Pharmacological management of epilepsy: recent advances and future prospects

Development of SV2A Ligands for Epilepsy Treatment: A Review of Levetiracetam, Brivaracetam, and Padsevonil

Epilepsy is a common neurological disorder that is primarily treated with antiseizure medications (ASMs). Although dozens of ASMs are available in the clinic, approximately 30% of epileptic patients have medically refractory seizures; other limitations in most traditional ASMs include poor tolerability and drug-drug interactions. Therefore, there is an urgent need to develop alternative ASMs. Levetiracetam (LEV) is a first-line ASM that is well tolerated, has promising efficacy, and has little drug-drug interaction. Although it is widely accepted that LEV acts through a unique therapeutic target synaptic vesicle protein (SV) 2A, the molecular basis of its action remains unknown. Even so, the next-generation SV2A ligands against epilepsy based on the structure of LEV have achieved clinical success. This review highlights the research and development (R&D) process of LEV and its analogs, brivaracetam and padsevonil, to provide ideas and experience for the R&D of novel ASMs.

Brivaracetam add-on therapy for drug-resistant epilepsy

BACKGROUND

This is an updated version of the Cochrane Review previously published in 2019. Epilepsy is one of the most common neurological disorders. It is estimated that up to 30% of individuals with epilepsy continue to have epileptic seizures despite treatment with an antiepileptic drug. These patients are classified as drug-resistant and require treatment with a combination of multiple antiepileptic drugs. Brivaracetam is a third-generation antiepileptic drug that is a high-affinity ligand for synaptic vesicle protein 2A. In this review we investigated the use of brivaracetam as add-on therapy for epilepsy.

OBJECTIVES

To evaluate the efficacy and tolerability of brivaracetam when used as add-on treatment for people with drug-resistant epilepsy.

SEARCH METHODS

For the latest update we searched the following databases on 7 September 2021: the Cochrane Register of Studies (CRS Web); MEDLINE (Ovid) 1946 to 3 September 2021. CRS Web includes randomised controlled trials (RCTs) and quasi-RCTs from PubMed, Embase, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform, the Cochrane Central Register of Controlled Trials (CENTRAL), and the specialised registers of Cochrane Review Groups including Cochrane Epilepsy.

SELECTION CRITERIA

We searched for parallel-group RCTs that recruited people of any age with drug-resistant epilepsy. We accepted studies with any level of blinding (double-blind, single-blind, or unblinded).

DATA COLLECTION AND ANALYSIS

In accordance with standard Cochrane methodological procedures, two review authors independently assessed trials for inclusion before evaluating trial quality and extracting relevant data. The primary outcome to be assessed was 50% or greater reduction in seizure frequency. Secondary outcomes were: seizure freedom, treatment withdrawal for any reason, treatment withdrawal due to adverse events, the proportion of participants who experienced any adverse events, and drug interactions. We used an intention-to-treat population for all primary analyses, and presented results as risk ratios (RRs) with 95% confidence intervals (CIs).

MAIN RESULTS

We did not identify any new studies for this update, therefore the results and conclusions of the review are unchanged. The previous review included six studies involving a total of 2411 participants. Only one study included participants with both focal and generalised onset seizures; the other five trials included participants with focal onset seizures only. Study participants were aged 16 to 80 years. Treatment periods ranged from 7 to 16 weeks. We judged two studies to have low risk of bias and four to have unclear risk of bias. Details on the method used for allocation concealment and how blinding was maintained were insufficient in one study each. One study did not report all outcomes prespecified in the trial protocol, and there were discrepancies in reporting in a further study. Participants receiving brivaracetam add-on were more likely to experience a 50% or greater reduction in seizure frequency than those receiving placebo (RR 1.81, 95% CI 1.53 to 2.14; 6 studies; moderate-certainty evidence). Participants receiving brivaracetam were more likely to attain seizure freedom; however, the evidence is of low certainty (RR 5.89, 95% CI 2.30 to 15.13; 6 studies). The incidence of treatment withdrawal for any reason was slightly greater for participants receiving brivaracetam compared to those receiving placebo (RR 1.27, 95% CI 0.94 to 1.74; 6 studies; low-certainty evidence). The risk of participants experiencing one or more adverse events did not differ significantly following treatment with brivaracetam compared to placebo (RR 1.08, 95% CI 1.00 to 1.17; 5 studies; moderate-certainty evidence). However, participants receiving brivaracetam did appear to be more likely to withdraw from treatment due to adverse events compared with those receiving placebo (RR 1.54, 95% CI 1.02 to 2.33; 6 studies; low-certainty evidence).

AUTHORS' CONCLUSIONS

When used as add-on therapy for individuals with drug-resistant epilepsy, brivaracetam may be effective in reducing seizure frequency and may aid patients in achieving seizure freedom. However, add-on brivaracetam is probably associated with a greater proportion of treatment withdrawals due to adverse events compared with placebo. It is important to note that only one of the eligible studies included participants with generalised epilepsy. None of the included studies involved participants under the age of 16, and all studies were of short duration. Consequently, the findings of this review are mainly applicable to adult patients with drug-resistant focal epilepsy. Future research should focus on investigating the tolerability and efficacy of brivaracetam during longer-term follow-up, as well as assess the efficacy and tolerability of add-on brivaracetam in managing other types of seizures and in other age groups.

