Design, synthesis, and docking studies of new 1,3,4-thiadiazole-2-thione derivatives with carbonic anhydrase inhibitory activity

A new series of 1,3,4-thiadiazole-2-thione derivatives have been prepared and assayed for the inhibition of three physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isozymes, the cytosolic human isozymes I and II, and the transmembrane, tumor-associated hCA IX. Against hCA I the investigated thiones, showed inhibition constants in the range of 2.55-222 microM, against hCA II in the range of 2.0-433 microM, and against hCA IX in the range of 1.25-148 microM. Compound 5c, 4-(4,5-dihydro-5-thioxo-1,3,4-thiadiazol-2-yl)-1-(5-nitro-2-oxoindolin-3-ylidene)semicarbazide showed interesting inhibition of the tumor-associated hCA IX with K(I) value of 1.25 microM, being the first non-sulfonamide type inhibitor of such activity. This result is rather important taking into consideration the known antitumor activity of thiones. In addition, docking of the tested compounds into CA II active site was performed in order to predict the affinity and orientation of these compounds at the isozyme active site. The results showed similar orientation of the target compounds at CA II active site compared with reported sulfonamide type CAIs with the thione group acting as a zinc-binding moiety.     

Carbonic anhydrase inhibitors: inhibition of the human isozymes I, II, VA, and IX with a library of substituted difluoromethanesulfonamides

An inhibition study of the human cytosolic isozymes I, and II, the mitochondrial isoform VA, and the tumor-associated, transmembrane isozyme IX of carbonic anhydrase (CA, EC 4.2.1.1) with a library of aromatic/heteroaromatic/polycyclic difluoromethanesulfonamides is reported. Most of the inhibitors were derivatives of benzenedifluoromethanesulfonamide incorporating substituted-phenyl moieties, or were methylsulfonamide and difluoromethyl-sulfonamide derivatives of the sulfamates COUMATE and EMATE, respectively. Except for the methylsulfonamide-COUMATE derivative which behaved as a potent CA II inhibitor (K(I) of 32nM), these sulfonamides were moderate inhibitors of all isozymes, with inhibition constants in the range of 96-5200nM against hCA I, of 80-670nM against hCA II, and of 195-9280nM against hCA IX, respectively. Remarkably, some derivatives, such as 3-bromophenyl-difluoromethanesulfonamide, showed a trend to selectively inhibit the mitochondrial isoform CA VA, showing selectivity ratios for inhibiting CA VA over CA II of 3.53; over CA I of 6.84 and over CA IX of 9.34, respectively, although it is a moderate inhibitor (K(I) of 160nM). Some of these derivatives may be considered as leads for the design of isozyme selective CA inhibitors targeting the mitochondrial isozyme CA VA, with potential use as anti-obesity agents.     

Carbonic anhydrase inhibitors: synthesis and inhibition of cytosolic/tumor-associated carbonic anhydrase isozymes I, II, IX, and XII with N-hydroxysulfamides--a new zinc-binding function in the design of inhibitors

A small library of N-hydroxysulfamides was synthesized by an original approach in order to investigate whether this zinc-binding function is efficient for the design of inhibitors targeting the cytosolic (hCA I and II) and transmembrane, tumor-associated (hCA IX and XII) isozymes of carbonic anhydrase (CA, EC 4.2.1.1). The parent derivative, N-hydroxysulfamide was a more potent inhibitor as compared to sulfamide or sulfamic acid against all isozymes, with inhibition constants in the range of 473 nM-4.05 microM. Its substituted n-decyl-, n-dodecyl-, benzyl-, and biphenylmethyl-derivatives were less inhibitory against hCA I (K(I)s in the range of 5.8-8.2 microM) but more inhibitory against hCA II (K(I)s in the range of 50.5-473 nM). The same situation was true for the tumor-associated isozymes, with K(I)s in the range of 353-790 nM against hCA IX and 372-874 nM against hCA XII. Some sulfamides/sulfamates possessing similar substitution patterns have also been investigated for the inhibition of these isozymes, being shown that in some particular cases sulfamides are more efficient inhibitors as compared to the corresponding sulfamates. Potent CA inhibitors targeting the cytosolic or tumor-associated CA isozymes can thus be designed from various classes of sulfonamides, sulfamides, or sulfamates and their derivatives, considering the extensive interactions in which the inhibitor and the enzyme active site are engaged, based on recent X-ray crystallographic data.     

