Perampanel: A novel, orally active, noncompetitive AMPA-receptor antagonist that reduces seizure activity in rodent models of epilepsy

EGAR, A Food Protein-Derived Tetrapeptide, Reduces Seizure Activity in Pentylenetetrazole-Induced Epilepsy Models Through α-Amino-3-Hydroxy-5-Methyl-4-Isoxazole Propionate Receptors

A primary pathogeny of epilepsy is excessive activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors (AMPARs). To find potential molecules to inhibit AMPARs, high-throughput screening was performed in a library of tetrapeptides in silico. Computational results suggest that some tetrapeptides bind stably to the AMPAR. We aligned these sequences of tetrapeptide candidates with those from in vitro digestion of the trout skin protein. Among salmon-derived products, Glu-Gly-Ala-Arg (EGAR) showed a high biological affinity toward AMPAR when tested in silico. Accordingly, natural EGAR was hypothesized to have anticonvulsant activity, and in vitro experiments showed that EGAR selectively inhibited AMPAR-mediated synaptic transmission without affecting the electrophysiological properties of hippocampal pyramidal neurons. In addition, EGAR reduced neuronal spiking in an in vitro seizure model. Moreover, the ability of EGAR to reduce seizures was evaluated in a rodent epilepsy model. Briefer and less severe seizures versus controls were shown after mice were treated with EGAR. In conclusion, the promising experimental results suggest that EGAR inhibitor against AMPARs may be a target for antiepilepsy pharmaceuticals. Epilepsy is a common brain disorder characterized by the occurrence of recurring, unprovoked seizures. Twenty to 30 % of persons with epilepsy do not achieve adequate seizure control with any drug. Here we provide a possibility in which a natural and edible tetrapeptide, EGAR, can act as an antiepileptic agent. We have combined computation with in vitro experiments to show how EGAR modulates epilepsy. We also used an animal model of epilepsy to prove that EGAR can inhibit seizures in vivo. This study suggests EGAR as a potential pharmaceutical for the treatment of epilepsy.

Pyridine C3-arylation of nicotinic acids accessible via a multicomponent reaction: an entry to all-substituted-3,4-diarylated pyridines

An efficient route for the synthesis of all-substituted/functionalized pyridines has been developed. Several of the synthesized compounds exhibited significant anti-proliferative properties.

Hippocampal encoding of interoceptive context during fear conditioning

Rodent models of auditory fear conditioning are often used to understand the molecular mechanisms regulating fear- and anxiety-related behaviors. Conditioning and extinction memories are influenced by contextual cues, and the reinstatement of conditioned fear occurs when the conditioning stimulus is presented in a context different from the extinction context. Although it has been proposed that internal state is a feature of context that could influence extinction, contributions of interoception to conditioning have not been experimentally addressed. Here we use ethanol (EtOH) to show that interoceptive cues are encoded through the hippocampus by mechanisms that involve increased phosphorylation of GluR1 on serine 845, and biophysical alterations in neuronal membranes that facilitate stabilization of surface-located calcium-permeable n-2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl) propanoic acid (AMPA) receptor (AMPAR) into membrane microdomains. Conflicting interoceptive cues during extinction and fear relapse testing resulted in a failure to consolidate extinction that was reversed by the administration of AMPAR antagonists immediately following the retrieval cue.

Perampanel effects in the WAG/Rij rat model of epileptogenesis, absence epilepsy, and comorbid depressive-like behavior

OBJECTIVE

Perampanel (PER), a selective non-competitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-receptor antagonist, exhibits broad-spectrum anticonvulsant activity in several seizure models, but its potential disease-modifying effects have not been investigated. Because of the relevance of AMPA receptors in epileptogenesis and psychiatric comorbidities, we studied the effects of PER in the WAG/Rij rat model of epileptogenesis, absence epilepsy, and depressive-like comorbidity.

METHODS

We investigated the effects of acute, subchronic, and chronic treatment with PER (0.25-3 mg/kg) on absence seizures, their development, and related psychiatric/neurologic comorbidity in WAG/Rij rats. Depression-related behavior was studied by using the forced swimming and the sucrose preference test; anxiety-related behavior by using the open field and elevated plus maze test; and memory by using the passive avoidance test.

RESULTS

PER (3 mg/kg/day orally for 17 weeks starting from P30) significantly reduced the development of absence seizures at 6 months of age (1 month after treatment withdrawal), but this effect was not maintained when reassessed 4 months later. Attenuated absence seizure development was accompanied by reduced depressive-like behavior in the forced swimming test (FST), whereas no effects were observed on anxiety-related behavior and memory. Subchronic (1 and 3 mg/kg/day orally for 1 week) and acute PER (0.25-1 mg/kg, i.p.) dosing did not affect established absence seizures and behavior.

SIGNIFICANCE

These results suggest that AMPA receptors are involved in mechanisms of epileptogenesis in an established model of absence epilepsy, and that these mechanisms differ from those responsible for seizure generation and spread when epilepsy has become established.

AMPA Receptor Antagonist NBQX Decreased Seizures by Normalization of Perineuronal Nets

