Carbonic anhydrase inhibitors. Preparation of potent sulfonamides inhibitors incorporating bile acid tails

Reaction of TBDMS-protected bile acids (cholic, chenodeoxycholic, deoxycholic, lithocholic, ursodeoxycholic acids) or dehydrocholic acid with aromatic/heterocyclic sulfonamides possessing free amino/hydroxy moieties, in the presence of carbodiimides, afforded after deprotection of the OTBDMS ethers, a series of sulfonamides incorporating bile acid moieties in their molecules. Many such derivatives showed strong inhibitory properties against three isozymes of carbonic anhydrase (CA, EC 4.2.1.1), that is CA I, II and IV, zinc enzymes playing critical roles in many pathologies, and which represent interesting targets for developing diverse pharmacological agents. Some of the most active derivatives, incorporating 1,3,4-thiadiazole-2-sulfonamide or benzothiazole-2-sulfonamide functionalities in their molecules, showed low nanomolar affinity for CA II and CAIV. Furthermore, the bioavailability of these derivatives in rabbits is comparable to that of acetazolamide, being in the range of 85-90%, showing them as promising candidates for systemically acting CA inhibitors.     

Synthesis and carbonic anhydrase I,II, IV and XII inhibitory properties of N-protected amino acid – sulfonamide conjugates

N-protected amino acids (Gly, Ala and Phe protected with Boc and Z groups) were reacted with sulfonamide derivatives, leading to the corresponding N-protected amino acid–sulfonamide conjugates. 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 IV and hCA XII. Among them, hCA II, IV and XII are antiglaucoma drug targets, being involved in aqueous humor secretion within the eye. Low nanomolar inhibition was measured against all four isoforms with the 20 reported sulfonamides, but no selective inhibitory profiles, except for some CA XII-selective derivatives, were observed. hCA I, II and XII were generally better inhibited by sulfonamides incorporating longer scaffolds and Gly/Ala, whereas the best hCA IV inhibitors were homosulfanilamide derivatives, incorporating Phe moieties. The amino acid–sulfonamide conjugates show good water solubility and effective hCA II, IV and XII inhibition, and may be considered as interesting candidates for antiglaucoma studies.     

Carbonic anhydrase inhibitors; phosphoryl-sulfonamides--a new class of high affinity inhibitors of isozymes I and II

A series of phosphorylated aromatic/heterocyclic sulfonamides with the general formula ArSO2NHPO3H2 have been prepared by condensing ArSO2NH2 with phosphorus pentachloride, followed by controlled hydrolysis in the presence of formic acid. The new derivatives generally act as stronger inhibitors of two carbonic anhydrase (CA) isozymes, CA I and CA II, as compared to the parent unsubstituted sulfonamides from which they were obtained. The inhibition mechanism by this new class of CA inhibitors, as well as structure activity correlations for the series of investigated derivatives, are also discussed.     

Carbonic anhydrase inhibitors. Design of anticonvulsant sulfonamides incorporating indane moieties

A series of aromatic sulfonamides incorporating indane moieties were prepared starting from commercially available 1- and 2-indanamine, and their activity as inhibitors of two carbonic anhydrase (CA, EC 4.2.1.1) isozymes, hCA I and II was studied. The new sulfonamides incorporating acetamido, 4-chloro-benzoyl, valproyl, tetra-, and pentafluorobenzoyl moieties acted as very potent inhibitors of the slow red blood cell isozyme hCA I (K(i)s in the range of 1.6-8.5 nM), which usually has a lower affinity for such inhibitors, as compared to isozyme II. Some derivatives also showed excellent hCA II inhibitory properties (K(i)s in the range of 2.3-12 nM), but the anticonvulsant activity of these sulfonamides was rather low as compared to that of other sulfonamide/sulfamate CA inhibitors, such as methazolamide. Furthermore, the 2-amino/acetamido-indane-5-sulfonic acids prepared during this work also showed interesting CA inhibitory properties, with inhibition constants in the range of 43-89 nM against the two isozymes, being among the most potent sulfonic acid CA inhibitors reported so far.     

