Antiepileptic drugs in development

Antiseizure medication-induced obsessive-compulsive disorder and tic disorder: a pragmatic review

INTRODUCTION

With a lifetime prevalence of 2.3%, obsessive compulsive disorder is a chronic, disabling condition that is associated with significant social and occupational impairment. Up to 30% of individuals with obsessive-compulsive disorder have a lifetime diagnosis of tic disorders. Antiseizure medication is increasingly used for a variety of physical and psychiatric illnesses. Clarification of the relationship between these symptoms/disorders and use of antiseizure medication is critically important for diagnostic and treatment purposes.

AREAS COVERED

Studies on antiseizure-induced obsessive-compulsive disorder and tic disorders are reviewed. The literature search strategy identified 89 articles. Twenty-nine articles were included in the final results. Of these, 24 are case reports or case studies, 2 cross-sectional studies, 1 chart review, 1 population-based case-control study and 1 observational prospective study assessing lamotrigine, levetiracetam, topiramate, zonisamide, and carbamazepine.

EXPERT OPINION

This study highlighted the temporal relationship of antiseizure medication use and onset of obsessive-compulsive symptoms and tics. Monitoring for medication-induced obsessive compulsions or tics should be undertaken when prescribing antiseizure medication for treatment of mood disorders or epilepsy. Further research identifying the causal relationship between antiseizure medication and de novo onset of obsessive-compulsive symptoms, obsessive-compulsive disorder and tic disorder is required.

Development of novel indole-linked pyrazoles as anticonvulsant agents: A molecular hybridization approach

A series of 3-{2-[1-acetyl-5-(substitutedphenyl)-4,5-dihydropyrazol-3-yl]hydrazinylidene}-1,3-dihydro-2H-indol-2-ones 24-43 was synthesized using an appropriate synthetic route and evaluated experimentally by the maximal electroshock test. These compounds were evaluated for antidepressant and antianxiety activities. The most active compound, 3-{2-[1-acetyl-5-(4-chlorophenyl)-4,5-dihydropyrazol-3-yl]hydrazinylidene}-1,3-dihydro-2H-indol-2-one 25, exhibited an ED₅₀ of 13.19 mmol/kg, a TD₅₀ of 43.49 mmol/kg, and a high protective index of 3.29, compared with the standard drug diazepam. To get insights into the intermolecular interactions, molecular docking studies were performed at the active site of the GABA_A receptor and the MAO-A enzyme. Molecular docking studies are also in agreement with the pharmacological evaluation with potent compounds, exhibiting docking scores of -1.5180 and 0.7458 for the GABA_A receptor and MAO-A, respectively. The 3D-QSAR analysis was carried out by Vlife MDS engine 4.3.1, and a statistically reliable model with good predictive power (r²  = 0.7523, q²  = 0.3773) was achieved. The 3D-QSAR plots gave insights into the structure-activity relationship of these compounds, which may aid in the design of potent benzopyrrole derivatives as anticonvulsant agents. So, our research can make a great impact on those medicinal chemists who work on the development of anticonvulsant agents.

Novel 3-{4-[2-Amino-4-(Substitutedphenyl)-2H-[1, 3] Oxazin/Thiazin-6-Yl} -2-Phenyl-3H-Quinazolin-4-One Derivatives as Enhancer of GABA Mediated Inhibition: Synthesis, Molecular Modeling and Pharmacological Studies

Background:

According to WHO, the 50 million people worldwide are suffering from epilepsy, making it one of the most common neurological diseases globally. Epilepsy is often characterized by neurobiological, cognitive, psychological and behavioral changes and that may enhance the susceptibility to seizures and affect the quality of life.

Objective:

The aim of the present work was to develop 2, 3 disubstituted 4-(3H)-quinazolinone derivatives in order to find an effective and highly lipophilic compound with lesser side effects and to evaluate them for anticonvulsant and neurotoxic activity.

