Aryl-4,5-dihydro-1H-pyrazole-1-carboxamide Derivatives Bearing a Sulfonamide Moiety Show Single-digit Nanomolar-to-Subnanomolar Inhibition Constants against the Tumor-associated Human Carbonic Anhydrases IX and XII.

A series of new 3-phenyl-5-aryl-N-(4-sulfamoylphenyl)-4,5-dihydro-1H-pyrazole-1-carboxamide derivatives was designed here, synthesized, and studied for carbonic anhydrase (CAs, EC 4.2.1.1) inhibitory activity against the human (h) isozymes I, II, and VII (cytosolic, off-target isoforms), and IX and XII (anticancer drug targets). Generally, CA I was not effectively inhibited, whereas effective inhibitors were identified against both CAs II (KIs in the range of 5.2-233 nM) and VII (KIs in the range of 2.3-350 nM). Nonetheless, CAs IX and XII were the most susceptible isoforms to this class of inhibitors. In particular, compounds bearing an unsubstituted phenyl ring at the pyrazoline 3 position showed 1.3-1.5 nM KIs against CA IX. In contrast, a subset of derivatives having a 4-halo-phenyl at the same position of the aromatic scaffold even reached subnanomolar KIs against CA XII (0.62-0.99 nM). Docking studies with CA IX and XII were used to shed light on the derivative binding mode driving the preferential inhibition of the tumor-associated CAs. The identified potent and selective CA IX/XII inhibitors are of interest as leads for the development of new anticancer strategies.

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

The two ß-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.

Structure-Activity Relationships of Benzenesulfonamide-Based Inhibitors towards Carbonic Anhydrase Isoform Specificity.

Carbonic anhydrases (CAs) are implicated in a wide range of diseases, including the upregulation of isoforms CA IX and XII in many aggressive cancers. However, effective inhibition of disease-implicated CAs should minimally affect the ubiquitously expressed isoforms, including CA I and II, to improve directed distribution of the inhibitors to the cancer-associated isoforms and reduce side effects. Four benzenesulfonamide-based inhibitors were synthesized by using the tail approach and displayed nanomolar affinities for several CA isoforms. The crystal structures of the inhibitors bound to a CA IX mimic and CA II are presented. Further in silico modeling was performed with the inhibitors docked into CA I and XII to identify residues that contributed to or hindered their binding interactions. These structural studies demonstrated that active-site residues lining the hydrophobic pocket, especially positions 92 and 131, dictate the positional binding and affinity of inhibitors, whereas the tail groups modulate CA isoform specificity. Geometry optimizations were performed on each ligand in the crystal structures and showed that the energetic penalties of the inhibitor conformations were negligible compared to the gains from active-site interactions. These studies further our understanding of obtaining isoform specificity when designing small molecule CA inhibitors.

Inhibition of the α-carbonic anhydrase from Vibrio cholerae with amides and sulfonamides incorporating imidazole moieties.

We discovered novel and selective sulfonamides/amides acting as inhibitors of the α-carbonic anhydrase (CA, EC 4.2.1.1) from the pathogenic bacterium Vibrio cholerae (VchCA). This Gram-negative bacterium is the causative agent of cholera and colonises the upper small intestine where sodium bicarbonate is present at a high concentration. The secondary sulfonamides and amides investigated here were potent, low nanomolar VchCA inhibitors whereas their inhibition of the human cytosolic isoforms CA I and II was in the micromolar range or higher. The molecules represent an interesting lead for antibacterial agents with a possibly new mechanism of action, although their CA inhibition mechanism is unknown for the moment.

Open saccharin-based secondary sulfonamides as potent and selective inhibitors of cancer-related carbonic anhydrase IX and XII isoforms.

A large number of novel secondary sulfonamides based on the open saccharin scaffold were synthesized and evaluated as selective inhibitors of four different isoforms of human carbonic anhydrase (hCA I, II, IX and XII, EC 4.2.1.1). They were obtained by reductive ring opening of the newly synthesized N-alkylated saccharin derivatives and were shown to be inactive against the two cytosolic off-target hCA I and II (Kis > 10 µM). Interestingly, these compounds inhibited hCA IX in the low nanomolar range with Kis ranging between 20 and 298 nM and were extremely potent inhibitors of hCA XII isoenzyme (Kis ranging between 4.3 and 432 nM). Since hCA IX and XII are the cancer-related isoforms recently validated as drug targets, these results represent an important goal in the development of new anticancer candidates. Finally, a computational approach has been performed to better correlate the biological data to the binding mode of these inhibitors.

Novel sulfonamide bearing coumarin scaffolds as selective inhibitors of tumor associated carbonic anhydrase isoforms IX and XII.