Carbonic Anhydrase Inhibitors. Arylsulfonylureido-and Arylureido-Substituted Aromatic and Heterocyclic Sulfonamides: Towards Selective Inhibitors of Carbonic Anhydrase Isozyme I

Abstract

Reaction of twenty aromatic/heterocyclic sulfonamides containing a free amino, imino, hydra-zino or hydroxyl group, with tosyl isocyanate or 3,4-dichlorophenyl isocyanate afforded two series of derivatives containing arylsulfonylureido or diarylureido moieties in their molecule respectively. The new derivatives were assayed as inhibitors of three carbonic anhydrase (CA) isozymes, CA I, II (cytosolic forms) and IV (membrane-bound form). Potent inhibition was observed against all three isozymes but especially against CA I, which is generally 10-75 times less susceptible to inhibition by the classical sulfonamides in clinical use as compared to the other major red cell isozyme, CA II, or the membrane-bound one, CA IV. The derivatives obtained from tosyl isocyanate were generally more potent than the corresponding ones obtained from 3,4-dichlorophenyl isocyanate. This is the first reported example of selective inhibition of CA I and might lead to more selective drugs/diagnostic agents from this class of pharmacologically relevant compounds.     

Carbonic anhydrase inhibitors: 4-sulfamoyl-benzenecarboxamides and 4-chloro-3-sulfamoyl-benzenecarboxamides with strong topical antiglaucoma properties.

Reaction of 4-carboxy-benzenesulfonamide or 4-chloro-3-sulfamoyl benzoic acid with carboxy-protected amino acids/dipeptides, or aromatic/heterocyclic sulfonamides/mercaptans afforded the corresponding benzene-carboxamide derivatives. These were tested as inhibitors of three carbonic anhydrase (CA) isozymes, CA I, II and IV. Some of the new derivatives showed affinity in the low nanomolar range for isozymes CA II and IV, involved in aqueous humor secretion within the eye, and were tested as topically acting anti-glaucoma agents, in normotensive and glaucomatous rabbits. Good in vivo activity and prolonged duration of action has been observed for some of these derivatives, as compared to the clinically used drugs dorzolamide and brinzolamide. Some of the 4-chloro-3-sulfamoyl benzenecarboxamides reported here showed higher affinity for CA I than for the sulfonamide avid isozyme CA II.     

Carbonic anhydrase inhibitors: inhibition of human cytosolic isozyme II and mitochondrial isozyme V with a series of benzene sulfonamide derivatives

Among the 14 human isozymes of carbonic anhydrase (CA, EC 4.2.1.1) presently known, the cytosolic hCA II is the most active and plays a host of physiological functions, whereas the mitochondrial hCA V is unique due to its role in several biosynthetic reactions. An inhibition study of these isozymes with a series of sulfonamides is reported here, with the scope to detect lead molecules for the design of isozyme-specific CA inhibitors (CAIs) targeting the mitochondrial isoform. Indeed, recently it has been shown that CA V is a novel target for the drug design of anti-obesity agents among others. Compounds included in this study were mainly ortho-, meta-, and para-substituted-benzenesulfonamides, together with several halogeno-substituted sulfanilamides and disubstituted-benzene-1,3-disulfonamide derivatives. Isozyme V showed an inhibition profile with these sulfonamides different of that of hCA II. Thus, IC(50) values in the range of 80 nM to 74 microM against hCA II, and 0.78-63.7 microM against hCA V with these derivatives have been obtained. Only one compound, 2-carboxymethyl-benzenesulfonamide, was more active against hCA V over hCA II (selectivity ratio of 1.39), whereas all other derivatives investigated here were much better hCA II inhibitors (selectivity ratios CA II/CA V in the range of 0.0008-0.73) than hCA V inhibitors.     

Carbonic anhydrase inhibitors: design of thioureido sulfonamides with potent isozyme II and XII inhibitory properties and intraocular pressure lowering activity in a rabbit model of glaucoma

A new series of thioureido-substituted sulfonamides were prepared by reacting 4-isothiocyanato- or 4-isothiocyanatoethyl-benzenesulfonamide with amines, hydrazines, or amino acids bearing moieties that can lead to an enhanced hydrosolubility, such as 2-dimethylamino-ethylamine, fluorine-containing aromatic amines/hydrazines, an aminodiol, heterocyclic polyamines (derivatives of morpholine and piperazine), 4-aminobenzoic acid, or natural amino acids (Gly, Cys, Asn, Arg, and Phe). The new compounds showed good inhibitory properties against three physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isozymes, with K(I)s in the range of 24-324 nM against the cytosolic isoform CA I, of 6-185 nM against the other cytosolic isozyme CA II, and of 1.5-144 nM against the transmembrane isozyme CA XII. Some of the new derivatives were also very effective in reducing elevated intraocular pressure in hypertensive rabbits as a glaucoma animal model. Considering that this is the first study in which potent CA II/CA XII inhibitors are designed and investigated in vivo, it may be assumed that the target isozymes of the antiglaucoma sulfonamides are indeed the cytosolic CA II and the transmembrane CA XII.     

