Seletracetam (UCB 44212)

A protocol for controlled reactivity shift in the 2,2-difluorovinyl motif used for selective S-18F and C-18F bond formation

Positron emission tomography (PET) is a powerful imaging technique for biomedical research, drug development and medical diagnosis. The power of PET lies in biochemically selective radiotracers, labelled with positron emitters like fluorine-18 image chemical processes in vivo. A rapid and remarkably efficient, unprecedented protocol to select between S-F and C-F bond formation based on activation of 1,1-difluoroethylene groups followed by selective oxidation or reduction is described. While transition metal mediated conditions can be employed, the reaction proceeds in high yield using unobjectionable chemical reagents amenable to routine radiotracer production. The latter bodes well for facile clinical translation of the method. The new technique affords radiotracers and the labelling reagent 2,2-difluoro-2-(fluoro-18F)ethyl 4-methylbenzenesulfonate ([18F]1b) in excellent yield. Following oxygenation of the reaction mixture with medical oxygen or air, sulfonyl fluorides are obtained as the primary product. The new protocol was employed in a proof of principle to develop a radiometric assay for quantitation of sulfonylation yield with sulfonyl fluoride reagents. With operational ease and mild conditions, the method bodes a high potential for radiolabelling of biomolecules, known enzyme inhibitors and other temperature-sensitive compounds.

Nickel-catalyzed electrophiles-controlled enantioselective reductive arylative cyclization and enantiospecific reductive alkylative cyclization of 1,6-enynes

Transition metal-catalyzed asymmetric cyclization of 1,6-enynes is a powerful tool for the construction of chiral nitrogen-containing heterocycles. Despite notable achievements, these transformations have been largely limited to the use of aryl or alkenyl metal reagents, and stereoselective or stereospecific alkylative cyclization of 1,6-enynes remains unexploited. Herein, we report Ni-catalyzed enantioselective reductive anti-arylative cyclization of 1,6-enynes with aryl iodides, providing enantioenriched six-membered carbo- and heterocycles in good yields with excellent enantioselectivities. Additionally, we have realized Ni-catalyzed enantiospecific reductive cis-alkylative cyclization of 1,6-enynes with alkyl bromides, furnishing chiral five-membered heterocycles with high regioselectivity and stereochemical fidelity. Mechanistic studies reveal that the arylative cyclization of 1,6-enynes is initiated by the oxidative addition of Ni(0) to aryl halides and the alkylative cyclization is triggered by the oxidative addition of Ni(0) to allylic acetates. The utility of this strategy is further demonstrated in the enantioselective synthesis of the antiepileptic drug Brivaracetam.

Copper-Catalyzed C-H (Phenylsulfonyl)difluoromethylation of Acrylamides: Scope, Mechanism, and Critical Role of Additives

Herein, we report the Cu-complex catalyzed, native functional group-assisted, and TFA/NMF additives promoted (phenylsulfonyl)difluoromethylation of vinylic C(sp2 )-H bond of acrylamides. Using our in-home designed reagent, this reaction enables the construction of the C(sp2 )-CF2 SO2 Ph bond from simple C-H bond activation by copper catalysis under mild reaction conditions with total Z-selectivity. The versatility of utilized fluorinated group was illustrated by its conversion into value-added CF2 moieties as well as the remarkable =CHF residue. The performed experimental and computational mechanistic studies enabled to identify the true nature of active catalyst and substrate, as well as establish critical roles of TFA and NMF additives. In this reaction, the TFA acts as a promoter of the much-needed CuII /CuII →CuIII /CuI disproportionation, while the NMF facilitates the following ligand exchange and C-C coupling processes. We ruled out the generation of radical intermediates and established the C-H activation to be irreversible and the rate-determining step of the entire process.

