Carbonic anhydrase inhibitors: aromatic sulfonamides and disulfonamides act as efficient tumor growth inhibitors

Aromatic/heterocyclic sulfonamides generally act as strong inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). Here we report the unexpected finding that potent aromatic sulfonamide inhibitors of CA, possessing inhibition constants in the range of 10(-8)-10(-9) M (against all the isozymes), also act as efficient in vitro tumor cell growth inhibitors, with GI50 (molarity of inhibitor producing a 50% inhibition of tumor cell growth) values of 10 nM-35 microM against several leukemia, non-small cell lung cancer, ovarian, melanoma, colon, CNS, renal, prostate and breast cancer cell lines. The investigated compounds were sulfanilyl-sulfanilamide-, 4-thioureido-benzenesulfonamide- and benzene-1,3-disulfonamide-derivatives. The mechanism of antitumor action with these sulfonamides is unknown, but it might involve either inhibition of several CA isozymes (such as CA IX, CA XII, CA XIV) predominantly present in tumor cells, a reduced provision of bicarbonate for the nucleotide synthesis (mediated by carbamoyl phosphate synthetase II), the acidification of the intracellular milieu as a consequence of CA inhibition or uncoupling of mitochondria and potent CA V inhibition among others. A combination of several such mechanisms is also plausible. Optimization of such derivatives from the SAR point of view, might lead to the development of effective novel types of anticancer agents/therapies.     

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: sulfonamides as antitumor agents?

Novel sulfonamide inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1) were prepared by reaction of aromatic or heterocyclic sulfonamides containing amino, imino, or hydrazino moieties with N,N-dialkyldithiocarbamates in the presence of oxidizing agents (sodium hypochlorite or iodine). The N,N-dialkylthiocarbamylsulfenamido-sulfonamides synthesized in this way behaved as strong inhibitors of human CA I and CA II (hCA I and hCA II) and bovine CA IV (bCA IV). For the most active compounds, inhibition constants ranged from 10(-8) to 10(-9) M (for isozymes II and IV). Three of the derivatives belonging to this new class of CA inhibitors were also tested as inhibitors of tumor cell growth in vitro. These sulfonamides showed potent inhibition of growth against several leukemia, non-small cell lung, ovarian, melanoma, colon, CNS, renal, prostate and breast cancer cell lines. With several cell lines. GI50 values of 10-75 nM were observed. The mechanism of antitumor action with the new sulfonamides reported here remains obscure, but may involve inhibition of CA isozymes which predominate in tumor cell membranes (CA IX and CA XII), perhaps causing acidification of the intercellular milieu, or inhibition of intracellular isozymes which provide bicarbonate for the synthesis of nucleotides and other essential cell components (CA II and CA V). Optimization of these derivatives from the SAR point of view, might lead to the development of effective novel types of anticancer agents.     

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 k_cat of 1.2·10⁶ s^{? 1} and k_cat/K_M of 1.8·10⁷ 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 (K_I = 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 K_I values in the range 25–72 nM.     

Carbonic Anhydrase Inhibitors. Schiff Bases of some Aromatic Sulfonamides and Their Metal Complexes: Towards More Selective Inhibitors of Carbonic Anhydrase Isozyme IV

Abstract

Reaction of three aromatic sulfonamides possessing a primary amino group, i.e., sulfanilamide, homosulfanilamide and p-aminoethyl-benzenesulfonamide with heterocyclic and aromatic aldehydes afforded a series of Schiff bases. Metal complexes of some of these Schiff bases with divalent transition ions such as Zn(II), Cu(II), Co(II) and Ni(II) have also been obtained. The new compounds were assayed as inhibitors of three isozymes of carbonic anhydrase (CA). Several of the new compounds showed a modest selectivity for the membrane-bound (bovine) isozyme CA IV (bCA IV) as compared to the cytosolic human isozymes hCA I and II, in contrast to classical inhibitors which generally possess a 17-33 times lower affinity for bCA IV. This greater selectivity toward bCA IV is due mainly to a slightly decreased potency against hCA II relative to classical inhibitors. However, metal complexes of these Schiff bases possessed an increased affinity for hCA II, being less inhibitory against bCA IV. The first type of compounds reported here (i.e., the Schiff bases of aromatic sulfonamides with heterocyclic aldehydes) might thus lead to the development of low molecular weight isozyme specific CA IV inhibitors. The difference in affinity for the three isozymes of the inhibitors reported by us here is tentatively explained on the basis of recent X-ray crystallographic studies of these isozymes and their adducts with substratesiinhibitors     

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.     