Methods:

A novel series of 3-4-[2-amino-4-(substitutedphenyl)-2H-[1.3] oxazin/thiazin-6-yl 2- phenyl-3H-quinazolin-4-one derivatives were synthesized and evaluated for their anticonvulsant activity. The structures of the compound have been confirmed by spectral analysis. The molecular docking study was performed for finding the binding affinity with GABAA receptor in order to rationalize their anticonvulsant activities in a qualitative way. Quantitative estimate of drug-likeness was also performed which calculate the molecular properties and screen the molecules based on drug-likeness rules. Anticonvulsant activities of synthesized compounds were done by using (Maximal electroshock) MES induced seizures and subcutaneous pentylenetetrazole (scPTZ) induced seizure models in Wistar rats of either sex. None of the compounds demonstrated any sign of neurotoxicity.

Results:

Compounds 3-4-[2-amino-4-(fluorophenyl)-2H- [1, 3] oxazin-6-yl 2-phenyl-3H quinazolin-4-one (5i) and 3-4-[2-amino-4-(fluorophenyl)-2H- [1, 3] thiazin -6-yl 2-phenyl-3H quinazolin-4-one (5n) have shown significant activity against tonic seizure by the MES model and clonic seizure by scPTZ induced seizure model.

Conclusion:

These ten novels synthesized compounds had significant anticonvulsant activity. As a result, the compound (5i) and (5n) emerged out as the pilot molecule with a better anticonvulsant activity without any neurotoxicity, while the other compounds have moderate activity. QED analysis of compounds (5i) and (5n) also indicated that these compounds will have good oral absorption. The proposed work is to make efforts towards the development and identification of novel molecules as anticonvulsant agents by the synthesis of some novel quinazolinone derivatives with improved biological activity.

Evaluation of brivaracetam: a new drug to treat epilepsy

INTRODUCTION

High prevalence of therapy-resistant epilepsy demands development of anticonvulsants with new mechanisms of action. Brivaracetam is an analogue of levetiracetam which binds to the synaptic vesicle protein 2A (SV2A) and decreases release of excitatory neurotransmitters. Areas covered: Relevant published studies were searched for by predefined strategy in MEDLINE, EBSCO and SCINDEKS electronic databases. Brivaracetam is effective as adjunctive therapy for uncontrolled partial-onset seizures with or without secondary generalization in patients 16 years and older with epilepsy. It reduces baseline-adjusted focal seizure frequency per week from 7.3 to 12.8% over placebo. Adverse events rate in patients with brivaracetam is not higher than in patients with placebo. Expert opinion: Brivaracetam is an important step forward in the treatment of therapy-resistant partial-onset seizures with or without secondary generalization. Its development was systematic and targeted. Due to its efficacy and excellent safety profile, it is likely that brivaracetam will be often prescribed. In future, efficacy and safety of brivaracetam should be tested in monotherapy settings and also in the first-line therapy of partial-onset seizures.

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.

New benzo[d]thiazol-2-yl-aminoacetamides as potential anticonvulsants: synthesis, activity and prediction of molecular properties

A series of N-(substituted-2-oxo-4-phenylazetidin-1-yl)-2-((6-substitutedbenzo[d]thiazol-2-yl)amino)acetamide derivatives were synthesized using pharmacophoric features with aromatic hydrophobic aryl ring (A), NH-C=O as hydrogen bonding domain, the nitrogen atom as electron donor (D), and phenyl as distal aryl ring (C). The synthesized molecules were initially screened for anticonvulsant activity using the maximal electroshock seizure (MES) test and the subcutaneous pentylenetetrazole test in albino mice. An acute neurotoxicity study on the synthesized molecules was also carried out using the rotarod test. The results of these tests revealed that two compounds, 5b and 5q, showed promising activity with ED50 values of 15.4 and 18.6 mg/kg and protective indices of 20.7 and 34.9 in the MES test, respectively, which are found to be approximately fourfold higher than those of the standard drugs phenytoin (6.9) and carbamazepine (8.1). These molecules may act as lead of the designed scheme. The pharmacokinetic profiles of all the synthesized compounds were estimated using Molinspiration software. None of the compounds violated Lipinski's "rule of five". The possible structure-activity relationship was discussed. In conclusion, this manuscript shows that the developed model has a highly prognostic power for the further investigation of better benzothiazole derivatives for future discovery and development.

