Perampanel: A Review in Drug-Resistant Epilepsy

An update on the novel methods for the discovery of antiseizure and antiepileptogenic medications: where are we in 2024?

INTRODUCTION

Despite the availability of around 30 antiseizure medications, 1/3 of patients with epilepsy fail to become seizure-free upon pharmacological treatment. Available medications provide adequate symptomatic control in two-thirds of patients, but disease-modifying drugs are still scarce. Recently, though, new paradigms have been explored.

AREAS COVERED

Three areas are reviewed in which a high degree of innovation in the search for novel antiseizure and antiepileptogenic medications has been implemented: development of novel screening approaches, search for novel therapeutic targets, and adoption of new drug discovery paradigms aligned with a systems pharmacology perspective.

EXPERT OPINION

In the past, worldwide leaders in epilepsy have reiteratively stated that the lack of progress in the field may be explained by the recurrent use of the same molecular targets and screening procedures to identify novel medications. This landscape has changed recently, as reflected by the new Epilepsy Therapy Screening Program and the introduction of many in vitro and in vivo models that could possibly improve our chances of identifying first-in-class medications that may control drug-resistant epilepsy or modify the course of disease. Other milestones include the study of new molecular targets for disease-modifying drugs and exploration of a systems pharmacology perspective to design new drugs.

Gold(I)-catalyzed synthesis of N-alkenyl 2-pyridonyl sec-amines

N-Alkenyl 2-pyridonyl amines are afforded in high yields via a gold-catalyzed rearrangement of 2-propargyloxypyridine and 2-(but-3-yn-1-yloxy)pyridine under acidic conditions. This approach exhibits significant utility due to its outstanding efficiency of conversion in the synthesis of secondary amines as a one-pot reaction. The initial step of the method involves a cyclization reaction for the production of pyridinium salts, followed by the next stage, where rearrangement is accomplished through the nucleophilic addition phenomenon. This approach provides the conversion of primary amines into secondary amines, resulting in a single product. Furthermore, the methodology presents a high degree of tolerance towards several pyridine and aniline derivatives, resulting in the formation of products with excellent yields.

Investigating Perampanel Antiepileptic Drug by DFT Calculations and SERS with Custom Spinning Cell

SERS, a clinical practice where medical doctors can monitor the drug concentration in biological fluids, has been proposed as a viable approach to therapeutic drug monitoring (TDM) of the antiepileptic drug Perampanel. The adoption of an acidic environment during the SERS experiments was found to be effective in enhancing the spectroscopic signal. In this work, we combine SERS experiments, conducted with a custom spinning cell in controlled acidic conditions, with DFT calculations aimed at investigating the possible protonated forms of Perampanel. The DFT-simulated Raman spectra of protonated Perampanel accounts for most of the observed SERS signals, thus explaining the effective role of protonation of the analyte. Our results suggest protonation as a viable approach to fostering SERS of alkaline drugs.

Potential of Capric Acid in Neurological Disorders: An Overview

To solve the restrictions of a classical ketogenic diet, a modified medium-chain triglyceride diet was introduced which required only around 60% of dietary energy. Capric acid (CA), a small molecule, is one of the main components because its metabolic profile offers itself as an alternate source of energy to the brain in the form of ketone bodies. This is possible with the combined capability of CA to cross the blood-brain barrier and achieve a concentration of 50% concentration in the brain more than any other fatty acid in plasma. Natural sources of CA include vegetable oils such as palm oil and coconut oil, mammalian milk and some seeds. Several studies have shown that CA has varied action on targets that include AMPA receptors, PPAR-γ, inflammatory/oxidative stress pathways and gut dysbiosis. Based on these lines of evidence, CA has proved to be effective in the amelioration of neurological diseases such as epilepsy, affective disorders and Alzheimer's disease. But these studies still warrant more pre-clinical and clinical studies that would further prove its efficacy. Hence, to understand the potential of CA in brain disease and associated comorbid conditions, an advance and rigorous molecular mechanistic study, apart from the reported in-vitro/in-vivo studies, is urgently required for the development of this compound through clinical setups.