Brivaracetam add-on therapy for drug-resistant epilepsy

BACKGROUND

Epilepsy is one of the most common neurological disorders. It is estimated that up to 30% of patients with epilepsy continue to have epileptic seizures despite treatment with an antiepileptic drug. These patients are classified as drug-resistant and require treatment with a combination of multiple antiepileptic drugs. Brivaracetam is a third-generation antiepileptic drug that is a high-affinity ligand for synaptic vesicle protein 2A. This review investigates the use of brivaracetam as add-on therapy for epilepsy.

OBJECTIVES

To evaluate the efficacy and tolerability of brivaracetam when used as add-on treatment for people with drug-resistant epilepsy.

SEARCH METHODS

We searched the following databases on 9 October 2018: the Cochrane Register of Studies (CRS Web), which includes the Cochrane Epilepsy Group Specialized Register and the Cochrane Central Register of Controlled Trials (CENTRAL); Medline (Ovid) 1946 to 8 October 2018; ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). Originally we also searched SCOPUS as a substitute for Embase, but this is no longer necessary, because randomised and quasi-randomised controlled trials in Embase are now included in CENTRAL.

SELECTION CRITERIA

We sought randomised controlled trials with parallel-group design, recruiting people of any age with drug-resistant epilepsy. We accepted studies with any level of blinding (double-blind, single-blind, or unblind).

DATA COLLECTION AND ANALYSIS

In accordance with standard methodological procedures expected by the Cochrane Collaboration, two review authors independently assessed trials for inclusion before evaluating trial quality and extracting relevant data. The primary outcome to be assessed was 50% or greater reduction in seizure frequency. Secondary outcomes were: seizure freedom, treatment withdrawal for any reason, treatment withdrawal due to adverse events, the proportion of participants who experienced any adverse events, and drug interactions. We used an intention-to-treat (ITT) population for all primary analyses, and we presented results as risk ratios (RRs) with 95% confidence intervals (CIs).

MAIN RESULTS

The review included six trials representing 2411 participants. Only one study included participants with both focal and generalised onset seizures; the other five trials included participants with focal onset seizures only. All six studies included adult participants between 16 and 80 years old, and treatment periods ranged from 7 to 16 weeks. We judged two studies to have low risk of bias and four to have unclear risk of bias. One study failed to provide details on the method used for allocation concealment, and one did not report all outcomes prespecified in the trial protocol. One study did not describe how blinding was maintained, and another noted discrepancies in reporting.Participants receiving brivaracetam add-on were significantly more likely to experience a 50% or greater reduction in seizure frequency than those receiving placebo (RR 1.81, 95% CI 1.53 to 2.14; 6 studies; moderate-quality evidence). Participants receiving brivaracetam were also significantly more likely to attain seizure freedom (RR 5.89, 95% CI 2.30 to 15.13; 6 studies; moderate-quality evidence). The incidence of treatment withdrawal for any reason (RR 1.27, 95% CI 0.94 to 1.74; 6 studies; low-quality evidence), as well as the risk of participants experiencing one or more adverse events (RR 1.08, 95% CI 1.00 to 1.17; 5 studies; moderate-quality evidence), was not significantly different following treatment with brivaracetam compared to placebo. However, participants receiving brivaracetam did appear to be significantly more likely to withdraw from treatment specifically because of adverse events compared with those receiving placebo (RR 1.54, 95% CI 1.02 to 2.33; 6 studies; low-quality evidence).

AUTHORS' CONCLUSIONS

Brivaracetam, when used as add-on therapy for patients with drug-resistant epilepsy, is effective in reducing seizure frequency and can aid patients in achieving seizure freedom. However, add-on brivaracetam is associated with a greater proportion of treatment withdrawals due to adverse events compared with placebo. It is important to note that only one of the eligible studies included participants with generalised epilepsy. None of the studies included participants under the age of 16, and all studies were of short duration. Consequently, these findings are mainly applicable to adult patients with drug-resistant focal epilepsy. Future research should thus focus on investigating the tolerability and efficacy of brivaracetam during longer-term follow-up, and should also assess the efficacy and tolerability of add-on brivaracetam in managing other types of seizures and its use in other age groups.

Exploring the pathogenesis of canine epilepsy using a systems genetics method and implications for anti-epilepsy drug discovery

Epilepsy is a common neurological disorder in domestic dogs. However, its complex mechanism involves multiple genetic and environmental factors that make it challenging to identify the real pathogenic factors contributing to epilepsy, particularly for idiopathic epilepsy. Conventional genome-wide association studies (GWASs) can detect various genes associated with epilepsy, although they primarily detect the effects of single-site mutations in epilepsy while ignoring their interactions. In this study, we used a systems genetics method combining both GWAS and gene interactions and obtained 26 significantly mutated subnetworks. Among these subnetworks, seven genes were reported to be involved in neurological disorders. Combined with gene ontology enrichment analysis, we focused on 4 subnetworks that included traditional GWAS-neglected genes. Moreover, we performed a drug enrichment analysis for each subnetwork and identified significantly enriched candidate anti-epilepsy drugs using a hypergeometric test. We discovered 22 potential drug combinations that induced possible synergistic effects for epilepsy treatment, and one of these drug combinations has been confirmed in the Drug Combination database (DCDB) to have beneficial anti-epileptic effects. The method proposed in this study provides deep insight into the pathogenesis of canine epilepsy and implications for anti-epilepsy drug discovery.

