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

Effectiveness and tolerability of adjunctive perampanel in the treatment of pediatric patients with uncontrolled epilepsy: A retrospective, single-center, real-world study

OBJECTIVE

The main aim of this study was to assess the efficacy, safety, and tolerability of adjunctive perampanel (PER) in the treatment of children and adolescents with epilepsy.

METHODS

Pediatric patients who visited the pediatric epilepsy clinic of Henan Provincial People's Hospital between May 2020 and December 2021 were recruited. All participants were treated with PER as adjunctive therapy and were seen routinely (minimum: a baseline and 12-week visit). The efficacy and tolerability of adjunctive PER for the treatment of epilepsy were investigated.

RESULTS

One hundred and fourteen patients were enrolled, among whom 7 (6.1%) were lost to follow-up. At 12 weeks, the responder rate and the seizure-free rate were 56.1% (60/107) and 32.7% (35/107), respectively. The responder rate increased with the duration of PER administration and was significantly higher when PER was used as an early add-on (after ≤2 prior antiseizure medications (ASMs)) than a late add-on (after >2 prior ASMs). However, there was no significant difference in the treatment efficacy of adjunctive PER in patients with different epilepsy etiologies or types. Adverse events, including irritability, dizziness, somnolence, ataxic gait, weight gain, and tinnitus, were reported in thirty-two patients (29.9%).

CONCLUSIONS

In a routine clinical setting of pediatric patients with epilepsy, good effectiveness and tolerability of adjunctive PER were demonstrated. Notably, patients initiating PER as an early add-on showed a better seizure outcome than those initiating PER as a late add-on.

Perampanel monotherapy for the treatment of epilepsy: Clinical trial and real-world evidence

Perampanel, a selective, non-competitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist, is a once-daily oral anti-seizure medication (ASM) for focal-onset seizures (FOS) and generalized tonic-clonic seizures (GTCS). In the US, perampanel is approved for the treatment of FOS (adjunctive and monotherapy), with or without focal to bilateral tonic-clonic seizures (FBTCS), in patients aged ≥4 years, and as adjunctive treatment of GTCS in patients aged ≥12 years. The monotherapy approvals in the US were based on the Food and Drug Administration's (FDA's) policy allowing extrapolation of adjunctive data to the monotherapy setting in the absence of randomized controlled monotherapy trials; since then, perampanel monotherapy has received approvals in approximately 48 countries. As there are key differences in clinical evidence of perampanel as adjunctive therapy vs monotherapy, we review the clinical outcomes of perampanel when administered as primary or secondary monotherapy. Eight publications reporting the efficacy and safety outcomes of perampanel monotherapy in clinical trial and real-world settings were selected during our literature search and are included; these comprise three Eisai-sponsored studies in patients with epilepsy: one prospective, open-label, Phase III clinical trial of patients with newly diagnosed epilepsy (Study 342 [FREEDOM]) and two retrospective, real-world Phase IV studies of patients with epilepsy who received perampanel during routine clinical care (Studies 504 and 506 [PROVE]); and five retrospective, real-world studies in patients with epilepsy who were prescribed perampanel during routine clinical care. Results from these studies demonstrated that seizure freedom may be achieved following treatment with perampanel monotherapy (either primary or secondary), with favorable retention rates and safety profiles. Overall, the clinical evidence supports the use of perampanel monotherapy both in newly diagnosed patients and in those who have been unable to control their seizures with other ASMs.

Safety evaluation of perampanel as monotherapy or first adjunctive therapy in patients with epilepsy

INTRODUCTION

There is a need for anti-seizure medications (ASMs) that are well tolerated and effective as monotherapy or first adjunctive therapy to reduce the need for adjunctive ASMs to treat newly diagnosed epilepsy, and to reduce the number of concomitant ASMs in patients with refractory epilepsy. Although the pivotal trials of perampanel evaluated its adjunctive use in patients with refractory seizures, open-label/real-world studies support its use in first/second-line settings.

AREAS COVERED

This paper reviews the pharmacology, efficacy, and safety/tolerability of perampanel, focusing on its use as monotherapy or first adjunctive therapy. The safety of perampanel in special populations and its safety/tolerability compared with that of other ASMs is also discussed.

EXPERT OPINION

Perampanel is a favorable candidate for initial or first adjunctive therapy due to its favorable efficacy and safety/tolerability as monotherapy and adjunctive therapy, its long half-life and ease of use, and its limited drug-drug interactions. The proposed mitigation strategies for managing the risk of serious psychiatric adverse events are appropriate patient selection, use of low doses, and slow titration. The growing body of evidence might shift current treatment strategies towards the early use of perampanel and its use at a low dose (4 mg/day).

Dietary effects on antiseizure drug metabolism and management of epilepsy

In recent years, there has been growing interest in the influences of food-drug interactions on the metabolism of antiseizure medications (ASM) and the management of epilepsy. Studies have proven the effectiveness of the ketogenic diet (KD) in controlling refractory epilepsy. However, dietary interventions such as the KD or its variants may induce significant changes in serum drug concentrations which counteracts the anticonvulsive effects of ASMs, leading to an increased risk of developing seizures. Interactions with enzymes within the cytochrome P450 system may also explain the dietary influences on serum concentrations of antiseizure drugs. The bioavailability of ASMs is also affected by several foods and nutritional supplements. Nevertheless, more studies are warranted to explore the mechanisms underlying food-drug interactions and the risks and benefits of combined drug-diet therapy.

Seratrodast, a thromboxane A2 receptor antagonist, inhibits neuronal ferroptosis by promoting GPX4 expression and suppressing JNK phosphorylation

More than 30 % of individuals with epilepsy are refractory to currently available drugs, highlighting the urgent need to develop novel candidate drugs. Accumulating evidence implicates the key role of ferroptosis in the pathophysiology of epileptic seizuresand its potential as a new drug target. Drug repurposing is a promising strategy for the rapid generation of new candidate drugs from the market drugs with new therapeutic indications, such as the best-selling drug thalidomide. Herein, we reported the discovery of Seratrodast, a market drug of thromboxane A2 receptor antagonist as a new ferroptosis inhibitor (IC₅₀: 4.5 μmol·L^-1). Seratrodast could reduce lipid ROS production, regulate the system x_c^-/glutathione (GSH)/glutathione peroxidase 4 (GPX4) axis, and inhibit JNK phosphorylation and p53 expression. In addition, Seratrodast elevated GPX4 expression and decreased JNK phosphorylation in pentylenetetrazole-induced seizures in mice. Seratrodast increased the latency of seizures and reduced seizure duration in pentylenetetrazole-induced seizures. Our results suggest Seratrodast might be either a ferroptosis inhibitor or a novel lead compound for further optimization of novel drug discovery.

Converging Mechanisms of Epileptogenesis and Their Insight in Glioblastoma

Glioblastoma (GBM) is the most common and advanced form of primary malignant tumor occurring in the adult central nervous system, and it is frequently associated with epilepsy, a debilitating comorbidity. Seizures are observed both pre- and post-surgical resection, indicating that several pathophysiological mechanisms are shared but also prompting questions about how the process of epileptogenesis evolves throughout GBM progression. Molecular mutations commonly seen in primary GBM, i.e., in PTEN and p53, and their associated downstream effects are known to influence seizure likelihood. Similarly, various intratumoral mechanisms, such as GBM-induced blood-brain barrier breakdown and glioma-immune cell interactions within the tumor microenvironment are also cited as contributing to network hyperexcitability. Substantial alterations to peri-tumoral glutamate and chloride transporter expressions, as well as widespread dysregulation of GABAergic signaling are known to confer increased epileptogenicity and excitotoxicity. The abnormal characteristics of GBM alter neuronal network function to result in metabolically vulnerable and hyperexcitable peri-tumoral tissue, properties the tumor then exploits to favor its own growth even post-resection. It is evident that there is a complex, dynamic interplay between GBM and epilepsy that promotes the progression of both pathologies. This interaction is only more complicated by the concomitant presence of spreading depolarization (SD). The spontaneous, high-frequency nature of GBM-associated epileptiform activity and SD-associated direct current (DC) shifts require technologies capable of recording brain signals over a wide bandwidth, presenting major challenges for comprehensive electrophysiological investigations. This review will initially provide a detailed examination of the underlying mechanisms that promote network hyperexcitability in GBM. We will then discuss how an investigation of these pathologies from a network level, and utilization of novel electrophysiological tools, will yield a more-effective, clinically-relevant understanding of GBM-related epileptogenesis. Further to this, we will evaluate the clinical relevance of current preclinical research and consider how future therapeutic advancements may impact the bidirectional relationship between GBM, SDs, and seizures.