Recent advances in the chemistry and biology of benzothiazoles

Benzothiazole is a privileged heterocyclic scaffold having a benzene ring fused with a five-membered thiazole ring. This moiety has attracted considerable attention because of its wide range of pharmacological activities such as antitubercular, antimicrobial, antimalarial, anticonvulsant, anthelmintic, analgesic, anti-inflammatory, antidiabetic, antitumor activity, etc. In the last few years, some novel benzothiazoles have been developed with varied biological activities. To access this scaffold in high yield and to introduce diversity, a variety of new synthetic methods have been invented. In this review, we highlight the development of novel benzothiazoles for various biological activities along with the best synthetic protocols for their synthesis.

Synthesis, anticonvulsant properties, and SAR analysis of differently substituted pyrrolidine-2,5-diones and piperidine-2,6-diones

Twenty-two differently substituted 1H-isoindole-1,3(2H)-diones (30-39), 8-azaspiro[4.5]decane-7,9-diones (40-45), and 3-azaspiro[5.5]undecane-2,4-diones (46-51) were synthesized and tested for anticonvulsant activity. These molecules were designed as analogs of previously obtained azaspirosuccinimides (1-24). Initial anticonvulsant screening was performed in mice using the maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure tests. The acute neurological toxicity was determined applying the minimal motor impairment rotorod test. The preliminary pharmacological results showed that 15 new compounds were effective in at least one animal model of epilepsy, from which nine molecules showed protection against both MES and scPTZ seizures. The structure-activity relationship analysis revealed that anticonvulsant activity was connected closely with the structure of the imide fragment; the most favorable one was the hexahydro-1H-isoindole-1,3(2H)-dione core. 2-(2-Chlorophenyl)hexahydro-1H-isoindole-1,3(2H)-dione (31) showed activity in the 6-Hz psychomotor seizure model, which identifies substances effective in partial and therapy-resistant epilepsy. 3-[(4-Chlorophenyl)amino]-3-azaspiro[5.5]undecane-2,4-dione (47) was active in the in vitro hippocampal slice culture neuroprotection assay.

Evaluation of anticonvulsant actions of dibromophenyl enaminones using in vitro and in vivo seizure models

Epilepsy and other seizure disorders are not adequately managed with currently available drugs. We recently synthesized a series of dibromophenyl enaminones and demonstrated that AK6 and E249 were equipotent to previous analogs but more efficacious in suppressing neuronal excitation. Here we examined the actions of these lead compounds on in vitro and in vivo seizure models. In vitro seizures were induced in the hippocampal slice chemically (zero Mg2+ buffer and picrotoxin) and electrically using patterned high frequency stimulation (HFS) of afferents. In vivo seizures were induced in rats using the 6 Hz and the maximal electroshock models. AK6 (10 µM) and E249 (10 µM) depressed the amplitude of population spikes recorded in area CA1 of the hippocampus by -50.5±4.3% and -40.1±3.1% respectively, with partial recovery after washout. In the zero Mg2+ model, AK6 (10 µM) depressed multiple population spiking (mPS) by -59.3±6.9% and spontaneous bursts (SBs) by -65.9±7.2% and in the picrotoxin-model by -43.3±7.2% and -50.0±8.3%, respectively. Likewise, E249 (10 µM) depressed the zero-Mg2+-induced mPS by -48.8±9.5% and SBs by -55.8±15.5%, and in the picrotoxin model by -37.1±5.5% and -56.5±11.4%, respectively. They both suppressed post-HFS induced afterdischarges and SBs. AK6 and E249 dose-dependently protected rats in maximal electroshock and 6 Hz models of in vivo seizures after 30 min pretreatment. Their level of protection in both models was similar to that obtained with phenytoin Finally, while AK6 had no effect on locomotion in rats, phenytoin significantly decreased locomotion. AK6 and E249, suppressed in vitro and in vivo seizures to a similar extent. Their in vivo activities are comparable with but not superior to phenytoin. The most efficacious, AK6 produced no locomotor suppression while phenytoin did. Thus, AK6 and E249 may be excellent candidates for further investigation as potential agents for the treatment of epilepsy syndromes with possibly less CNS side effects.