Carbonic anhydrase inhibitors. Novel sulfanilamide/acetazolamide derivatives obtained by the tail approach and their interaction with the cytosolic isozymes I and II, and the tumor-associated isozyme IX

A series of sulfonamides has been obtained by reacting sulfanilamide or 5-amino-1,3,4-thiadiazole-2-sulfonamide with omega-chloroalkanoyl chlorides, followed by replacement of the omega-chlorine atom with secondary amines. Tails incorporating heterocyclic amines belonging to the morpholine, piperidine and piperazine ring systems have been attached to these sulfonamides, by means of an alkanoyl-carboxamido linker containing from two to five carbon atoms. The new derivatives prepared in this way were tested as inhibitors of three carbonic anhydrase (CA, EC 4.2.1.1) isozymes, the cytosolic isozymes CA I and II, and the catalytic domain of the transmembrane, tumor-associated isozyme CA IX. Several low nanomolar CA I and CA II inhibitors were detected both in the aromatic and heterocyclic sulfonamide series, whereas the best hCA IX inhibitors (inhibition constants in the range of 22-35 nM) all belonged to the acetazolamide-like derivatives.     

Carbonic anhydrase inhibitors. Biphenylsulfonamides with inhibitory action towards the transmembrane, tumor-associated isozymes IX possess cytotoxic activity against human colon, lung and breast cancer cell lines

Reaction of 4,4-biphenyl-disulfonyl chloride with aromatic/heterocyclic sulfonamides also incorporating a free amino group, such as 4-aminobenzenesulfonamide, 4-aminoethyl-benzenesulfonamide, 6-chloro-4-aminobenzene-1,3-disulfonamide or 5-amino-1,3,4-thiadiazole-2-sulfonamide afforded bis-sulfonamides which have been tested as inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4..2.1.1). The compounds were rather modest inhibitors of isozymes CA I and XII, but were more efficient as inhibitors of the cytosolic CA II and transmembrane, tumor-associated CA IX (inhibition constants in the range of 21-129 nM gainst hCA II, and 23-79 nM against hCA IX, respectively). The new bis-sulfonamides also showed inhibition of growth of several tumor cell lines (ex vivo), with GI(50) values in the range of 0.74-10.0 microg/mL against the human colon cancer cell line HCT116, the human lung cancer cell line H460 and the human breast cancer cell line MCF-7.     

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.     

Carbonic anhydrase inhibitors: synthesis and inhibition of cytosolic/tumor-associated carbonic anhydrase isozymes I, II, and IX with sulfonamides derived from 4-isothiocyanato-benzolamide

A series of sulfonamides incorporating 4-thioureido-benzolamide moieties have been prepared from aminobenzolamide and thiophosgene followed by the reaction of the thiocyanato intermediate with aliphatic/aromatic amines or hydrazines. The new derivatives have been investigated as inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), and more precisely of the cytosolic isozymes hCA I and II, as well as the tumor-associated isozyme hCA IX (all of human origin). The new compounds showed excellent inhibitory properties against all three isozymes with inhibition constants in the range of 0.6-62 nM against hCA I, 0.5-1.7 nM against hCA II and 3.2-23 nM against hCA IX, respectively. These derivatives are interesting candidates for the development of novel therapies targeting hypoxic tumors.     