Four novel scaffolds consisting of total 24 compounds (1a-1o, 2a-2c, 3a-3c and 4a-4c) bearing aromatic sulfonamide and coumarin moieties connected through various linkers were synthesized in order to synergize the inhibition potential of both the moieties against four selected human carbonic anhydrase isoforms (hCA I, II, IX & XII). All compounds were found to be potent inhibitors of tumor associated hCA IX & XII while at the same time required large amounts to inhibit off-targeted housekeeping hCA I & II. Selectivity was more pronounced against hCA II over I, and hCA XII over IX. Results were compared with antitumor drug acetazolamide. One derivative 2b of series 2 was found to be a better selective inhibitor of hCA IX and XII.

Synthesis of 4-sulfamoylphenyl-benzylamine derivatives with inhibitory activity against human carbonic anhydrase isoforms I, II, IX and XII.

Imine derivatives were obtained by condensation of sulfanilamide with substituted aromatic aldehydes. The Schiff bases were thereafter reduced with sodium borohydride, leading to the corresponding amines, derivatives of 4-sulfamoylphenyl-benzylamine. These sulfonamides were investigated as inhibitors of the human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms hCA I and II (cytosolic isozymes), as well as hCA IX and XII (transmembrane, tumor-associated enzymes). We noted that the compounds incorporating secondary amine moieties showed a better inhibitory activity against all CA isozymes compared to the corresponding Schiff bases. Low nanomolar CA II, IX and XII inhibitors were detected, whereas the activity against hCA I was less potent. The secondary amines incorporating sulfonamide or similar zinc-binding groups, poorly investigated chemotypes for designing metalloenzyme inhibitors, may offer interesting opportunities in the field due to the facile preparation and possibility to explore a vast chemical space.

Pyrazolylbenzo[d]imidazoles as new potent and selective inhibitors of carbonic anhydrase isoforms hCA IX and XII.

Novel pyrazolylbenzo[d]imidazole derivatives (2a-2f) were designed, synthesized and evaluated against four human carbonic anhydrase isoforms belonging to α family comprising of two cytosolic isoforms hCA I and II as well as two transmembrane tumor associated isoforms hCA IX and XII. Starting from these derivatives that showed high potency but low selectivity in favor of tumor associated isoforms hCA IX and XII, we investigated the impact of removing the sulfonamide group. Thus, analogs 3a-3f without sulfonamide moiety were synthesized and biological assay revealed a good activity as well as an excellent selectivity as inhibitors for tumor associated hCA IX and hCA XII and the same was analyzed by molecular docking studies.

Inhibition of carbonic anhydrase isoforms I, II, IV, VII and XII with carboxylates and sulfonamides incorporating phthalimide/phthalic anhydride scaffolds.

We report a panel of carboxylates and sulfonamides incorporating phthalic anhydride and phthalimide moieties in their structure and their interaction with the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). They were synthesized from substituted anthranilic acids and trimellitic anhydride chloride, followed by reaction with primary amines and were tested for the inhibition of five physiologically relevant CA isoforms, the human (h) hCA I, II, IV, VII and XII, some of which are involved in serious pathologies (CA II, IV and XII in glaucoma; CA VII in epilepsy; CA XII in some solid tumors). The carboxylic acids were generally poor inhibitors of isoforms hCA I, II and IV but were highly effective, low nanomolar inhibitors of hCA VII and XII. The sulfonamides inhibited all isoforms significantly, and some of them were sub-nanomolar hCA VII inhibitors, although their isoform selectivity was lower compared to the carboxylates. This study proves that carboxylic acids incorporating a phthalic anhydride/phthalimide based scaffold may lead to isoform-selective inhibitors by applying the tail approach, mostly used up until now for obtaining sulfonamide, sulfamide and sulfamate CA inhibitors.

Synthesis 4-[2-(2-mercapto-4-oxo-4H-quinazolin-3-yl)-ethyl]-benzenesulfonamides with subnanomolar carbonic anhydrase II and XII inhibitory properties.

Condensation of substituted anthranilic acids with 4-isothiocyanatoethyl-benzenesulfonamide led to series of heterocyclic benzenesulfonamides incorporating 2-mercapto-quinazolin-4-one tails. These sulfonamides were investigated as inhibitors of the human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms hCA I and II (cytosolic isozymes), as well as hCA XII (a transmembrane, tumor-associated enzyme also involved in glaucoma-genesis). The new sulfonamides acted as medium potency inhibitors of hCA I (KIs of 28.5-2954nM), being highly effective as hCA II (KIs in the range of 0.62-12.4nM) and XII (KIs of 0.54-7.11nM) inhibitors. All substitution patterns present in these compounds (e.g., halogens, methyl and methoxy moieties, in positions 6, 7 and/or 8 of the 2-mercapto-quinazolin-4-one ring) led to highly effective hCA II/XII inhibitors. These compounds should thus be of interest as preclinical candidates in pathologies in which the activity of these enzymes should be inhibited, such as glaucoma (CA II and XII as targets) or some tumors in which the activity of isoforms CA II and XII is dysregulated.