Carbonic anhydrase inhibitors: Inhibition of the tumor-associated isozymes IX and XII with polyfluorinated aromatic/heterocyclic sulfonamides

The tumor-associated transmembrane carbonic anhydrase (CA, EC 4.2.1.1) isozymes IX (CA IX) and XII (CA XII) are involved in acidification of hypoxic tumors, a process correlated with poor prognosis and clinical outcome of patients harboring such tumors. This process may be reversed by inhibiting these enzymes with potent sulfonamide/sulfamate inhibitors. A series of such aromatic/heterocyclic sulfonamides incorporating 2,3,5,6-tetrafluorobenzoyl-, 2,3,5,6-tetrafluoro- phenylsulfonyl- and pentafluorophenylureido moieties has been investigated for its interaction with the catalytic domain of the human isozymes hCA IX and hCA XII. Some of these compounds showed excellent inhibitory properties against both isozymes IX and XII, with several subnanomolar inhibitors detected for the first time. These sulfonamides may constitute valuable candidates for the development of novel antitumor therapies based on the inhibition of such tumor-associated CA isozymes.     

Carbonic anhydrase inhibitors: Inhibition of the tumor-associated isozymes IX and XII with polyfluorinated aromatic/heterocyclic sulfonamides

The tumor-associated transmembrane carbonic anhydrase (CA, EC 4.2.1.1) isozymes IX (CA IX) and XII (CA XII) are involved in acidification of hypoxic tumors, a process correlated with poor prognosis and clinical outcome of patients harboring such tumors. This process may be reversed by inhibiting these enzymes with potent sulfonamide/sulfamate inhibitors. A series of such aromatic/heterocyclic sulfonamides incorporating 2,3,5,6-tetrafluorobenzoyl-, 2,3,5,6-tetrafluorophenylsulfonyl- and pentafluorophenylureido moieties has been investigated for its interaction with the catalytic domain of the human isozymes hCA IX and hCA XII. Some of these compounds showed excellent inhibitory properties against both isozymes IX and XII, with several subnanomolar inhibitors detected for the first time. These sulfonamides may constitute valuable candidates for the development of novel antitumor therapies based on the inhibition of such tumor-associated CA isozymes.     

Carbonic Anhydrase Inhibitors. Inhibition of Cytosolic Isozymes I and II and Transmembrane,Cancer-associated Isozyme IX with Lipophilic Sulfonamides

A series of new compounds was obtained by reaction of aromatic/heterocyclic sulfonamides incorporating amino groups with N,N-diphenylcarbamoyl chloride and diphenylacetyl chloride. These sulfonamides were assayed for the inhibition of three carbonic anhydrase (CA, EC 4.2.1.1) isozymes: the cytosolic CA I and CA II, and the transmembrane, cancer-associated isozyme CA IX. Good inhibitors against all these isoforms were detected, and the inhibition profile of the newly investigated isozyme IX was observed to be different from that of the cytosolic isozymes, I and II. This may lead to the development of novel anticancer therapies based on the selective inhibition of CA IX.     

Review Article

Carbonic anhydrases (CAs, EC 4.2.1.1) are wide-spread enzymes, present in mammals in at least 14 different isoforms. Some of these isozymes are cytosolic (CA I, CA II, CA III, CA VII, CA XIII), others are membrane-bound (CA IV, CA IX, CA XII and CA XIV), CA V is mitochondrial and CA VI is secreted in the saliva and milk. Three cytosolic acatalytic forms are also known (CARP VIII, CARP X and CARP XI). The catalytically active isoforms, which play important physiological and patho-physiological functions, are strongly inhibited by aromatic and heterocyclic sulfonamides. The catalytic and inhibition mechanisms of these enzymes are understood in great detail, and this greatly helped the design of potent inhibitors, some of which possess important clinical applications. The use of such CA inhibitors (CAIs) as antiglaucoma drugs are discussed in detail, together with the recent developments that led to isozyme-specific and organ-selective inhibitors. A recent discovery is connected with the involvement of CAs and their sulfonamide inhibitors in cancer: many potent CAIs were shown to inhibit the growth of several tumor cell lines in vitro and in vivo, thus constituting interesting leads for developing novel antitumor therapies. Future prospects for drug design of inhibitors of these ubiquitous enzymes are dealt with. Although activation of CAs has been a controversial issue for some time, recent kinetic, spectroscopic and X-ray crystallographic experiments offered an explanation of this phenomenon, based on the catalytic mechanism. It has been demonstrated recently, that molecules that act as carbonic anhydrase activators (CAAs) bind at the entrance of the enzyme active site participating in facilitated proton transfer processes between the active site and the reaction medium. In addition to CA II-activator adducts, X-ray crystallographic studies have been also reported for ternary complexes of this isozyme with activators and anion (azide) inhibitors. Structure-activity correlations for diverse classes of activators is discussed for the isozymes for which the phenomenon has been studied, i.e, CA I, II, III and IV. The possible physiological relevance of CA activation/inhibition is also addressed, together with recent pharmacological/biomedical applications of such compounds in different fields of life sciences.     