Design, synthesis and anticonvulsant properties of new N-Mannich bases derived from 3-phenylpyrrolidine-2,5-diones

The synthesis and anticonvulsant properties of new N-Mannich bases of 3-phenyl- (9a-d), 3-(2-chlorophenyl)- (10a-d), 3-(3-chlorophenyl)- (11a-d) and 3-(4-chlorophenyl)-pyrrolidine-2,5-diones (12a-d) were described. The key synthetic strategies involve the formation of 3-substituted pyrrolidine-2,5-diones (5-8), and then aminoalkylation reaction (Mannich-type) with formaldehyde and corresponding secondary amines, which let to obtain the final compounds 9a-d, 10a-d, 11a-d and 12a-d in good yields. Initial anticonvulsant screening was performed in mice (ip) using the maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizures tests. The most effective compounds in mice were tested after oral administration in rats. The acute neurological toxicity was determined applying the minimal motor impairment rotarod test. The in vivo results revealed that numerous compounds were effective especially in the MES test (model of human tonic-clonic seizures). The most active in the MES seizures in rats was 1-[(4-benzyl-1-piperidyl)methyl]-3-(2-chlorophenyl)pyrrolidine-2,5-dione (10c) which showed ED50 value of 37.64mg/kg. It should be stressed that this molecule along with 9a, 9d and 10d showed protection in the psychomotor seizure test (6-Hz), which is known as an animal model of therapy-resistant epilepsy. Furthermore compounds 9a, 9d and 10d were also tested in the pilocarpine-induced status prevention (PISP) test to assess their potential effectiveness in status epilepticus. For the most promising molecule 9d an influence on human CYP3A4 isoform of P-450 cytochrome was studied in vitro.

Synthesis and anticonvulsant activity evaluation of 8-alkoxy-5-(4H-1,2,4-triazol-4-yl)quinoline derivatives

Two series of 8-alkoxy-5-(4H-1,2,4-triazol-4-yl)quinolines and 8-alkoxy-5-(2H-1,2,4-triazol-3-one-4-yl)quinolines were synthesized. The anticonvulsant activity of these compounds was evaluated with maximal electroshock seizure test and rotarod test. Among the synthesized compounds, 8-octoxy-5-(4H-1,2,4-triazol-4-yl)quinoline (4g) was the most active compound with ED(50) of 8.80 mg/kg, TD(50) of 176.03 mg/kg and protective index of 20.0. Its neurotoxicity was lower than all other synthesized compounds and also markedly lower than that of the reference drug carbamazepine. In addition, the potency of compound 4g against seizures induced by pentylenetetrazole, 3-mercaptopropionic acid, and bicuculline suggested its broad spectrum activity, and the mechanisms of action including inhibition of voltage-gated ion channels and modulation of GABAergic activity might involve in its anticonvulsant activity.

Novel actions of oxazolidinones: in vitro screening of a triazolyloxazolidinone for anticonvulsant activity

OBJECTIVE

To test the hypothesis that a triazolyloxazolidinone (PH084) has anticonvulsant activity by examining its effects on in vitro seizure models in the rat hippocampus.

MATERIALS AND METHODS

Whole-cell synaptic currents, action potentials and extracellular population spikes (PS) were recorded in the cell body area of rat hippocampal CA1 region in acutely prepared slices. Chemical [picrotoxin (100 µM) and zero magnesium] and electrical seizures were induced and the effect of PH084 (10 µM) was tested on cellular responses, multiple spikes and spontaneous bursting frequencies.

RESULTS

PH084 depressed evoked excitatory postsynaptic currents, action potential firing frequency and PS amplitude. All of these responses did not recover to baseline after 15-20 min washout of PH084. Perfusion with zero magnesium ion (Mg(2+))-containing buffer converted a single PS to multiple PS (mPS) accompanied by spontaneous burst. PH084 suppressed the mPS and the spontaneous burst frequency and it also suppressed the picrotoxin-induced mPS number. However, it did not affect the frequency of stimulus train-induced after discharge or bursts. Furthermore, 8-10 min pretreatment with PH084 did not affect the ability of zero Mg(2+) buffer, picrotoxin or stimulus train to induce epileptiform activity.