Epilepsy is a serious brain disorder with diverse seizure types and epileptic syndromes. AMPA receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzoquinoxaline-2,3-dione (NBQX) attenuates spontaneous recurrent seizures in rats. However, the anti-epileptic effect of NBQX in chronic epilepsy model is poorly understood. Perineuronal nets (PNNs), specialized extracellular matrix structures, surround parvalbumin-positive inhibitory interneurons, and play a critical role in neuronal cell development and synaptic plasticity. Here, we focused on the potential involvement of PNNs in the treatment of epilepsy by NBQX. Rats were intraperitoneally (i.p.) injected with pentylenetetrazole (PTZ, 50 mg/kg) for 28 consecutive days to establish chronic epilepsy models. Subsequently, NBQX (20 mg/kg, i.p.) was injected for 3 days for the observation of behavioral measurements of epilepsy. The Wisteria floribundi agglutinin (WFA)-labeled PNNs were measured by immunohistochemical staining to evaluate the PNNs. The levels of three components of PNNs such as tenascin-R, aggrecan and neurocan were assayed by Western blot assay. The results showed that there are reduction of PNNs and decrease of tenascin-R, aggrecan and neurocan in the medial prefrontal cortex (mPFC) in the rats injected with PTZ. However, NBQX treatment normalized PNNs, tenascin-R, aggrecan and neurocan levels. NBQX was sufficient to decrease seizures through increasing the latency to seizures, decrease the duration of seizure onset, and reduce the scores for the severity of seizures. Furthermore, the degradation of mPFC PNNs by chondroitinase ABC (ChABC) exacerbated seizures in PTZ-treated rats. Finally, the anti-epileptic effect of NBQX was reversed by pretreatment with ChABC into mPFC. These findings revealed that PNNs degradation in mPFC is involved in the pathophysiology of epilepsy and enhancement of PNNs may be effective for the treatment of epilepsy.

25 years of advances in the definition, classification and treatment of status epilepticus

PURPOSE

Status epilepticus (SE) requires not only urgent symptomatic treatment with antiepileptic drugs but also rapid identification and treatment of its cause. This narrative review summarizes the most important advances in classification and treatment of SE.

METHOD

Data sources included MEDLINE, EMBASE, ClinicalTrials.gov, and back tracking of references in pertinent studies, reviews, and books.

RESULTS

SE is now defined as "a condition resulting either from the failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms, which lead to abnormally, prolonged seizures (after time point t1). It is a condition, which can have long-term consequences (after time point t2), including neuronal death, neuronal injury, and alteration of neuronal networks, depending on the type and duration of seizures." A new diagnostic classification system of SE introduces four axes: semiology, aetiology, EEG correlates, and age. For the acute treatment intravenous benzodiazepines (lorazepam, diazepam, clonazepam) and intramuscular midazolam appear as most effective treatments for early SE. In children, buccal or intranasal midazolam are useful alternatives. In established SE intravenous antiepileptic drugs (phenytoin, valproate, levetiracetam, phenobarbital, and lacosamide) are in use. Treatment options in refractory SE are intravenous anaesthetics; ketamine, magnesium, steroids and other drugs have been used in super-refractory SE with variable outcomes.

CONCLUSION

Over the past 25 years major advances in definition, classification and understanding of its mechanisms have been achieved. Despite this up to 40% of patients in early status cannot be controlled with first line drugs. The treatment of super-refractory status is still an almost evidence free zone.

Perampanel as add-on treatment in refractory focal epilepsy. The Dianalund experience

BACKGROUND

Perampanel (PER) is an antagonist of AMPA receptors that has been approved for adjunctive treatment of partial-onset seizures.

AIMS

To evaluate effectiveness and safety of PER as add-on treatment in patients with severely refractory focal epilepsy.

METHODS

PER was introduced as add-on treatment in 22 consecutive patients with drug-resistant focal epilepsy. PER was started with 2 mg/day at bedtime and was up-titrated by 2 mg/day every 2-4 weeks.

RESULTS

All patients suffered from severely refractory focal epilepsy (86% took 2 or more AEDs prior PER initiation; 40% had been submitted to surgery or were surgery candidates; 7 had VNS). After 12 months since PER initiation, the retention rate was 54.5% and the responder rate was 27.2%, including 9.1% seizure-free patients. Mean PER dose in the responders was 8 mg/day (range 4-10). Most common side effects were tiredness, behavioral changes (primarily aggressivity), dizziness and were reported in 59.1% of patients, leading to PER discontinuation in 31.8% of subjects.

CONCLUSIONS

PER as add-on treatment can achieve clinically meaningful improvement in patients suffering from severely refractory focal epilepses. Further studies are warranted to explore the tolerability profile, with particular focus on psychiatric adverse events.

Radiosynthesis and preliminary PET evaluation of (18)F-labeled 2-(1-(3-fluorophenyl)-2-oxo-5-(pyrimidin-2-yl)-1,2-dihydropyridin-3-yl)benzonitrile for imaging AMPA receptors

To prompt the development of (18)F-labeled positron emission tomography (PET) tracers for the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, we have prepared (18)F-labeled 2-(1-(3-fluorophenyl)-2-oxo-5-(pyrimidin-2-yl)-1,2-dihydropyridin-3-yl)benzonitrile ([(18)F]8). The radiosynthesis was achieved by a one-pot two-step method that utilized a spirocyclic hypervalent iodine(III) mediated radiofluorination to prepare the (18)F-labeled 1-bromo-3-fluorobenzene ([(18)F]15) intermediate with K(18)F. A subsequent copper(I) iodide mediated coupling reaction was carried out with 2-(2-oxo-5-(pyrimidin-2-yl)-1,2-dihydropyridin-3-yl)benzonitrile (10) to [(18)F]8 in 10±2% uncorrected radiochemical yield relative to starting (18)F-fluoride with >99% radiochemical purity and 29.6±7.4Gbq/μmol specific activity at the time of injection. PET imaging studies with the title radiotracer in normal mice demonstrated good brain uptake (peak standardized uptake value (SUV)=2.3±0.1) and warrants further in vivo validation.

Efficacy and tolerability of perampanel in ten patients with Lafora disease

Lafora disease (LD) is a fatal intractable adolescence-onset progressive myoclonus epilepsy. Recently, two single-case studies reported drastic reductions in seizures and myoclonus with the AMPA antagonist perampanel and improved activities of daily living. We proceeded to study the effect of perampanel on 10 patients with genetically confirmed LD with disease duration ranging from 2 to 27years. Open-label perampanel was added to ongoing medications to a mean dose of 6.7mg/day. Seizures, myoclonus, functional disability, and cognition scores were measured for the third and ninth months following initiation and compared with those of the month prior to the start of therapy. Three patients withdrew because of inefficacy or side effects. Four had significant reduction in seizures of greater than 74% from baseline. Seven had major improvement in myoclonus with group-adjusted sum score of myoclonus intensity reduced from 7.01 at baseline to 5.67 and 5.18 at 3 and 9months, respectively. There was no significant improvement in disability and cognition. While not universal, perampanel adjunctive therapy appears to confer particular benefit not commonly seen with other antiepileptic drugs on seizures and myoclonus in LD. Improvement in the extremely disabling myoclonus of LD is a major benefit in this devastating disease.