Levetiracetam Mechanisms of Action: From Molecules to Systems

Epilepsy is a chronic disease that affects millions of people worldwide. Antiepileptic drugs (AEDs) are used to control seizures. Even though parts of their mechanisms of action are known, there are still components that need to be studied. Therefore, the search for novel drugs, new molecular targets, and a better understanding of the mechanisms of action of existing drugs is still crucial. Levetiracetam (LEV) is an AED that has been shown to be effective in seizure control and is well-tolerable, with a novel mechanism of action through an interaction with the synaptic vesicle protein 2A (SV2A). Moreover, LEV has other molecular targets that involve calcium homeostasis, the GABAergic system, and AMPA receptors among others, that might be integrated into a single mechanism of action that could explain the antiepileptogenic, anti-inflammatory, neuroprotective, and antioxidant properties of LEV. This puts it as a possible multitarget drug with clinical applications other than for epilepsy. According to the above, the objective of this work was to carry out a comprehensive and integrative review of LEV in relation to its clinical uses, structural properties, therapeutical targets, and different molecular, genetic, and systemic action mechanisms in order to consider LEV as a candidate for drug repurposing.

C-H Electrophilic (phenylsulfonyl)difluoromethylation of (hetero)arenes with a newly designed reagent

The synthesis of an original electrophilic difluoromethylating reagent was successfully achieved upon a straightforward protocol (3 steps). Like a Swiss army knife, this bench-stable reagent allowed the functionalization of various classes of compounds under mild and transition metal-free conditions. Hence, an efficient and operationally simple tool for the construction of C(sp2)-, C(sp3)- and S-CF2SO2Ph bonds was provided, expanding the chemical space of PhSO2CF2-containing molecules. Late-stage functionalization of bioactive molecules and the synthesis of PhSO2CF2- and HCF2-analogs of Lidocaine were also successfully achieved.

A Novel Phenylpyrrolidine Derivative: Synthesis and Effect on Cognitive Functions in Rats with Experimental Ishemic Stroke

We performed an in silico, in vitro, and in vivo assessment of a potassium 2-[2-(2-oxo-4-phenylpyrrolidin-1-yl) acetamido]ethanesulfonate (compound 1) as a potential prodrug for cognitive function improvement in ischemic brain injury. Using in silico methods, we predicted the pharmacological efficacy and possible safety in rat models. In addition, in silico data showed neuroprotective features of compound 1, which were further supported by in vitro experiments in a glutamate excitotoxicity-induced model in newborn rat cortical neuron cultures. Next, we checked whether compound 1 is capable of crossing the blood-brain barrier in intact and ischemic animals. Compound 1 improved animal behavior both in intact and ischemic rats and, even though the concentration in intact brains was low, we still observed a significant anxiety reduction and activity escalation. We used molecular docking and molecular dynamics to support our hypothesis that compound 1 could affect the AMPA receptor function. In a rat model of acute focal cerebral ischemia, we studied the effects of compound 1 on the behavior and neurological deficit. An in vivo experiment demonstrated that compound 1 significantly reduced the neurological deficit and improved neurological symptom regression, exploratory behavior, and anxiety. Thus, here, for the first time, we show that compound 1 can be considered as an agent for restoring cognitive functions.

Sc(OTf)3-Catalyzed C2-Selective Cyanation/Defluorination Cascade of Perfluoroalkylated 3-Indolylmethanols and Application to the Synthesis of 3-Fluoro(perfluoroalkyl)-β-carbolines

An unprecedented Sc(OTf)₃-catalyzed C2-selective cyanation/defluorination cascade of perfluoroalkylated 3-indolylmethanols with TMSCN is described, which provides a novel and practical strategy for the synthesis of structurally diverse 3-(2-cyano)-indolyl substituted gem-difluoroalkenes and β-fluoro-β-perfluoroalkylalkenes. The reaction features excellent regio- and stereoselectivity and broad substrate scope. Notably, the obtained gem-difluoroalkenes and β-fluoro-β-perfluoroalkylalkenes could be easily transformed into 3-fluoro(perfluoroalkyl)-β-carbolines with excellent efficiency simply by treating them with Grignard reagents or DIBAL-H under mild reaction conditions.

Aluminum-catalyzed tunable halodefluorination of trifluoromethyl- and difluoroalkyl-substituted olefins

Herein, we report unprecedented aluminum-catalyzed halodefluorination reactions of trifluoromethyl- and difluoroalkyl-substituted olefins with bromo- or chlorotrimethylsilane. The interesting feature of these reactions is that one, two, or three fluorine atoms can be selectively replaced with bromine or chlorine atoms by modification of the reaction conditions. The generated products can undergo a variety of subsequent transformations, thus constituting a valuable stock of building blocks for installing fluorine-containing olefin motifs in other molecules.