Efficacy and safety of antiepileptic drugs for refractory partial-onset epilepsy: a network meta-analysis

The optimal combination of antiepileptic drugs (AEDs) for the treatment of refractory partial-onset epilepsy is a perpetual point of debate. While several network meta-analyses (NMAs) have been published, conclusions remain controversial, especially since newer AEDs have been introduced. In our review, we included the newer AEDs to evaluate the comparative efficacy and safety of AEDs for the treatment of refractory partial-onset epilepsy. We searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials (Cochrane Library 2017, Issue 1) from their inception to February 18, 2017. The risk of bias in the included randomized controlled trials (RCTs) was evaluated according to the Cochrane Collaboration's risk of bias tool. An NMA was performed with a Bayesian random-effects model, and we used the surface under the cumulative ranking curve to detect the optimal AEDs. Seventy-six RCTs with 17 AEDs and 20,711 patients were included in the NMAs, which showed that Brivaracetam (BRV), Levetiracetam (LEV), Oxcarbazepine (OXC), Topiramate, Vigabatrin (VGB), and Valproate (VPA) had a greater likelihood of allowing patients to achieve seizure freedom. We also found that LEV was associated with a lower withdrawal rate due to adverse effects than Lacosamide, Eslicarbazepine acetate, OXC, Pregabalin, and Retigabine. LEV, VGB, VPA, and BRV emerged as the agents with the best combination of properties when considering the efficacy and safety outcomes based on the full double-blind treatment period. However, it is critical to perform RCTs and to obtain prospective data from representative cohort studies.

Prevalence of Different Combinations of Antiepileptic Drugs and CNS Drugs in Elderly Home Care Service and Nursing Home Patients in Norway

Introduction. Antiepileptic drugs (AEDs) are used to treat different conditions in elderly patients and are among the drug classes most susceptible to be involved in drug-drug interactions (DDI). The aim of the study was to describe and compare use of AEDs between home care service and nursing home patients, as these patients are not included in nationwide databases of drug utilization. In the combined population, we investigate DDI of AEDs with other central nervous system- (CNS-) active drugs and DDIs involving AEDs in general. Materials and Methods. Point-prevalence study of Norwegian patients in home care services and nursing homes in 2009. At the patient level, we screened for different DDIs involving AEDs. Results. In total, 882 patients (7.8%) of 11,254 patients used AEDs and number of users did not differ between home care services and nursing homes (8.2% versus 7.7%). In the combined population, we identified 436 potential DDIs in 45% of the patients. Conclusions. In a large population of elderly, home care service and nursing home patients do not differ with respect to exposure of AEDs but use more AEDs as compared to the general population of similar age. The risk of DDIs with AEDs and other CNS-active drugs should be taken into consideration and individual clinical evaluations are assessed in this population.

Emerging drugs for partial-onset epilepsy: a review of brivaracetam

There are more than 12 new antiepileptic drugs approved in the last 2 decades. Even with these newer agents, seizure remission is still unachievable in around 30% of patients with partial-onset seizures (POS). Brivaracetam (BRV) is chemically related to levetiracetam (LEV) and possesses a strong binding affinity for the synaptic vesicle protein 2A tenfold above that of LEV, and other possible modes of antiepileptic actions. BRV is now under Phase III development for POS, but data from one Phase III trial also suggested its potential efficacy for primary generalized seizures. The purpose of this review is to provide updated information on the mechanisms of action of the available antiepileptic drugs, with a focus on BRV to assess its pharmacology, pharmacokinetics, clinical efficacy, safety, and tolerability in patients with uncontrolled POS. To date, six Phase IIb and III clinical trials have been performed to investigate the efficacy, safety, and tolerability of BRV as an adjunctive treatment for patients with POS. Generally, BRV was well tolerated and did not show significant difference in safety profile, compared to placebo. The efficacy outcomes of BRV, although not consistent across trials, did indicate that BRV was a promising add-on therapy for patients with POS. In conclusion, the many favorable attributes of BRV, like its high oral efficacy, good tolerability, dosing regimen, and minimal drug interaction, make it a promising antiepileptic therapy for patients with uncontrolled partial-onset epilepsy.

The efficacy and safety of brivaracetam at different doses for partial-onset epilepsy: a meta-analysis of placebo-controlled studies

OBJECTIVE

This meta-analysis systematically assessed the efficacy and safety of different doses of brivaracetam (BRV) compared with placebo as adjunctive therapy for adults with partial-onset epilepsy.

