Anticonvulsant/antiepileptic carbonic anhydrase inhibitors: a patent review

Monothiocarbamates Strongly Inhibit Carbonic Anhydrases in Vitro and Possess Intraocular Pressure Lowering Activity in an Animal Model of Glaucoma

A series of monothiocarbamates (MTCs) were prepared from primary/secondary amines and COS as potential carbonic anhydrase (CA, EC 4.2.1.1) inhibitors, using the dithiocarbamates, the xanthates, and the trithiocarbonates as lead compounds. The MTCs effectively inhibited the pharmacologically relevant human (h) hCAs isoforms I, II, IX, and XII in vitro and showed KIs spanning between the low and medium nanomolar range. By means of a computational study, the MTC moiety binding mode on the CAs was explained. Furthermore, a selection of MTCs were evaluated in a normotensive glaucoma rabbit model for their intraocular pressure (IOP) lowering effects and showed interesting activity.

Mutations in the Na(+)/citrate cotransporter NaCT (SLC13A5) in pediatric patients with epilepsy and developmental delay

Mutations in the SLC13A5 gene that codes for the Na(+)/citrate cotransporter, NaCT, are associated with early onset epilepsy, developmental delay and tooth dysplasia in children. In the present study we identify additional SLC13A5 mutations in nine epilepsy patients from six families. To better characterize the syndrome, families with affected children answered questions about the scope of illness and treatment strategies. There are currently no effective treatments, but some anti-epileptic drugs targeting the GABA system reduce seizure frequency. Acetazolamide, a carbonic anhydrase inhibitor and atypical anti-seizure medication decreases seizures in 4 patients. In contrast to previous reports, the ketogenic diet and fasting produce worsening of symptoms. The effects of the mutations on NaCT transport function and protein expression were examined by transient transfections of COS-7 cells. There was no transport activity from any of the mutant transporters, although some of the mutant transporter proteins were present on the plasma membrane. The structural model of NaCT suggests that these mutations can affect helix packing or substrate binding. We tested various treatments, including chemical chaperones and low temperatures, but none improve transport function in the NaCT mutants. Interestingly, coexpression of NaCT and the mutants results in decreased protein expression and activity of the wild-type transporter, indicating functional interaction. In conclusion, our study has identified additional SLC13A5 mutations in patients with chronic epilepsy starting in the neonatal period, with the mutations producing inactive Na(+)/citrate transporters.

Emerging roles of Na⁺/H⁺ exchangers in epilepsy and developmental brain disorders

Epilepsy is a common central nervous system (CNS) disease characterized by recurrent transient neurological events occurring due to abnormally excessive or synchronous neuronal activity in the brain. The CNS is affected by systemic acid-base disorders, and epileptic seizures are sensitive indicators of underlying imbalances in cellular pH regulation. Na(+)/H(+) exchangers (NHEs) are a family of membrane transporter proteins actively involved in regulating intracellular and organellar pH by extruding H(+) in exchange for Na(+) influx. Altering NHE function significantly influences neuronal excitability and plays a role in epilepsy. This review gives an overview of pH regulatory mechanisms in the brain with a special focus on the NHE family and the relationship between epilepsy and dysfunction of NHE isoforms. We first discuss how cells translocate acids and bases across the membrane and establish pH homeostasis as a result of the concerted effort of enzymes and ion transporters. We focus on the specific roles of the NHE family by detailing how the loss of NHE1 in two NHE mutant mice results in enhanced neuronal excitability in these animals. Furthermore, we highlight new findings on the link between mutations of NHE6 and NHE9 and developmental brain disorders including epilepsy, autism, and attention deficit hyperactivity disorder (ADHD). These studies demonstrate the importance of NHE proteins in maintaining H(+) homeostasis and their intricate roles in the regulation of neuronal function. A better understanding of the mechanisms underlying NHE1, 6, and 9 dysfunctions in epilepsy formation may advance the development of new epilepsy treatment strategies.

