonic Anhydrase Modulators for Biomedical Purposes

The current review is intended to highlight recent advances in the search of new and effective modulators of the metalloenzymes Carbonic Anhydrases (CAs, EC 4.2.1.1) expressed in humans (h). CAs reversibly catalyze the CO2 hydration reaction, which is of crucial importance in the regulation of a plethora of fundamental processes at cellular level as well as in complex organisms. The first section of this review will be dedicated to compounds acting as activators of the hCAs (CAAs) and their promising effects on central nervous system affecting pathologies mainly characterized from memory and learning impairments. The second part will focus on the emerging chemical classes acting as hCA inhibitors (CAIs) and their potential use for the treatment of diseases.

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.

Thermostability enhancement of the α-carbonic anhydrase from Sulfurihydrogenibium yellowstonense by using the anchoring-and-self-labelling-protein-tag system (ASLtag)

Carbonic anhydrases (CAs, EC 4.2.1.1) are a superfamily of ubiquitous metalloenzymes present in all living organisms on the planet. They are classified into seven genetically distinct families and catalyse the hydration reaction of carbon dioxide to bicarbonate and protons, as well as the opposite reaction. CAs were proposed to be used for biotechnological applications, such as the post-combustion carbon capture processes. In this context, there is a great interest in searching CAs with robust chemical and physical properties. Here, we describe the enhancement of thermostability of the α-CA from Sulfurihydrogenibium yellowstonense (SspCA) by using the anchoring-and-self-labelling-protein-tag system (ASL^tag). The anchored chimeric H⁵-SspCA was active for the CO₂ hydration reaction and its thermostability increased when the cells were heated for a prolonged period at high temperatures (e.g. 70 °C). The ASL^tag can be considered as a useful method for enhancing the thermostability of a protein useful for biotechnological applications, which often need harsh operating conditions.

Indole-Based Hydrazones Containing A Sulfonamide Moiety as Selective Inhibitors of Tumor-Associated Human Carbonic Anhydrase Isoforms IX and XII

Novel sulfonamidoindole-based hydrazones with a 2-(hydrazinocarbonyl)-3-phenyl-1H-indole-5-sulfonamide scaffold were synthesized and tested in enzyme inhibition assays against the tumor-associated carbonic anhydrase isoforms, hCA IX and XII, and the off-targets, hCA I and II. The compounds showed selectivity against hCA IX and XII over hCA I and II. Six compounds showed K_I values lower than 10 nM against hCA IX or XII. Molecular modeling studies were performed to suggest binding interactions between the ligand and the hCA active sites.

New chalcone-sulfonamide hybrids exhibiting anticancer and antituberculosis activity

New sulfonamides 5/6 derived from 4-methoxyacetophenone 1 were synthesized by N-sulfonation reaction of ammonia (3) and aminopyrimidinone (4) with its sulfonyl chloride derivative 2. Sulfonamides 5 and 6 were used as precursors of two new series of chalcones 8a-f and 9a-f, which were obtained through Claisen-Schmidt condensation with aromatic aldehydes 7a-f. Compounds 5/6, 8a-d, 8f, 9a-d, and 9f were screened by the US National Cancer Institute (NCI) at 10 μM against sixty different human cancer cell lines (one-dose trial). Chalcones 8b and 9b satisfied the pre-determined threshold inhibition criteria and were selected for screening at five different concentrations (100, 10, 1.0, 0.1, and 0.01 μM). Compound 8b exhibited remarkable GI₅₀ values ranging from 0.57 to 12.4 μM, with cytotoxic effects being observed in almost all cases, especially against the cell lines K-562 of Leukemia and LOX IMVI of Melanoma with GI₅₀ = 0.57 and 1.28 μM, respectively. Moreover, all compounds were screened against Mycobacterium tuberculosis H37Rv, chalcones 8a-c and 9a-c were the most active showing MIC values between 14 and 42 μM, and interestingly they were devoid of antibacterial activity against Mycobacterium smegmatis and Staphylococcus aureus. These antituberculosis hits showed however low selectivity, being equally inhibitory to M. tuberculosis and mammalian T3T cells. The chalcone-sulfonamide hybrids 8a-f and 9a-f resulted to be appealing cytotoxic agents with significant antituberculosis activity.