Carbonic anhydrase inhibitors: 2-substituted-1,3,4-thiadiazole-5-sulfamides act as powerful and selective inhibitors of the mitochondrial isozymes VA and VB over the cytosolic and membrane-associated carbonic anhydrases I, II and IV

A series of 2-substituted-1,3,4-thiadiazole-5-sulfamides was prepared and assayed as inhibitors of several carbonic anhydrase (CA, EC 4.2.1.1) isoforms, the cytosolic CA I and II, the membrane-associated CA IV and the mitochondrial CA VA and VB. The new compounds showed weak inhibitory activity against hCA I (K(I)s of 102 nM-7.42 microM), hCA II (K(I)s of 0.54-7.42 microM) and hCA IV (K(I)s of 4.32-10.05 microM) but were low nanomolar inhibitors of hCA VA and hCA VB, with inhibition constants in the range of 4.2-32 nM and 1.3-74 nM, respectively. Furthermore, the selectivity ratios for inhibiting the mitochondrial enzymes over CA II were in the range of 67.5-415, making these sulfamides the first selective CA VA/VB inhibitors.     

Carbonic anhydrase inhibitors: inhibition of human cytosolic isozymes I and II and tumor-associated isozymes IX and XII with S-substituted 4-chloro-2-mercapto-5-methyl-benzenesulfonamides

A series of S-substituted 4-chloro-2-mercapto-5-methyl-benzenesulfonamides has been investigated as inhibitors of four isoforms of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), that is, the cytosolic, ubiquitous isozymes CA I and II, as well as the transmembrane, tumor-associated isozymes CA IX and XII. The new derivatives were inefficient inhibitors of isoform I (K(I)s in the range of 2.7-18.7 microM) but generally had low nanomolar affinity for the inhibition of the other three isoforms (K(I)s in the range of 2.4-214 nM against hCA II; 1.4-47.5 nM against hCA IX, and 1.7-569 nM against hCA XII, respectively). Some selectivity for the inhibition of the tumor-associated versus the cyctosolic isoform II with some of these compounds has also been evidenced. As CA IX is an important marker of tumor hypoxia and its predictive, prognostic, and druggability potentials for designing antitumor therapies were recently validated, detection of selective, potent CA IX inhibitors may be relevant in the fight against cancers overexpressing CA isozymes.     

Carbonic anhydrase inhibitors. Biphenylsulfonamides with inhibitory action towards the transmembrane,tumor-associated isozymes IX possess cytotoxic activity against human colon,lung and breast cancer cell lines

Reaction of 4,4-biphenyl-disulfonyl chloride with aromatic/heterocyclic sulfonamides also incorporating a free amino group, such as 4-aminobenzenesulfonamide, 4-aminoethyl-benzenesulfonamide, 6-chloro-4-aminobenzene-1,3-disulfonamide or 5-amino-1,3,4-thiadiazole-2-sulfonamide afforded bis-sulfonamides which have been tested as inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4..2.1.1). The compounds were rather modest inhibitors of isozymes CA I and XII, but were more efficient as inhibitors of the cytosolic CA II and transmembrane, tumor-associated CA IX (inhibition constants in the range of 21–129 nM gainst hCA II, and 23–79 nM against hCA IX, respectively). The new bis-sulfonamides also showed inhibition of growth of several tumor cell lines (ex vivo), with GI₅₀ values in the range of 0.74–10.0 μg/mL against the human colon cancer cell line HCT116, the human lung cancer cell line H460 and the human breast cancer cell line MCF-7.     

Inhibition of membrane-associated carbonic anhydrase isozymes IX, XII and XIV with a library of glycoconjugate benzenesulfonamides