Hippocampal Proteomic Analysis in Male Mice Following Aggressive Behavior Induced by Long-Term Administration of Perampanel

Antiepileptic drugs have been shown to be associated with inducing or exacerbating adverse psychotropic reaction, including aggressive behavior. Perampanel, the first pharmacological compound approved by the FDA in 2012, is an effective antiepileptic drug for intractable epilepsy but induces severe aggression. So far, the underlying molecular mechanisms of aggression induced by perampanel remain incompletely understood. In the present study, a model of aggressive behavior based on the clinical use of perampanel was established and resident-intruder test and open field test were performed. Changes in hippocampal protein profiles were detected by tandem mass tag (TMT) proteomics. The behavioral results indicated that long-term use of perampanel increased the aggressive behavior of C57BL/6J mice. Proteomic analysis revealed that 93 proteins were significantly altered in the hippocampus of the perampanel-treated group (corrected p < 0.05), which were divided into multiple functional groups, mainly related to synaptic function, synaptogenesis, postsynaptic density protein, neurite outgrowth, AMPA-type glutamate receptor immobilization, and others. Bioinformatic analysis showed that differentially expressed proteins were involved in synaptic plasticity and the Ras signaling pathway. Furthermore, validation results by western blot demonstrated that glutamate receptor 1 (GluA1) and phosphorylation of mitogen-activated protein kinase (ERK1/2) were notably up-regulated, and synaptophysin (Syn) and postsynaptic density 95 (PSD95) were down-regulated in perampanel-treated mice. Therefore, our results provide valuable insight into the molecular mechanisms of aggressive behavior induced by perampanel, as well as potential options for safety treatment of perampanel in the future.

Perampanel Reduces Brain Damage via Induction of M2 Microglia in a Neonatal Rat Stroke Model

Purpose

Ischemic stroke is a leading cause of death and disability worldwide. Additionally, neonatal ischemia is a common cause of neonatal brain injury, resulting in cerebral palsy with subsequent learning disabilities and epilepsy. However, there is currently a lack of effective treatments available for patients with perinatal ischemic stroke. In this study, we investigated the effect of perampanel (PER)-loaded poly lactic-co-glycolic acid (PLGA) by targeting microglia in perinatal stroke.

Methods

After formation of focal ischemic stroke by photothrombosis in P7 rats, PER-loaded PLGA was injected intrathecally. Proinflammatory markers (TNF-α, IL-1β, IL-6, COX2, and iNOS) and M2 polarization markers (Ym1 and Arg1) were evaluated. We investigated whether PER increased M2 microglial polarization in vitro.

Results

PER-loaded PLGA nanoparticles decreased the pro-inflammatory cytokines compared to the control group. Furthermore, they increased M2 polarization.

Conclusion

PER-loaded PLGA nanoparticles decreased the size of the infarct and increased motor function in a perinatal ischemic stroke rat model. Pro-inflammatory cytokines were also reduced compared to the control group. Finally, this development of a drug delivery system targeting microglia confirms the potential to develop new therapeutic agents for perinatal ischemic stroke.

Intranasal delivery of lipid-based nanosystems as a promising approach for brain targeting of the new-generation antiepileptic drug perampanel

Perampanel (PER), a new-generation antiepileptic drug effective against different types of seizures, has already demonstrated a potential in status epilepticus therapy. Considering the growing interest of intranasal (IN) administration for nose-to-brain delivery, PER could be envisioned as a good candidate for this route, especially if formulated in a lipid-based nanosystem. With that purpose, a hydrophobic formulation (FO1.2) and a self-microemulsifying drug delivery system (SMEDDS) (FH5) loaded with PER were developed and characterized. Following PER IN administration (1 mg/kg) to mice, its pharmacokinetics was characterized and compared with intravenous and oral routes. Histopathological toxicity was also examined after a 7-day repeated dose study. FH5 homogeneously formed nanodroplets upon dispersion (20.07 ± 0.03 nm), showing a sustained in vitro PER release profile up to 4 h. By IN route, PER brain delivery was more extensive with FH5 (C_max and AUC of 52.32 ng/g and 190.35 ng.h/g for FO1.2; 93.87 ng/g and 257.75 ng.h/g for FH5). Maximum brain concentration and total brain exposure were higher than those obtained after oral dosage, with maximum PER concentrations reached significantly faster than post-oral administration (15 min vs 2 h). An improvement in PER plasmatic concentration was also obtained, demonstrated by high relative bioavailability values (134.1% for FH5 and 107.8% for FO1.2). PER absolute plasma bioavailability after IN delivery was 55.5% for FH5 and 44.6% for FO1.2, ensuring a somewhat improved targeting of PER to the brain by the IN route compared to the IV route. No signs of toxicity were found by histopathologic evaluation. Results suggest that IN administration of PER might be a feasible and safe approach for acute and chronic epilepsy management, especially using delivery systems as SMEDDS.

Intravenous Perampanel as an Interchangeable Alternative to Oral Perampanel: A Randomized, Crossover, Phase I Pharmacokinetic and Safety Study

Intravenous (IV) drug administration enables treatment of epilepsy when oral administration is temporarily not feasible. Perampanel is a once‐daily antiseizure medication currently available as oral formulations. Study 050 (NCT03376997) was an open‐label, randomized, single‐dose, crossover study to evaluate the interchangeability of oral and IV perampanel in healthy subjects (N = 48). Bioequivalence of single 12‐mg doses of IV (30‐, 60‐, or 90‐minute infusion) and oral perampanel, ≥6 weeks apart, was assessed. Analyses indicated bioequivalence of area under the plasma concentration–time curve extrapolated to infinity for 30‐ and 60‐minute IV infusions and oral perampanel doses (geometric mean ratio [90% confidence interval], 0.93 [0.84–1.02] and 1.03 [0.97–1.09], respectively); however, IV maximum observed drug concentration (C_max) values were 1.35‐ to 1.61‐fold higher than C_max. Simulated plasma concentration–time profiles using pooled pharmacokinetic data further supported oral and IV perampanel interchangeability in two scenarios: 12‐mg per day IV dosing during a temporary 7‐day switch from oral steady‐state maintenance therapy, and treatment initiation with 2‐mg perampanel. Thirty‐four (70.8%) subjects experienced treatment‐related adverse events. The IV perampanel safety profile was similar to that of oral perampanel without new safety concerns. Perampanel IV infusions may be a suitable temporary alternative to oral perampanel for treatment maintenance and/or initiation.

Pyridone Directed Ru-Catalyzed Olefination of sp2(C-H) Bond Using Michael Acceptors: Creation of Drug Analogues

Herein, the ruthenium-catalyzed regioselective sp²(C-H) monoalkenylation of N-arylpyridones has been demonstrated, where the pyridone was utilized as a weakly coordinating directing group. Importantly, the current methodology has been effectively applied to the synthesis of many drug analogues such as pirfenidone, naproxen, ibuprofen, geraniol, umbelliferone, pregnenolone, and estrone. This methodology tolerates a wide range of functional groups and yields up to 93% yield. A six-membered ruthenium complex was also detected by HRMS.

Psychiatric and Behavioural Side Effects Associated With Perampanel in Patients With Temporal Lobe Epilepsy. A Real-World Experience

Psychiatric and behavioural side effects are common, undesirable effects associated with antiseizure medication use. Temporal lobe epilepsy is the most common focal epilepsy in adults and it is frequently associated with drug resistance. Patients with intractable epilepsy are more likely to have psychiatric and behavioural side effects when taking antiseizure medications and seem to be at higher risk for psychiatric comorbidities. Perampanel is a novel anti-seizure medication approved for focal and generalised epilepsies as add-on therapy. This is a 12-week short-term observational prospective study on people with focal epilepsy consecutively recruited from an Italian tertiary epilepsy centre, aimed to compare incidence and severity of psychiatric and behavioural side effects associated with perampanel use in patients with temporal lobe epilepsy as compared to other focal epilepsies. All patients received add-on perampanel according to indication and clinical judgement. Incidence and severity of psychiatric and behavioural side effects were rated by Neuropsychiatric Inventory Questionnaire. All patients enrolled answered the questionnaire before starting perampanel and after 12 weeks of treatment. We found no significant difference in terms of incidence and severity of psychiatric and behavioural side effects associated with perampanel in patients with temporal lobe epilepsy as compared to other focal epilepsies. In line with the literature, the most common adverse effects were “irritability” for both groups and “aggression” for patients with other focal epilepsies.