METHODS

Electronic and clinical trials databases were searched for randomized controlled trials of BRV published up to May 2015. We assessed the risk of bias of the included studies using the Cochrane Risk of Bias tool. The outcomes of interest included 50% responder rates, seizure freedom, the incidence of withdrawal and treatment-emergent adverse events (TEAEs).

RESULTS

Five trials met the inclusion criteria. Compared with placebo, 20, 50, 100 and 150 mg/day BRV was associated with significantly higher 50% responder rates. In addition, the effect of 50 mg BRV on seizure freedom was significantly different than that of placebo. Both fatigue and nasopharyngitis were significantly associated with 20 mg BRV, whereas fatigue and irritability were associated with 50 mg BRV. Somnolence was associated with 150 mg BRV. No significant differences were observed for the other common TEAEs.

CONCLUSION

The use of BRV at doses > 5 mg/day resulted in statistically significant reduction in seizure frequency in respect to the 50% responder rate. BRV was reasonably tolerated by patients. These findings warrant confirmation in future studies.

Implantable stimulator for epileptic seizure suppression with loading impedance adaptability

The implantable stimulator for epileptic seizure suppression with loading impedance adaptability was proposed in this work. The stimulator consisted of the high voltage generator, output driver, adaptor, and switches, can constantly provide the required 40-μA stimulus currents, as the loading impedance varied within 10 kΩ -300 kΩ. The performances of this design have been successfully verified in silicon chip fabricated by a 0.35- μm 3.3-V/24-V CMOS process. The power consumption of this work was only 1.1 mW-1.4 mW. The animal test results with the fabricated chip of proposed design have successfully verified in the Long-Evans rats with epileptic seizures.

Ontogenetic influence on rat susceptibility to lindane seizure after pretreatment with phencyclidine

The aim of the study was to determine the effects of early postnatal PCP treatment on the sensitivity of pubertal and adult rats to lindane proepileptogenic effects. Rat pups were treated with NaCl (0.9%) or PCP (10 mg/kg) at postnatal days 2, 6, 9 and 12. One control (NaCl-35) and one experimental (PCP-35) group have received lindane (4 mg/kg) at postnatal day 35, while others received lindane at postnatal day 65 (NaCl-65 and PCP-65). One week prior to lindane treatment three gold-plated EEG electrodes were implanted. Pubertal rats had significantly shorter latency time. After lindane, a prompt increase in power spectral density seen in PCP-treated groups vs. control was evident earlier in PCP-65 rats. The theta waves were significantly increased in PCP-35 and alpha rhythm in PCP-65 rats, when compared with corresponding controls. Postnatal PCP treatment increases the synchronization of brain electrical activity, thus contributing to the increased susceptibility to lindane.

Antiepileptic drug effects on mood and behavior: molecular targets

With almost 100 years of clinical experience, antiepileptic drugs (AEDs) remain the mainstay of epilepsy treatment. They suppress epileptic seizures by acting on a variety of mechanisms and molecular targets involved in the regulation of neuronal excitability. These include inhibitory-GABAergic and excitatory-glutamatergic neurotransmission, as well as ion (sodium and calcium) conductance through voltage-gated channels. On the other hand, accruing evidence indicates that these mechanisms and targets are also implicated in the regulation of mood and behavior, which may explain why each AED is associated with specific psychotropic effects. These effects, however, cannot be explained solely on the basis of the known mode of action of each AED, and other mechanisms or targets are likely to be implicated. In this article, we review positive and negative effects of AEDs on mood and behavior, discuss putative underlying mechanisms, and highlight knowledge gaps which should be addressed in future studies.

Neurogenetic disorders and treatment of associated seizures

Seizures are a frequent complication associated with several neurogenetic disorders. Antiepileptic medications remain the mainstay of treatment in these patients. We summarized the available data associated with various antiepileptic therapies used to treat patients with neurogenetic disorders who experienced recurrent seizures. A MEDLINE search was conducted to identify articles and abstracts describing the use of antiepileptic therapy for the treatment of various neurogenetic syndromes. Of all the neurogenetic syndromes, only autism spectrum disorders, Angelman syndrome, Rett syndrome, Dravet syndrome, and tuberous sclerosis complex were identified as having sufficient published information to evaluate therapy. Some efficacy trends were identified, including frequent successes with valproic acid with clonazepam for epilepsy with Angelman syndrome; valproic acid, stiripentol, and clobazam (triple combination therapy) for epilepsy with Dravet syndrome; and vigabatrin for infantile spasms associated with tuberous sclerosis complex. Due to a paucity of information regarding the mechanisms by which seizures are generated in the various disorders, approach to seizure control is primarily based on clinical experience and a limited amount of study data exploring patient outcomes. Although exposure of the developing brain to antiepileptic medications is of some concern, the control of epileptic activity is an important undertaking in these individuals, as the severity of eventual developmental delay often appears to correlate with the severity of seizures. As such, early aggressive therapy is warranted.

Retigabine (ezogabine) as add-on therapy for partial-onset seizures: an update for clinicians

OBJECTIVE

The present study reviewed the pharmacology, pharmacokinetics, efficacy, and safety of retigabine (ezogabine), a potential agent for use as adjunctive treatment in refractory partial-onset seizures.