A library of glycoconjugate benzenesulfonamides that contain diverse carbohydrate-triazole tails were investigated for their ability to inhibit the enzymatic activity of the three human transmembrane carbonic anhydrase (CA) isozymes hCA IX, hCA XII and hCA XIV. These isozymes have their CA domains located extracellularly, unlike the physiologically dominant hCA II, and are of immense current interest as druggable targets. Elevated expression of isozymes IX and XII is a marker for a broad spectrum of hypoxic tumors-this physiology may facilitate a novel approach to discriminate between healthy cells and cancerous cells. Many of these glycoconjugates were potent inhibitors (low nM), but importantly exhibited different isozyme selectivity profiles. The most potent hCA IX inhibitor was the glucuronic acid derivative 20 (K(i)=23nM). This compound was uniquely hCA IX selective cf. all other isozymes (16.4-, 16.8- and 4.6-fold selective against hCA II, XII, and XIV, respectively). At hCA XII there were many inhibitors with K(i)s<10nM that also demonstrated excellent selectivity (up to 344-fold) against other isozymes. Potent hCA XIV inhibitors were also identified, several with K(i)s approximately 10nM, however no hCA XIV-selective derivatives were evidenced from this library. The sugar tails of this study have shown promise as a valuable approach to both solubilize the aromatic sulfonamide CA recognition pharmacophore and to deliver potent inhibition and isozyme differentiation of the transmembrane CAs.     

Carbonic anhydrase inhibitors. Interaction of isozymes I, II, IV, V, and IX with organic phosphates and phosphonates

The interaction of five human carbonic anhydrase (hCA, EC 4.2.1.1) isozymes, that is, hCA I, II, IV, V, and IX with a small library of phosphonic acids/organic phosphates, including methylphosphonic acid, MPA; phenylphosphonic acid, PPA; N-(phosphonoacetyl)-L-aspartic acid, PALA, methylene diphosphonic acid MDPA, the O-phosphates of serine (Ser-OP) and threonine (Thr-OP) as well as the antiviral phosphonate foscarnet has been studied. hCA I was activated by all these compounds, with the best activators being MPA and PPA (K(A)s of 0.10-1.20 microM). MPA and PPA were on the other hand nanomolar inhibitors of hCA II (K(I)s of 98-99 nM). PALA showed an affinity of 7.8 microM, whereas the other compounds were weak, millimolar inhibitors of this isozyme. The best hCA IV inhibitors were PALA (79 nM) and PPA (5.4 microM), whereas the other compounds showed K(I)s in the range of 0.31-5.34 mM. The mitochondrial isozyme was weakly inhibited by all these compounds (K(I)s in the range of 0.09-41.7 mM), similarly to the transmembrane, tumor-associated isozyme (K(I)s in the range of 0.86-2.25 mM). Thus, phosphonates may lead to CA inhibitors with selectivity against two physiologically relevant isozymes, the cytosolic hCA II or the membrane-bound hCA IV.     

Carbonic anhydrase inhibitors: aliphatic N-phosphorylated sulfamates--a novel zinc-anchoring group leading to nanomolar inhibitors

A small library of phosphorylated sulfamates (N-(O-alkylsulfamoyl)-phosphoramidic acids) incorporating long aliphatic chains (C8-C16) has been synthesized and investigated for their interaction with two physiologically relevant carbonic anhydrase (CA) isozymes. These compounds behaved as very potent inhibitors of both isozymes, with inhibition constants in the range of 8.2-16.1nM against isozyme hCA I, and 5.3-11.9nM against isozyme hCA II. Activity was optimal for the n-octyl derivative (similarly with that of the corresponding unsubstituted sulfamates) and gradually decreased for the longer chain derivatives. Some of these compounds are much more effective CA inhibitors as compared to the clinically used derivatives acetazolamide, sulfanilamide or topiramate, which are used as standards for the enzymatic determinations. The phosphorylated sulfamate moiety represents a novel zinc-binding group for the design of effective CA inhibitors.     