Off-Label Use of Bumetanide for Brain Disorders: An Overview

Bumetanide (BTN or BUM) is a FDA-approved potent loop diuretic (LD) that acts by antagonizing sodium-potassium-chloride (Na-K-Cl) cotransporters, NKCC1 (SLc12a2) and NKCC2. While NKCC1 is expressed both in the CNS and in systemic organs, NKCC2 is kidney-specific. The off-label use of BTN to modulate neuronal transmembrane Cl⁻ gradients by blocking NKCC1 in the CNS has now been tested as an anti-seizure agent and as an intervention for neurological disorders in pre-clinical studies with varying results. BTN safety and efficacy for its off-label use has also been tested in several clinical trials for neonates, children, adolescents, and adults. It failed to meet efficacy criteria for hypoxic-ischemic encephalopathy (HIE) neonatal seizures. In contrast, positive outcomes in temporal lobe epilepsy (TLE), autism, and schizophrenia trials have been attributed to BTN in studies evaluating its off-label use. NKCC1 is an electroneutral neuronal Cl⁻ importer and the dominance of NKCC1 function has been proposed as the common pathology for HIE seizures, TLE, autism, and schizophrenia. Therefore, the use of BTN to antagonize neuronal NKCC1 with the goal to lower internal Cl⁻ levels and promote GABAergic mediated hyperpolarization has been proposed. In this review, we summarize the data and results for pre-clinical and clinical studies that have tested off-label BTN interventions and report variable outcomes. We also compare the data underlying the developmental expression profile of NKCC1 and KCC2, highlight the limitations of BTN’s brain-availability and consider its actions on non-neuronal cells.

Pain Relieving Effect of-NSAIDs-CAIs Hybrid Molecules: Systemic and Intra-Articular Treatments against Rheumatoid Arthritis

To study new target-oriented molecules that are active against rheumatoid arthritis-dependent pain, new dual inhibitors incorporating both a carbonic anhydrase (CA)-binding moiety and a cyclooxygenase inhibitor (NSAID) were tested in a rat model of rheumatoid arthritis induced by CFA intra-articular (i.a.) injection. A comparison between a repeated per os treatment and a single i.a. injection was performed. CFA (50 µL) was injected in the tibiotarsal joint, and the effect of per os repeated treatment (1 mg kg⁻¹) or single i.a injection (1 mg mL⁻¹, 50 µL) with NSAIDs-CAIs hybrid molecules, named 4 and 5, was evaluated. The molecules 4 and 5, which were administered daily for 14 days, significantly prevented CFA-induced hypersensitivity to mechanical noxious (Paw pressure test) and non-noxious stimuli (von Frey test), the postural unbalance related to spontaneous pain (Incapacitance test) and motor alterations (Beam balance test). Moreover, to study a possible localized activity, 4 and 5 were formulated in liposomes (lipo 4 and lipo 5, both 1 mg mL⁻¹) and directly administered by a single i.a. injection seven days after CFA injection. Lipo 5 decreased the mechanical hypersensitivity to noxious and non-noxious stimuli and improved motor coordination. Oral and i.a. treatments did not rescue the joint, as shown by the histological analysis. This new class of potent molecules, which is able to inhibit at the same time CA and cyclooxygenase, shows high activity in a preclinical condition of rheumatoid arthritis, strongly suggesting a novel attractive pharmacodynamic profile.

Discovery of new ureido benzenesulfonamides incorporating 1,3,5-triazine moieties as carbonic anhydrase I, II, IX and XII inhibitors

A series of twenty novel ureido benzenesulfonamides incorporating 1,3,5-triazine moieties substituted on one side with aromatic amines and on the other side with dimethylamine, morpholine and piperidine is reported. The compounds were synthesized from the 4-(3-(4,6-dichloro-1,3,5-triazin-2-yl)ureido)benzensulfonamide (1) by using stepwise nucleophilic substitution of the chlorine atoms of cyanuric chloride. The intermediates 2(a-e) and final compounds 3(a-o) were tested for their efficiency as carbonic anhydrase (CA) inhibitors against four selected physiologically relevant human carbonic anhydrase (CA, EC 4.2.1.1) isoforms, namely, the cytosolic ones hCA I and II, and the transmembrane, tumor associated ones hCA IX, and XII. The compounds 2a, 2e and 3m showed the highest activity for hCA IX with Kis in the range of 11.8-14.6 nM. Most of the compounds showed high hCA IX selectivity over the abundant off-target isoforms hCA I and II. Since hCA IX is a validated drug target for anticancer/antimetastatic agents, these isoform-selective and potent inhibitors may be considered of interest for further medicinal/pharmacologic studies.