Aluminum-catalyzed halodefluorination reactions of fluoroalkyl-substituted olefins are developed. The reactions can selectively deliver mono-, di-, or trisubstituted products.

Chirality as an Important Factor for the Development of New Antiepileptic Drugs

In recent years, chiral molecules (especially enantiomers) have occupied a significant place in pharmaceutical industry and have played a prominent role in the development of new drugs. Individual stereoisomers exhibit marked differences in pharmacodynamic, pharmacokinetic, and toxicological properties. Therefore, there is currently considerable interest in fully characterizing and examining both enantiomers in the early stages of new drug development. Despite the fact that epilepsy is a complex disease and that a given drug's mechanism of action may be multidirectional and not always fully understood, significant differences have been observed in the anticonvulsant activity of individual stereoisomers. Therefore, between 1996 and 2018, among 14 new antiepileptic drugs (AEDs) approved for the treatment of epilepsy, as many as seven are chiral and introduced to the market in the single-enantiomer (or diastereomer) form. This review provides an overview of the impact of chirality on the development and discovery of new AEDs that have entered into clinical trials or preclinical studies. These new AEDs were developed by applying the single-enantiomer approval strategy. Herein we focus our attention on the main synthetic pathways of stereoisomers, as well as on the influence of chirality on pharmacodynamic, pharmacokinetic, and/or toxicological properties.

The Synaptic Vesicle Glycoprotein 2: Structure, Function, and Disease Relevance

The synaptic vesicle glycoprotein 2 (SV2) family is comprised of three paralogues: SV2A, SV2B, and SV2C. In vertebrates, SV2s are 12-transmembrane proteins present on every secretory vesicle, including synaptic vesicles, and are critical to neurotransmission. Structural and functional studies suggest that SV2 proteins may play several roles to promote proper vesicular function. Among these roles are their potential to stabilize the transmitter content of vesicles, to maintain and orient the releasable pool of vesicles, and to regulate vesicular calcium sensitivity to ensure efficient, coordinated release of the transmitter. The SV2 family is highly relevant to human health in a number of ways. First, SV2A plays a role in neuronal excitability and as such is the specific target for the antiepileptic drug levetiracetam. SV2 proteins also act as the target by which potent neurotoxins, particularly botulinum, gain access to neurons and exert their toxicity. Both SV2B and SV2C are increasingly implicated in diseases such as Alzheimer's disease and Parkinson's disease. Interestingly, despite decades of intensive research, their exact function remains elusive. Thus, SV2 proteins are intriguing in their potentially diverse roles within the presynaptic terminal, and several recent developments have enhanced our understanding and appreciation of the protein family. Here, we review the structure and function of SV2 proteins as well as their relevance to disease and therapeutic development.

Synthesis and Derivatization of 1,1-[18 F]Difluorinated Alkenes

A general method for the synthesis of 1,1-[¹⁸ F]difluorinated alkenes from [¹⁸ F]fluoride is reported. This transformation is highly regioselective giving the desired ¹⁸ F-fluoroalkenes with radiochemical purities of up to 77 % within 20 minutes and a molar activity (A_m ) of 1 GBq μmol^-1 . The transformations are operationally simple to perform and were readily translated onto a commercial automated synthesis unit. The resultant 1,1-[¹⁸ F]difluorinated alkene motif is prevalent in numerous drug molecules, and this is the first general method to synthesize this motif with fluorine-18. ¹⁸ F-fluorinated alkenes are excellent building blocks and participate in a number of post-labeling transformations to access a range of ¹⁸ F-perfluorinated functional groups that have never before been radiolabeled with non-carrier-added [¹⁸ F]fluoride. This method considerably expands the range of ¹⁸ F-motifs accessible to radiochemists.