Carbonic anhydrase inhibitors. Selective inhibition of human tumor-associated isozymes IX and XII and cytosolic isozymes I and II with some substituted-2-mercapto-benzenesulfonamides

A series of 2-mercapto-substituted-benzenesulfonamides has been prepared by a unique two-step procedure starting from the corresponding 2-chloro-substituted benzenesulfonamides. Compounds bearing an unsubstituted mercapto group and the corresponding S-benzoyl derivatives were investigated as inhibitors of four isoforms of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), i.e., the cytosolic, ubiquitous isozymes CA I and II, as well as the transmembrane, tumor associated isozymes CA IX and XII. These derivatives were medium potency hCA I inhibitors (K(I)s in the range of 1.5-5.7 microM), two derivatives were strong hCA II inhibitors (K(I)s in the range of 15-16 nM), whereas the others showed weak activity. These compounds inhibited hCA IX with inhibition constants in the range 160-1950 nM and hCA XII with inhibition constants in the range 1.2-413 nM. Some of these derivatives showed a certain degree of selectivity for inhibition of the tumor-associated over the cytosolic isoforms, being thus interesting leads for the development of potentially novel applications in the management of hypoxic tumors which overexpress CA IX and XII.     

Carbonic anhydrase inhibitors: inhibition of cytosolic/tumor-associated isoforms I, II, and IX with iminodiacetic carboxylates/hydroxamates also incorporating benzenesulfonamide moieties

The synthesis of a new class of sulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitors (CAIs), also possessing carboxylate/hydroxamate moieties in their molecule, is reported. These compounds may act on dual antitumor targets, the tumor-associated CA isozymes (CA IX) and some matrix metalloproteinases (MMPs). The compounds were prepared by an original method starting from iminodiacetic acid, and assayed as inhibitors of three isozymes, hCA I, II (cytosolic), and IX (transmembrane). The new derivatives showed weak inhibitory activity against isozyme I (K(I)s in the range of 95-8300 nM), were excellent to moderate CA II inhibitors (K(I)s in the range of 8.4-65 nM), and very good and selective CA IX inhibitors (K(I)s in the range of 3.8-26 nM). The primary sulfonamide moiety is a better zinc-binding group in the design of CAIs as compared to the carboxylate/hydroxamate one, but the presence of hydroxamate functionalities in the molecule of CAIs leads to selectivity for the tumor-associated isozyme IX over the ubiquitous, cytosolic isoform II.     

Carbonic anhydrase inhibitors: inhibition of the tumor-associated isozymes IX and XII with a library of aromatic and heteroaromatic sulfonamides

The inhibition of the two transmembrane, tumor-associated isozymes of carbonic anhydrase (CA, EC 4.2.1.1) of human origin, hCA IX and XII, with a library of aromatic and heteroaromatic sulfonamides has been investigated. Most of them were sulfanilamide, homosulfanilamide, and 4-aminoethyl-benzenesulfonamide derivatives, to which tails that should induce diverse physico-chemical properties have been attached at the amino moiety, whereas several of these compounds were derived from metanilamide, benzene-1,3-disulfonamide or the 1,3,4-thiadiazole/thiadiazoline-2-sulfonamides. The tails were of the alkyl/aryl-carboxamido/sulfonamido-, ureido or thioureido type. Against hCA IX the investigated compounds showed inhibition constants in the range of 3-294 nM, whereas against hCA XII in the range of 1.9-348 nM, respectively. The best hCA IX inhibitors were ureas/thioureas incorporating 4-aminoethyl-benzenesulfonamide and metanilamide moieties. The best hCA XII inhibitors were 1,3,4-thiadiazole/thiadiazoline-2-sulfonamides incorporating 5-acylamido or 5-arylsulfonylamido moieties. These compounds also inhibited appreciably the cytosolic isozymes hCA I and II, but some selectivity for the transmembrane, tumor-associated isozymes was observed for some of them, which is an encouraging result for the design of novel therapies targeting hypoxic tumors, in which these carbonic anhydrases are highly overexpressed.     