Solubility advantage of sulfanilamide and sulfacetamide in natural deep eutectic systems: experimental and theoretical investigations

Objective: The aim of this study was to explore the possibility of using natural deep eutectic solvents (NADES) as solvation media for enhancement of solubility of sulfonamides, as well as gaining some thermodynamic characteristics of the analyzed systems. Significance: Low solubility of many active pharmaceutical ingredients is a well-recognized difficulty in pharmaceutical industry, hence the need for different strategies addressing this problem. Among such strategies, those that are environmentally and economically beneficial are of particular interest. Methods: The solubility of sulfanilamide and sulfacetamide in 21 different NADES compositions comprising choline chloride with sugars or sugar alcohols was measured spectrophotometrically. Thermodynamic parameters describing the studied systems were determined using the COSMO-RS computational protocol. Results: All of the considered NADES compositions gave an increase in solubility of the studied sulfonamides, with the highest solubilities obtained for the system comprising choline chloride and glycerol in unimolar proportions, which gave a solubility advantage of 83.7 and 73.8 for sulfanilamide and sulfacetamide, respectively. Theoretical studies indicated that the dissolution of both considered sulfonamides has a low endothermic character, with the lowest enthalpy values obtained for the most optimal, i.e. unimolar, proportions. The non-monotonous trend of enthalpy of dissolution was also discussed in terms of intermolecular interactions. Conclusions: The obtained results show the feasibility of using NADES as solubility enhancers for sulfonamides and encourage for further exploration in this field.

New sulfonamides containing organometallic-acylhydrazones: synthesis, characterisation and biological evaluation as inhibitors of human carbonic anhydrases

A series of organometallic acylhydrazones was prepared, incorporating Re(CO)₃, Mn(CO)₃ and ferrocenyl moieties, which were subsequently reacted with amino-sulfonamides in order to obtain carbonic anhydrase (CA, EC 4.2.1.1) inhibitors possessing organometallic moieties in their molecules. The new derivatives were investigated as inhibitors of four human (h) CA isoforms with pharmaceutical applications, such as the cytosolic hCA I, II and VII and the mitochondrial hCA VA. An interesting inhibitory profile against these isoforms was obtained, with some of these metal complexes acting as subnanomolar or low nanomolar inhibitors. They were also thoroughly characterised from the chemical point of view, making them of interest for further developments in the field of metal complexes of sulfonamides with CA inhibitory action.

Novel 8-Substituted Coumarins That Selectively Inhibit Human Carbonic Anhydrase IX and XII

A novel series of 8-substituted coumarin-based compounds, characterized by the presence of alkylpiperazine and arylpiperazine chains, were synthesized and tested for their inhibitory activity against four human carbonic anhydrase (hCA) isoforms. All compounds displayed nanomolar potency against the cancer-related hCA IX and hCA XII; moreover, they were shown to be devoid of any inhibitory activity toward the cytosolic hCA I and hCA II up to 10 µM concentration in the assay system. Therefore, the synthesized coumarin ligands demonstrated to be potent and selective hCA IX/XII inhibitors, and were shown to be as potent as the reference inhibitor acetazolamide against hCA XII, with single-digit nanomolar K_i values. Molecular modeling studies provided a rationale for explaining the selectivity profile of these non-classic hCA inhibitors and their interactions with the enzymes, according to their specific mechanism of action, thus paving the way for future structure-based lead optimization studies.