Synaptic Vesicle Glycoprotein 2A Ligands in the Treatment of Epilepsy and Beyond

The synaptic vesicle glycoprotein SV2A belongs to the major facilitator superfamily (MFS) of transporters and is an integral constituent of synaptic vesicle membranes. SV2A has been demonstrated to be involved in vesicle trafficking and exocytosis, processes crucial for neurotransmission. The anti-seizure drug levetiracetam was the first ligand to target SV2A and displays a broad spectrum of anti-seizure activity in various preclinical models. Several lines of preclinical and clinical evidence, including genetics and protein expression changes, support an important role of SV2A in epilepsy pathophysiology. While the functional consequences of SV2A ligand binding are not fully elucidated, studies suggest that subsequent SV2A conformational changes may contribute to seizure protection. Conversely, the recently discovered negative SV2A modulators, such as UCB0255, counteract the anti-seizure effect of levetiracetam and display procognitive properties in preclinical models. More broadly, dysfunction of SV2A may also be involved in Alzheimer's disease and other types of cognitive impairment, suggesting potential novel therapies for levetiracetam and its congeners. Furthermore, emerging data indicate that there may be important roles for two other SV2 isoforms (SV2B and SV2C) in the pathogenesis of epilepsy, as well as other neurodegenerative diseases. Utilization of recently developed SV2A positron emission tomography ligands will strengthen and reinforce the pharmacological evidence that SV2A is a druggable target, and will provide a better understanding of its role in epilepsy and other neurological diseases, aiding in further defining the full therapeutic potential of SV2A modulation.

Antiepileptic drugs in development pipeline: A recent update

Epilepsy is the most common neurological disorder which significantly affects the quality of life and poses a health as well as economic burden on society. Epilepsy affects approximately 70 million people in the world. The present article reviews the scientific rationale, brief pathophysiology of epilepsy and newer antiepileptic drugs which are presently under clinical development. We have searched the investigational drugs using the key words ‘antiepileptic drugs,’ ‘epilepsy,’ ‘Phase I,’ ‘Phase II’ and ‘Phase III’ in American clinical trial registers (clinicaltrials.gov), the relevant published articles using National Library of Medicine's PubMed database, company websites and supplemented results with a manual search of cross-references and conference abstracts. This review provides a brief description about the antiepileptic drugs which are targeting different mechanisms and the clinical development status of these drugs. Besides the presence of old as well as new AEDs, still there is a need of new drugs or the modified version of old drugs in order to make affected people free of seizures. An optimistic approach should be used to translate the success of preclinical testing to clinical practice. There is an urgent need to improve animal models and to explore new targets with better understanding in order to develop the novel drugs with more efficacy and safety.

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This review primarily focused on antiepileptic drugs under clinical development.

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The more realistic approach is needed to discover and develop the novel antiepileptic drugs.

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Modification of conventional drugs or search of newer targets can lead to development of promising antiepileptic drugs.

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To develop more efficacious and safe drugs for treatment of epilepsy and refractory seizures

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There are a number of novel antiepileptic compounds which are under various stages of drug development.

Synaptic vesicle protein2A decreases in amygdaloid-kindling pharmcoresistant epileptic rats

Synaptic vesicle protein 2A (SV2A) involvement has been reported in the animal models of epilepsy and in human intractable epilepsy. The difference between pharmacosensitive epilepsy and pharmacoresistant epilepsy remains poorly understood. The present study aimed to observe the hippocampus SV2A protein expression in amygdale-kindling pharmacoresistant epileptic rats. The pharmacosensitive epileptic rats served as control. Amygdaloid-kindling model of epilepsy was established in 100 healthy adult male Sprague-Dawley rats. The kindled rat model of epilepsy was used to select pharmacoresistance by testing their seizure response to phenytoin and phenobarbital. The selected pharmacoresistant rats were assigned to a pharmacoresistant epileptic group (PRE group). Another 12 pharmacosensitive epileptic rats (PSE group) served as control. Immunohistochemistry, real-time PCR and Western blotting were used to determine SV2A expression in the hippocampus tissue samples from both the PRE and the PSE rats. Immunohistochemistry staining showed that SV2A was mainly accumulated in the cytoplasm of the neurons, as well as along their dendrites throughout all subfields of the hippocampus. Immunoreactive staining level of SV2A-positive cells was 0.483 ± 0.304 in the PRE group and 0.866 ± 0.090 in the PSE group (P < 0.05). Real-time PCR analysis demonstrated that 2(-ΔΔCt) value of SV2A mRNA was 0.30 ± 0.43 in the PRE group and 0.76 ± 0.18 in the PSE group (P < 0.05). Western blotting analysis obtained the similar findings (0.27 ± 0.21 versus 1.12 ± 0.21, P < 0.05). PRE rats displayed a significant decrease of SV2A in the brain. SV2A may be associated with the pathogenesis of intractable epilepsy of the amygdaloid-kindling rats.