CONCLUSIONS

Thus, while PH084 may have potential for anticonvulsant activity against chemically induced seizures, it has little or no potential against electrically induced seizures or in preventing epileptiform discharge.

Design, synthesis and antiepileptic properties of novel 1-(substituted benzylidene)-3-(1-(morpholino/piperidino methyl)-2,3-dioxoindolin-5-yl)urea derivatives

Twenty new 1-(substituted benzylidene)-3-(1-(morpholino/piperidino methyl)-2,3-dioxoindolin-5-yl) urea derivatives were designed and synthesized. Antiepileptic screening was performed using MES and scPTZ seizures tests. The neurotoxicity was determined by rotorod test. In the preliminary screening, compounds 5c, 5g, 5j and 5n were found active in MES model, while 5o showed significant antiepileptic activity in scPTZ model. Further all these five compounds were administered orally to rats, 5c, 5g and 5n showed better activity than Phenytoin in oral route. Among these compounds 5c revealed protection in MES at a dose of 30 mg/kg and 100 mg/kg 0.5 h and 4 h after i.p. administration respectively. This molecule provided also protection in the scPTZ at a dose of 300 mg/kg in both time intervals.

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 8-alkoxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one derivatives

A series of novel 8-alkoxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one derivatives were synthesized and screened for their anticonvulsant activities by the maximal electroshock (MES) test, subcutaneous pentylenetetrazol (scPTZ) test, and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). The results of these tests demonstrated that 8-heptyloxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3f) and 8-hexyloxy -5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3e) were the most promising compounds, with median effective dose (ED(50)) of 17.6 and 17.9 mg/kg, and protective index (PI) of greater than 63.4 and 62.4 in the MES test, respectively. These PI values were higher than the PI value of the prototype antiepileptic drug carbamazepine. The scPTZ test showed that 8-pentyloxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3d) was the most potent with ED(50) value of 38.0 mg/kg and PI value of greater than 29.4, which is much safer than marketed drug carbamazepine. The possible structure-activity relationship was discussed.

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.

New and investigational antiepileptic drugs

In the last fifteen years, new antiepileptic medications have been offered for the treatment of patients with epilepsy. Nevertheless, despite optimal medical treatment, up to 30% of patients still experience recurrent seizures and the challenge for new, more efficacious and better-tolerated drugs continues. New antiepileptic drugs include the evolution of pre-existing drugs and new compounds identified through the investigation of additional molecular targets, such as SV2A synaptic vesicle protein, voltage-gated potassium channels, ionotropic and metabotropic glutamate receptors, and gap junctions. This paper reviews the available information on various classes of molecules that are in the pipeline as well as on the innovative approaches to the treatment of epilepsy.

Intractable epilepsy: management and therapeutic alternatives

More than half of patients with newly diagnosed epilepsy achieve complete seizure control without major side-effects. Patients who continue to have seizures after initial medical therapy should have an early and detailed assessment to confirm the diagnosis, to determine the underlying cause and epilepsy syndrome, and to choose an adequate treatment strategy. The risks and potential benefits of surgical procedures or experimental therapy have to be weighed against the chance of improvement and the potential side-effects of additional medical therapy. Surgery for temporal lobe epilepsy, the most common cause of focal epilepsy, can control seizures and improve quality of life in appropriately selected patients. However, around 20-30% of patients do not respond to medical or surgical treatment. The management of chronic intractable epilepsy requires comprehensive care to address the adverse events of medical treatment, quality of life issues, and comorbid disorders. Much research focuses on the experimental treatment options that offer hope of seizure reduction or cure.

Brivaracetam: a new drug in development for epilepsy and neuropathic pain

BACKGROUND

Epilepsy is a neurological disorder with a worldwide prevalence estimated to be 0.5-1.0% of the population. Many potent antiepileptic drugs (AED) have been used for treatment but still about 30% of patients are resistant to current AEDs. Some AEDs are also used for the treatment of neuropathic pain.

OBJECTIVE

The aim of this report is to present preclinical and clinical studies of brivaracetam (UCB-34714), a new drug developed by UCB Pharma.

METHODS

Published results of preclinical studies in several animal models of epilepsy, neuropathic pain, essential tremor and results of Phase I and II evaluations of brivaracetam have been analysed.