Targeted treatment of anaerobic cancer. Patent evaluation of US2016279084 and US2017056350

INTRODUCTION

Based on the initial studies of J. Folkman in 1970s, which led to the proposal of the antiangiogenic therapy, many drugs targeting VEGF or its receptors have been developed with some of them approved for cancer treatment. However, these molecules so far have shown only a limited effect on survival benefits in patients. Thus, new approaches are needed to treat this disease. Considering that cancer utilizes both aerobic and anaerobic glycolytic pathway, authors of patents US2016279084 and US2017056350 propose a method to eradicate the disease, able to affect both metabolic pathways. Areas covered: Patent US2016279084 describes a method consisting of the utilization of either a pharmaceutical cocktail containing antiglycolytic agents (a lactate transporter inhibitor and a NKCC inhibitor) and an angiogenesis inhibitor or a pharmaceutical cocktail containing a lactate transporter inhibitor and an angiogenesis inhibitor in combination with blood vessel occlusion. Patent US2017056350 is strictly related to US2016279084; indeed, it proposes a method consisting of blood vessel occlusion and treatment with a pharmaceutical cocktail, containing the carbonic anhydrase inhibitor bumetanide in presence or absence of an angiogenesis inhibitor. Expert opinion: Although the proposed methodology is very interesting and promising, further studies are necessary to assess the clinical applicability of the inventions.

Inhibition studies of Brucella suis β-carbonic anhydrases with a series of 4-substituted pyridine-3-sulphonamides

The two β-carbonic anhydrases (CAs, EC 4.2.1.1) from the pathogenic bacterium Brucella suis, BsuCA1 and BsuCA2, were investigated for their inhibition profile with a series of pyridine-3-sulphonamide derivatives incorporating 4-hetaryl moieties. BsuCA1 was effectively inhibited by these sulphonamides with inhibition constants ranging between 34 and 624 nM. BsuCA2 was less sensitive to these inhibitors, with KIs in the range of 62 nM - > 10 µM. The nature of the 4-substituent present on the pyridine ring was the main factor influencing the inhibitory profile against both isoforms, with 4-halogenophenylpiperazin-1-yl and 3,4,5-trisubstituted-pyrazol-1-yl derivatives showing the most effective inhibition. Some of these sulphonamides were most effective bacterial CA than human (h) CA I and II inhibitors, making them selective for the prokaryotic enzymes. Investigation of bacterial CA inhibitors may be relevant for finding antibiotics with a new mechanism of action compared to the clinically used agents for which substantial drug resistance emerged.

Carbon- versus sulphur-based zinc binding groups for carbonic anhydrase inhibitors?

A set of compounds incorporating carbon-based zinc-binding groups (ZBGs), of the type PhX (X = COOH, CONH2, CONHNH2, CONHOH, CONHOMe), and the corresponding derivatives with sulphur(VI)-based ZBGs (X = SO3H, SO2NH2, SO2NHNH2, SO2NHOH, SO2NHOMe) were tested as inhibitors of all mammalian isoforms of carbonic anhydrase (CA, EC 4.2.1.1), CA I-XV. Three factors connected with the ZBG influenced the efficacy as CA inhibitor (CAI) of the investigated compounds: (i) the pKa of the ZBG; (ii) its geometry (tetrahedral, i.e. sulphur-based, versus trigonal, i.e. carbon-based ZBGs), and (iii) orientation of the organic scaffold induced by the nature of the ZBG. Benzenesulphonamide was the best inhibitor of all isoforms, but other ZBGs led to interesting inhibition profiles, although with an efficacy generally reduced when compared to the sulphonamide. The nature of the ZBG also influenced the CA inhibition mechanism. Most of these derivatives were zinc binders, but some of them (sulfonates, carboxylates) may interact with the enzyme by anchoring to the zinc-coordinated water molecule or by other inhibition mechanisms (occlusion of the active site entrance, out of the active site binding, etc.). Exploring structurally diverse ZBGs may lead to interesting new developments in the field of CAIs.