Testing of the therapeutic efficacy and safety of AMPA receptor RNA aptamers in an ALS mouse model

In motor neurons of sporadic amyotrophic lateral sclerosis (ALS) patients, the RNA editing at the glutamine/arginine site of the GluA2 subunit of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors is defective or incomplete. As a result, AMPA receptors containing the abnormally expressed, unedited isoform of GluA2 are highly Ca²⁺-permeable, and are responsible for mediating abnormal Ca²⁺ influx, thereby triggering motor neuron degeneration and cell death. Thus, blocking the AMPA receptor-mediated, abnormal Ca²⁺ influx is a potential therapeutic strategy for treatment of sporadic ALS. Here, we report a study of the efficacy and safety of two RNA aptamers targeting AMPA receptors on the ALS phenotype of AR2 mice. A 12-wk continuous, intracerebroventricular infusion of aptamers to AR2 mice reduced the progression of motor dysfunction, normalized TDP-43 mislocalization, and prevented death of motor neurons. Our results demonstrate that the use of AMPA receptor aptamers as a novel class of AMPA receptor antagonists is a promising strategy for developing an ALS treatment approach.

A pharmacovigilance approach for assessing the occurrence of suicide-related events induced by antiepileptic drugs using the Japanese adverse drug event report database

Increased suicidality after antiepileptic drug (AED) treatment remains controversial. This study aimed to investigate the occurrence of suicide-related events (SREs) in Japan. SREs signals with AEDs used orally were evaluated by calculating reporting odds ratios (RORs) and information components (ICs) using the Japanese Adverse Drug Event Report (JADER) database from April 2004 to December 2021. Additionally, factors affecting the occurrence of SREs and time-to-onset from the initial AED treatment were analyzed. Of 22 AEDs, 12 (perampanel hydrate, nitrazepam, levetiracetam, clonazepam, clobazam, sodium valproate, phenobarbital, lamotrigine, lacosamide, gabapentin, zonisamide, and carbamazepine) showed signals of SREs. Patients in their 20 and 30 s, female sex, and concomitant use of multiple AEDs affected the occurrence of SREs. In six AEDs, the median time-to-onset of SREs in patients taking all AEDs was <100 days. The pharmacovigilance approach revealed that several AEDs displayed suicidality signals. Female patients, those in their 20 and 30 s, undergoing combination therapy with ≥2 AEDs, and patients early (<100 days from the initial treatment) in the course of AED therapy should be cautioned about SREs.

Adjunctive perampanel therapy for patients with epileptic spasms

BACKGROUND

Perampanel is an antiepileptic drug. Some studies have documented the efficacy of perampanel in epileptic spasms. We aimed to evaluate the efficacy and safety of adjunctive perampanel therapy (PT) in patients with epileptic spasms.

METHODS

We retrospectively surveyed the efficacy and safety of adjunctive PT in 14 patients with epileptic spasms at the Saitama Children's Medical Center between June 2016 and September 2021. Seizure outcomes and safety were evaluated 12 months after commencing PT. Response to perampanel was defined as complete remission of epileptic spasms for more than 3 months.

RESULTS

The median age at onset of epileptic spasms was 0.4 years (range, 0.1-1.3 years). The etiology was structural in 11 patients, genetic in two, and unknown in one. The median age at the commencement of PT was 3.2 years (1.5-10.3 years). The initial and maintenance doses of perampanel were administered at 0.04 (range, 0.02-0.05) mg/kg/day and 0.12 (range, 0.03-0.24) mg/kg/day, respectively. Five of the 14 patients (35.7%) showed remission of epileptic spasms for more than 3 months at 12 months after PT; these patients had a structural etiology. The median duration between commencement of perampanel and spasm remission was 2 months (range, 1-6 months). No serious adverse effects occurred.

CONCLUSIONS

This is the first case series evaluating adjunctive PT for epileptic spasms. PT is worth investigating to treat epileptic spasms in patients with structural etiologies. As our study population primarily comprised children aged 2 years and older, PT may be useful for epileptic spasms beyond infancy.

A post-approval observational study to evaluate the safety and tolerability of perampanel as an add-on therapy in adolescent, adult, and elderly patients with epilepsy

OBJECTIVE

Perampanel is a once-daily oral anti-seizure medication for focal-onset seizures, with or without focal to bilateral tonic-clonic seizures (FBTCS), and generalized tonic-clonic seizures. Study 402 (NCT02033902) collected safety information on clinically important treatment-emergent adverse events (TEAEs) from real-world clinical practice in patients aged ≥12 years with refractory epilepsy who were receiving perampanel as an add-on therapy.

METHODS

Study 402 was a multicenter, observational, 52-week cohort study conducted in Austria, Belgium, Czech Republic, Denmark, France, Israel, Sweden, and the United Kingdom. Safety data were gathered prospectively from patients at clinic visits. The primary endpoint was the incidence of clinically important TEAEs defined as dizziness; blurred vision; somnolence; aggression; balance disorders (including ataxia and falls); weight gain; suicidality; drug abuse, misuse, dependence, and withdrawal; skin photosensitivity; and unintended pregnancy while taking levonorgestrel-containing contraceptives. Off-label use of perampanel and outcomes associated with any suspected drug-drug interaction were also monitored and recorded. Secondary endpoints included the Hospital Anxiety and Depression Scale (HADS) and Clinical Global Impression of Change.

RESULTS

Of 483 patients in the Safety Analysis Set, mean (standard deviation [SD]) age was 38.3 (15.1) years, 48.4% were female, mean (SD) time since diagnosis was 23 (14.8) years, 56.5% had focal impaired awareness seizures, and 48.7% had FBTCS. Overall, 243 (49.3%) patients treated with perampanel completed the study and 227 (46.0%) patients discontinued. The most common primary reason for discontinuation was adverse events (n = 130 [26.4%]). A total of 301 (62.3%) patients reported at least one TEAE, of which 45 (15.0%) patients had severe TEAEs and 256 (85.0%) patients had TEAEs judged as mild to moderate in severity. Overall, 51 (10.6%) patients had serious TEAEs, including two deaths that were judged as not related to perampanel, and 136 (28.2%) patients experienced a TEAE that led to treatment discontinuation. Clinically important TEAEs were reported by 153 (31.7%) patients, with the most common being dizziness (13.9%), balance disorders (5.6%), aggression (5.4%), and weight gain (5.4%). In general, the frequencies of clinically important TEAEs were lower in this study compared with previous interventional clinical studies, except for the incidence of suicidality (2.1% vs 1.0%) and aggression (5.4% vs 5.1%). Mean total HADS scores were similar at the end of the study compared with baseline; at the end of treatment, most (>60%) patients had no shift in HADS score category; ∼15% of patients moved to a worse category vs baseline and ∼20% of patients moved to an improved category vs baseline for both anxiety and depression. Based on investigator assessment, disease severity was improved in 185/415 (44.6%) patients. A subanalysis in elderly patients aged ≥65 years showed similar results to the overall population.

CONCLUSIONS

The data from this observational study are consistent with the known safety profile of perampanel derived from previous interventional phase II and III clinical studies. No unusual or unexpected TEAEs were observed in this real-world clinical practice setting.