Sulfonamide inhibition studies of the α-carbonic anhydrase from the gammaproteobacterium Thiomicrospira crunogena XCL-2, TcruCA

We report a sulfonamide/sulfamate inhibition study of the α-carbonic anhydrase (CA, EC 4.2.1.1) present in the gammaproteobacterium Thiomicrospira crunogena XCL-2, a mesophilic hydrothermal vent-isolate organism, TcruCA. As Thiomicrospira crunogena is one of thousands of marine organisms that uses CA for metabolic regulation, the effect of sulfonamide inhibition has been considered. Sulfonamide-based drugs have been widely used in a variety of antibiotics, and bioelimination of these compounds results in exposure of these compounds to marine life. The enzyme was highly inhibited, with Ki values ranging from 2.5 to 40.7nM by a variety of sulfonamides including acetazolamide, methazolamide, ethoxzolamide, dichlorophenamide, dorzolamide, brinzolamide, benzolamide and benzenesulfonamides incorporating 4-hydroxyalkyl moieties. Less effective inhibitors were topiramate, zonisamide, celecoxib, saccharin and hydrochlorothiazide as well as simple benzenesulfonamides incorporating amino, halogeno, alkyl, aminoalkyl and other moieties in the ortho- or para-positions of the aromatic ring (Kis of 202-933nM). The active site interactions between TcruCA and three clinically-used CA inhibitors, acetazolamide (Diamox®), dorzolamide (Trusopt®), and brinzolamide (Azopt®) are studied using molecular docking to provide insight into the reported Ki values. Comparison between various enzymes belonging to this family may also bring interesting hints in these fascinating phenomena.

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.

Acetazolamide in vestibular migraine prophylaxis: a retrospective study

The aim of this study is to check the efficacy of acetazolamide in the prophylaxis of vestibular migraine (VM). Treatment options in VM are mainly based on migraine guidelines. We tried to assess the efficacy of acetazolamide in these patients depending on clinical similarities with episodic ataxia type 2 and familial hemiplegic migraine responding to the drug. This is a retrospective cohort study. Among 50 patients with VM and prescribed acetazolamide 500 mg/day, 39 patients were studied as five had been lost on follow-up and six had stopped taking the drug due to side effects. Vertigo and headache frequency determined by number of attacks per month, and the severity determined by visual analog scales measured in centimeters from 0 to 10 were collected from the records. Initial reported figures for frequency and severity were compared with the results gathered after 3 months of treatment. The results were compared. Acetazolamide was effective in reducing both the frequency and severity of vertigo and headache attacks and this effect was more prominent for vertigo frequency and severity.

Benzenesulfonamides incorporating bulky aromatic/heterocyclic tails with potent carbonic anhydrase inhibitory activity

Three series of sulfonamides incorporating long, bulky tails were obtained by applying synthetic strategies in which substituted anthranilic acids, quinazolines and aromatic sulfonamides have been used as starting materials. They incorporate long, bulky diamide-, 4-oxoquinazoline-3-yl- or quinazoline-4-yl moieties in their molecules, and were investigated for the inhibition of four physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isoforms, the cytosolic human (h) hCA I and II, as well as the transmembrane hCA IX and XII. Most of the new sulfonamides showed excellent inhibitory effects against the four isoforms, with KIs of 7.6-322nM against hCA I, of 0.06-85.4nM against hCA II; of 6.7-152nM against hCA IX and of 0.49-237nM against hCA XII; respectively. However no relevant isoform-selective behavior has been observed for any of them, although hCA II and XII, isoforms involved in glaucoma-genesis were the most inhibited ones. The structure-activity relationship for inhibiting the four CAs with these derivatives is discussed in detail.

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.

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.