Carbonic anhydrase inhibitors: synthesis and inhibition against isozymes I, II and IV of topically acting antiglaucoma sulfonamides incorporating cis-5-norbornene-endo-3-carboxy-2-carboxamido moieties

Sulfonamides incorporating cis-5-norbornene-endo-3-carboxy-2-carboxamido moieties in their molecules were prepared by reaction of cis-5-norbornene-endo-2,3-dicarboxylic anhydride with aromatic/heterocyclic sulfonamides possessing free amino, hydrazino, or imino groups. Some of these compounds showed very good CA II and CA IV inhibitory properties, with affinities for the enzymes in the low nanomolar range. Some of the most active CA II inhibitors reported here have been formulated as aqueous solutions for topical administration as antiglaucoma agents in normotensive rabbits. Some of the derivatives incorporating cis-5-norbornene-endo-3-carboxy-2-carboxamido and aromatic sulfonamide moieties (as sodium salts) showed effective and longer lasting intraocular pressure (IOP) lowering as compared to dorzolamide, a widely used topical antiglaucoma drug. Compounds incorporating cis-5-norbornene-endo-2,3-carboximido moieties, although stronger in vitro CA inhibitors as compared to the corresponding cis-5-norbornene-endo-3-carboxy-2-carboxamido-;derivatives, showed no topical IOP lowering properties, probably due to their very poor water solubility.     

Carbonic anhydrase inhibitors. Inhibition of cytosolic/tumor-associated carbonic anhydrase isozymes I, II, IX, and XII with Schiff's bases incorporating chromone and aromatic sulfonamide moieties, and their zinc complexes

A series of Schiff's bases was prepared by reaction of 3-formyl-chromone or 6-methyl-3-formyl-chromone with aromatic sulfonamides, such as sulfanilamide, homosulfanilamide, 4-aminoethyl-benzenesulfonamide, a pyrimidinyl-substituted sulfanilamide derivative, sulfaguanidine and 4-amino-6-trifluoromethyl-benzene-1,3-disulfonamide. The zinc complexes of these sulfonamides have also been obtained. The new derivatives and their Zn(II) complexes were investigated for the inhibition of four physiologically relevant isozymes of carbonic anhydrase (CA, EC 4.2.1.1): the cytosolic isoforms I and II, as well as the tumor-associated, transmembrane isozymes CA IX and XII. Except for the sulfaguanidine-derived compounds which were devoid of activity against all isozymes, the other sulfonamides and their metal complexes showed interesting inhibitory activity. Against isozyme CA I, the inhibition constants were in the range of 13-100 nM, against isozyme CA II in the range of 1.9-102 nM, against isozyme CA IX in the range of 6.3-48nM, and against CA XII in the range of 5.9-50nM. Generally, the formyl-chromone derived compounds were better CA inhibitors as compared to the corresponding 6-methyl-chromone derivatives, and for the simple, benzenesulfonamide derivatives activity increased with an increase of the spacer from sulfanilamide to homosulfanilamide and 4-aminoethylbenzenesulfonamide derivatives, respectively. Some of these compounds may show applications for the development of therapies targeting hypoxic tumors in which CA IX and XII are often highly overexpressed.     

Carbonic anhydrase inhibitors. Inhibition of the prokariotic beta and gamma-class enzymes from Archaea with sulfonamides

A detailed inhibition study of carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the beta- and gamma-families from Archaea with sulfonamides has been performed. Compounds included in this study were the clinically used sulfonamide CA inhibitors, such as acetazolamide, methazolamide, ethoxzolamide, topiramate, valdecoxib, celecoxib, dorzolamide, sulfanilamide, dichlorophanamide, as well as sulfanilamide analogs, halogenated sulfanilamides, and some 1,3-benzenedisulfonamide derivatives. The two gamma-CAs from Methanosarcina thermophila (Zn-Cam and Co-Cam) showed very different inhibitory properties with these compounds, as compared to the alpha-CA isozymes hCA I, II, and IX, and the beta-CA from Methanobacterium thermoautotrophicum (Cab). The best Zn-Cam inhibitors were sulfamic acid and acetazolamide, with inhibition constants in the range of 63-96 nM, whereas other investigated aromatic/heterocylic sulfonamides showed a rather levelled behavior, with KIs in the range of 0.12-1.70 microM. The best Co-Cam inhibitors were topiramate and p-aminoethyl-benzenesulfonamide, with KIs in the range of 0.12-0.13 microM, whereas the worst one was homosulfanilamide (KI of 8.50 microM). In the case of Cab, the inhibitory power of these compounds varied to a much larger extent, with sulfamic acid and sulfamide showing millimolar affinities (KIs in the range of 44-103 mM), whereas the best inhibitor was ethoxzolamide, with a KI of 5.35 microM. Most of these sulfonamides showed inhibition constants in the range of 12-100 microM against Cab. Thus, the three CA families investigated up to now possess a very diverse affinity for sulfonamides, the inhibitors with important medicinal, and environmental applications.     