METHODS

A MEDLINE search (1966-May 2011) was conducted using the key words retigabine, ezogabine, D-23129, epilepsy, and anticonvulsant. Bibliographies of all articles retrieved were also reviewed. All studies including humans and published in English with data describing retigabine for the adjunctive treatment of partial-onset seizures were reviewed.

RESULTS

Retigabine has been shown to interact with the KCNQ2/KCNQ3 subunits of the potassium channels, GABA(A) receptors, and weakly block sodium and calcium channels. Retigabine is 50-60% bioavailable, metabolized by N-glucuronidation and N-acetylation, 80% protein bound, and has few drug-drug interactions. Recent data suggest that retigabine may have a role as adjunctive treatment for refractory partial-onset seizures. Placebo-controlled trials demonstrated a 23.4-44.3% reduction in seizure frequency with 50% responder rates ranging from 23.2% to 47.0% with varying doses of retigabine. The most common adverse effects, occurring in greater than 10% of subjects in the clinical trials, include abnormal gait, confusion, dizziness, fatigue, headache, nausea, somnolence, speech disorder, tremor, urinary tract infection, and blurred vision.

CONCLUSIONS

Retigabine is a promising agent for adjunctive treatment of refractory partial-onset seizures.

Pediatric indications for deep brain stimulation

PURPOSE

Based on the success of deep brain stimulation (DBS) in the treatment of adult disorders, it is reasonable to assume that the application of DBS in the pediatric population is an emerging area worthy of study. The purpose of this paper is to outline the current movement disorder indications for DBS in the pediatric population, and to describe areas of investigation, including possible medically refractory psychiatric indications.

METHODS

We performed a structured review of the English language literature from 1990 to 2011 related to studies of DBS in pediatrics using Medline and PubMed search results.

RESULTS

Twenty-four reports of DBS in the pediatric population were found. Based on published data on the use of DBS for pediatric indications, there is a spectrum of clinical evidence for the use of DBS to treat different disorders. Dystonia, a disease associated with a low rate of remission and significant disability, is routinely treated with DBS and is currently the most promising pediatric application of DBS. We caution the application of DBS to conditions associated with a high remission rate later in adulthood, like obsessive-compulsive disorder and Tourette's syndrome. Moreover, epilepsy and obesity are currently being investigated as indications for DBS in the adult population; however, both are associated with significant morbidity in pediatrics.

CONCLUSION

While currently dystonia is the most promising application of DBS in the pediatric population, multiple conditions currently being investigated in adults also afflict children and adolescents, and thus warrant further research.

Utilization patterns of antiepileptic drugs among adult epileptic patients at a tertiary hospital in Oman

Objectives

To describe utilization patterns of antiepileptic drugs (AEDs) among adult epileptic patients at a tertiary hospital in Oman.

Methods

Data were collected retrospectively from January 2006 to December 2009. The study included all adult (>18 years) epileptic patients on AEDs and followed up at a neurology clinic at Sultan Qaboos University Hospital in Oman. All reported therapeutic drug monitoring (TDM) requests for serum AED concentrations were also collected. Institutional ethical approval was sought and obtained.

Key findings

The study included a total of 372 patients with a mean age of 34 ± 15 years. Monotherapy AEDs accounted for 53% of the prescriptions, whereas polytherapy with two or three AED combinations accounted for 27% and 20% respectively. The most frequently prescribed AED was sodium valproate (27%) followed by carbamazepine (23%). The commonly prescribed AED combinations were sodium valproate with clonazepam (12%) followed by sodium valproate with lamotrigine (12%). Evaluation of 574 TDM requests for three AEDs showed that 57% of carbamazepine, 78% of phenytoin and 54% of valproic acid requests were either above or below the recommended therapeutic threshold. Most of these requests were ordered from the hospital's emergency department for suspected insufficient serum concentrations.

Conclusions

Antiepileptic drug monotherapy is still the most frequently employed therapeutic strategy in adult patients with epilepsy in keeping with the standard therapeutic guidelines. Sodium valproate is commonly used for different types of seizures reflecting its wide spectrum of anticonvulsant potential. Newer AED utilizations are becoming increasingly popular in our subjects particularly as add-on with other standard AEDs.

Pharmacological management of binge eating disorder: current and emerging treatment options

Growing evidence suggests that pharmacotherapy may be beneficial for some patients with binge eating disorder (BED), an eating disorder characterized by repetitive episodes of uncontrollable consumption of abnormally large amounts of food without inappropriate weight loss behaviors. In this paper, we provide a brief overview of BED and review the rationales and data supporting the effectiveness of specific medications or medication classes in treating patients with BED. We conclude by summarizing these data, discussing the role of pharmacotherapy in the BED treatment armamentarium, and suggesting future areas for research.