Review of clinical studies of perampanel in adolescent patients

AIM

To assess the clinical trial and real-world data for adjunctive perampanel in adolescents and develop consensus recommendations to guide the use of perampanel in this population in clinical practice.

METHODS

In May 2015, 15 epilepsy experts attended a Consensus Development Meeting to assess the clinical trial data for perampanel, specific to the adolescent age group (12-17 years) and develop consensus treatment recommendations.

RESULTS AND DISCUSSION

Analysis of the adolescent subgroup data of three pivotal placebo-controlled, double-blind, phase 3 trials investigating perampanel in patients with ongoing focal epileptic seizures despite receiving one to three antiepileptic drugs found that perampanel 4-12 mg was superior to placebo. The tolerability profile of perampanel was generally acceptable. Adolescent patients receiving long-term treatment with perampanel in an open-label extension study maintained improvements in seizure control compared with baseline, with a favorable risk-benefit profile. A phase 2 study showed that perampanel had no clinically important effects on cognitive function, growth, and development.

CONCLUSION

Perampanel is a welcome addition to the armamentarium of existing antiepileptic drugs as it represents a new approach in the management of epilepsy, with a novel mechanism of action, and the potential to have a considerable impact on the treatment of adolescents with epilepsy.

Ca2+-permeable AMPA receptor: A new perspective on amyloid-beta mediated pathophysiology of Alzheimer's disease

α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are the primary conduits of excitatory synaptic transmission. AMPARs are predominantly Ca²⁺-impermeable in the matured excitatory synapse, except under certain circumstances. Growing evidence implicates the Ca²⁺ permeability of AMPARs in the regulation of long-term synaptic plasticity and in the pathophysiology of several neurological disorders. Therefore, the Ca²⁺ conductance of AMPARs may have both physiological and pathological roles at synapses. However, our understanding of the role of Ca²⁺ permeable AMPARs (CP-AMPARs) in Alzheimer's disease is limited. Here we discuss insights into the potential CP-AMPAR mediated pathophysiology of Alzheimer's disease, including: 1. Ca²⁺-mediated aberrant regulation of synapse weakening mechanisms, and 2. neuronal network dysfunction in the brain. Consideration of CP-AMPARs as primary drivers of pathophysiology could help in understanding synaptopathologies, and highlights the potential of CP-AMPARs as therapeutic targets in Alzheimer's disease. This article is part of the Special Issue entitled 'Ionotropic glutamate receptors'.

Effectiveness and tolerability of perampanel in children and adolescents with refractory epilepsies-An Italian observational multicenter study

PURPOSE

To evaluate the efficacy and tolerability of Perampanel (PER) in children and adolescents with refractory epilepsies in daily clinical practice conditions.

PATIENTS AND METHODS

This Italian multicenter retrospective observational study was performed in 16 paediatric epilepsy centres. Inclusion criteria were: (i) ≤18 years of age, (ii) history of refractory epilepsy, (iii) a follow-up ≥5 months of PER add-on therapy. Exclusion criteria were: (i) a diagnosis of primary idiopathic generalized epilepsy, (ii) variation of concomitant AEDs during the previous 4 weeks. Response was defined as a ≥50% reduction in monthly seizure frequency compared with the baseline.

RESULTS

62 patients suffering from various refractory epilepsies were included in this study: 53% were males, the mean age was 14.2 years (range 6-18 years), 8 patients aged <12 years. Mean age at epilepsy onset was 3.4 years and the mean duration of epilepsy was 10.8 years (range 1-16), which ranged from 2 seizures per-month up to several seizures per-day (mean number=96.5). Symptomatic focal epilepsy was reported in 62.9% of cases. Mean number of AEDs used in the past was 7.1; mean number of concomitant AEDs was 2.48, with carbamazepine used in 43.5% of patients. Mean PER daily dose was 7.1mg (2-12mg). After an average of 6.6 months of follow-up (5-13 months), the retention rate was 77.4% (48/62). The response rate was 50%; 16% of patients achieved ≥75% seizure frequency reduction and 5% became completely seizure free. Seizure aggravation was observed in 9.7% of patients. Adverse events were reported in 19 patients (30.6%) and led to PER discontinuation in 4 patients (6.5%). The most common adverse events were behaviour disturbance (irritability and aggressiveness), dizziness, sedation and fatigue.

CONCLUSION

PER was found to be a safe and effective treatment when used as adjunctive therapy in paediatric patients with uncontrolled epilepsy.

Fit for purpose application of currently existing animal models in the discovery of novel epilepsy therapies

Animal seizure and epilepsy models continue to play an important role in the early discovery of new therapies for the symptomatic treatment of epilepsy. Since 1937, with the discovery of phenytoin, almost all anti-seizure drugs (ASDs) have been identified by their effects in animal models, and millions of patients world-wide have benefited from the successful translation of animal data into the clinic. However, several unmet clinical needs remain, including resistance to ASDs in about 30% of patients with epilepsy, adverse effects of ASDs that can reduce quality of life, and the lack of treatments that can prevent development of epilepsy in patients at risk following brain injury. The aim of this review is to critically discuss the translational value of currently used animal models of seizures and epilepsy, particularly what animal models can tell us about epilepsy therapies in patients and which limitations exist. Principles of translational medicine will be used for this discussion. An essential requirement for translational medicine to improve success in drug development is the availability of animal models with high predictive validity for a therapeutic drug response. For this requirement, the model, by definition, does not need to be a perfect replication of the clinical condition, but it is important that the validation provided for a given model is fit for purpose. The present review should guide researchers in both academia and industry what can and cannot be expected from animal models in preclinical development of epilepsy therapies, which models are best suited for which purpose, and for which aspects suitable models are as yet not available. Overall further development is needed to improve and validate animal models for the diverse areas in epilepsy research where suitable fit for purpose models are urgently needed in the search for more effective treatments.