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 tumor-associated isozyme IX with fluorine-containing sulfonamides. The first subnanomolar CA IX inhibitor discovered

Polyfluorinated CAIs show very good inhibitory properties against different carbonic anhydrase (CA) isozymes, such as CA I, II, and IV, but such compounds have not been tested for their interaction with the transmembrane, tumor-associated isozyme CA IX. Thus, a series of such compounds has been obtained by attaching 2,3,5,6-tetrafluorobenzoyl- and 2,3,5,6-tetrafluorophenylsulfonyl- moieties to aromatic/heterocyclic sulfonamides possessing derivatizable amino moieties. Some of these compounds showed excellent CA IX inhibitory properties and also selectivity ratios favorable to CA IX over CA II, the other physiologically relevant isozyme with high affinity for sulfonamide inhibitors. The first subnanomolar and rather selective CA IX inhibitor has been discovered, as the 2,3,5,6-tetrafluorobenzoyl derivative of metanilamide showed an inhibition constant of 0.8 nM against hCA IX, and a selectivity ratio of 26.25 against CA IX over CA II. Several other low nanomolar CA IX inhibitors were detected among the new derivatives reported here. The reported derivatives constitute valuable candidates for the development of novel antitumor therapies based on the selective inhibition of tumor-associated CA isozymes.     

Carbonic anhydrase inhibitors. Inhibition of red blood cell ostrich (Struthio camelus) carbonic anhydrase with a series of aromatic and heterocyclic sulfonamides

The purification of red blood cell carbonic anhydrase (CA, EC 4.2.1.1) from ostrich (scCA) blood is reported, as well as an inhibition study of this enzyme with a series of aromatic and heterocylic sulfonamides. The ostrich enzyme showed a high activity, comparable to that of the human isozyme II, with kcat, of 1.2 x 10(6) s(-1) and kcat/KM of 1.8 x 10(7) M(-1)s(-1), and an inhibition profile quite different from that of the human red blood cell cytosolic isozymes hCA I and II. scCA has generally a lower affinity for sulfonamide inhibitors as compared to hCA I and II. The only sulfonamide which behaved as a very potent inhibitor of this enzyme was ethoxzolamide (KI = 3.9 nM) whereas acetazolamide and sulfanilamide behaved as weaker inhibitors (inhibition constants in the range 303-570 nM). Several other aromatic and heterocyclic sulfonamides, mostly derivatives of sulfanilamide, homosulfanilamide, 4-aminoethylbenzenesulfonamide or 5-amino-1,3,4-thiadiazole-2-sulfonamide, showed good affinities for the ostrich enzyme, with KI values in the range 25-72 nM.     

Carbonic anhydrase inhibitors: novel sulfonamides incorporating 1,3,5-triazine moieties as inhibitors of the cytosolic and tumour-associated carbonic anhydrase isozymes I, II and IX

A new series of aromatic benzenesulfonamides incorporating 1,3,5-triazine moieties in their molecules is reported. This series was obtained by reaction of cyanuric chloride with sulfanilamide, homosulfanilamide or 4-aminoethylbenzenesulfonamide. The prepared dichlorotriazinyl-benzenesulfonamides were subsequently derivatized by reacting them with various nucleophiles, such as ammonia, hydrazine, primary and secondary amines, amino acid derivatives or phenol. The library of sulfonamides incorporating triazinyl moieties was tested for the inhibition of three physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isozymes, the cytosolic hCA I and II, and the transmembrane, tumour-associated hCA IX. The new compounds inhibited hCA I with inhibition constants in the range of 31-8500 nM, hCA II with inhibition constants in the range of 14-765 nM and hCA IX with inhibition constants in the range of 1.0-640 nM. Structure-activity relationship was straightforward and rather simple in this class of CA inhibitors, with the compounds incorporating compact moieties at the triazine ring (such as amino, hydrazino, ethylamino, dimethylamino or amino acyl) being the most active ones, and the derivatives incorporating such bulky moieties (n-propyl, n-butyl, diethylaminoethyl, piperazinylethyl, pyridoxal amine or phenoxy) being less effective hCA I, II and IX inhibitors. Some of the new derivatives also showed selectivity for inhibition of hCA IX over hCA II (selectivity ratios of 23.33-32.00), thus constituting excellent leads for the development of novel approaches for the management of hypoxic tumours.