Screening for Activity Against AMPA Receptors Among Anticonvulsants-Focus on Phenytoin

The interest in AMPA receptors as a target for epilepsy treatment increased substantially after the approval of perampanel, a negative AMPA receptor allosteric antagonist, for the treatment of partial-onset seizures and generalized tonic-clonic seizures. Here we performed a screening for activity against native calcium-permeable AMPA receptors (CP-AMPARs) and calcium-impermeable AMPA receptors (CI-AMPARs) among different anticonvulsants using the whole-cell patch-clamp method on isolated Wistar rat brain neurons. Lamotrigine, topiramate, levetiracetam, felbamate, carbamazepine, tiagabin, vigabatrin, zonisamide, and gabapentin in 100-µM concentration were practically inactive against both major subtypes of AMPARs, while phenytoin reversibly inhibited them with IC50 of 30 ± 4 μM and 250 ± 60 µM for CI-AMPARs and CP-AMPARs, respectively. The action of phenytoin on CI-AMPARs was attenuated in experiments with high agonist concentrations, in the presence of cyclothiazide and at pH 9.0. Features of phenytoin action matched those of the CI-AMPARs pore blocker pentobarbital, being different from classical competitive inhibitors, negative allosteric inhibitors, and CP-AMPARs selective channel blockers. Close 3D similarity between phenytoin and pentobarbital also suggests a common binding site in the pore and mechanism of inhibition. The main target for phenytoin in the brain, which is believed to underlie its anticonvulsant properties, are voltage-gated sodium channels. Here we have shown for the first time that phenytoin inhibits CI-AMPARs with similar potency. Thus, AMPAR inhibition by phenytoin may contribute to its anticonvulsant properties as well as its side effects.

Long-term efficacy and safety of perampanel as a first add-on therapy in patients with focal epilepsy: Three-year extension study

PURPOSE

We investigated the long-term efficacy and safety of perampanel as a first add-on therapy in patients with focal epilepsy.

METHODS

This retrospective study represented the 3-year extension phase of a multicenter, open-label, phase 4, prospective study of perampanel as a first add-on therapy in patients with focal epilepsy. Seizure and safety outcomes were assessed annually from the start of the extension study, and the retention rate was calculated from the start of perampanel exposure in the original study.

RESULTS

The 50% responder and seizure freedom rates were 84.8% and 58.7%, respectively, during the third year and 71.7% and 32.6%, respectively, during the entire 3-year period of the extension study. The 1-, 2-, and 3-year retention rates were 62.5%, 53.1%, and 52.1%, respectively. Efficacies were higher in patients that were aged >55 years, male, and receiving ≤4 mg of perampanel. Perampanel was generally well tolerated; 47.3% of patients experienced at least one adverse event during the 3 years of extension (46 adverse events (AEs) in 35 patients). The most common AEs were dizziness (33.8%), somnolence (5.4%), anger (4.1%), and irritability (4.1%). AEs were resolved with perampanel dose reduction or discontinuation in 10 (13.5%) and 12 (16.2%) patients, respectively.

CONCLUSION

Long-term treatment with perampanel as a first add-on therapy did not raise new safety signals in patients with focal epilepsy. Especially at low perampanel doses (≤4 mg/day), sustained improvement in seizure control was achieved, which could potentially avoid adverse drug reactions.

Single-Target Versus Multi-Target Drugs Versus Combinations of Drugs With Multiple Targets: Preclinical and Clinical Evidence for the Treatment or Prevention of Epilepsy

Rationally designed multi-target drugs (also termed multimodal drugs, network therapeutics, or designed multiple ligands) have emerged as an attractive drug discovery paradigm in the last 10-20 years, as potential therapeutic solutions for diseases of complex etiology and diseases with significant drug-resistance problems. Such agents that modulate multiple targets simultaneously are developed with the aim of enhancing efficacy or improving safety relative to drugs that address only a single target or to combinations of single-target drugs. Although this strategy has been proposed for epilepsy therapy >25 years ago, to my knowledge, only one antiseizure medication (ASM), padsevonil, has been intentionally developed as a single molecular entity that could target two different mechanisms. This novel drug exhibited promising effects in numerous preclinical models of difficult-to-treat seizures. However, in a recent randomized placebo-controlled phase IIb add-on trial in treatment-resistant focal epilepsy patients, padsevonil did not separate from placebo in its primary endpoints. At about the same time, a novel ASM, cenobamate, exhibited efficacy in several randomized controlled trials in such patients that far surpassed the efficacy of any other of the newer ASMs. Yet, cenobamate was discovered purely by phenotype-based screening and its presumed dual mechanism of action was only described recently. In this review, I will survey the efficacy of single-target vs. multi-target drugs vs. combinations of drugs with multiple targets in the treatment and prevention of epilepsy. Most clinically approved ASMs already act at multiple targets, but it will be important to identify and validate new target combinations that are more effective in drug-resistant epilepsy and eventually may prevent the development or progression of epilepsy.

Long-term Efficacy of Perampanel in a Child with Dravet Syndrome

Dravet syndrome is a genetic developmental and epileptic encephalopathy (DEE) mostly due to mutations in SCN1A gene. Perampanel is a selective and non-competitive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist. There is increasing experience in the use of perampanel in this syndrome; however, there is still a lack of evidence of sustained benefit years after the beginning of the treatment.

We report a twelve-year-old girl who was diagnosed with Dravet Syndrome when she was 2 years old and has been on perampanel since she was 7. Her genetic test showed a de novo previously described heterozygous SCN1A mutation in the 24th exon (c.4547C>A, p.Ser1516*). She received previous antiseizure drug combinations with little benefit. When perampanel was started, there was a complete resolution of her spontaneous seizures that has continued five years later. More studies are needed to investigate if there is an association between this excellent response and the genotype of our patient.

The AMPA receptor antagonist perampanel suppresses epileptic activity in human focal cortical dysplasia

Focal cortical dysplasia (FCD) is one of the most common malformations causing refractory epilepsy. Dysregulation of glutamatergic systems plays a critical role in the hyperexcitability of dysplastic neurons in FCD lesions. The pharmacoresistant nature of epilepsy associated with FCD may be due to a lack of well‐tolerated and precise antiepileptic drugs that can target glutamate receptors. Here, for the first time in human FCD brain slices, we show that the established, noncompetitive α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptor antagonist, perampanel has potent antiepileptic action. Moreover, we demonstrate that this effect is due to a reduction in burst firing behavior in human FCD microcircuits. These data support a potential role for the treatment of refractory epilepsy associated with FCD in human patients.

Structure, Function, and Pharmacology of Glutamate Receptor Ion Channels

Many physiologic effects of l-glutamate, the major excitatory neurotransmitter in the mammalian central nervous system, are mediated via signaling by ionotropic glutamate receptors (iGluRs). These ligand-gated ion channels are critical to brain function and are centrally implicated in numerous psychiatric and neurologic disorders. There are different classes of iGluRs with a variety of receptor subtypes in each class that play distinct roles in neuronal functions. The diversity in iGluR subtypes, with their unique functional properties and physiologic roles, has motivated a large number of studies. Our understanding of receptor subtypes has advanced considerably since the first iGluR subunit gene was cloned in 1989, and the research focus has expanded to encompass facets of biology that have been recently discovered and to exploit experimental paradigms made possible by technological advances. Here, we review insights from more than 3 decades of iGluR studies with an emphasis on the progress that has occurred in the past decade. We cover structure, function, pharmacology, roles in neurophysiology, and therapeutic implications for all classes of receptors assembled from the subunits encoded by the 18 ionotropic glutamate receptor genes. SIGNIFICANCE STATEMENT: Glutamate receptors play important roles in virtually all aspects of brain function and are either involved in mediating some clinical features of neurological disease or represent a therapeutic target for treatment. Therefore, understanding the structure, function, and pharmacology of this class of receptors will advance our understanding of many aspects of brain function at molecular, cellular, and system levels and provide new opportunities to treat patients.

Synthesis, antiepileptic effects, and structure-activity relationships of α-asarone derivatives: In vitro and in vivo neuroprotective effect of selected derivatives

In the present study, we compared the antiepileptic effects of α-asarone derivatives to explore their structure-activity relationships using the PTZ-induced seizure model. Our research revealed that electron-donating methoxy groups in the 3,4,5-position on phenyl ring increased antiepileptic potency but the placement of other groups at different positions decreased activity. Besides, in allyl moiety, the optimal activity was reached with either an allyl or a 1-butenyl group in conjugation with the benzene ring. The compounds 5 and 19 exerted better neuroprotective effects against epilepsy in vitro (cell) and in vivo (mouse) models. This study provides valuable data for further exploration and application of these compounds as potential anti-seizure medicines.

Activated N-methyl-D-aspartate receptor ion channels detected in focal epilepsy with [18 F]GE-179 positron emission tomography

OBJECTIVE

Imaging activated glutamate N-methyl-D-aspartate receptor ion channels (NMDAR-ICs) using positron emission tomography (PET) has proved challenging due to low brain uptake, poor affinity and selectivity, and high metabolism and dissociation rates of candidate radioligands. The radioligand [¹⁸ F]GE-179 is a known use-dependent marker of NMDAR-ICs. We studied whether interictal [¹⁸ F]GE-179 PET would detect foci of abnormal NMDAR-IC activation in patients with refractory focal epilepsy.