Safety and efficacy of perampanel in children and adults with various epilepsy syndromes: A single-center postmarketing study

INTRODUCTION

Perampanel is an AMPA receptor antagonist recently approved for the treatment of partial and generalized epilepsies with tonic-clonic seizures as an add-on therapy.

METHODS

This single-center postmarketing study retrospectively evaluated the efficacy of perampanel in patients with partial onset and other seizure types, with a special emphasis on its efficacy, safety, and tolerability.

RESULTS

Review of medical records revealed that adequate data were available on 101 patients taking perampanel. Fifty-seven patients were female. Sixteen patients were of pediatric age range. The average dose of perampanel was 6.5mg, and average treatment duration was 8.2months. After treatment, median seizure frequency reduction was 50% overall, 50% in children, and 33% in adults; 44% in primary generalized, 38% in secondarily generalized, and 33% in partial seizures. Responder rate (50% seizure frequency reduction) was 51% overall, 63% in children, and 49% in adults; 60% in partial seizures, 43% in secondarily generalized tonic-clonic seizures, 53% in primary generalized tonic-clonic seizures, and 56% in other seizure types. Seizure freedom was attained in 6% of cases. Most common adverse events were sleepiness/fatigue (35%), behavioral problems (30%), and dizziness (22%). Adverse events were correlated with dosage. Average dose was 7.3mg in patients with adverse events vs. 5.5mg in those without adverse events. Patients who developed fatigue, cognitive decline, headaches, and weight gain were more likely to discontinue perampanel than those patients who experienced coordination issues and behavioral problems.

CONCLUSIONS

These findings suggest that perampanel is safe, well-tolerated, and effective in treatment of various types of adult and pediatric epilepsy syndromes. Fatigue, cognitive decline, headache and weight gain were the main causes of perampanel discontinuation.

AMPA-Kainate Receptor Inhibition Promotes Neurologic Recovery in Premature Rabbits with Intraventricular Hemorrhage

Intraventricular hemorrhage (IVH) in preterm infants leads to cerebral inflammation, reduced myelination of the white matter, and neurological deficits. No therapeutic strategy exists against the IVH-induced white matter injury. AMPA-kainate receptor induced excitotoxicity contributes to oligodendrocyte precursor cell (OPC) damage and hypomyelination in both neonatal and adult models of brain injury. Here, we hypothesized that IVH damages white matter via AMPA receptor activation, and that AMPA-kainate receptor inhibition suppresses inflammation and restores OPC maturation, myelination, and neurologic recovery in preterm newborns with IVH. We tested these hypotheses in a rabbit model of glycerol-induced IVH and evaluated the expression of AMPA receptors in autopsy samples from human preterm infants. GluR1-GluR4 expressions were comparable between preterm humans and rabbits with and without IVH. However, GluR1 and GluR2 levels were significantly lower in the embryonic white matter and germinal matrix relative to the neocortex in both infants with and without IVH. Pharmacological blockade of AMPA-kainate receptors with systemic NBQX, or selective AMPA receptor inhibition by intramuscular perampanel restored myelination and neurologic recovery in rabbits with IVH. NBQX administration also reduced the population of apoptotic OPCs, levels of several cytokines (TNFα, IL-β, IL-6, LIF), and the density of Iba1(+) microglia in pups with IVH. Additionally, NBQX treatment inhibited STAT-3 phosphorylation, but not astrogliosis or transcription factors regulating gliosis. Our data suggest that AMPA-kainate receptor inhibition alleviates OPC loss and IVH-induced inflammation and restores myelination and neurologic recovery in preterm rabbits with IVH. Therapeutic use of FDA-approved perampanel treatment might enhance neurologic outcome in premature infants with IVH.

SIGNIFICANCE STATEMENT

Intraventricular hemorrhage (IVH) is a major complication of prematurity and a large number of survivors with IVH develop cerebral palsy and cognitive deficits. The development of IVH leads to inflammation of the periventricular white matter, apoptosis and arrested maturation of oligodendrocyte precursor cells, and hypomyelination. Here, we show that AMPA-kainate receptor inhibition by NBQX suppresses inflammation, attenuates apoptosis of oligodendrocyte precursor cells, and promotes myelination as well as clinical recovery in preterm rabbits with IVH. Importantly, AMPA-specific inhibition by the FDA-approved perampanel, which unlike NBQX has a low side-effect profile, also enhances myelination and neurological recovery in rabbits with IVH. Hence, the present study highlights the role of AMPA-kainate receptor in IVH-induced white matter injury and identifies a novel strategy of neuroprotection, which might improve the neurological outcome for premature infants with IVH.

The Noncompetitive AMPAR Antagonist Perampanel Abrogates Brain Endothelial Cell Permeability in Response to Ischemia: Involvement of Claudin-5

The blood-brain barrier (BBB) is formed by brain endothelial cells, and decreased BBB integrity contributes to vasogenic cerebral edema and increased mortality after stroke. In the present study, we investigated the protective effect of perampanel, an orally active noncompetitive AMPA receptor antagonist, on BBB permeability in an in vitro ischemia model in murine brain endothelial cells (mBECs). The results showed that perampanel significantly attenuated oxygen glucose deprivation (OGD)-induced loss of cell viability, release of lactate dehydrogenase, and apoptotic cell death in a dose-dependent manner. Perampanel treatment did not alter the expression and surface distribution of various glutamate receptors. Furthermore, the results of calcium imaging showed that perampanel had no effect on OGD-induced increase in intracellular Ca(2+) concentrations. Treatment with perampanel markedly reduced the paracellular permeability of mBECs after OGD in different time points, as measured by transepithelial electrical resistance assay. In addition, the expression of claudin-5 at protein level, but not at mRNA level, was increased by perampanel treatment after OGD. Knockdown of claudin-5 partially prevented perampanel-induced protection in cell viability and BBB integrity in OGD-injured mBECs. These data show that the noncompetitive AMPA receptor antagonist perampanel affords protection against ischemic stroke through caludin-5 mediated regulation of BBB permeability.