Carbonic anhydrase inhibitors. Synthesis and inhibition of cytosolic/tumor-associated carbonic anhydrase isozymes I, II, and IX with boron-containing sulfonamides, sulfamides, and sulfamates: toward agents for boron neutron capture therapy of hypoxic tumors

A library of boron-containing carbonic anhydrase (CA, EC 4.2.1.1) inhibitors, including sulfonamides, sulfamides, and sulfamates is reported. The new compounds have been synthesized by derivatization reactions of 4-carboxy-/amino-/hydroxy-phenylboronic acid pinacol esters with amino/isothiocyanato-substituted aromatic/heteroaromatic sulfonamides or by sulfamoylation reactions with sulfamoyl chloride. The new derivatives have been assayed for the inhibition of three physiologically relevant CA isozymes, the cytosolic CA I and II, and the transmembrane, tumor-associated isozyme CA IX. Effective inhibitors were detected both among sulfonamides, sulfamates, and sulfamides. Against the human isozyme hCA I the new compounds showed inhibition constants in the range of 34-94nM, against hCA II in the range of 3.1-48nM, and against hCA IX in the range of 7.3-89nM, respectively. As hypoxic tumors highly overexpress CA IX, the design of boron-containing inhibitors with high affinity for the tumor-associated CA isozymes may lead to important advances in boron neutron capture therapy (BNCT) applications targeting such tumors, which are non-responsive to both classical chemo- and radiotherapy.     

Design and synthesis of thiourea compounds that inhibit transmembrane anchored carbonic anhydrases

A library of 32 novel glycoconjugate thiourea-bridged benzene sulfonamides have been synthesized from the reaction of glycosyl isothiocyanates with a panel of simple benzene sulfonamides comprising either a free amine or hydrazide. All compounds were investigated for their ability to inhibit the enzymatic activity of five human carbonic anhydrase (hCA) isozymes: hCA I, II and membrane-associated isozymes IX, XII and XIV. A physicochemical feature of the free sugar thioureido glycoconjugates was high water solubility (> 20 mg/mL), as well many of these compounds exhibited a desirable potency and CA isozyme selectivity profile. From this library several inhibitors displayed excellent potency-selectivity profiles for transmembrane anchored CAs over off-target CA I and II. These molecules provide potential dual-acting candidates for the development of inhibitors that target the extracellular CAs (IX, XII and XIV)-either directly as free sugars (membrane impermeable) or indirectly as acetylated prodrugs, becoming free sugars upon esterase hydrolysis.     

Carbonic anhydrase inhibitors: Schiff's bases of aromatic and heterocyclic sulfonamides and their metal complexes

Schiff's bases were obtained from aromatic/heterocyclic sulfonamides and amino-sulfonamide derivatives, such as sulfanilamide, homosulfanilamide, 4-aminoethyl-benzenesulfonamide and 5-amino-1,3,4-thiadiazole-2-sulfonamide. Metal complexes of some of these Schiff's bases, incorporating Zn(II), Co(lI), Ni(II) and Cu(II) ions, were also prepared and tested as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more specifically the red blood cell isozymes I and II. The Schiff's bases behaved as medium potency CA I and CA II inhibitors, whereas their metal complexes showed a highly enhanced potency, with several low nanomolar CA II inhibitors detected.     

Carbonic anhydrase inhibitors: copper(II) complexes of polyamino-polycarboxylamido aromatic/heterocyclic sulfonamides are very potent inhibitors of the tumor-associated isoforms IX and XII

Reaction of EDTA/DTPA dianhydride with aromatic/heterocyclic sulfonamides afforded a series of derivatives incorporating polyaminopolycarboxylate tails and benzenesulfonamide or 1,3,4-thiadiazole-2-sulfonamide heads. These compounds have been used as ligands to prepare Cu(II) complexes. Both parent sulfonamides as well as their copper complexes behaved as potent inhibitors of four carbonic anhydrase (CA, EC 4.2.1.1) isoforms, the cytosolic CA I and II, and transmembrane CA IX and XII. Some Cu(II) complexes showed subnanomolar affinities and some selectivity for the inhibition of the tumor-associated isoforms IX and XII and might be used as PET hypoxia markers of tumors.     