Sulfonamide inhibition studies of two β-carbonic anhydrases from the ascomycete fungus Sordaria macrospora, CAS1 and CAS2

The two β-carbonic anhydrases (CAs, EC 4.2.1.1) recently cloned and purified from the ascomycete fungus Sordaria macrospora, CAS1 and CAS2, were investigated for their inhibition with a panel of 39 aromatic, heterocyclic, and aliphatic sulfonamides and one sulfamate, many of which are clinically used agents. CAS1 was efficiently inhibited by tosylamide, 3-fluorosulfanilamide, and 3-chlorosulfanilamide (KIs in the range of 43.2-79.6 nM), whereas acetazolamide, methazolamide, topiramate, ethoxzolamide, dorzolamide, and brinzolamide were medium potency inhibitors (KIs in the range of 360-445 nM). CAS2 was less sensitive to sulfonamide inhibitors. The best CAS2 inhibitors were 5-amino-1,3,4-thiadiazole-2-sulfonamide (the deacetylated acetazolamide precursor) and 4-hydroxymethyl-benzenesulfonamide, with KIs in the range of 48.1-92.5 nM. Acetazolamide, dorzolamide, ethoxzolamide, topiramate, sulpiride, indisulam, celecoxib, and sulthiame were medium potency CAS2 inhibitors (KIs of 143-857 nM). Many other sulfonamides showed affinities in the high micromolar range or were ineffective as CAS1/2 inhibitors. Small changes in the structure of the inhibitor led to important differences of the activity. As these enzymes may show applications for the removal of anthropically generated polluting gases, finding modulators of their activity may be crucial for designing environmental-friendly CO2 capture processes.

Investigation of piperazines as human carbonic anhydrase I, II, IV and VII activators

Four human (h) carbonic anhydrase isoforms (CA, EC 4.2.1.1), hCA I, II, IV, and VII, were investigated for their activation profile with piperazines belonging to various classes, such as N-aryl-, N-alkyl-, N-acyl-piperazines as well as 2,4-disubstituted derivatives. As the activation mechanism involves participation of the activator in the proton shuttling between the zinc-coordinated water molecule and the external milieu, these derivatives possessing diverse basicity and different scaffolds were appropriate for being investigated as CA activators (CAAs). Most of these derivatives showed CA activating properties against hCA I, II, and VII (cytosolic isoforms) but were devoid of activity against the membrane-associated hCA IV. For hCA I, the KAs were in the range of 32.6-131 µM; for hCA II of 16.2-116 µM, and for hCA VII of 17.1-131 µM. The structure-activity relationship was intricate and not easy to rationalize, but the most effective activators were 1-(2-piperidinyl)-piperazine (KA of 16.2 µM for hCA II), 2-benzyl-piperazine (KA of 17.1 µM for hCA VII), and 1-(3-benzylpiperazin-1-yl)propan-1-one (KA of 32.6 µM for hCA I). As CAAs may have interesting pharmacologic applications in cognition and for artificial tissue engineering, investigation of new classes of activators may be crucial for this relatively new research field.

Activation studies with amines and amino acids of the β-carbonic anhydrase encoded by the Rv3273 gene from the pathogenic bacterium Mycobacterium tuberculosis

The activation of a β-class carbonic anhydrase (CAs, EC 4.2.1.1) from Mycobacterium tuberculosis, encoded by the gene Rv3273 (mtCA 3), was investigated using a panel of natural and non-natural amino acids and amines. mtCA 3 was effectively activated by D-DOPA, L-Trp, dopamine and serotonin, with KAs ranging between 8.98 and 12.1 µM. L-His and D-Tyr showed medium potency activating effects, with KAs in the range of 17.6-18.2 µM, whereas other amines and amino acids were relatively ineffective activators, with KAs in the range of 28.9-52.2 µM. As the physiological roles of the three mtCAs present in this pathogen are currently poorly understood and considering that inhibition of these enzymes has strong antibacterial effects, discovering molecules that modulate their enzymatic activity may lead to a better understanding of the factors related to the invasion and colonisation of the host during Mycobacterium tuberculosis infection.