Synthesis and anticonvulsant activity of trans- and cis-2-(2,6-dimethylphenoxy)-N-(2- or 4-hydroxycyclohexyl)acetamides and their amine analogs

A group of trans- and cis-2-(2,6-dimethylphenoxy)-N-(2-hydroxycyclohexyl)acetamides (1-7) and -ethylamines (8-9) have been synthesized and investigated for their anticonvulsant activity. One of them, racemic trans-2-(2,6-dimethylphenoxy)-N-(2-hydroxycyclohexyl)acetamide proved to be the most effective in MES (mice, ip), exhibiting ED(50)=42.97 mg/kg b.w. and TD(50)=105.67 mg/kg b.w. It also proved protection in focal seizures (electric kindling, rats, ip) and it raises seizure threshold. The mechanism of action is inhibition of voltage-gated sodium currents and enhancement of GABA effect. Safety pharmacology assay on threshold tonic extension revealed no lowering of the seizure threshold.

Antiepileptic drug therapy: does mechanism of action matter?

This article represents a synthesis of presentations made by the authors during a scientific meeting held in London on 7 June 2010 and organized by GlaxoSmithKline. Each speaker produced a short précis of his lecture to answer a specific question, resulting in an overview of what we know about the relevance of the mechanisms of action of antiepileptic drugs in determining appropriate combination therapies for the treatment of drug-resistant epilepsy.

Antiepileptic drug interactions - principles and clinical implications

Antiepileptic drugs (AEDs) are widely used as long-term adjunctive therapy or as monotherapy in epilepsy and other indications and consist of a group of drugs that are highly susceptible to drug interactions. The purpose of the present review is to focus upon clinically relevant interactions where AEDs are involved and especially on pharmacokinetic interactions. The older AEDs are susceptible to cause induction (carbamazepine, phenobarbital, phenytoin, primidone) or inhibition (valproic acid), resulting in a decrease or increase, respectively, in the serum concentration of other AEDs, as well as other drug classes (anticoagulants, oral contraceptives, antidepressants, antipsychotics, antimicrobal drugs, antineoplastic drugs, and immunosupressants). Conversely, the serum concentrations of AEDs may be increased by enzyme inhibitors among antidepressants and antipsychotics, antimicrobal drugs (as macrolides or isoniazid) and decreased by other mechanisms as induction, reduced absorption or excretion (as oral contraceptives, cimetidine, probenicid and antacides). Pharmacokinetic interactions involving newer AEDs include the enzyme inhibitors felbamate, rufinamide, and stiripentol and the inducers oxcarbazepine and topiramate. Lamotrigine is affected by these drugs, older AEDs and other drug classes as oral contraceptives. Individual AED interactions may be divided into three levels depending on the clinical consequences of alterations in serum concentrations. This approach may point to interactions of specific importance, although it should be implemented with caution, as it is not meant to oversimplify fact matters. Level 1 involves serious clinical consequences, and the combination should be avoided. Level 2 usually implies cautiousness and possible dosage adjustments, as the combination may not be possible to avoid. Level 3 refers to interactions where dosage adjustments are usually not necessary. Updated knowledge regarding drug interactions is important to predict the potential for harmful or lacking effects involving AEDs.

Synthesis, in silico metabolic and toxicity prediction of some novel imidazolinones derivatives as potent anticonvulsant agents

A series of 1,2,4-trisubstituted 5-imidazolinone derivatives were synthesized by Erlenmeyer condensation of benzoylglycine (hippuric acid) with different aldehydes in the presence of sodium acetate and acetic anhydride. The derivatives of the compounds were prepared by condensation of some known sulpha drugs with 5-oxazolone derivatives. The anticonvulsant activity of the compounds was determined by the protection of pentylenetetrazole-induced convulsions that was ranged from 10 to 60%. The compounds with p-OCH₃, p-OH and o-Cl substitutions in the phenyl ring on 4(th) position of the imidazolinone ring exhibited good anticonvulsant activity. In silico metabolic and toxicity studies showed that all the compounds in the series are not likely to exhibit toxicity except the compounds IIIa, IIIb, VIa and VIb, that is predicted to show 29% mutagenicity and 53% irritation in comparison to the other compounds. The predicted lethal effect and hERG toxicity of the compounds showed that IIa, IVa, Va and Vb might be toxic at higher concentrations. The results successfully establish the synthesized imidazolinone derivatives as novel compounds with anticonvulsant properties, low predicted cardiotoxicity and lethal effects thus can be promising leads for further development as novel anticonvulsants.

The effects of stiripentol on GABA(A) receptors

The anticonvulsant stiripentol (Diacomittm) has been shown to have a positive impact on control of seizures for many patients with Dravet syndrome. As with most antiepileptic drugs, stiripentol has multiple mechanisms of action. Its direct anticonvulsant activity is likely due to enhancement of inhibitory, γ-aminobutyric acid (GABA)ergic neurotransmission. Stiripentol was shown to increase the activity of both neuronal and recombinant GABA(A) receptors at clinically relevant concentrations. At recombinant receptors, stiripentol was found to act through a unique site in a subunit-dependent manner. Positive modulation by stiripentol was most effective at GABA(A) receptors containing an α3 subunit. The expression of the α3 subunit is developmentally regulated, with highest levels in the immature brain. This subunit selectivity may explain the greater clinical efficacy of stiripentol in childhood-onset epilepsies, including Dravet syndrome.