Development of 3-(4-aminosulphonyl)-phenyl-2-mercapto-3H-quinazolin-4-ones as inhibitors of carbonic anhydrase isoforms involved in tumorigenesis and glaucoma.

A series of heterocyclic benzenesulfonamides incorporating 2-mercapto-3H-quinazolin-4-one tails were prepared by condensation of substituted anthranilic acids with 4-isothiocyanato-benzenesulfonamide. These sulfonamides were investigated as inhibitors of the human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms hCA I and II (cytosolic isozymes), as well as hCA IX and XII (trans-membrane, tumor-associated enzymes). They acted as medium potency inhibitors of hCA I (KIs of 81.0-3084 nM), being highly effective as hCA II (KIs in the range of 0.25-10.8 nM), IX (KIs of 3.7-50.4 nM) and XII (KIs of 0.60-52.9 nM) inhibitors. These compounds should thus be of interest as preclinical candidates in pathologies in which the activity of these enzymes should be inhibited, such as glaucoma (CA II and XII as targets) or some tumors in which the activity of three isoforms (CA II, IX and XII) is dysregulated.

A novel library of saccharin and acesulfame derivatives as potent and selective inhibitors of carbonic anhydrase IX and XII isoforms.

Small libraries of N-substituted saccharin and N-/O-substituted acesulfame derivatives were synthesized and tested as atypical and selective inhibitors of four different isoforms of human carbonic anhydrase (hCA I, II, IX and XII, EC 4.2.1.1). Most of them inhibited hCA XII in the low nanomolar range, hCA IX with KIs ranging between 19 and 2482nM, whereas they were poorly active against hCA II (KIs >10µM) and hCA I (KIs ranging between 318nM and 50µM). Since hCA I and II are ubiquitous off-target isoforms, whereas the cancer-related isoforms hCA IX and XII were recently validated as drug targets, these results represent an encouraging achievement in the development of new anticancer candidates. Moreover, the lack of a classical zinc binding group in the structure of these inhibitors opens innovative, yet unexplored scenarios for different mechanisms of inhibition that could explain the high inhibitory selectivity. A computational approach has been carried out to further rationalize the biological data and to characterize the binding mode of some of these inhibitors.

Sulfamide derivatives with selective carbonic anhydrase VII inhibitory action.

A set of N,N'-disubstituted sulfamides and sodium cyclamate have been tested for their inhibitory action against six isoforms of carbonic anhydrase (CA, EC 4.2.1.1) found in the brain, that is, CA I, CA II, CA VII, CA IX, CA XII and CA XIV, some of which are involved in epileptogenesis. The biological data showed interesting results for CA VII inhibition, the isozyme thought to be a novel antiepileptic target. Strong CA VII inhibitors, with Ki values in the low nanomolar-subnanomolar range were identified. Some of these derivatives showed selectivity for inhibition of CA VII versus the ubiquitous isoform CA II, for which the Ki values were in the micromolar range. Molecular modeling approaches were employed to understand the binding interactions between these compounds and the two CA isoforms, since the mechanism of action of such disubstituted sulfamides was not yet investigated by means of X-ray crystallography.

7-Aryl-triazolyl-substituted sulfocoumarins are potent, selective inhibitors of the tumor-associated carbonic anhydrase IX and XII.

Sulfocoumarins behave as interesting inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). Here, we report a new series of 7-substituted derivatives which were obtained by the click chemistry approach from 7-propargyloxy-sulfocoumarin and aryl azides incorporating halogens, hydroxy, methoxy and carboxyl moieties in their molecules. The new compounds were screened for the inhibition on four physiologically relevant human CA (hCA) isoforms, the cytosolic hCA I and II and the transmembrane tumor-associated hCA IX and XII. The new compounds did not inhibit the cytosolic isoforms but were low nanomolar inhibitors of the tumor-associated ones hCA IX and XII.

Synthesis and inhibition potency of novel ureido benzenesulfonamides incorporating GABA as tumor-associated carbonic anhydrase IX and XII inhibitors.

New ureido benzenesulfonamides incorporating a GABA moiety as a linker between the ureido and the sulfonamide functionalities were synthesized and their inhibition potency determined against both the predominant cytosolic (hCA I and II) and the transmembrane tumor-associated (hCA IX and XII) isoforms of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). The majority of these compounds were medium potency inhibitors of the cytosolic isoform hCA I and effective hCA II inhibitors, whereas they showed strong inhibition of the two transmembrane tumor-associated isoforms hCA IX and XII, with KIs in nanomolar range. Only one derivative had a good selectivity for inhibition of the tumor-associated hCA IX target isoform over the cytosolic and physiologically dominant off-target hCA I and II, being thus a potential tool to develop new anticancer agents.