Pyrazolo[4,3-e][1,2,4]triazine sulfonamides as carbonic anhydrase inhibitors with antitumor activity

A series of sildenafil analogues and aniline substituted pyrazolo[4,3-e][1,2,4]triazine sulfonamides were prepared and evaluated as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors and for their anticancer activity against two human breast cancer cell lines (MCF-7, MDA-MB-231). The new compounds were ineffective as CA I inhibitors, poorly inhibited CA II, but were more effective against the tumor-associated isoforms CA IX and XII, with some compounds acting as low nanomolar inhibitors. Evaluation of the cytotoxicity by using an MTT assay, the inhibition of [³H]thymidine incorporation into DNA as well as collagen synthesis inhibition, demonstrated that these sulfonamides exhibit cytotoxic effects on breast cancer cell lines ex vivo.     

Carbonic anhydrase inhibitors: synthesis and inhibition of cytosolic/tumor-associated carbonic anhydrase isozymes I, II, and IX with sulfonamides incorporating thioureido-sulfanilyl scaffolds

The tumor-associated transmembrane carbonic anhydrase (CA, EC 4.2.1.1) isozyme IX (CA IX) is overexpressed in hypoxic tumors and appears to be involved in acidification of the tumor microenvironment, a process correlated with cancer progression and bad prognosis. The acidification may be reduced by inhibiting the enzyme with potent sulfonamide/sulfamate CA inhibitors. A series of such aromatic sulfonamides incorporating thioureido-sulfanilyl moieties has been prepared and investigated for its interaction with the catalytic domain of the human isozyme hCA IX. The key intermediates in the synthesis were obtained by reacting sulfanilamide, homosulfanilamide, or 4-aminoethylbenzenesulfonamide with 4-acetamido-benzenesulfonyl chloride followed by deacetylation and reaction with thiophosgene. The obtained isothiocyanato sulfonamides were reacted with aliphatic or aromatic primary amines or hydrazines, leading to the corresponding thioureas. Some of these compounds showed excellent inhibitory properties against isozymes I, II, and IX, with several inhibitors also presenting selectivity for the inhibition of CA IX over that of the ubiquitous isozyme CA II. Such sulfonamides may constitute interesting candidates for the development of novel antitumor therapies based on the inhibition of the CA isozymes overexpressed in hypoxic tumors. Due to the highest expression of CA IX in clear renal cell carcinoma and its chemo/radioresistance, our efforts are first of all directed to generate effective therapeutic strategies for the cure of this malignancy.     

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 anhydrases: current state of the art, therapeutic applications and future prospects

Carbonic anhydrases (CAs, EC 4.2.1.1) are wide-spread enzymes, present in mammals in at least 14 different isoforms. Some of these isozymes are cytosolic (CA I, CA II, CA III, CA VII, CA XIII), others are membrane-bound (CA IV, CA IX, CA XII and CA XIV), CA V is mitochondrial and CA VI is secreted in the saliva and milk. Three cytosolic acatalytic forms are also known (CARP VIII, CARP X and CARP XI). The catalytically active isoforms, which play important physiological and patho-physiological functions, are strongly inhibited by aromatic and heterocyclic sulfonamides. The catalytic and inhibition mechanisms of these enzymes are understood in great detail, and this greatly helped the design of potent inhibitors, some of which possess important clinical applications. The use of such CA inhibitors (CAIs) as antiglaucoma drugs are discussed in detail, together with the recent developments that led to isozyme-specific and organ-selective inhibitors. A recent discovery is connected with the involvement of CAs and their sulfonamide inhibitors in cancer: many potent CAIs were shown to inhibit the growth of several tumor cell lines in vitro and in vivo, thus constituting interesting leads for developing novel antitumor therapies. Future prospects for drug design of inhibitors of these ubiquitous enzymes are dealt with. Although activation of CAs has been a controversial issue for some time, recent kinetic, spectroscopic and X-ray crystallographic experiments offered an explanation of this phenomenon, based on the catalytic mechanism. It has been demonstrated recently, that molecules that act as carbonic anhydrase activators (CAAs) bind at the entrance of the enzyme active site participating in facilitated proton transfer processes between the active site and the reaction medium. In addition to CA II-activator adducts, X-ray crystallographic studies have been also reported for ternary complexes of this isozyme with activators and anion (azide) inhibitors. Structure-activity correlations for diverse classes of activators is discussed for the isozymes for which the phenomenon has been studied, i.e., CA I, II, III and IV. The possible physiological relevance of CA activation/inhibition is also addressed, together with recent pharmacological/ biomedical applications of such compounds in different fields of life sciences.     