Inhibition of mammalian carbonic anhydrase isoforms I-XIV with a series of phenolic acid esters

A series of phenolic acid esters incorporating caffeic, ferulic, and p-coumaric acid, and benzyl, m/p-hydroxyphenethyl- as well as p-hydroxy-phenethoxy-phenethyl moieties were investigated for their inhibitory effects against the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). Many of the mammalian isozymes of human (h) or murine (m) origin, hCA I-hCA XII, mCA XIII and hCA XIV, were inhibited in the submicromolar range by these derivatives (with KIs of 0.31-1.03 μM against hCA VA, VB, VI, VII, IX and XIV). The off-target, highly abundant isoforms hCA I and II, as well as hCA III, IV and XII were poorly inhibited by many of these esters, although the original phenolic acids were micromolar inhibitors. These phenols, like others investigated earlier, possess a CA inhibition mechanism distinct of the sulfonamides/sulfamates, clinically used drugs for the treatment of a multitude of pathologies, but with severe side effects due to hCA I/II inhibition. Unlike the sulfonamides, which bind to the catalytic zinc ion, phenols are anchored at the Zn(II)-coordinated water molecule, binding more externally within the active site cavity, and making contacts with amino acid residues at the entrance of the active site. As this is the region with the highest variability between the many CA isozymes found in mammals, this class of compounds shows isoform-selective inhibitory profiles, which may be exploited for obtaining pharmacological agents with less side effects compared to other classes of inhibitors.

Poly(amidoamine) dendrimers show carbonic anhydrase inhibitory activity against α-, β-, γ- and η-class enzymes

Four generations of poly(amidoamine) (PAMAM) dendrimers incorporating benzenesulfonamide moieties were investigated as inhibitors of carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the α-, β-, γ- and η-classes which are present in pathogenic bacteria, fungi or protozoa. The following bacterial, fungal and protozoan organisms were included in the study: Vibrio cholerae, Trypanosoma cruzi, Leishmania donovani chagasi, Porphyromonas gingivalis, Cryptococcus neoformans, Candida glabrata, and Plasmodium falciparum. The eight pathozymes present in these organisms were efficiently inhibited by the four generations PAMAM-sulfonamide dendrimers, but multivalency effects were highly variable among the different enzyme classes. The Vibrio enzyme VchCA was best inhibited by the G3 dendrimer incorporating 32 sulfamoyl moieties. The Trypanosoma enzyme TcCA on the other hand was best inhibited by the first generation dendrimer G0 (with 4 sulfamoyl groups), whereas for other enzymes the optimal inhibitory power was observed for the G1 or G2 dendrimers, with 8 and 16 sulfonamide functionalities. This study thus proves that the multivalency may be highly relevant for enzyme inhibition for some but not all CAs from pathogenic organisms. On the other hand, some dendrimers investigated here showed a better inhibitory power compared to acetazolamide for enzymes from widespread pathogens, such as the η-CA from Plasmodium falciparum. Overall, the main conclusion is that this class of molecules may lead to important developments in the field of anti-infective CA inhibitors.

Levetiracetam in the Treatment of Epileptic Seizures After Liver Transplantation

After liver transplantation, patients may develop seizures or epilepsy due to a variety of etiologies. The ideal antiepileptic drugs for these patients are those with fewer drug interactions and less hepatic toxicity. In this study, we present patients using levetiracetam to control seizures after liver transplantation. We retrospectively enrolled patients who received levetiracetam for seizure control after liver transplantation. We analyzed the etiology of liver failure that required liver transplantation, etiology of the seizures, outcomes of seizure control, and the condition of the patient after follow-up at the outpatient department. Hematological and biochemical data before and after the use of levetiracetam were also collected. Fifteen patients who received intravenous or oral levetiracetam monotherapy for seizure control after liver transplantation were enrolled into this study. All of the patients remained seizure-free during levetiracetam treatment. Two patients died during the follow-up, and the other 13 patients were alive at the end of the study period and all were seizure-free without neurological sequelae that interfered with their daily activities. No patients experienced liver failure or rejection of the donor liver due to ineffective immunosuppressant medications. The dosage of immunosuppressants did not change before and after levetiracetam treatment, and there were no changes in hematological and biochemical data before and after treatment. Levetiracetam may be a suitable antiepileptic drug for patients who undergo liver transplantation due to fewer drug interactions and a favorable safety profile.