Imidazolylchromanone oxime ethers as potential anticonvulsant agents: Anticonvulsive evaluation in PTZ-kindling model of epilepsy and SAR study

As a continuation of our efforts to develop the azolylchromanone derivatives as potential anticonvulsant agents, we explored (Z)- and (E)-oxime ether derivatives of imidazolylchromanones bearing different lipophilic O-benzyl groups and tested their anticonvulsant activities in PTZ-kindling model of epilepsy. O-(2,4-Dichlorobenzyl) oximes 8a, 16a and 20a were significantly effective in delaying the onset of the PTZ-evoked seizures at the dose of 30mg/kg in kindled animals. The most effective compounds in delaying seizures were 7-chlorochromanone-O-(2,4-dichlorobenzyl) oximes 8a and 20a. SAR studies showed that introduction of a chlorine atom to the 7-position and/or a methyl group to the 2-position of the chroman ring resulted in an improvement of anti-seizure efficacy in O-(2,4-dichlorobenzyl) oxime series.

New drugs for pediatric epilepsy

The last 2 decades have witnessed an unprecedented period of new antiepileptic drug (AED) development. Newer-generation AEDs have been developed with the intention of improving the ease of use, decreasing drug interactions, decreasing adverse side effects, and identifying drugs with unique mechanisms of action, some of which may bear relevance to potential neuroprotective activity. Drug trials have also been refined in some cases to evaluate AED efficacy in children and against distinct epilepsy syndromes. This progress provides many new treatment options for the child neurologist facing children with epilepsy but also introduces the burden of determining appropriate AED choices. Here we highlight 6 new antiepileptic medications recently approved or pending approval for use in the United States: lacosamide, rufinamide, vigabatrin, retigabine, brivaracetam, and clobazam. For each of these medications, we present information regarding the history of drug development, proposed mechanism(s) of action, pharmacokinetics and recommended dosing, evidence for clinical efficacy, tolerability, and when, available, any unique features that are relevant for the pediatric population.

Update on treatment of partial onset epilepsy: role of eslicarbazepine

Partial epilepsy comprises simple partial seizures, complex partial seizures, and secondarily generalized seizures, and covers more than 60% of patients with epilepsy. Antiepileptic drugs are generally considered to be the major therapeutic intervention for epilepsy but, despite a broad range of commonly used antiepileptic drugs, approximately 30% of adult patients and approximately 25% of children with epilepsy have inadequate seizure control. Eslicarbazepine acetate (ESL) is a novel voltage-gated sodium channel-blocking agent with presumed good safety and efficacy for adjunctive treatment of patients with drug-resistant partial epilepsy. ESL is a prodrug of eslicarbazepine (the active entity responsible for pharmacologic effects), and is rapidly and extensively hydrolyzed during first pass by liver esterases after oral administration. The half-life of eslicarbazepine at steady-state plasma concentrations is 20-24 hours, compatible with once-daily administration. ESL 800 mg and 1200 mg significantly reduces seizure frequency and shows a favorable safety profile in adult patients with drug-resistant partial-onset seizures, as demonstrated in previous Phase II and III trials. In children, ESL showed a clear dose-dependent decrease in seizure frequency with good tolerability. The most commonly reported adverse events associated with ESL are dizziness, somnolence, nausea, diplopia, headache, vomiting, blurred vision, vertigo, and fatigue. In conclusion, these characteristics suggest that ESL might be a valid and well tolerated treatment option for patients with drug-resistant partial-onset epilepsy. The convenience of once-daily dosing and a short, simple titration regimen would be of special interest for children, although conclusive published data are lacking to date. Hence, there is an urgent need to establish the therapeutic value of ESL in this special population in the near future.

Treating Lennox-Gastaut syndrome in epileptic pediatric patients with third-generation rufinamide

Lennox-Gastaut syndrome (LGS) is a rare but debilitating pediatric epileptic encephalopathy characterized by multiple intractable seizure types. Treatment of LGS is challenging because of the small number of antiepileptic drugs (AEDs) which are effective for this syndrome, as well as the need for polytherapy in the majority of patients. This review focuses on the treatment of LGS with rufinamide, a recently approved third-generation AED with reported efficacy as adjunctive therapy for LGS. All relevant papers identified through a PubMed search on the treatment of LGS with rufinamide were reviewed. To date, the literature suggests improvements in seizure frequency for pediatric patients with LGS on rufinamide. Rufinamide appears to be especially effective for atonic or drop attack seizures. Rufinamide also displays a favorable adverse event profile compared with the older anticonvulsants, as well as a minimal number of drug interactions, making it a promising option for the adjunctive treatment of seizures associated with LGS.