Carbonic anhydrase inhibitors: design of spin-labeled sulfonamides incorporating TEMPO moieties as probes for cytosolic or transmembrane isozymes

A series of spin-labeled sulfonamides incorporating TEMPO moieties were synthesized by a procedure involving the formation of a thiourea functionality between the benzenesulfonamide and free radical fragment of the molecules. The new compounds were tested as inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) and showed efficient inhibition of the physiologically relevant isozymes hCA II and hCA IX (hCA IX being predominantly found in tumors) and moderate to weak inhibitory activity against hCA I. Some derivatives were also selective for inhibiting the tumor-associated isoform over the cytosolic one CA II, and presented significant changes in their ESR signals when complexed to the enzyme active site, being interesting candidates for the investigation of hypoxic tumors overexpressing CA IX by ESR techniques, as well as for imaging/treatment purposes.     

Carbonic Anhydrase Inhibitors: Schiff's Bases of Aromatic and Heterocyclic Sulfonamides and their Metal Complexes

Schiff's bases were obtained from aromatic/heterocyclic sulfonamides and amino-sulfonamide derivatives, such as sulfanilamide, homosulfanilamide, 4-aminoethyl-benzenesulfonamide and 5-amino-1,3,4-thiadiazole-2-sulfonamide. Metal complexes of some of these Schiff's bases, incorporating Zn(II), Co(II), Ni(II) and Cu(II) ions, were also prepared and tested as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more specifically the red blood cell isozymes I and II. The Schiff's bases behaved as medium potency CA I and CA II inhibitors, whereas their metal complexes showed a highly enhanced potency, with several low nanomolar CA II inhibitors detected.     

Carbonic Anhydrase Inhibitors: Allylsulfonamide,Styrene Sulfonamide,N -allyl Sulfonamides and Some of Their Si,Ge, and B Derivatives

Unsubstituted aromatic, heterocyclic and perfluoroalkylic sulfonamides possessing the general formula RSO 2 NH 2 act as powerful inhibitors of the zinc enzyme carbonic anhydrase (CA). Unsaturated primary/substituted sulfonamides have never been investigated for their interaction with the enzyme. Here it is shown that such compounds, and more precisely allyl-sulfonamide and trans -styrene sulfonamide possessing the above general formula (with R=CH 2 =CH-CH 2 - and C 6 H 5 -CH=CH-, respectively) behave as nanomolar inhibitors of the physiologically relevant isozymes CA I and CA II. Some other derivatives of these two leads (incorporating Si(IV), Ge(IV) and B(III) moieties among others) were also synthesized and investigated for their interaction with CA, but showed decreased affinity for both isozymes. The structure-activity relationship for this class of CA inhibitors is discussed. Furthermore, it was observed that allylsulfonyl chloride is a strong CA inactivator, probably by reacting with amino acid residues critical for the catalytic cycle.     

Microwave assisted synthesis of novel tetrazole/sulfonamide derivatives based on octahydroacridine,xanthene and chromene skeletons as inhibitors of the carbonic anhydrases isoforms I,II, IV and VII

The synthesis of novel tetrazole/sulfonamide derivatives based on octahydroacridine, xanthene and chromene scaffold by using microwave (MW) assisted techniques is reported in this study. These synthesized hybrid compounds were assayed for the inhibition of carbonic anhydrase (CA, EC 4.2.1.1). The inhibitory activities were determined against three cytosolic human isoforms (hCA I, II and VII) and one membrane-associated (hCA IV) isoform. Some of the newly synthesized sulfonamides showed micromolar to nanomolar inhibitory activity against these enzymes.     

Europium complexes as novel indicators of paracellular diffusion

Measurement of paracellular permeation is an important assay for tight-junction investigations of drug toxicity, especially for metal-based drugs, and routine validation of the integrity of cell monolayers for models of drug absorption. Great efforts have been made in discovery and validation of novel paracellular diffusion indicators. In the present work, we prepared three Eu complexes, i.e., [Eu(dtpa)] (dtpa=diethylenetriaminepentaacetic acid), [Eu(dtpa)(BSA)], and [Eu(dtpa)(PLL)] (PLL=poly(L-lysine)), and tested their permeation properties on Madin?Darby canine kidney (MDCK) cells. The experimental results showed that all three probes were nontoxic to MDCK cells, permeated across MDCK monolayer exclusively via the paracellular pathways, and responded well to the changes on tight junction with high correlation of P(app) values to the decrease of trans-epithelial electric resistance (TEER). In addition, time-resolved fluorescence assays were conducted in a high-sensitivity and background-free mode. All these results confirmed the Eu complexes as novel and practical paracellular indicators.