RESULTS/CONCLUSION

Brivaracetam represents a new mechanism of action being a ligand of synaptic vesicle protein 2A. It is undergoing Phase III evaluation after a successful Phase II programme in which was effective as an adjunctive treatment in partial-onset epilepsy (50 mg/day). It is well tolerated, without serious adverse side effects.

Emerging drugs for epilepsy

Epilepsy affects < or = 1% of the world's population. Antiepileptic drugs (AEDs) are the mainstay of treatment, although more than a third of patients are not rendered seizure free with existing medications. Uncontrolled epilepsy is associated with increased mortality and physical injuries, and a range of psychosocial morbidities, posing a substantial economic burden on individuals and society. Limitations of the present AEDs include suboptimal efficacy and their association with a host of adverse reactions. Continued efforts are being made in drug development to overcome these shortcomings employing a range of strategies, including modification of the structure of existing drugs, targeting novel molecular substrates and non-mechanism-based drug screening of compounds in traditional and newer animal models. This article reviews the need for new treatments and discusses some of the emerging compounds that have entered clinical development. The ultimate goal is to develop novel agents that can prevent the occurrence of seizures and the progression of epilepsy in at risk individuals.

Development of new antiepileptic drugs: challenges, incentives, and recent advances

Despite the introduction of many second-generation antiepileptic drugs (AEDs) in the past 15 years, a third of patients with epilepsy remain refractory to available treatments, and newer and more effective therapies are needed. Although our understanding of the mechanisms of drug resistance is fragmented, novel AED targets have been identified, and models of refractory epilepsy have been developed that can help to select candidate compounds for development. There are more than 20 compounds with potential antiepileptic activity in various stages of clinical development, and for many of these promising clinical trial results are already available. Several incentives justify further investment into the discovery of newer and more effective AEDs. Moreover, developments in clinical trial methodology enable easier completion of proof-of-concept studies, earlier definition of the therapeutic potential of candidate compounds, and more efficient completion of trials for various epilepsy indications.

Anticonvulsant enaminone E139 suppresses epileptiform activity in rat hippocampal slices

Some enaminones are reported to have in vivo anticonvulsant activity. We asked if methyl 4-(4'-bromophenyl)aminocyclohex-3-en-6-methyl-2-oxo-1-oate (E139), one of such enaminones produced in vitro effects that may underlie or explain these in vivo anticonvulsant actions by testing if E139 suppressed in vitro seizures. In vitro seizures were generated chemically in hippocampal slices using picrotoxin and zero Mg(2+) buffer and electrically by high frequency stimulation (HFS). E139 (10 microM) depressed evoked field population spike (PS) amplitude by -28.6+/-4.5% (n=5), an effect that was blocked by 1 microM CGP55845 (2.7+/-5.5%, n=6). Picrotoxin (100 microM) transformed single PS into multiple PS (4.5+/-0.2, n=5) and E139 reversibly reduced the number of these multiple PS by -23.4+/-1.8% (n=5). Similarly, zero Mg(2+) buffer produced multiple spikes (3.6+/-0.6, n=5) that were suppressed by E139 (-54.8+/-9.7%, n=5). This effect was also blocked by CGP55845 (2.3+/-5.7%, n=6). Furthermore, E139 suppressed the frequency of spontaneous bursts (SB) that were recorded in zero Mg(2+) by -65.8+/-10.5% (n=12). CGP55845 significantly reduced this E139-induced SB suppression (-21.7+/-9.6%, n=6). In the electrical model, afterdischarges (AD) and SB recorded in area CA3 after a pattern of HFS (100Hz) were suppressed by E139 (-48.6+/-14.3% and -66.7+/-6.7%, respectively, n=6). These E139 effects on AD and SB were reduced, but not completely blocked, by CGP55845 (-32.1+/-5.3% and -44.4+/-9.7%, respectively, n=7). Finally, pretreatment of slices with E139 did not prevent zero Mg(2+)-induced multiple spikes and SB. We conclude that E139 suppresses in vitro seizures in the hippocampus by synaptic and non-synaptic mechanisms. These actions on network activity may underlie their reported in vivo anticonvulsant effects.