Carbonic Anhydrase Inhibitors: Inhibition of Isozymes I,II and IV by Sulfamide and Sulfamic Acid Derivatives

Abstract

Sulfamide and sulfamic acid are the simplest compounds containing the SO₂NH₂ moiety, responsible for binding to the Zn(II) ion within carbonic anhydrase (CA, EC 4.2.1.1) active site, and thus acting as inhibitors of the many CA isozymes presently known. Here we describe two novel classes of CA inhibitors obtained by derivatizations of the lead molecules mentioned above. The new compounds, possessing the general formula RSO₂NH-SO₂X (X = OH, NH₂), were obtained by reaction of sulfamide or sulfamic acid with alkyl/arylsulfonyl halides or aryl-sulfonyl isocyanates. A smaller series of derivatives has been obtained by reaction of aromatic aldehydes with sulfamide, leading to Schiff bases of the type ArCH=NSO₂NH₂. All the new compounds act as strong inhibitors of isozymes I, II and IV of carbonic anhydrase. Their mechanism of CA inhibition is also discussed based on electronic spectroscopic measurements on adducts with the Co(II)-substituted enzyme. These experiments led to the conclusion that the new inhibitors are directly coordinated (in a monodentate manner) to the metal ion within the enzyme active site, similarly to the classical inhibitors, the aromatic/heterocyclic sulfonamides.     

Carbonic Anhydrase Inhibitors Induce Developmental Toxicity During Zebrafish Embryogenesis,Especially in the Inner Ear

In vertebrates, carbonic anhydrases (CAs) play important roles in ion transport and pH regulation in many organs, including the eyes, kidneys, central nervous system, and inner ear. In aquatic organisms, the enzyme is inhibited by various chemicals present in the environment, such as heavy metals, pesticides, and pharmaceuticals. In this study, the effects of CA inhibitors, i.e., sulfonamides [ethoxyzolamide (EZA), acetazolamide (AZA), and dorzolamide (DZA)], on zebrafish embryogenesis were investigated. In embryos treated with the sulfonamides, abnormal development, such as smaller otoliths, an enlarged heart, an irregular pectoral fin, and aberrant swimming behavior, was observed. Especially, the development of otoliths and locomotor activity was severely affected by all the sulfonamides, and EZA was a consistently stronger inhibitor than AZA or DZA. In the embryos treated with EZA, inner ear hair cells containing several CA isoforms, which provide HCO₃ ^? to the endolymph for otolith calcification and maintain an appropriate pH there, were affected. Acridine orange/ethidium bromide staining indicated that the hair cell damage in the inner ear and pectral fin is due to apoptosis. Moreover, RNA measurement demonstrated that altered gene expression of cell cycle arrest- and apoptosis-related proteins p53, p21, p27, and Bcl-2 occurred even at 0.08 ppm with which normal development was observed. This finding suggests that a low concentration of EZA may affect embryogenesis via the apoptosis pathway. Thus, our findings demonstrated the importance of potential risk assessment of CA inhibition, especially regarding the formation of otoliths as a one of the most sensitive organs in embryogenesis.     

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. 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: 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.     

Attachment of carbohydrates to methoxyaryl moieties leads to highly selective inhibitors of the cancer associated carbonic anhydrase isoforms IX and XII

The transmembrane isoforms of carbonic anhydrase (hCA IX and XII) have been shown to be linked to carcinogenesis and their inhibition to arrest primary tumor and metastases growth. In this paper, we present a new class of C-glycosides incorporating the methoxyaryl moiety, that was designed to selectively target and inhibit the extracellular domains of the cancer-relevant CA isozymes. The glycosides have been prepared by aldol reaction of glycosyl ketones with the appropriate aromatic aldehydes. We also present the inhibition profile of our new glycomimetics, against four isozymes of carbonic anhydrase comprising hCAs I and II (cytosolic, ubiquitous isozymes) and hCAs IX and XII (tumor associated isozymes). In this study, per-O-acetylated glycoside 4, 6 and deprotected compounds 7, 9, 10 and 12 were identified as potent and highly selective inhibitors of hCA IX and XII. These results confirm that attaching carbohydrate moieties to CA methoxyaryl pharmacophore improves and enhances its inhibitory activity. These CA inhibitors have developmental potential to selectively target cancer cells, leading to cell death.