NMDAR-dependent presynaptic homeostasis in adult hippocampus: Synapse growth and cross-modal inhibitory plasticity

Homeostatic plasticity (HP) encompasses a suite of compensatory physiological processes that counteract neuronal perturbations, enabling brain resilience. Currently, we lack a complete description of the homeostatic processes that operate within the mammalian brain. Here, we demonstrate that acute, partial AMPAR-specific antagonism induces potentiation of presynaptic neurotransmitter release in adult hippocampus, a form of compensatory plasticity that is consistent with the expression of presynaptic homeostatic plasticity (PHP) documented at peripheral synapses. We show that this compensatory plasticity can be induced within minutes, requires postsynaptic NMDARs, and is expressed via correlated increases in dendritic spine volume, active zone area, and docked vesicle number. Further, simultaneous postsynaptic genetic reduction of GluA1, GluA2, and GluA3 in triple heterozygous knockouts induces potentiation of presynaptic release. Finally, induction of compensatory plasticity at excitatory synapses induces a parallel, NMDAR-dependent potentiation of inhibitory transmission, a cross-modal effect consistent with the anti-epileptic activity of AMPAR-specific antagonists used in humans.

Structural basis of AMPA receptor inhibition by trans-4-butylcyclohexane carboxylic acid

BACKGROUND AND PURPOSE

AMPA receptors, which shape excitatory postsynaptic currents and are directly involved in overactivation of synaptic function during seizures, represent a well-accepted target for anti-epileptic drugs. Trans-4-butylcyclohexane carboxylic acid (4-BCCA) has emerged as a new promising anti-epileptic drug in several in vitro and in vivo seizure models, but the mechanism of its action remained unknown. The purpose of this study is to characterize structure and dynamics of 4-BCCA interaction with AMPA receptors.

EXPERIMENTAL APPROACH

We studied the molecular mechanism of AMPA receptor inhibition by 4-BCCA using a combination of X-ray crystallography, mutagenesis, electrophysiological assays, and molecular dynamics simulations.

KEY RESULTS

We identified 4-BCCA binding sites in the transmembrane domain (TMD) of AMPA receptor, at the lateral portals formed by transmembrane segments M1-M4. At this binding site, 4-BCCA is very dynamic, assumes multiple poses, and can enter the ion channel pore.

CONCLUSION AND IMPLICATIONS

4-BCCA represents a low-affinity inhibitor of AMPA receptors that acts at the TMD sites distinct from non-competitive inhibitors, such as the anti-epileptic drug perampanel and the ion channel blockers. Further studies might examine the possibsility of synergistic use of these inhibitors in treatment of epilepsy and a wide range of neurological disorders and gliomas.

LINKED ARTICLES

This article is part of a themed issue on Structure Guided Pharmacology of Membrane Proteins (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.14/issuetoc.

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.

Successful Treatment of Drug-Resistant Seizures Secondary to Ring 20 Mosaicism with Perampanel as an Add-On Antiepileptic Drug

We report a girl with drug-resistant seizures, progressive behavioral changes, and cognitive decline. Investigations showed abnormal EEG with frequent high-voltage bifrontotemporal sharp and slow waves, especially during sleep. Seizures were difficult to control, despite the usage of various antiepileptic drugs. Perampanel as an add-on antiepileptic drug appeared efficacious. Due to the recognizable pattern of seizures and EEG findings, a karyotype study was performed which revealed 46 chromosomes with a ring 20 chromosome mosaicism. Ring 20 chromosome is associated with drug-resistant refractory seizures, cognitive decline, and behavioral problems. This case highlights the difficulty and challenge faced in managing drug-resistant refractory seizures associated with ring 20 chromosome. While ring 20 chromosome is often underdiagnosed, one should have a high index of awareness and suspicion of such rare epilepsy syndrome, so that an early diagnosis can be made.

Patient-Reported Outcome Measures in Adult Patients Diagnosed with Epilepsy Being Treated with Perampanel

Background

Epilepsy is a complex disorder that can affect patients’ medical, psychological, and social well-being. The purpose of this study was to evaluate the patient-reported outcome (PRO) measures of health-related quality of life (HRQoL), satisfaction, and adherence in adult patients diagnosed with epilepsy treated with perampanel in the United States (US).