METHODS

Ten patients with refractory focal epilepsy and 18 healthy controls had structural magnetic resonance imaging (MRI) followed by a 90-min dynamic [¹⁸ F]GE-179 PET scan with simultaneous electroencephalography (EEG). PET and EEG findings were compared with MRI and previous EEGs. Standard uptake value (SUV) images of [¹⁸ F]GE-179 were generated and global gray matter uptake was measured for each individual. To localize focal increases in uptake of [¹⁸ F]GE-179, the individual SUV images were interrogated with statistical parametric mapping in comparison to a normal database. Additionally, individual healthy control SUV images were compared with the rest of the control database to determine their prevalence of increased focal [¹⁸ F]GE-179 uptake.

RESULTS

Interictal [¹⁸ F]GE-179 PET detected clusters of significantly increased binding in eight of 10 patients with focal epilepsy but none of the controls. The number of clusters of raised [¹⁸ F]GE-179 uptake in the patients with epilepsy exceeded the focal abnormalities revealed by the simultaneously recorded EEG. Patients with extensive clusters of raised [¹⁸ F]GE-179 uptake showed the most abnormal EEGs.

SIGNIFICANCE

Detection of multiple foci of abnormal NMDAR-IC activation in 80% of our patients with refractory focal epilepsy using interictal [¹⁸ F]GE-179 PET could reflect enhanced neuronal excitability due to chronic seizure activity. This indicates that chronic epileptic activity is associated with abnormal NMDAR ion channel activation beyond the initial irritative zones. [¹⁸ F]GE-179 PET could be a candidate marker for identifying pathological brain areas in patients with treatment-resistant focal epilepsy.

Efficacy and Tolerability of Perampanel as Adjunctive Therapy in Chinese Patients With Focal-Onset Seizures: An Observational, Prospective Study

Purpose: To evaluate the efficacy and tolerability of adjunctive perampanel (PER) in Chinese patients with focal-onset seizures, with or without secondarily generalized tonic-clonic seizures. Methods: Fifty-six patients aged 14-72 years were recruited consecutively in this single-center prospective observational study. All patients received PER as add-on treatment on the basis of clinical judgment. Seizure frequency, adverse events (AEs), and retention rates were obtained at 3 and 6 months after PER introduction. Results: The overall response rates were 60 and 71.1% after 3 and 6 months, respectively, and the freedom of seizures at the same points were reached in 8 and 15.8%. The retention rates were 89.3% at the 3-month follow-up and 67.9% at the 6-month follow-up. The overall incidence of adverse events was 55.4%. The leading reported AEs were dizziness (39.3%) and somnolence (25%). Conclusions: Our study confirmed the efficacy and tolerability of adjunctive PER in Chinese patients in real-life conditions. Based on our treatment experience, a lower maintenance dose of PER would be needed in Chinese patients.

Kainate and AMPA receptors in epilepsy: Cell biology, signalling pathways and possible crosstalk

Epilepsy is caused when rhythmic neuronal network activity escapes normal control mechanisms, resulting in seizures. There is an extensive and growing body of evidence that the onset and maintenance of epilepsy involves alterations in the trafficking, synaptic surface expression and signalling of kainate and AMPA receptors (KARs and AMPARs). The KAR subunit GluK2 and AMPAR subunit GluA2 are key determinants of the properties of their respective assembled receptors. Both subunits are subject to extensive protein interactions, RNA editing and post-translational modifications. In this review we focus on the cell biology of GluK2-containing KARs and GluA2-containing AMPARs and outline how their regulation and dysregulation is implicated in, and affected by, seizure activity. Further, we discuss role of KARs in regulating AMPAR surface expression and plasticity, and the relevance of this to epilepsy. This article is part of the special issue on 'Glutamate Receptors - Kainate receptors'.

PERMIT study: a global pooled analysis study of the effectiveness and tolerability of perampanel in routine clinical practice

The PERaMpanel pooled analysIs of effecTiveness and tolerability (PERMIT) study was a pooled analysis of data from 44 real-world studies from 17 countries, in which people with epilepsy (PWE; focal and generalized) were treated with perampanel (PER). Retention and effectiveness were assessed after 3, 6, and 12 months, and at the last visit (last observation carried forward). Effectiveness assessments included 50% responder rate (≥ 50% reduction in seizure frequency from baseline) and seizure freedom rate (no seizures since at least the prior visit); in PWE with status epilepticus, response was defined as seizures under control. Safety and tolerability were assessed by evaluating adverse events (AEs) and discontinuation due to AEs. The Full Analysis Set included 5193 PWE. Retention, effectiveness and safety/tolerability were assessed in 4721, 4392 and 4617, respectively. Retention on PER treatment at 3, 6, and 12 months was 90.5%, 79.8%, and 64.2%, respectively. Mean retention time on PER treatment was 10.8 months. The 50% responder rate was 58.3% at 12 months and 50.0% at the last visit, and the corresponding seizure freedom rates were 23.2% and 20.5%, respectively; 52.7% of PWE with status epilepticus responded to PER treatment. Overall, 49.9% of PWE reported AEs and the most frequently reported AEs (≥ 5% of PWE) were dizziness/vertigo (15.2%), somnolence (10.6%), irritability (8.4%), and behavioral disorders (5.4%). At 12 months, 17.6% of PWEs had discontinued due to AEs. PERMIT demonstrated that PER is effective and generally well tolerated when used to treat people with focal and/or generalized epilepsy in everyday clinical practice.

A Severe Dementia Case in End of Life Care with Psychiatric Symptoms Treated by Perampanel

Epilepsy is known to comorbid with Alzheimer’s disease. It can promote cognitive decline, and eventually worsen their prognosis and mortality. It is sometimes difficult to find a suitable drug because of the adverse effects. Perampanel has a unique mechanism of action that antagonizes α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid type glutamate receptor. Here, we report a case of severe dementia due to Alzheimer’s disease with intractable epilepsy, which perampanel effected for controlling seizures with less adverse effects. The subject is an 89-year-old Japanese woman with severe dementia due to Alzheimer’s disease and intractable myoclonic epilepsy. She also had psychiatric symptoms, such as circadian rhythm disorder and irritability. Valproic acid, lacosamide, or carbamazepine were prescribed, but none of them was effective. Shortly after perampanel started, however, myoclonus and these psychiatric symptoms improved. Moreover, it did not cause any obvious adverse effects, which made it possible to continue perampanel until the end of her life. Perampanel may be useful for controlling intractable epilepsy accompanied by Alzheimer’s disease. It may also improve psychiatric symptoms with less adverse effect. Accumulation of studies is necessary to evaluate the effectiveness of perampanel on the epilepsy of Alzheimer’s disease patients and further understand that mechanism.

21st century excitatory amino acid research: A Q & A with Jeff Watkins and Dick Evans

In 1981 Jeff Watkins and Dick Evans wrote what was to become a seminal review on excitatory amino acids (EAAs) and their receptors (Watkins and Evans, 1981). Bringing together various lines of evidence dating back over several decades on: the distribution in the nervous system of putative amino acid neurotransmitters; enzymes involved in their production and metabolism; the uptake and release of amino acids; binding of EAAs to membranes; the pharmacological action of endogenous excitatory amino acids and their synthetic analogues, and notably the actions of antagonists for the excitations caused by both nerve stimulation and exogenous agonists, often using pharmacological tools developed by Jeff and his colleagues, they provided a compelling account for EAAs, especially l-glutamate, as a bona fide neurotransmitter in the nervous system. The rest, as they say, is history, but far from being consigned to history, EAA research is in rude health well into the 21st Century as this series of Special Issues of Neuropharmacology exemplifies. With EAAs and their receptors flourishing across a wide range of disciplines and clinical conditions, we enter into a dialogue with two of the most prominent and influential figures in the early days of EAA research: Jeff Watkins and Dick Evans.