Overexpression of the transmembrane carbonic anhydrase isoforms IX and XII in the inflamed synovium.

Juvenile idiopathic arthritis (JIA) is the most common form of chronic rheumatic disease affecting children worldwide, with some features similar to adult rheumatoid arthritis (RA). In the present study, we aim at investigating novel markers that will allow in the future for tailored, more personalized treatment strategies. Hence, taking notice of several reports proving the role of local acidosis as a causal link between inflammatory diseases and related pain, and the involvement of several carbonic anhydrases (CA, EC 4.2.1.1) isoforms in articular diseases, we evaluated in JIA patients the expression of these metalloenzymes. We identified that JIA patients show high levels of active CA IX and XII isoforms. Our results represent the first evidence of the identification of these enzymes as potential therapeutic targets and development of novel innovative therapies for arthritis, also considering that the two isoforms are validated antitumor targets.

Synthesis of Schiff base derivatives of 4-(2-aminoethyl)-benzenesulfonamide with inhibitory activity against carbonic anhydrase isoforms I, II, IX and XII.

Schiff base derivatives were obtained by reaction of 4-(2-aminoethyl)benzenesulfonamide with aromatic aldehydes. The corresponding secondary amine derivatives were also prepared by reduction of the imine compounds with NaBH4. These derivatives were investigated as inhibitors of four human carbonic anhydrase (CA, EC 4.2.1.1) isoforms, the cytosolic isozymes hCA I and II, as well as, the transmembrane, tumor-associated hCA IX and XII. Some of the newly synthesised compounds showed effective inhibitory activities against these CA isozymes. Many low nanomolar inhibitors were detected against all isoforms among the secondary amines whereas the Schiff bases were by far less active compared to the corresponding reduced derivatives among all investigated isoforms.

Sulfonamide bearing pyrazolylpyrazolines as potent inhibitors of carbonic anhydrase isoforms I, II, IX and XII.

A series of pyrazolylpyrazolines was designed, synthesized and evaluated for carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity against cytosolic human (h) isozymes hCA I and hCA II as well as transmembrane tumor associated isozymes, hCA IX and hCA XII. All the tested compounds exhibited an excellent CA activity profile against hCA I, hCA II and hCA XII when compared to the reference drug acetazolamide (AZA). Compounds 6d, 6f and 7a-7f have exhibited better inhibition profile against hCA XII (Ki = 0.47-5.1 nM) as compared with AZA (Ki = 5.7 nM) especially, compounds 6a, 7a, 7c and 7d which were nearly 10-fold better than reference drug. Against hCA II, all of the tested compounds were better than the standard drug especially compounds 6c, 6d, 7c and 7d (Ki = 1.1-1.7 nM) were many fold better inhibitors than AZA (Ki = 12.1 nM). In addition, they acted as selective CA inhibitors of isoform hCA XII over the physiological isoform hCA I.

New 4-[(3-cyclohexyl-4-aryl-2,3-dihydro-1,3-thiazol-2-ylidene)amino]benzene-1-sulfonamides, synthesis and inhibitory activity toward carbonic anhydrase I, II, IX, XII.

A series of 4-[(3-cyclohexyl-4-aryl-2,3-dihydro-1,3-thiazol-2-ylidene)amino]benzene-1-sulfonamides was synthesised and the activity of the new compounds as inhibitors of hCA I, II, IX, and XII was evaluated. These new derivatives exhibited some peculiarities with respect to previously reported sulfonamide based inhibitors of CA. We observed that the nature of the substituents in the position 3 and 4 of the dihydro-thiazole ring was relevant in determining both activity and selectivity profiles.

New natural product carbonic anhydrase inhibitors incorporating phenol moieties.

Carbonic anhydrases (CAs, EC 4.2.1.1) catalyze the fundamental reaction of CO2 hydration in all living organisms, being actively involved in the regulation of a plethora of patho/physiological conditions. They represent a typical example of enzyme convergent evolution, as six genetically unrelated families of such enzymes were described so far. The need to find selective CA inhibitors (CAIs) triggered the investigation of natural product libraries, which proved to be a valid source of agents with such an activity, as demonstrated for the phenols, polyamines and coumarins. Herein we report an in vitro inhibition study of human (h) CA isoforms hCAs I, II, IV, VII and XII with a panel of natural polyphenols including flavones, flavonols, flavanones, flavanols, isoflavones and depsides, some of which extracted from Quercus ilex and Salvia miltiorrhiza. Several of the investigated derivatives showed interesting inhibition activity and selectivities for inhibiting some important isoforms over the off-target ones hCA I and II.