Identification of the antiepileptic racetam binding site in the synaptic vesicle protein 2A by molecular dynamics and docking simulations

Synaptic vesicle protein 2A (SV2A) is an integral membrane protein necessary for the proper function of the central nervous system and is associated to the physiopathology of epilepsy. SV2A is the molecular target of the anti-epileptic drug levetiracetam and its racetam analogs. The racetam binding site in SV2A and the non-covalent interactions between racetams and SV2A are currently unknown; therefore, an in silico study was performed to explore these issues. Since SV2A has not been structurally characterized with X-ray crystallography or nuclear magnetic resonance, a three-dimensional (3D) model was built. The model was refined by performing a molecular dynamics simulation (MDS) and the interactions of SV2A with the racetams were determined by docking studies. A reliable 3D model of SV2A was obtained; it reached structural equilibrium during the last 15 ns of the MDS (50 ns) with remaining structural motions in the N-terminus and long cytoplasmic loop. The docking studies revealed that hydrophobic interactions and hydrogen bonds participate importantly in ligand recognition within the binding site. Residues T456, S665, W666, D670 and L689 were important for racetam binding within the trans-membrane hydrophilic core of SV2A. Identifying the racetam binding site within SV2A should facilitate the synthesis of suitable radio-ligands to study treatment response and possibly epilepsy progression.

Regulators of synaptic transmission: roles in the pathogenesis and treatment of epilepsy

Synaptic transmission is the communication between a presynaptic and a postsynaptic neuron, and the subsequent processing of the signal. These processes are complex and highly regulated, reflecting their importance in normal brain functioning and homeostasis. Sustaining synaptic transmission depends on the continuing cycle of synaptic vesicle formation, release, and endocytosis, which requires proteins such as dynamin, syndapin, synapsin, and synaptic vesicle protein 2A. Synaptic transmission is regulated by diverse mechanisms, including presynaptic modulators of synaptic vesicle formation and release, postsynaptic receptors and signaling, and modulators of neurotransmission. Neurotransmitters released presynaptically can bind to their postsynaptic receptors, the inhibitory γ-aminobutyric acid (GABA)ergic receptors or the excitatory glutamate receptors. Once released, glutamate activates a variety of postsynaptic receptors including α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), N-methyl-D-aspartate (NMDA), kainate, and metabotropic receptors. The activation of the receptors triggers downstream signaling cascades generating a vast array of effects, which can be modulated by a numerous auxiliary regulatory subunits. Moreover, different neuropeptides such as neuropeptide Y, brain-derived neurotrophic factor (BDNF), somatostatin, ghrelin, and galanin, act as regulators of diverse synaptic functions and along with the classic neurotransmitters. Abnormalities in the regulation of synaptic transmission play a critical role in the pathogenesis of numerous brain diseases, including epilepsy. This review focuses on the different mechanisms involved in the regulation of synaptic transmission, which may play a role in the pathogenesis of epilepsy: the presynaptic modulators of synaptic vesicle formation and release, postsynaptic receptors, and modulators of neurotransmission, including the mechanism by which drugs can modulate the frequency and severity of epileptic seizures.