Inhibition of α-, β-, γ-, and δ-carbonic anhydrases from bacteria and diatoms with N'-aryl-N-hydroxy-ureas

The inhibition of α-, β-, γ-, and δ-class carbonic anhydrases (CAs, EC 4.2.1.1) from bacteria (Vibrio cholerae and Porphyromonas gingivalis) and diatoms (Thalassiosira weissflogii) with a panel of N'-aryl-N-hydroxy-ureas is reported. The α-/β-CAs from V. cholerae (VchCAα and VchCAβ) were effectively inhibited by some of these derivatives, with KIs in the range of 97.5 nM - 7.26 µM and 52.5 nM - 1.81 µM, respectively, whereas the γ-class enzyme VchCAγ was less sensitive to inhibition (KIs of 4.75 - 8.87 µM). The β-CA from the pathogenic bacterium Porphyromonas gingivalis (PgiCAβ) was not inhibited by these compounds (KIs > 10 µM) whereas the corresponding γ-class enzyme (PgiCAγ) was effectively inhibited (KIs of 59.8 nM - 6.42 µM). The δ-CA from the diatom Thalassiosira weissflogii (TweCAδ) showed effective inhibition with these derivatives (KIs of 33.3 nM - 8.74 µM). As most of these N-hydroxyureas are also ineffective as inhibitors of the human (h) widespread isoforms hCA I and II (KIs > 10 µM), this class of derivatives may lead to the development of CA inhibitors selective for bacterial/diatom enzymes over their human counterparts and thus to anti-infectives or agents with environmental applications.

Mono- and di-thiocarbamate inhibition studies of the δ-carbonic anhydrase TweCAδ from the marine diatom Thalassiosira weissflogii

The inhibition of the δ-class carbonic anhydrase (CAs, EC 4.2.1.1) from the diatom Thalassiosira weissflogii, TweCAδ, was investigated using a panel of 36 mono- and di-thiocarbamates chemotypes that have recently been shown to inhibit mammalian and pathogenic CAs belonging to the α- and β-classes. TweCAδ was not significantly inhibited by most of such compounds (KI values above 20 µM). However, some aliphatic, heterocyclic, and aromatic mono and di-thiocarbamates inhibited TweCAδ in the low micromolar range. For some compounds incorporating the piperazine ring, TweCAδ was effectively inhibited (KIs from 129 to 791 nM). The most effective inhibitors identified in this study were 3,4-dimethoxyphenyl-ethyl-mono-thiocarbamate (KI of 67.7 nM) and the R-enantiomer of the nipecotic acid di-thiocarbamate (KI of 93.6 nM). Given that the activity and inhibition of this class of enzyme have received limited attention until now, this study provides new molecular probes and information for investigating the role of δ-CAs in the carbon fixation processes in diatoms, which are responsible for significant amounts of CO2 taken from the atmosphere by these marine organisms.

Nanoemulsions of sulfonamide carbonic anhydrase inhibitors strongly inhibit the growth of Trypanosoma cruzi

Sulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitors targeting the α-class enzyme from the protozoan pathogen Trypanosoma cruzi, responsible of Chagas disease, were recently reported. Although many such derivatives showed low nanomolar activity in vitro, they were inefficient anti-T. cruzi agents in vivo. Here, we show that by formulating such sulfonamides as nanoemulsions in clove (Eugenia caryophyllus) oil, highly efficient anti-protozoan effects are observed against two different strains of T. cruzi. These effects are probably due to an enhanced permeation of the enzyme inhibitor through the nanoemulsion formulation, interfering in this way with the life cycle of the pathogen either by inhibiting pH regulation or carboxylating reactions in which bicarbonate/CO2 are involved. This type of formulation of sulfonamides with T. cruzi CA inhibitory effects may lead to novel therapeutic approaches against this orphan disease.

Evaluation of sulphonamide derivatives acting as inhibitors of human carbonic anhydrase isoforms I, II and Mycobacterium tuberculosis β-class enzyme Rv3273

A series of novel sulphonamide derivatives was obtained from sulphanilamide which was N4-alkylated with ethyl bromoacetate followed by reaction with hydrazine hydrate. The hydrazide obtained was further reacted with various aromatic aldehydes. The novel sulphonamides were characterised by infrared, mass spectrometry, 1H- and 13C-NMR and purity was determined by high-performance liquid chromatography (HPLC). Human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA I and II and Mycobacterium tuberculosis β-CA encoded by the gene Rv3273 (mtCA 3) inhibition activity was investigated with the synthesised compounds which showed promising inhibition. The KIs were in the range of 54.6 nM-1.8 µM against hCA I, in the range of 32.1 nM-5.5 µM against hCA II and of 127 nM-2.12 µM against mtCA 3.