Perampanel Reduces Hyperthermia-Induced Seizures in Dravet Syndrome Mouse Model

Treatment options for Dravet syndrome are limited. The aim of this study was to evaluate the antiepileptic effect of the AMPA receptor antagonist perampanel (PER) on a mouse model of Dravet syndrome (Scn1a^E1099X/+). We report here that the PER (2 mg/kg) treatment inhibited the spontaneous recurrent seizures and attenuated epileptic activity in Scn1a^E1099X/+ mice. In the hyperthermia-induced seizure experiment, PER clearly increased temperature tolerance and significantly ameliorated seizure frequency and discharge duration. PER also demonstrated antiepileptic effects in a cross-over study and a synergistic effect for attenuating heat-induced seizure when given in combination with stiripentol or valproic acid. The results showed that PER effectively decreased the occurrence of spontaneous recurrent seizures and showed significant therapeutic potential for hyperthermia-induced seizures with regard to both susceptibility and severity in a Dravet syndrome mouse model. Potential therapeutic effects of PER for treatment of Dravet syndrome were demonstrated.

Efficacy and tolerability of adjuvant perampanel: an Australian multicenter real-world observational study in refractory focal and generalized epilepsy syndromes

PURPOSE

To explore the efficacy and tolerability of adjuvant perampanel (PER) and their associated risk factors in late add-on drug-resistant epilepsy.

METHOD

Retrospective multicenter 'real-world' observational study. Consecutively identified patients commenced on PER, with mixed epilepsy syndromes, from nine Australian epilepsy centers. Primary efficacy endpoints were at least 50% reduction in seizure frequency (responders), seizure freedom, and retention at 6 and 12 months, following a 3-month titration period. Tolerability endpoints were cessation of PER for any reason, cessation of PER due to treatment-emergent adverse events (TEAE), or cessation due to inefficacy. Outcomes were assessed for a-priori risk factors associated with efficacy and tolerability.

RESULTS

Three-hundred and eighty seven adults were identified and followed up for a median of 12.1 months (IQR 7.0-25.2). Focal epilepsy accounted for 79.6% (FE), idiopathic generalized epilepsy (IGE), 10.3% and developmental epileptic encephalopathy (DEE) 10.1%, of the cohort. All patients had drug-resistant epilepsy, 71.6% had never experienced six months of seizure freedom, and the mean number of antiepileptic medications (AEDs) prior to starting PER was six. At 12 months, with missing cases classified as treatment failure, retention was 40.0%, responder 21.7%, and seizure freedom 9.0%, whereas, using last outcome carried forward (LOCF), responder and seizure freedom rates were 41.3% and 14.7%, respectively. Older age of epilepsy onset was associated with a marginal increase in the likelihood of seizure freedom at 12-month maintenance (OR 1.04, 95% CI 1.02, 1.06). Male sex (adjusted OR [aOR] 2.06 95% CI 1.33, 3.19), lower number of prior AEDs (aOR 0.84, 95% CI 0.74, 0.96) and no previous seizure-free period of at least 6-month duration (aOR 2.04 95% CI 1.21, 3.47) were associated with retention. Perampanel combined with a GABA receptor AED was associated with a lower responder rate at 12 months but reduced cessation of PER. The most common TEAEs were neuropsychiatric (18.86%), followed by dizziness (13.70%), and sleepiness (5.68%).

CONCLUSIONS

Adjuvant PER treatment, even in late-add on drug-resistant epilepsy is an effective and well-tolerated treatment for drug-resistant epilepsy.

Current Pharmacologic Strategies for Treatment of Intractable Epilepsy in Children

Epileptic encephalopathy (EE) is a devastating pediatric disease that features medically resistant seizures, which can contribute to global developmental delays. Despite technological advancements in genetics, the neurobiological mechanisms of EEs are not fully understood, leaving few therapeutic options for affected patients. In this review, we introduce the most common EEs in pediatrics (i.e., Ohtahara syndrome, Dravet syndrome, and Lennox-Gastaut syndrome) and their molecular mechanisms that cause excitation/inhibition imbalances. We then discuss some of the essential molecules that are frequently dysregulated in EEs. Specifically, we explore voltage-gated ion channels, synaptic transmission-related proteins, and ligand-gated ion channels in association with the pathophysiology of Ohtahara syndrome, Dravet syndrome, and Lennox-Gastaut syndrome. Finally, we review currently available antiepileptic drugs used to treat seizures in patients with EEs. Since these patients often fail to achieve seizure relief even with the combination therapy, further extensive research efforts to explore the involved molecular mechanisms will be required to develop new drugs for patients with intractable epilepsy.

The Effect of Anti-seizure Medications on the Propagation of Epileptic Activity: A Review

The propagation of epileptiform events is a highly interesting phenomenon from the pathophysiological point of view, as it involves several mechanisms of recruitment of neural networks. Extensive in vivo and in vitro research has been performed, suggesting that multiple networks as well as cellular candidate mechanisms govern this process, including the co-existence of wave propagation, coupled oscillator dynamics, and more. The clinical importance of seizure propagation stems mainly from the fact that the epileptic manifestations cannot be attributed solely to the activity in the seizure focus itself, but rather to the propagation of epileptic activity to other brain structures. Propagation, especially when causing secondary generalizations, poses a risk to patients due to recurrent falls, traumatic injuries, and poor neurological outcome. Anti-seizure medications (ASMs) affect propagation in diverse ways and with different potencies. Importantly, for drug-resistant patients, targeting seizure propagation may improve the quality of life even without a major reduction in simple focal events. Motivated by the extensive impact of this phenomenon, we sought to review the literature regarding the propagation of epileptic activity and specifically the effect of commonly used ASMs on it. Based on this body of knowledge, we propose a novel classification of ASMs into three main categories: major, minor, and intermediate efficacy in reducing the propagation of epileptiform activity.

Determination of Impurities in Perampanel Bulk Drugs by High- Performance Liquid Chromatography and Gas Chromatography

Background:

High-performance liquid chromatography (HPLC) method has been used to detect related impurities of perampanel. However, the detection of impurities is incomplete, and the limits of quantification and detection are high. A sensitive, reliable method is in badly to be developed and applied for impurity detection of perampanel bulk drug.

Objective:

Methodologies utilising HPLC and gas chromatography (GC) were established and validated for quantitative determination of perampanel and its related impurities (a total of 10 impurities including 2 genotoxic impurities).

Methods:

The separation was achieved on a Dikma Diamonsil C18 column (250 mm × 4.6 mm, 5 μm) with the mobile phase of 0.01 mol/L potassium dihydrogen phosphate solution (A) and acetonitrile (B) in gradient elution mode. The compound 2-bromopropane was determined on an Agilent DB-624 column (0.32 mm × 30 m, 1.8 μm) by electron capture detector (μ-ECD) with split injection ratio of 1:5 and proper gradient temperature program.

Result:

Both HPLC and GC methods were established and validated to be sensitive, accurate and robust according to the International Council for Harmonization (ICH) guidelines. The methods developed were linear in the selected concentration range (R2≥0.9944). The average recovery of all impurities was between 92.6% and 103.3%. The possible production mechanism of impurities during the synthesis and degradation processes of perampanel bulk drug was also discussed. Five impurities were analyzed by liquid chromatography–mass spectrometry (LC-MS). Moreover, two of them were simultaneously characterized by LC-MS, IR and NMR.

Conclusion:

The HPLC and GC methods were developed and optimized, which could be applied for quantitative detection of the impurities, and further stability study of perampanel.

Differential acute impact of therapeutically effective and overdose concentrations of lithium on human neuronal single cell and network function

Lithium salts are used as mood-balancing medication prescribed to patients suffering from neuropsychiatric disorders, such as bipolar disorder and major depressive disorder. Lithium salts cross the blood-brain barrier and reach the brain parenchyma within few hours after oral application, however, how lithium influences directly human neuronal function is unknown. We applied patch-clamp and microelectrode array technology on human induced pluripotent stem cell (iPSC)-derived cortical neurons acutely exposed to therapeutic (<1 mM) and overdose concentrations (>1 mM) of lithium chloride (LiCl) to assess how therapeutically effective and overdose concentrations of LiCl directly influence human neuronal electrophysiological function at the synapse, single-cell, and neuronal network level. We describe that human iPSC-cortical neurons exposed to lithium showed an increased neuronal activity under all tested concentrations. Furthermore, we reveal a lithium-induced, concentration-dependent, transition of regular synchronous neuronal network activity using therapeutically effective concentration (<1 mM LiCl) to epileptiform-like neuronal discharges using overdose concentration (>1 mM LiCl). The overdose concentration lithium-induced epileptiform-like activity was similar to the epileptiform-like activity caused by the GABA_A-receptor antagonist. Patch-clamp recordings reveal that lithium reduces action potential threshold at all concentrations, however, only overdose concentration causes increased frequency of spontaneous AMPA-receptor mediated transmission. By applying the AMPA-receptor antagonist and anti-epileptic drug Perampanel, we demonstrate that Perampanel suppresses lithium-induced epileptiform-like activity in human cortical neurons. We provide insights in how therapeutically effective and overdose concentration of lithium directly influences human neuronal function at synapse, a single neuron, and neuronal network levels. Furthermore, we provide evidence that Perampanel suppresses pathological neuronal discharges caused by overdose concentrations of lithium in human neurons.