Synthesis, biological evaluation, and docking studies of novel thiourea derivatives of bisindolylmethane as carbonic anhydrase II inhibitor

This article describes discovery of 29 novel bisindolylmethanes consisting of thiourea moiety, which had been synthesized through three steps. These novel bisindolylmethane derivatives evaluated for their potential inhibitory activity against carbonic anhydrase (CA) II. The results for in vitro assay of carbonic anhydrase II inhibition activity showed that some of the compounds are capable of suppressing the activity of carbonic anhydrase II. Bisindoles having halogen at fifth position showed better inhibitory activity as compared to unsubstituted bisindoles. Derivatives showing inhibition activity docked to further, understand the binding behavior of these compounds with carbonic anhydrase II. Docking studies for the active compound 3j showed that nitro substituent at para position fits into the core of the active site. The nitro substituent of compound 3j is capable of interacting with Zn ion. This interaction believed to be the main factor causing inhibition activity to take place.

Inhibition studies of new ureido-substituted sulfonamides incorporating a GABA moiety against human carbonic anhydrase isoforms I-XIV

Reaction of γ-Boc-GABA, prepared by protecting the γ-amino moiety of the amino butyric acid with the tert-butyloxycarbonyl (Boc) protecting group, with 4-methyl/ethyl benzenesulfonamide, followed by removal of the Boc protecting group in 3 M HCl afforded the corresponding hydrochlorides, which were further derivatized by reaction with a varying of aryl isocyanates to give a new classes of ureido substituted benzenesulfonamide containing a GABA moiety. Inhibition studies of the human carbonic anhydrase(CA, EC 4.2.1.1) isoforms, CA I–XIV with these new compounds revealed that they possess moderate-weak inhibition potency against hCA III, IV, VA, VI and XIII, rather efficient inhibitory power against hCA I, VI, and IX, and excellent inhibition of the physiologically relevant hCA II and VII, as well as of the two tumor-associated isoforms CA IX and XII. The inhibition profile of the new ureido-substituted benzenesulfonamides reported here is thus very different from the corresponding ureido-substituted analogs incorporating sulfanilamide, which were previously investigated as inhibitors of some of these enzymes.

Synthesis of sulfonamides incorporating piperazinyl-ureido moieties and their carbonic anhydrase I, II, IX and XII inhibitory activity

By using SLC-0111 (4-fluorophenylureido-benzenesulfonamide), a sulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitor in Phase I clinical trials as an antitumor agent as lead molecule, a series of benzenesulfonamide derivatives incorporating ureido moieties was synthesized. The new compounds contain a 4-N-substituted piperazine fragment in which the ureido linker has been included, and were tested as inhibitors of the cytosolic human (h) hCA I and II isoforms, as well as the transmembrane, tumor-associated enzymes hCA IX and XII. Depending on the substitution pattern at the piperazine ring, low nanomolar inhibitors were detected against all four isoforms, making the new class of sulfonamides of interest for various pharmacologic applications.

Discovery of novel isatin-based sulfonamides with potent and selective inhibition of the tumor-associated carbonic anhydrase isoforms IX and XII

A series of 2/3/4-[(2-oxo-1,2-dihydro-3H-indol-3-ylidene)amino]benzenesulfonamides, obtained from substituted isatins and 2-, 3- or 4-aminobenzenesulfonamide, showed low nanomolar inhibitory activity against the tumor associated carbonic anhydrase (CA, EC 4.2.1.1) isoforms IX and XII - recently validated antitumor drug targets, being much less effective as inhibitors of the off-target cytosolic isoforms CA I and II.