The AMPA receptor antagonist perampanel robustly rescues amyotrophic lateral sclerosis (ALS) pathology in sporadic ALS model mice

Both TDP-43 pathology and failure of RNA editing of AMPA receptor subunit GluA2, are etiology-linked molecular abnormalities that concomitantly occur in the motor neurons of the majority of patients with amyotrophic lateral sclerosis (ALS). AR2 mice, in which an RNA editing enzyme adenosine deaminase acting on RNA 2 (ADAR2) is conditionally knocked out in the motor neurons, exhibit a progressive ALS phenotype with TDP-43 pathology in the motor neurons through a Ca²⁺-permeable AMPA receptor-mediated mechanism. Therefore, amelioration of the increased Ca²⁺ influx by AMPA receptor antagonists may be a potential ALS therapy. Here, we showed that orally administered perampanel, a selective, non-competitive AMPA receptor antagonist significantly prevented the progression of the ALS phenotype and normalized the TDP-43 pathology-associated death of motor neurons in the AR2 mice. Given that perampanel is an approved anti-epileptic drug, perampanel is a potential candidate ALS drug worthy of a clinical trial.

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 antiepileptic drugs: focus on ezogabine, clobazam, and perampanel

Ezogabine, clobazam, and perampanel are among the newest antiseizure drugs approved by the Food and Drug Administration between 2011 and 2012. Ezogabine and perampanel are approved for adjunctive treatment of partial epilepsy. Perampanel is also approved for adjunctive treatment of primary generalized tonic–clonic seizures. Ezogabine and perampanel have novel mechanisms of action. Ezogabine binds to voltage-gated potassium channels and increases the M-current thereby causing membrane hyperpolarization. Perampanel is a selective, non-competitive 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid receptor antagonist, which reduces neuronal excitation. Clobazam has been used worldwide since the 1970s and is approved for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome. Clobazam is the only 1,5-benzodiazepine currently in clinical use, which is less sedating than the commonly used 1,4-benzodiazepines. Phase III multicenter, randomized, double-blind, placebo-controlled trials demonstrated efficacy and good tolerability of these 3 new antiepileptic drugs. These drugs represent a welcome addition to the armamentarium of practitioners, but it remains to be seen how they will affect the landscape of pharmacoresistant epilepsy.

Russian experience of using perampanel in daily clinical practice. Preliminary report

Introduction. Perampanel (PER) (Fycompa) 5′-(2-cyanophenyl)-1′-phenyl-2,3′-bipyridinyl-6′(1′H)-on is the newest antiepileptic drug and is the first-in-class selective non-competitive antagonist of ionotropic AMPA glutamate receptors of the postsynaptic neuronal membrane.

The aim was to summarize Russian experience in using PER in daily clinical practice, and for this purpose the results of its use as an add-on treatment for focal epilepsy were assessed retrospectively

Material and Method. The results of the study of PER efficacy and safety in 52 patients with refractory focal epilepsy are presented. Mean age was 28.9 ± 14.0 years; proportion of male patients was 56%, duration of the disease over 10 years - 69.2%, symptomatic epilepsy - 76.9%, with frontal - 46.2% and temporal - 44.2% localization of epileptic lesion. Majority of patients - 71.2% started PER treatment after 3 preceding lines of therapy

Results. The baseline seizure frequency of all types was 127.3 ± 82.3 per month; secondary generalized seizures - 6.7 ± 1.9 per month. After PER was added, a significant decrease in seizure frequency was observed already during the first month, to 52.1 ± 29.3 seizures per month (Sign test, p = 0.00001) for seizures of all types and to 3.7 ± 1.7 (Sign test, p = 0.00001) for secondary generalized seizures. In an overwhelming majority of cases, duration of PER treatment was more than 6 months. In 58% of patients, seizure frequency decreased by more than 50% (responders). Seizure-free status for all seizure types was observed in 9% of cases at 12 month, and absence of secondary generalized seizures only was achieved in 31% of patients. Adverse events were observed in 30.1% of patients: aggression - 11.5% and drowsiness - 9.6%, with all other AEs observed more rarely. PER dose was reduced due to side effects in 7 patients (13.5%), and in 4 patients (7.7%) PER was discontinued. Average PER dose in adult patients was as low as 6 mg.

Conclusions. PER was effective in the treatment of refractory forms of focal epilepsy, reducing seizure frequency on average by 76% by the second month of treatment. In addition to a good clinical effect, PER demonstrated a rather acceptable and predictable safety profile.

Targeted Treatment in Childhood Epilepsy Syndromes

OPINION STATEMENT

The mainstay of treatment of epilepsy has been antiepileptic drugs; however, despite the emergence of new agents, a consistent proportion remain drug-resistant. Newer AEDs show promise. However, as it becomes clear that the epilepsies are a group of diseases rather than a single disorder the prospect of targeted treatment in some may become a reality.