A multivariable prediction model of a major treatment response for focal-onset seizures: A post-hoc analysis of Phase III trials of perampanel

OBJECTIVE

Although 50 % reduction in seizure frequency is a common efficacy endpoint in clinical trials of antiepileptic drugs (AEDs), 75 % or greater reductions may be required to improve patients' health-related quality of life. Identification of clinical factors that are associated with high responder rates may help to inform clinicians on which patients may optimally benefit from treatment. We evaluated potential predictive factors for achieving major treatment responses (≥75 % reduction in seizure frequency per 28 days from study baseline) in patients with drug-resistant focal-onset seizures, with/without focal to bilateral tonic-clonic (FBTC) seizures in perampanel trials designed for regulatory approval.

METHODS

Univariate analyses using logistic regression were performed using data from three double-blind, placebo-controlled Phase III studies of adjunctive perampanel (Studies 304 [NCT00699972], 305 [NCT00699582], 306 [NCT00700310]), and their open-label extension study (OLEx; Study 307 [NCT00735397]). For the double-blind studies, baseline seizure frequency, number of baseline AEDs, baseline seizure type, baseline concomitant enzyme-inducing AEDs (EIAEDs), baseline carbamazepine, lamotrigine, or valproic acid, age at diagnosis, time since diagnosis, etiology, and perampanel plasma concentration were included individually with study treatment. The same factors were included for the OLEx analysis except for plasma concentration and treatment. Variables found to be significant predictors for a major treatment response in univariate analyses were subsequently included in multivariable analyses using backwards and forwards selection.

RESULTS

In the double-blind studies, 175/1374 patients had a major response to placebo (n = 25) or perampanel (n = 150). The best predictors of a major treatment response in multivariable models with forwards and backwards selection were: the presence of FBTC seizures during baseline (P = 0.0002), higher perampanel plasma concentration (P < 0.0001), older age at diagnosis (P = 0.0024 and 0.0045, respectively), and lower baseline seizure frequency (P = 0.0364 and 0.0127, respectively). In the OLEx, 217/1090 patients had a major treatment response. The best predictors of a major treatment response in the final multivariable model, regardless of backwards or forwards selection, were a lower baseline seizure frequency (P = 0.0022), the absence of focal impaired awareness seizures during baseline (P = 0.0011), the presence of FBTC seizures during baseline (P = 0.0164), lower number(s) of baseline AEDs (P = 0.0002), the absence of EIAEDs during baseline (P = 0.0059), an older age at diagnosis (P = 0.0054), and absence of structural etiologies (P = 0.0138).

SIGNIFICANCE

These analyses of placebo-controlled and long-term extension trial data identified a number of potential predictive factors for patients with focal-onset seizures achieving a major treatment response. These factors may help guide clinicians when predicting a patient's response to treatment and optimizing individual treatment regimens.

Perampanel, a potent AMPA receptor antagonist, protects against tetramethylenedisulfotetramine-induced seizures and lethality in mice: comparison with diazepam

Tetramethylenedisulfotetramine (TETS), a noncompetitive GABA_A receptor antagonist, is a potent, highly lethal convulsant that is considered to be a chemical threat agent. Here, we assessed the ability of the AMPA receptor antagonist perampanel to protect against TETS-induced seizures and lethality in mice when administered before or after treatment with the toxicant. For comparison, we conducted parallel testing with diazepam, which is a first-line treatment for chemically induced seizures in humans. Pre-treatment of mice with either perampanel (1–4 mg/kg, i.p.) or diazepam (1–5 mg/kg, i.p.) conferred protection in a dose-dependent fashion against tonic seizures and lethality following a dose of TETS (0.2 mg/kg, i.p.) that rapidly induces seizures and death. The ED₅₀ values for protection against mortality were 1.6 mg/kg for perampanel and 2.1 mg/kg for diazepam. Clonic seizures were unaffected by perampanel and only prevented in a minority of animals by high-dose diazepam. Neither treatment prevented myoclonic body twitches. Perampanel and diazepam also conferred protection against tonic seizures and lethality when administered 15 min following a 0.14 mg/kg, i.p., dose of TETS and 5 min following a 0.2 mg/kg, i.p., dose of TETS. Both posttreatments were highly potent at reducing tonic seizures and lethality in animals exposed to the lower dose of TETS whereas greater doses of both treatments were required in animals exposed to the larger dose of TETS. Neither treatment was as effective suppressing clonic seizures. In an experiment where 0.4 mg/kg TETS was administered by oral gavage and the treatment drugs were administered 5 min later, perampanel only partially protected against lethality whereas diazepam produced nearly complete protection. We conclude that perampanel and diazepam protect against TETS-induced tonic seizures and lethality but have less impact on clonic seizures. Both drugs could have utility in the treatment of TETS intoxication but neither eliminates all seizure activity.

Perampanel Inhibits α-Synuclein Transmission in Parkinson's Disease Models

BACKGROUND

The intercellular transmission of pathogenic proteins plays a key role in the clinicopathological progression of neurodegenerative diseases. Previous studies have demonstrated that this uptake and release process is regulated by neuronal activity.

OBJECTIVE

The objective of this study was to examine the effect of perampanel, an antiepileptic drug, on α-synuclein transmission in cultured cells and mouse models of Parkinson's disease.

METHODS

Mouse primary hippocampal neurons were transduced with α-synuclein preformed fibrils to examine the effect of perampanel on the development of α-synuclein pathology and its mechanisms of action. An α-synuclein preformed fibril-injected mouse model was used to validate the effect of oral administration of perampanel on the α-synuclein pathology in vivo.

RESULTS

Perampanel inhibited the development of α-synuclein pathology in mouse hippocampal neurons transduced with α-synuclein preformed fibrils. Interestingly, perampanel blocked the neuronal uptake of α-synuclein preformed fibrils by inhibiting macropinocytosis in a neuronal activity-dependent manner. We confirmed that oral administration of perampanel ameliorated the development of α-synuclein pathology in wild-type mice inoculated with α-synuclein preformed fibrils.

CONCLUSION

Modulation of neuronal activity could be a promising therapeutic target for Parkinson's disease, and perampanel could be a novel disease-modifying drug for Parkinson's disease. © 2021 International Parkinson and Movement Disorder Society.

White matter injury in infants with intraventricular haemorrhage: mechanisms and therapies

Intraventricular haemorrhage (IVH) continues to be a major complication of prematurity that can result in cerebral palsy and cognitive impairment in survivors. No optimal therapy exists to prevent IVH or to treat its consequences. IVH varies in severity and can present as a bleed confined to the germinal matrix, small-to-large IVH or periventricular haemorrhagic infarction. Moderate-to-severe haemorrhage dilates the ventricle and damages the periventricular white matter. This white matter injury results from a constellation of blood-induced pathological reactions, including oxidative stress, glutamate excitotoxicity, inflammation, perturbed signalling pathways and remodelling of the extracellular matrix. Potential therapies for IVH are currently undergoing investigation in preclinical models and evidence from clinical trials suggests that stem cell treatment and/or endoscopic removal of clots from the cerebral ventricles could transform the outcome of infants with IVH. This Review presents an integrated view of new insights into the mechanisms underlying white matter injury in premature infants with IVH and highlights the importance of early detection of disability and immediate intervention in optimizing the outcomes of IVH survivors.

Cortico-muscular and cortico-cortical coherence changes resulting from Perampanel treatment in patients with cortical myoclonus

OBJECTIVE

To investigate the mechanisms by which Perampanel (PER) reduces the severity of action myoclonus, we studied on MEG signals the changes occurring in cortico-muscular coherence (CMC) and cortico-cortical connectivity in patients with progressive myoclonus epilepsies.