Dendrimers incorporating benzenesulfonamide moieties strongly inhibit carbonic anhydrase isoforms I-XIV

As extension of our previous study herein we report a comprehensive investigation of poly(amidoamine) (PAMAM) dendrimers as modulators of the human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms I-XIV. Interestingly inhibitory activity was observed for the non-functionalized dendrimers against the hCA I, VII, IX, XII and XIV isoforms, whereas activation properties were reported only for the cytosolic abundant hCA II. Highly efficient inhibitory action against many isoforms having medicinal chemistry applications, such as hCA II, V, VII, IX, XII and XIV, was observed for the PAMAM functionalized counterparts bearing 4, 8, 16 and 32 benzenesulfonamide moieties. Possible applications of dendrimer-CA inhibitors as therapeutic/diagnostic agents are envisaged.

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.

Design and synthesis of benzothiazole-6-sulfonamides acting as highly potent inhibitors of carbonic anhydrase isoforms I, II, IX and XII

A series of novel 2-aminobenzothiazole derivatives bearing sulfonamide at position 6 was designed, synthesized and investigated as inhibitors of four isoforms of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1), the cytosolic CA I and II, and the tumor-associated isozymes CA IX and XII. Docking and binding energy studies were carried out to reveal details regarding the favorable interactions between the scaffolds of these new inhibitors and the active sites of the investigated CA isoforms. Most of the novel compounds were acting as highly potent inhibitors of the tumor-associated hCA IX and hCA XII with KIs in the nanomolar range. The ubiquitous and dominant rapid cytosolic isozyme hCA II was also inhibited with KIs ranging from 3.5 to 45.4 nM. The favorable interactions between some of the new compounds and the active site of different CA isoforms were delineated by using molecular docking which may be useful for designing compounds with high affinity and selectivity for some CAs with biomedical applications.

Poly(amidoamine) Dendrimers with Carbonic Anhydrase Inhibitory Activity and Antiglaucoma Action

Four generations of poly(amidoamine) (PAMAM) dendrimers decorated with benzenesulfonamide moieties were prepared by derivatizing the amino groups of the dendrimer with 4-carboxy-benzenesulfonamide functionalities. Compounds incorporating 4, 8, 16, and 32 sulfonamide moieties were thus obtained, which showed an increasing carbonic anhydrase (CA, EC 4.2.1.1) inhibitory action with the increase of the number of sulfamoyl groups in the dendrimer. Best inhibitory activity (in the low nanomolar-subnanomolar range) was observed for isoforms CA II and XII, involved among others in glaucoma. In an animal model of this disease, the chronic administration of such dendrimers for 5 days led to a much more efficient drop of intraocular pressure compared to the standard drug dorzolamide.

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.

Sulfonamides and their isosters as carbonic anhydrase inhibitors

Molecules containing the sulfonamide group (R-SO2NH2) as well as its structurally related isosters, sulfamido (R-NH-SO2NH2) and sulfamato (R-O-SO2NH2), constitute the most important class of inhibitors acting on the metalloenzyme carbonic anhydrase (EC 4.2.1.1). Despite their presence in the literature, in general the reports lack of a clear and organic overview linking the main structural features of the clinically used inhibitors with the therapeutic aspects. The current review is intended to highlight the structural basis of the interactions of sulfonamide-like groups within the active site of the carbonic anhydrases and will summarize the clinical use of the most interesting molecules for the treatment of relevant pathologies, such as glaucoma, obesity, cancer and CNS-affecting diseases.