Mechanisms of Action of Antiseizure Drugs and the Ketogenic Diet

Antiseizure drugs (ASDs), also termed antiepileptic drugs, are the main form of symptomatic treatment for people with epilepsy, but not all patients become free of seizures. The ketogenic diet is one treatment option for drug-resistant patients. Both types of therapy exert their clinical effects through interactions with one or more of a diverse set of molecular targets in the brain. ASDs act by modulation of voltage-gated ion channels, including sodium, calcium, and potassium channels; by enhancement of γ-aminobutyric acid (GABA)-mediated inhibition through effects on GABAA receptors, the GABA transporter 1 (GAT1) GABA uptake transporter, or GABA transaminase; through interactions with elements of the synaptic release machinery, including synaptic vesicle 2A (SV2A) and α2δ; or by blockade of ionotropic glutamate receptors, including α-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors. The ketogenic diet leads to increases in circulating ketones, which may contribute to the efficacy in treating pharmacoresistant seizures. Production in the brain of inhibitory mediators, such as adenosine, or ion channel modulators, such as polyunsaturated fatty acids, may also play a role. Metabolic effects, including diversion from glycolysis, are a further postulated mechanism. For some ASDs and the ketogenic diet, effects on multiple targets may contribute to activity. Better understanding of the ketogenic diet will inform the development of improved drug therapies to treat refractory seizures.

Discovery and Characterization of AMPA Receptor Modulators Selective for TARP-γ8

Members of the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) subtype of ionotropic glutamate receptors mediate the majority of fast synaptic transmission within the mammalian brain and spinal cord, representing attractive targets for therapeutic intervention. Here, we describe novel AMPA receptor modulators that require the presence of the accessory protein CACNG8, also known as transmembrane AMPA receptor regulatory protein γ8 (TARP-γ8). Using calcium flux, radioligand binding, and electrophysiological assays of wild-type and mutant forms of TARP-γ8, we demonstrate that these compounds possess a novel mechanism of action consistent with a partial disruption of the interaction between the TARP and the pore-forming subunit of the channel. One of the molecules, 5-[2-chloro-6-(trifluoromethoxy)phenyl]-1,3-dihydrobenzimidazol-2-one (JNJ-55511118), had excellent pharmacokinetic properties and achieved high receptor occupancy following oral administration. This molecule showed strong, dose-dependent inhibition of neurotransmission within the hippocampus, and a strong anticonvulsant effect. At high levels of receptor occupancy in rodent in vivo models, JNJ-55511118 showed a strong reduction in certain bands on electroencephalogram, transient hyperlocomotion, no motor impairment on rotarod, and a mild impairment in learning and memory. JNJ-55511118 is a novel tool for reversible AMPA receptor inhibition, particularly within the hippocampus, with potential therapeutic utility as an anticonvulsant or neuroprotectant. The existence of a molecule with this mechanism of action demonstrates the possibility of pharmacological targeting of accessory proteins, increasing the potential number of druggable targets.

Contribution of NRG1 Gene Polymorphisms in Temporal Lobe Epilepsy

The purpose of the present study was to investigate the possible association between temporal lobe epilepsy and NRG1 gene polymorphisms. A total of 73 patients and 69 controls were involved in this study. Genomic DNAs from the patients and controls were genotyped by polymerase chain reaction-ligase detection reaction method. There was an association of rs35753505 (T>C) with temporal lobe epilepsy (χ(2) = 6.730, P = .035). The frequency of risk allele C of rs35753505 was significantly higher (69.9%) in patients compared to controls (55.8%) (χ(2) = 6.023, P = .014). Interestingly, the significant difference of NRG1 genotype and allele frequency only existed among males, but not females. In addition, no statistically significant association was found between rs6994992, rs62510682 polymorphisms, and temporal lobe epilepsy. These data indicate that rs35753505 of NRG1 plays an important role in conferring susceptibility to the temporal lobe epilepsy in a Chinese Han population.

Synergism of perampanel and zonisamide in the rat amygdala kindling model of temporal lobe epilepsy

OBJECTIVE

Anticonvulsive monotherapy fails to be effective in one third of patients with epilepsy resulting in the need for polytherapy regimens. However, with the still limited knowledge, drug choices for polytherapy remain empirical. Here we report experimental data from a chronic epilepsy model for the combination of perampanel and zonisamide, which can render guidance for clinical studies and individual drug choices.

METHODS

The anticonvulsant effects of the combination of perampanel and zonisamide were evaluated in a rat amygdala kindling model. Furthermore, the potential for motor impairment was evaluated. The type of interaction was quantitatively assessed based on isobolographic analysis.

RESULTS

When administered alone, zonisamide dose-dependently increased the afterdischarge threshold in fully kindled rats. Moreover, data confirmed efficacy of perampanel to inhibit seizure initiation and progression with an impact on propagation of activity from the focus. Pronounced threshold increases were observed following administration of a constant zonisamide dosage combined with different doses of perampanel. Isobolographic analysis of drug responses, which is based on individual drug dose-effect data, revealed a synergistic interaction substantiating the high efficacy of the combination. Furthermore, rotarod data indicated that the combination has a favorable tolerability profile when zonisamide is coadministered with low doses of perampanel. Plasma concentration analysis argued against a pharmacokinetic interaction as a basis for the synergism.

SIGNIFICANCE

The findings clearly indicate a pronounced synergistic anticonvulsant effect for the combination of the noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist perampanel with zonisamide, which modulates voltage-sensitive sodium channels and T-type calcium currents. Consequently, polytherapy using these two antiepileptic drugs might be efficacious for clinical management of partial-onset seizures. The findings indicate that the impact of dose ratios on tolerability needs be taken into account. With regard to conclusions about the extent of the synergism and its implications further antiepileptic drug combinations need to be evaluated allowing direct comparison.

Cognitive effects of adjunctive perampanel for partial-onset seizures: A randomized trial

Objective

Assess cognitive effects of adjunctive perampanel in adolescents.

Methods

In this double‐blind study (ClinicalTrials.gov identifier: NCT01161524), patients aged 12 to <18 years with partial‐onset seizures despite receiving 1–3 antiepileptic drugs were randomized (2:1) to perampanel or placebo. Perampanel was increased weekly in 2‐mg increments to 8–12 mg/day (6‐week titration; 13‐week maintenance). Changes in neuropsychological outcomes were assessed at end of maintenance: Cognitive Drug Research (CDR) System Global Cognition Score (primary end point), five CDR System domain T‐scores (secondary end points), letter fluency, category fluency, and Lafayette Grooved Pegboard Test (LGPT).