METHODS

The subjects performed an isometric extension of the hand; CMC and cortico-cortical connectivity were assessed using autoregressive models and generalized partial-directed coherence. The contralateral (Co) sensors showing average CMC values >0.7 of the maximum (set to 1) were grouped as central (C) regions of interest (ROI), while adjacent sensors showing CMC values >0.3 were grouped as Surrounding (Sr) ROIs.

RESULTS

Under PER treatment, CMC decreased on Co C and Sr ROIs, but also on homologous ipsilateral (Ip) ROIs; out-degrees and betweenness centrality increased in Co ROIs and decreased in Ip ROIs. The flow from Ip to Co ROIs and from activated muscles to Ip C ROI decreased.

CONCLUSION

The improvement of myoclonus corresponded to decreased CMC and recovered leadership of the cortical regions directly involved in the motor task, with a reduced interference of ipsilateral areas.

SIGNIFICANCE

Our study highlights on mechanisms suitable to treating myoclonus and suggests the role of a reduced local synchronization together a better control of distant synaptic effects.

Adult Neurogenesis in Epileptogenesis: An Update for Preclinical Finding and Potential Clinical Translation

Epileptogenesis refers to the process in which a normal brain becomes epileptic, and is characterized by hypersynchronous spontaneous recurrent seizures involving a complex epileptogenic network. Current available pharmacological treatment of epilepsy is generally symptomatic in controlling seizures but is not disease-modifying in epileptogenesis. Cumulative evidence suggests that adult neurogenesis, specifically in the subgranular zone of the hippocampal dentate gyrus, is crucial in epileptogenesis. In this review, we describe the pathological changes that occur in adult neurogenesis in the epileptic brain and how adult neurogenesis is involved in epileptogenesis through different interventions. This is followed by a discussion of some of the molecular signaling pathways involved in regulating adult neurogenesis, which could be potential druggable targets for epileptogenesis. Finally, we provide perspectives on some possible research directions for future studies.

Lance-Adams Syndrome Treated by Perampanel in the Acute Term

Lance-Adams syndrome (LAS) is chronic post-hypoxic myoclonus after a hypoxic encephalopathy. Recently, the report on LAS in the chronic term treated by perampanel (PER) is increasing. However, PER’s efficacy in the “acute term” has not been reported. Here, we report an LAS patient who markedly improved when PER was added to his existing treatment regime in the acute term. The 65-year-old patient presented with a return of spontaneous circulation after cardiopulmonary arrest. He developed myoclonus on the admission day, and it led to tonic-clonic convulsion. We started levetiracetam 3000 mg/day, lacosamide 400 mg/day, general anesthesia using midazolam 180 mg/day, dexmedetomidine 1000 μg/day, and fentanyl 1.2 mg/day. We could stop the convulsions after 18 h from the onset. We tried to reduce sedatives, but his convulsion recurred. We added PER 2 mg/day for three days, PER 4 mg/day for next four days, then used PER 8 mg/day and we could gradually reduce the sedatives. Single-photon emission computed tomography on day 40 showed cerebral blood flow (CBF) increase at the bilateral anterior lobes of the cerebellum, medial temporal lobes, and supplementary motor and premotor areas, while CBF decrease at the brain surface of the frontal, parietal, and temporal lobes. The myoclonus disappeared since day 12, and he was transferred to another rehabilitation hospital on day 56. The optimal treatment strategy has not been established for LAS, but our case suggested that PER could be one of the choices to treat LAS in the acute term.

Analgesic and Anti-Inflammatory Effects of Perampanel in Acute and Chronic Pain Models in Mice: Interaction With the Cannabinergic System

Pain conditions, such as neuropathic pain (NP) and persistent inflammatory pain are therapeutically difficult to manage. Previous studies have shown the involvement of glutamate receptor in pain modulation and in particular same of these showed the key role of the AMPA ionotropic glutamate receptor subtype. Antiseizure medications (ASMs) are often used to treat this symptom, however the effect of perampanel (PER), an ASM acting as selective, non-competitive inhibitor of the AMPA receptor on the management of pain has not well been investigated yet. Here we tested the potential analgesic and anti-inflammatory effects of PER, in acute and chronic pain models. PER was given orally either in acute (5 mg/kg) or repeated administration (3 mg/kg/d for 4 days). Pain response was assessed using models of nociceptive sensitivity, visceral and inflammatory pain, and mechanical allodynia and hyperalgesia induced by chronic constriction injury to the sciatic nerve. PER significantly reduced pain perception in all behavioral tests as well as CCI-induced mechanical allodynia and hyperalgesia in acute regimen (5 mg/kg). This effect was also observed after repeated treatment using the dose of 3 mg/kg/d. The antinociceptive, antiallodynic and antihyperalgesic effects of PER were attenuated when the CB₁ antagonist AM251 (1 mg/kg/i.p.) was administered before PER treatment, suggesting the involvement of the cannabinergic system. Moreover, Ex vivo analyses showed that PER significantly increased CB₁ receptor expression and reduced inflammatory cytokines (i.e. TNFα, IL-1β, and IL-6) in the spinal cord. In conclusion, these results extend our knowledge on PER antinociceptive and antiallodynic effects and support the involvement of cannabinergic system on its mode of action.

Perampanel Stimulates Mitochondrial Biogenesis in Neuronal Cells through Activation of the SIRT1/PGC-1α Signaling Pathway

Mitochondrial biogenesis plays an important role in maintaining mitochondrial integrity in the central nervous system. Perampanel is an antiepilepsy reagent, which has been recently reported to exert neuroprotective effects. In the present study, we aim to investigate the protective effects of perampanel on mitochondrial biogenesis and mitochondrial bioenergetics in human neuronal cells. The human SH-SY-5Y neuronal cells were incubated with 1 and 2 μM perampanel for 24 h. The ratio of mtDNA to nDNA (mtDNA/nDNA) and the gene expression levels of Tomm20, Timm50, Atp5c1, and complex I subunit NDUFB8 were determined using real-time PCR and the Western blot analysis. Spare respiratory capacity was indicated using maximum oxygen consumption rates (OCRs) calculated as a percentage of baseline OCR and ATP concentrations, which were determined using a luciferin/luciferase ATP bioluminescence kit. The siRNA against PGC-1α was designed and transfected to knock down the expression of PGC-1α. Our results indicate that perampanel stimulated mitochondrial biogenesis by increasing mtDNA/nDNA, gene expressions of Tomm20, Timm50, Atp5c1, and the protein level of the complex I subunit NDUFB8. Additionally, perampanel improved mitochondrial bioenergetics by increasing spare respiratory capacity and ATP production. Importantly, perampanel increased the expressions of PGC-1α, NRF1, TFAM, and SIRT1. Importantly, the effects of perampanel in mitochondrial biogenesis were abolished by the knockdown of PGC-1α or blockage of SIRT1 with its specific inhibitor EX-527. These findings suggest that perampanel might improve mitochondrial biogenesis in neuronal cells by activating the SIRT1/PGC-1α signaling pathway.

Biodistribution and radiation dosimetry of the positron emission tomography probe for AMPA receptor, [11C]K-2, in healthy human subjects

[¹¹C]K-2, a radiotracer exhibiting high affinity and selectivity for α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs), is suitable for the quantification of AMPARs in living human brains and potentially useful in the identification of epileptogenic foci in patients. This study aimed to estimate the radiation doses of [¹¹C]K-2 in various organs and calculate the effective dose after injection of [¹¹C]K-2 in healthy human subjects. Twelve healthy male subjects were registered and divided into two groups (370 or 555 MBq of [¹¹C]K-2), followed by 2 h whole-body scans. We estimated the radiation dose of each organ and then calculated the effective dose for each subject. The highest uptake of [¹¹C]K-2 was observed in the liver, while the brain also showed relatively high uptake. The urinary bladder exhibited the highest radiation dose. The kidneys and liver also showed high radiation doses after [¹¹C]K-2 injections. The effective dose of [¹¹C]K-2 ranged from 5.0 to 5.2 μSv/MBq. Our findings suggest that [¹¹C]K-2 is safe in terms of the radiation dose and adverse effects. The injection of 370–555 MBq (10 to 15 mCi) for PET studies using this radiotracer is applicable in healthy human subjects and enables serial PET scans in a single subject.