A class of sulfonamide carbonic anhydrase inhibitors with neuropathic pain modulating effects

A series of benzene sulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitors which incorporate lipophilic 4-alkoxy- and 4-aryloxy moieties, together with several derivatives of ethoxzolamide and sulfanilamide are reported. These derivatives were investigated as inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) of which multiple isoforms are known, and some appear to be involved in pain. These sulfonamides showed modest inhibition against the cytosolic isoform CA I, but were generally effective, low nanomolar CA II, VII, IX and XII inhibitors. X-ray crystallographic data for the adduct of several such sulfonamides with CA II allowed us to rationalize the good inhibition data. In a mice model of neuropathic pain induced by oxaliplatin, one of the strong CA II/VII inhibitors reported here induced a long lasting pain relieving effect, a fact never observed earlier. This is the first report of rationally designed sulfonamide CA inhibitors with pain effective modulating effects.

X-ray crystallographic and kinetic investigations of 6-sulfamoyl-saccharin as a carbonic anhydrase inhibitor

Sulfamoylated saccharin binds to human carbonic anhydrase II through the SO₂NH₂and not CONHSO₂moiety.

A class of 4-sulfamoylphenyl-ω-aminoalkyl ethers with effective carbonic anhydrase inhibitory action and antiglaucoma effects

We report a series of 4-sulfamoylphenyl-ω-aminoalkyl ethers as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. The structure–activity relationship was drawn for the inhibition of four physiologically relevant isoforms: hCA I, II, IX, and XII. Many of these compounds were highly effective, low nanomolar inhibitors of all CA isoforms, whereas several isoform-selective were also identified. X-ray crystal structures of two new sulfonamides bound to the physiologically dominant CA II isoform showed the tails of these derivatives bound within the hydrophobic half of the enzyme active site through van der Waals contacts with Val135, Leu198, Leu204, Trp209, Pro201, and Pro202 amino acids. One of the highly water-soluble compound (as trifluoroacetate salt) showed effective IOP lowering properties in an animal model of glaucoma. Several fluorescent sulfonamides incorporating either the fluorescein-thiourea (7a–c) or tetramethylrhodamine-thiourea (9a,b) moieties were also obtained and showed interesting CA inhibitory properties for the tumor-associated isoforms CA IX and XII.

The effects of anti-epileptic drugs on human erythrocyte carbonic anhydrase I and II isozymes

Carbonic anhydrase (CA) is an enzyme which plays a role in various homeostatic mechanisms, such as acid-base balance and electrolyte secretion in a various tissues. This study was aimed at determining and comparing possible alterations in activity of this enzyme caused by the use of old (Carbamazepine, Phenytoin Sodium, Sodium Valproate) and new (Levetiracetam, Pregabalin, Gabapentin, Oxcarbazepine) anti-epileptic drugs. Blood samples were collected from the volunteers. The blood samples were centrifuged to separate plasma and erythrocyte package. Hemolysate was prepared from the red cells. CA I and II were purified from human erythrocytes by a simple one step procedure using Sepharose 4B-L-tyrosine-sulfonamide affinity column. CA I and II isozymes were treated with some anti-epileptic drugs, then the inhibition or activation of enzyme determined. The results of this study show that Levetiracetam is the most effective inhibitor for human erythrocytes carbonic anhydrase compared with the other anti-epileptic drugs.

Carbonic anhydrase inhibitors: synthesis and inhibition of the human carbonic anhydrase isoforms I, II, IX and XII with benzene sulfonamides incorporating 4- and 3-nitrophthalimide moieties

A series of 4 and 5 nitro-1,3-dioxoisoindolin-2-yl benzenesulfonamide derivatives (compounds 1-8) was synthesized by reaction of benzenesulfonamide derivatives with 4 and 3-nitrophthalic anhydrides. These new sulfonamides were investigated as inhibitors of the zinc metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) and more specifically against the human (h) cytosolic isoforms hCA I and II and the transmembrane, tumor-associated hCA IX and XII. Most of the novel compounds were medium potency-weak hCA I inhibitors (Kis in the range of 295-10,000 nM), but were more effective hCA II inhibitors (Kis of 1.7-887 nM). The tumor-associated hCA IX was also inhibited, with Kis in the micromolar range, whereas against hCA XII the inhibition constants were in the range of 90-3,746 nM. The structure-activity relationship (SAR) with this series of sulfonamides is straightforward, with the main features leading to good activity for each isoforms being established. The high sequence hCA alignment homology and molecular docking studies was performed in order to rationalize the activities reported and binding mode to different hCA as inhibitors.