Results

One hundred thirty‐three patients were randomized. In the full analysis set, there were no differences of perampanel (n = 79) vs. placebo (n = 44) in CDR System Global Cognition Score (least squares mean change, −0.6 vs. 1.6; p = 0.145), Quality of Working Memory (1.1 vs. 2.0; p = 0.579), or Power of Attention (−6.9 vs. −2.7; p = 0.219). There were small differences with perampanel vs. placebo in other CDR System domains: improvements in Quality of Episodic Memory (3.0 vs. −1.2; p = 0.012), and worsening in Continuity of Attention (−3.3 vs. 1.6; p = 0.013) and Speed of Memory (0.3 vs. 7.0; p = 0.032). Letter fluency, category fluency, and LGPT were not significantly different between groups. The most frequent adverse events with perampanel were dizziness (30.6%) and somnolence (15.3%).

Significance

Perampanel did not differ from placebo in the global cognitive score, two of five subdomains, and four other cognitive measures. Perampanel was worse on two and better on one subdomain.

Clinical efficacy of perampanel for partial-onset and primary generalized tonic-clonic seizures

BACKGROUND AND PURPOSE

Perampanel, a selective noncompetitive antagonist at the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, is highly effective in a wide range of experimental models. Although initially licensed as adjunctive therapy for partial seizures with or without secondary generalization in patients aged 12 years or older, the US Food and Drug Administration has recently approved its use in the treatment of primary generalized tonic-clonic seizures (PGTCS). This paper reviews the pharmacokinetics, efficacy, and tolerability of perampanel as an antiepileptic drug.

RESULTS

After oral ingestion, perampanel is rapidly absorbed (T max, 0.5-2.5 hours), has a bioavailability of ~100%, and is highly protein bound (~95%) in plasma. It undergoes extensive (>90%) hepatic metabolism, primarily via cytochrome P450 3A4 (CYP3A4), with a half-life of 48 hours. Carbamazepine and other antiepileptic drugs can enhance its metabolism via induction of CYP3A4. Efficacy of perampanel in focal seizures has been extensively evaluated in Phase II and randomized, placebo-controlled Phase III trials. The efficacy in PGTCS has been reported in one class I study. In the treatment of focal seizures, perampanel showed significant dose-dependent median seizure reductions: 4 mg/d, 23%; 8 mg/d, 26%-31%; 12 mg/d, 18%-35%; and placebo, 10%-21%. The 50% responder rates were 15%-26%, 29%, 33%-38%, and 34%-36% for placebo, 4 mg/d, 8 mg/d, and 12 mg/d perampanel, respectively. Freedom from seizures was recorded in 0%-1.7% of the placebo group, 1.9% of the 2 mg group, 2.6%-4.4% of the 8 mg group, and 2.6%-6.5% of the 12 mg group. For PGTCS, the median seizure reduction was 76.5% for perampanel and 38.4% for placebo. The 50% responder rate was 64.2% for perampanel and 39.5% for placebo. Seizure freedom during maintenance phase was 30.9% for perampanel and 12.3% for placebo. Adverse effects included dose-dependent increases in the frequency of dizziness, somnolence, fatigue, irritability, falls, and probably nausea.

CONCLUSION

Perampanel is effective in treating both partial-onset seizures and PGTCS.

Perspectives on treatment options for mesial temporal lobe epilepsy with hippocampal sclerosis

INTRODUCTION

Mesial temporal lobe epilepsy associated with hippocampal sclerosis (MTLE-HS) is a syndrome that is often refractory to drug treatment. The effects on specific syndromes are not currently available from the pre-marketing clinical development of new AEDs; this does not allow the prediction of whether new drugs will be more effective in the treatment of some patients.

AREAS COVERED

We have reviewed all the existing literature relevant to the understanding of a potential effectiveness in MTLE-HS patients for the latest AEDs, namely brivaracetam, eslicarbazepine, lacosamide, perampanel and retigabine also including the most relevant clinical data and a brief description of their pharmacological profile. Records were identified using predefined search criteria using electronic databases (e.g., PubMed, Cochrane Library Database of Systematic Reviews). Primary peer-reviewed articles published up to the 15 June 2015 were included.

EXPERT OPINION

All the drugs considered have the potential to be effective in the treatment of MTLE-HS; in fact, they possess proven efficacy in animal models; currently considered valuable tools for predicting drug efficacy in TLE. Furthermore, for some of these (e.g., lacosamide and eslicarbazepine) data are already available from post-marketing studies while brivaracetam acting on SV2A like levetiracetam might have the same potential effectiveness with the possibility to be more efficacious considering its ability to inhibit voltage gated sodium channels; finally, perampanel and retigabine are very effective drugs in animal models of TLE.

Use of perampanel in one case of super-refractory hypoxic myoclonic status: Case report

Proper treatment of hypoxic myoclonic status is not clearly determined. Induced hypothermia is improving prognosis and a more aggressive treatment might be beneficial in some patients. Among the new options of antiepileptic drugs, perampanel (PER) is a drug with a novel mechanism, and it might be a promising drug for myoclonic status or as an antimyoclonic drug. We describe the use of PER in one patient with hypoxic super-refractory myoclonic status.

Description

A 51-year-old patient presented after an out-of-hospital cardiac arrest due to an acute myocardial infarction. The patient was diagnosed with clinical and electrical (EEG) myoclonic status at the rewarming phase. Several treatments were used, starting with clonazepam, valproate, sedation (midazolam, propofol), and subsequently barbiturate-induced coma with persistent myoclonic status. Finally, we decided to try PER (dose: 6–8 mg) through a nasogastric tube, resulting in a marked improvement of EEG activity and myoclonus decrease. The patient had a progressive clinical improvement, with a CPC (Cerebral Performance Category) scale score of 1.

Conclusion

This case shows the potential utility of PER as a therapeutic option in super-refractory hypoxic status and even its potential use before other aggressive alternatives considering their greater morbidity.