Difficulties in Treatment and Management of Epilepsy and Challenges in New Drug Development

Epilepsy is a serious neurological disorder that affects around 50 million people worldwide. Almost 30% of epileptic patients suffer from pharmacoresistance, which is associated with social isolation, dependent behaviour, low marriage rates, unemployment, psychological issues and reduced quality of life. Currently available antiepileptic drugs have a limited efficacy, and their negative properties limit their use and cause difficulties in patient management. Antiepileptic drugs can provide only symptomatic relief as these drugs suppress seizures but do not have ability to cure epileptogenesis. The long term use of antiepileptic drugs is limited due to their adverse effects, withdrawal symptoms, deleterious interactions with other drugs and economic burden, especially in developing countries. Furthermore, some of the available antiepileptic drugs may even potentiate certain type of seizures. Several in vivo and in vitro animal models have been proposed and many new antiepileptic drugs have been marketed recently, but large numbers of patients are still pharmacoresistant. This review will highlight the difficulties in treatment and management of epilepsy and the limitations of available antiepileptic drugs and animal seizure models.

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.

A 24-week multicenter, randomized, double-blind, parallel-group, dose-ranging study of rufinamide in adults and adolescents with inadequately controlled partial seizures

OBJECTIVE

To assess the efficacy, safety, tolerability, and pharmacokinetics of adjunctive rufinamide in adults and adolescents with inadequately controlled partial seizures receiving treatment with one to three concomitant antiepileptic drugs (AEDs).

METHODS

A 24-week multicenter Phase II clinical study was conducted (n=647), comprising a 12-week prospective baseline phase and a 12-week randomized double-blind, parallel-group, five-arm (placebo and rufinamide 200, 400, 800, and 1600mg/day) treatment phase.

RESULTS

The linear trend of dose response for seizure frequency per 28 days in the double-blind treatment phase - the primary efficacy outcome measure - was statistically significant in favor of rufinamide (estimated slope=-0.049, P=0.003; minimally efficacious dose, 400mg/day). Response rates, defined as a >or=50% reduction in seizure frequency per 28 days, also revealed a significant linear trend of dose response (P=0.0019, logistic regression analysis). Adverse events were comparable between placebo and all rufinamide groups except the 1600mg/day group; no safety signals were observed.

CONCLUSIONS

These results suggest that in the dose range of 400-1600mg/day, add-on rufinamide therapy may benefit patients with inadequately controlled partial seizures and is generally well tolerated. These data also suggest that higher doses may confer additional efficacy without adversely affecting safety and tolerability.

Management of epilepsy in drug-resistant patients

Epilepsy affects > 2 million people in the United States, making it one of the most common neurobiological conditions. Typically, epilepsy is treated with one of several available antiepileptic drugs and patients are able to experience freedom from seizures with minimal side effects. However, there are some patients who do not respond to treatment and require the use of multiple drug combinations or surgical intervention. Although there are few studies supporting its use, multi-drug regimens have been known to be helpful for patients, although clinicians should monitor patients for adverse side effects. Vagus nerve stimulation is the only US Food and Drug Administration-approved surgical neurostimulation therapy for epilepsy, and patients' conditions often progress for many years before epilepsy surgery options are considered. Lastly, due to the chronic nature of epilepsy, clinicians should be aware of the presence of comorbid psychiatric conditions as well. This supplement is Part One in the "Case in Point: Evidence-Based Insights for Epilepsy Management" series. In this Expert Review Supplement, Andrew J. Cole, MD, FRCPC, outlines a case of a patient with drug resistant epilepsy, and Brien J. Smith, MD, outlines the best practices for the case patient including discussion on defining drug resistance in patients as well as the benefits and risks of available and emerging drug and surgical treatments.

Antiepileptic potential and behavioral profile of L-pGlu-(2-propyl)-L-His-L-ProNH2, a newer thyrotropin-releasing hormone analog

Thyrotropin-releasing hormone (TRH) and its analogs have a number of neurobiological functions and therapeutic uses in disorders of the central nervous system. In this study, the newly synthesized TRH analogs were evaluated for central nervous system activity in pentobarbital-induced sleeping in mice. The most potent TRH analog (L-pGlu-(2-propyl)-L-His-L-ProNH(2) coded as NP-647) was evaluated for its antiepileptic potential in various seizure models in mice in comparison with TRH. Intravenous pretreatment with NP-647 (10 and 20 micromol/kg body wt) significantly delayed the onset and reduced the frequency of convulsions in the pentylenetetrazole model, but not in the maximum electroshock seizure model. Also, it was found to be protective against picrotoxin- and kainic acid-induced seizures. However, NP-647 did not significantly affect theophylline-induced seizures. Further study of the effect of NP-647 on locomotor activity and a functional observational battery revealed that it did not significantly exhibit any undesirable effects as compared with vehicle and TRH. NP-647 did not significantly affect cerebral blood flow, whereas the native peptide TRH markedly increased cerebral blood flow. Furthermore, NP-647 exerted antiepileptic activity without significantly altering plasma thyroid-stimulating hormone levels and mean arterial blood pressure. This suggests that NP-647 is more selective for central nervous system activity and devoid of hormonal and cerebrovascular system effects. In contrast, TRH exhibited cardiac and endocrine effects as marked by significant elevation in mean arterial blood pressure and plasma thyroid-stimulating hormone levels. This study demonstrates that NP-647 has potential antiepileptic activity devoid of undesirable effects and, thus, can be exploited for the prevention and treatment of epilepsy.