[How do antiepileptic drugs work?]

BACKGROUND

There are currently around 25 antiepileptic drugs in use in Norway, of which 15 have entered the market in the last 20 years. All have somewhat different effect- and adverse effect profiles and mechanisms of action. Here we present a brief overview of current knowledge regarding the basic mechanisms of action of these drugs.

METHOD

The review is based on a discretionary selection of relevant articles found through a literature search in PubMed and our own clinical and research experience.

RESULTS

There are, roughly speaking, four main mechanisms; 1) modulation of ion channels (sodium and calcium channel blockers, potassium channel openers), 2) potentiation of GABAergic inhibition, 3) reduction of glutamatergic excitation and 4) modulation of presynaptic neurotransmitter release. Some of the drugs have several mechanisms of action, and for some of them it is unclear which mechanism is clinically most important. To some extent, the drugs' mechanisms of action predict their effect against different types of epilepsy and seizures. For instance, sodium channel blockers work best against focal seizures, while calcium channel blockers work best against absences, a type of generalised seizure.

INTERPRETATION

Optimal treatment of patients with epilepsy requires not only thorough knowledge of seizure- and epilepsy classification, but also insight into the mechanisms of action of antiepileptic drugs.

Structure-based screening for the discovery of new carbonic anhydrase VII inhibitors

Among the different mammalian isoforms of Carbonic Anhydrase, the hCA VII is mainly expressed in the brain where it is involved in several neurological diseases. Thereby hCA VII has been validated as an attractive target for the discovery of selective inhibitors for the treatment of epilepsy and neurological pain. To identify new chemical entities as carbonic anhydrase inhibitors (CAIs) targeting hCA VII, we used a structure-based approach. By means of LigandScout software we built pharmacophore models from crystal structures of two well-known CAIs in complex with hCA VII. A merged pharmacophore hypothesis has been obtained. Subsequently, a focused library of compounds was screened against pharmacophore model and the most interesting hits were docked into the crystal structure of hCA VII. As a result, we identified new compounds displaying significant CA inhibitory effects in the nanomolar range.

Structural study of the location of the phenyl tail of benzene sulfonamides and the effect on human carbonic anhydrase inhibition

The crystal structure of 4-phenylacetamidomethyl-benzenesulfonamide (4ITP) bound to human carbonic anhydrase (hCA, EC 4.2.1.1) II is reported. 4ITP is a medium potency hCA I and II inhibitor (KIs of 54-75nM), a strong mitochondrial CA VA/VB inhibitor (KIs of 8.3-8.6nM) and a weak transmembrane CA inhibitor (KIs of 136-212nM against hCA IX and XII). This elongated compound binds in an extended conformation to hCA II, with its tail lying towards the hydrophobic half of the active site whereas the sulfonamide moiety coordinates the zinc ion. The present structure was compared to that of structurally related aromatic sulfonamides, such as 4-phenylacetamido-benzene-sulfonamide (3OYS), 4-(2-mercaptophenylacetamido)-benzene-sulfonamide (2HD6) and 4-(3-nitrophenyl)-ureido-benzenesulfonamide (3N2P). Homology models of the hCA I, VA, VB, IX and XII structures were build which afforded an understanding of the amino acids involved in the binding of these compounds to these isoforms. The main conclusion of the study is that the orientation of the tail moiety and the presence of flexible linkers as well polar groups in it, strongly influence the potency and the selectivity of the sulfonamides for the inhibition of cytosolic, mitochondrial or transmembrane CA isoforms.