Synthesis and anticonvulsant properties of new acetamide derivatives of phthalimide, and its saturated cyclohexane and norbornene analogs

The synthesis and anticonvulsant properties of new piperazine or morpholine acetamides derived from 2-(1,3-dioxoisoindolin-2-yl)-, 2-(1,3-dioxo-3a,4,5,6,7,7a-hexahydroisoindol-2-yl-) and (3,5-dioxo-4-azatricyclo[5.2.1.0(2,6)]dec-8-en-4-yl)-acetic acid were described. Initial anticonvulsant screening was performed using maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizures tests. The neurotoxicity was determined applying the minimal motor impairment rotarod test. The in vivo results revealed that numerous compounds were effective in the MES screen. The most active was 2-{2-[4-(4-fluorophenyl)piperazin-1-yl]-2-oxoethyl}isoindoline-1,3-dione (12) that revealed protection in the electrically induced seizures at a dose of 30 mg/kg and 100 mg/kg 0.5 h and 4 h after i.p. administration in mice respectively. This molecule given orally in rats at a dose of 30 mg/kg was more potent than reference anticonvulsant--phenytoin.

Synthesis and anticonvulsant activity of new n-mannich bases derived from 5-cyclopropyl-5-phenyl-hydantoins

Synthesis, physicochemical and anticonvulsant properties of new N-Mannich bases 3-24 derived from 5-cyclopropyl-5-phenyl- and 5-cyclopropyl-5-(4-chlorophenyl)-hydantoins were described here. Initial anticonvulsant screening was performed using intraperitoneal (i.p.) maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizures tests. Selected derivatives were also screened in the 6-Hz test. The neurotoxicity was determined applying the rotorod test. The pharmacological results revealed that the majority of compounds were effective in MES and/or scPTZ tests. The quantitative studies after oral administration into rats showed that several molecules were more potent than phenytoin and ethosuximide which were used as reference antiepileptic drugs. From the whole series the most active was 3-[(4-phenylpiperazin-1-yl)-methyl]-5-cyclopropyl-5-phenyl-imidazolidine-2,4-dione (3) with the ED(50) value of 5.29 mg/kg in the MES test.

SV2 regulates neurotransmitter release via multiple mechanisms

Among the proteins that mediate calcium-stimulated transmitter release, the synaptic vesicle protein 2 (SV2) stands out as a unique modulator specific to the neurons and endocrine cells of vertebrates. In synapses, SV2 regulates the expression and trafficking of the calcium sensor protein synaptotagmin, an action consistent with the reduced calcium-mediated exocytosis observed in neurons lacking SV2. Yet SV2 contains amino acid motifs consistent with it performing other actions that could regulate presynaptic functioning and that might underlie the mechanism of drug action. To test the role of these functional motifs, we performed a mutagenic analysis of SV2A and assessed the ability of mutant SV2A proteins to restore normal synaptic transmission in neurons from SV2A/B knockout mice. We report that SV2A-R231Q, harboring a mutation in a canonical transporter motif, restored normal synaptic depression (a measure of release probability and signature deficit of neurons lacking SV2). In contrast, normal synaptic depression was not restored by SV2A-W300A and SV2A-W666A, harboring mutations of conserved tryptophans in the 5th and 10th transmembrane domains. Although they did not rescue normal neurotransmission, SV2A-W300A and SV2A-W666A did restore normal levels of synaptotagmin expression and internalization. This indicates that tryptophans 300 and 666 support an essential action of SV2 that is unrelated to its role in synaptotagmin expression or trafficking. These results indicate that SV2 performs at least two actions at the synapse that contribute to neurotransmitter release.

Expression of synaptic vesicle protein 2A in epilepsy-associated brain tumors and in the peritumoral cortex