Efficacy and safety of perampanel in adolescent patients with drug-resistant partial seizures in three double-blind, placebo-controlled, phase III randomized clinical studies and a combined extension study

OBJECTIVE

Assess perampanel's efficacy and safety as adjunctive therapy in adolescents (ages 12-17) with drug-resistant partial seizures.

METHODS

Adolescent patients enrolled in multinational, double-blind, placebo-controlled, phase III core studies (studies 304, 305, or 306) completed 19-week, double-blind phase (6-week titration/13-week maintenance) with once-daily perampanel or placebo. Upon completion, patients were eligible for the extension (study 307), beginning with 16-week, blinded conversion, during which placebo patients switched to perampanel. Patients then entered the open-label treatment.

RESULTS

Of 1480 patients from the core studies, 143 were adolescents. Pooled adolescent data from these core studies demonstrated median percent decreases in seizure frequency for perampanel 8 mg (34.8%) and 12 mg (35.6%) were approximately twice that of placebo (18.0%). Responder rates increased with perampanel 8 mg (40.9%) and 12 mg (45.0%) versus placebo (22.2%). Adolescents receiving concomitant enzyme-inducing antiepileptic drugs (AEDs) had smaller reductions in seizure frequency (8 mg:31.6%; 12 mg:26.8%) than those taking non-inducing AEDs (8 mg:54.6%; 12 mg:52.7%). Relative to pre-perampanel baseline, seizure frequency and responder rates during the extension (Weeks 1-52) improved with perampanel. Most commonly reported adverse events in adolescents during the core studies were dizziness (20.4%), somnolence (15.3%), aggression (8.2%), decreased appetite (6.1%), and rhinitis (5.1%). Dizziness (13.2%), somnolence (11.6%), and aggression (6.6%) most often led to perampanel interruption/dose adjustment during the extension.

SIGNIFICANCE

Data demonstrated adjunctive perampanel treatment in adolescents with drug-resistant partial seizures produced better seizure control versus placebo, sustained seizure frequency improvements, and a generally favorable safety profile. Results were comparable to the overall study population.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov Identifiers: Study 304: NCT00699972; 305: NCT00699582; 306: NCT00700310; Study 307: NCT00735397.

Glutamatergic Mechanisms Associated with Seizures and Epilepsy

Epilepsy is broadly characterized by aberrant neuronal excitability. Glutamate is the predominant excitatory neurotransmitter in the adult mammalian brain; thus, much of past epilepsy research has attempted to understand the role of glutamate in seizures and epilepsy. Seizures induce elevations in extracellular glutamate, which then contribute to excitotoxic damage. Chronic seizures can alter neuronal and glial expression of glutamate receptors and uptake transporters, further contributing to epileptogenesis. Evidence points to a shared glutamate pathology for epilepsy and other central nervous system (CNS) disorders, including depression, which is often a comorbidity of epilepsy. Therapies that target glutamatergic neurotransmission are available, but many have met with difficulty because of untoward adverse effects. Better understanding of this system has generated novel therapeutic targets that directly and indirectly modulate glutamatergic signaling. Thus, future efforts to manage the epileptic patient with glutamatergic-centric treatments now hold greater potential.

The AMPA receptor antagonist perampanel in the adjunctive treatment of partial-onset seizures: clinical trial evidence and experience

More than 20 antiepileptic drugs (AEDs) are currently available for the medical treatment of epilepsies. However, still about 30% of all epilepsies have a drug-resistant course. Even worse, in the case of some epilepsy syndromes, freedom from seizures is almost never achieved. Therefore, new treatment options are still necessary, especially if theoretical concepts such as a new mode of action offer new horizons. Perampanel is the first-in-class orally active, selective, noncompetitive antagonist of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. The pharmacokinetic profile offers once-daily dosing in the evening as the best route of administration. According to the results of three pivotal placebo-controlled, double-blind phase III trials that investigated perampanel as an adjunctive AED in adult and adolescent patients from age 12 years who had ongoing focal epileptic seizures despite receiving one to three AEDs, perampanel has been widely licensed and introduced. Phase III trials showed superiority of adjunctive perampanel over placebo consistently in the range between 4 and 12 mg. Dizziness and somnolence were by far the leading adverse events. This review covers the clinical trial evidence but also clinical experience with perampanel after launch according to observational studies.

The AMPA receptor antagonist NBQX exerts anti-seizure but not antiepileptogenic effects in the intrahippocampal kainate mouse model of mesial temporal lobe epilepsy

The AMPA receptor subtype of glutamate receptors, which mediates fast synaptic excitation, is of primary importance in initiating epileptiform discharges, so that AMPA receptor antagonists exert anti-seizure activity in diverse animal models of partial and generalized seizures. Recently, the first AMPA receptor antagonist, perampanel, was approved for use as adjunctive therapy for the treatment of resistant partial seizures in patients. Interestingly, the competitive AMPA receptor antagonist NBQX has recently been reported to prevent development of spontaneous recurrent seizures (SRS) in a neonatal seizure model in rats, indicating the AMPA antagonists may exert also antiepileptogenic effects. This prompted us to evaluate competitive (NBQX) and noncompetitive (perampanel) AMPA receptor antagonists in an adult mouse model of mesial temporal lobe epilepsy. In this model, SRS develop after status epilepticus (SE) induced by intrahippocampal injection of kainate. Focal electrographic seizures in this model are resistant to several major antiepileptic drugs. In line with previous studies, phenytoin was not capable of blocking such seizures in the present experiments, while they were markedly suppressed by NBQX and perampanel. However, perampanel was less tolerable than NBQX in epileptic mice, so that only NBQX was subsequently tested for antiepileptogenic potential. When mice were treated over three days after kainate-induced SE with NBQX (20 mg/kg t.i.d.), no effect on development or frequency of seizures was found in comparison to vehicle controls. These results suggest that AMPA receptor antagonists, while being effective in suppressing resistant focal seizures, are not exerting antiepileptogenic effects in an adult mouse model of partial epilepsy.