Synaptic vesicle protein 2A (SV2A) has been identified as the binding site for the antiepileptic drug levetiracetam and is thought to decrease neuronal excitability. Since knockout of SV2A in mice leads to seizures, we hypothesized that a reduction in SV2A expression promotes seizure generation in epilepsy-associated brain tumors. We compared the SV2A expression and distribution in surgically removed tumor tissue (n = 63) and peritumoral cortex (n = 31) of patients with glial and glioneuronal tumors to normal control cortex obtained at autopsy in nonbrain tumor patients (n = 6). Additionally, we compared the SV2A expression and distribution in tumor patients with epilepsy (n = 39) with SV2A expression in tumor patients without epilepsy (n = 24). Immunohistochemistry in control cortex demonstrated strong and diffuse SV2A immunoreactivity (IR) throughout all cortical layers. Similar strong SV2A IR (with the same diffuse distribution pattern) was observed in the peritumoral cortical specimens in both patients with and without epilepsy. Modest SV2A IR was observed within the tumor area. The SV2A-positive cells detected within the tumor area were mainly entrapped neurons. Oligodendrogliomas and glioneuronal tumors displayed variable SV2A neuropil staining. In ganglioglioma (GG), strong SV2A IR was present along the dysplastic neuronal cell borders and processes. In both GG and dysembryoplastic neuroepithelial tumors, SV2A IR was occasionally observed within the neuronal perikarya. We found no differences in SV2A expression in the peritumoral cortex between the patients with and without epilepsy, which suggests that the role of SV2A in epileptogenesis in patients with glial tumors is questionable. The distinct pattern of SV2A IR in glioneuronal tumors suggests a redistribution of SV2A.

Expression patterns of synaptic vesicle protein 2A in focal cortical dysplasia and TSC-cortical tubers

PURPOSE

Synaptic vesicle protein 2A (SV2A), the binding site for the antiepileptic drug (AED) levetiracetam, has been shown to be involved in the control of neuronal excitability. The aim of the study was to define the expression and cell-specific distribution of SV2A in developmental focal lesions associated with medically intractable epilepsy.

METHODS

SV2A immunocytochemistry and Western blotting was performed in focal cortical dysplasia (FCD type IIB) and cortical tubers from patients with tuberous sclerosis complex (TSC).

RESULTS

Autopsy and surgical control neocortical specimens were characterized by strong SV2A immunoreactivity throughout all cortical layers, with punctate labeling around the somata and dendrites of neurons. In FCD and cortical tuber specimens less intense, SV2A immunoreactivity was observed in the neuropil. The reduction in expression was confirmed by Western blot analysis. In both FCD and tuber specimens, clusters of punctate labeling were detected along cell borders and processes (perisomatic synapses) of dysplastic neuronal cells localized in both gray and white matter. The large majority of balloon cells in FCD, or giant cells in tubers, did not show punctate labeling around their somata. SV2A immunoreactivity was observed occasionally within the neuronal perikarya.

CONCLUSIONS

The pattern of SV2A immunoreactivity with reduced neuropil expression and altered cellular and subcellular distribution suggests a possible contribution of SV2A to the epileptogenicity of these malformations of cortical development. Knowledge of the expression pattern of SV2A in epilepsy-associated pathologies may be valuable for the evaluation of the effectiveness of AEDs targeting this protein.

Treatment of Lennox-Gastaut syndrome: overview and recent findings

Lennox-Gastaut syndrome (LGS) is a rare, age-related syndrome, characterized by multiple seizure types, a specific electro-encephalographic pattern, and mental regression. However, published data on the etiology, evolution, and therapeutic approach of LGS are contradictory, partly because the precise definition of LGS used in the literature varies. In the most recent classification, LGS belongs to the epileptic encephalopathies and is highly refractory to all antiepileptic drugs. Numerous treatments, medical and non-medical, have been proposed and results mostly from open studies or case series have been published. Sometimes, patients with LGS are included in a more global group of patients with refractory epilepsy. Only 6 randomized double-blind controlled trials of medical treatments, which included patients with LGS, have been published. Overall, treatment is rarely effective and the final prognosis remains poor in spite of new therapeutic strategies. Co-morbidities need specific treatment. This paper summarizes the definition, diagnosis and therapeutic approach to LGS, including not only recognized antiepileptic drugs, but also "off label" medications, immune therapy, diet, surgery and some perspectives for the future.

Design, synthesis, and anticonvulsant activity of N-phenylamino derivatives of 3,3-dialkyl-pyrrolidine-2,5-diones and hexahydro-isoindole-1,3-diones

In the present study on the development of new anticonvulsants, the library of differently substituted N-phenylamino pyrrolidine-2,5-dione and hexahydro-isoindole-1,3-dione derivatives was synthesized. The anticonvulsant activity of all the compounds was evaluated using the maximal electroshock (MES) and pentylenetetrazole (scPTZ) screens, which are the most widely employed seizure models for early identification of candidate anticonvulsants. Their neurotoxicity was determined applying the rotorod test. The pharmacological results revealed that the majority of compounds were effective in electrical (MES) and/or pentylenetetrazole induced seizure (scPTZ) models. The quantitative in vivo anticonvulsant evaluation of N-phenylamino-3,3-dimethyl-pyrrolidine-2,5-dione (15), conducted at the time of peak pharmacodynamic activity (TPE), showed the MES ED(50) value of 69.89mg/kg in rats. The median toxic dose (TD(50)) was 500mg/kg, providing compound 15 with a protective index (TD(50)/ED(50)) of 7.15 in the MES test.

Modifications of Antiepileptic Drugs for Improved Tolerability and Efficacy

Introduction

A large number of antiepileptic drugs (AEDs) are available today, but they may not be satisfactory regarding clinical efficacy, tolerance, toxicity or pharmacokinetic properties. The purpose of this review is to focus upon the rationale behind the chemical modifications of several recently marketed AEDs or drugs in development and to categorize them according to the main purposes for the improvements: better efficacy or tolerability accompanied by improved pharmacokinetic properties.

Material and Method

AEDs that have been chemically modified to new derivatives during the last years are reviewed based on recent publications and PubMed-searches.

Results and Discussion

Improvement in pharmacokinetic parameters may affect both tolerability and efficacy. Modifications to improve tolerability include various valproate analogues, divided into aliphatic amides, cyclic derivatives or amino acid conjugates. Furthermore, there are the carbamazepine analogues oxcarbazepine and eslicarbazepine, the felbamate analogues fluorofelbamate and carisbamate (RWJ 33369), and the lamotrigine analogue JZP-4. The levetiracetam analogues brivaracetam and seletracetam and the derivatives of gabapentin, pregabalin and XP13512, have improved selectivity compared to their parent compounds. Other new drugs have new mechanisms of action related to GABA and glutamate receptors; the glutamate antagonists like topiramate (talampanel and NS-1209), and GABAA receptor agonists, benzodiazepine or progesterone analogues (ELB-139 and ganaxolone).

Conclusion

Further challenges for development of new AEDs include investigations of target molecules affected by pathophysiological processes and detailed structure-activity relationships with focus on stereoselectivity. These potential drugs may become of importance in future drug therapy in epilepsy and other CNS disorders.

Modifications of antiepileptic drugs for improved tolerability and efficacy

INTRODUCTION

A large number of antiepileptic drugs (AEDs) are available today, but they may not be satisfactory regarding clinical efficacy, tolerance, toxicity or pharmacokinetic properties. The purpose of this review is to focus upon the rationale behind the chemical modifications of several recently marketed AEDs or drugs in development and to categorize them according to the main purposes for the improvements: better efficacy or tolerability accompanied by improved pharmacokinetic properties.

MATERIAL AND METHOD

AEDs that have been chemically modified to new derivatives during the last years are reviewed based on recent publications and PubMed-searches.

RESULTS AND DISCUSSION

Improvement in pharmacokinetic parameters may affect both tolerability and efficacy. Modifications to improve tolerability include various valproate analogues, divided into aliphatic amides, cyclic derivatives or amino acid conjugates. Furthermore, there are the carbamazepine analogues oxcarbazepine and eslicarbazepine, the felbamate analogues fluorofelbamate and carisbamate (RWJ 33369), and the lamotrigine analogue JZP-4. The levetiracetam analogues brivaracetam and seletracetam and the derivatives of gabapentin, pregabalin and XP13512, have improved selectivity compared to their parent compounds. Other new drugs have new mechanisms of action related to GABA and glutamate receptors; the glutamate antagonists like topiramate (talampanel and NS-1209), and GABA(A) receptor agonists, benzodiazepine or progesterone analogues (ELB-139 and ganaxolone).

CONCLUSION

Further challenges for development of new AEDs include investigations of target molecules affected by pathophysiological processes and detailed structure-activity relationships with focus on stereoselectivity. These potential drugs may become of importance in future drug therapy in epilepsy and other CNS disorders.