Methods

A US-based, multicenter, observational cross-sectional survey was completed by 61 patients taking perampanel with or without other antiseizure medications (ASMs). Respondents were ≥18 years old, had a physician-confirmed diagnosis of epilepsy, used perampanel for ≥4 months, and provided informed consent. Patients responded to questions concerning their demographic characteristics, treatment history, experiences before perampanel, experiences while taking perampanel, HRQoL, treatment satisfaction, and medication adherence.

Results

Patients (N=61) were 42.8 years old on average; majority were female (63.9%) and white (75.4%). Mean time on perampanel was 2.5 years, with sodium channel blockers often (55.7%) used concomitantly with perampanel. Patients reported, on average, 5.5 (standard deviation [SD]=13.2) seizures/month after initiating perampanel, whereas these same patients reported experiencing 20.4 (SD=60.0) seizures/month prior to perampanel. When comparing their experience on perampanel with their experience with previous ASMs, more patients “strongly agreed” that perampanel allowed them to live a more normal life (36.1% vs 27.5%) and worked as intended if they missed taking a dose (16.4% vs 7.8%). Average satisfaction scores were high, with ratings of 71.8 for effectiveness, 84.0 for convenience, and 71.9 for global satisfaction (0–100 scores). Perampanel use was associated with improvements in HRQoL and fewer symptoms of depression and anxiety. The majority of patients were adherent (62.3%) to perampanel.

Discussion

Perampanel use was associated with reductions in number of seizures, better HRQoL, and high adherence rates. These results provide initial evidence that perampanel can be an effective, tolerable, and valid option for patients with epilepsy in the real world.

Effects of Vagus Nerve Stimulation following Corpus Callosotomy for Patients with Drug-Resistant Epilepsy

Objective: The effectiveness of vagus nerve stimulation (VNS) for residual seizures after corpus callosotomy (CC) has not yet been fully investigated. We hypothesized that seizure control would be improved by VNS after CC. The purpose of this study was to compare seizure frequency between patients with implantation of a VNS generator (post-VNS group) or without VNS (non-post-VNS group) following CC. Methods: We retrospectively reviewed patients who underwent CC between January 2009 and May 2019 in our institution. We evaluated proportions of ≥50% reduction in seizure frequency (responders) and seizure reduction rate 1 and 2 years after VNS. To investigate factors related to responders, uni- and multivariate logistic regression analyses were performed regarding age, number of anti-seizure medications (ASMs), addition of novel ASMs (levetiracetam, lacosamide or perampanel), and post-VNS or non-post-VNS status. Results: Thirteen post-VNS patients and 24 non-post-VNS patients were analyzed in this study. Responder rate at 1 year after VNS differed significantly between the post-VNS group (53.9%) and non-post-VNS group (12.5%, p = 0.017). Number of ASMs at the time of CC and post-VNS were significantly associated with responders in univariate analyses (odds ratio [OR] 0.34, 95% confidence interval [CI] 0.13–0.88, p = 0.025 and OR 8.2, 95%CI 1.6–41.6, p = 0.011, respectively), whereas age, sex, seizure frequency, and addition of novel ASMs were not. In multivariate analysis, the presence of VNS procedures after CC was the only factor favorably associated with responder status (OR 82.2, 95%CI 1.55–4355.7, p = 0.03). Conclusions: VNS therapy after CC may increase the proportion of responders independent of the addition of novel ASMs.

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.

Evaluation of Perampanel in the Presence of its Degradation Products and Process-Related Impurities by Validated Stability-Indicating Reverse Phase High Performance Liquid Chromatography Method

A novel stability-indicating isocratic reverse phase high-performance liquid chromatographic method was developed for the quantitative determination of perampanel in the presence of degradation products and its process-related impurities. Good resolution was achieved between the peaks corresponding to process-related impurities and degradation products from the analyte using Shim-pack GIST C18 column with mobile phase, potassium dihydrogen phosphate (pH 2.5; 30 mM)-acetonitrile (45: 55, v/v) at a wavelength of 294 nm. Perampanel and its impurities were well-separated within a run time of 7 min. To show the stability-indicating power of the method, forced degradation studies were performed on bulk samples of perampanel as per ICH prescribed stress condition using acid, base, hydrolytic, oxidative and photolytic degradation conditions. The degradation products were resolved from main peak and its impurities. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness. This method was also applied for assay and related substances determination of perampanel in bulk and pharmaceutical dosage form.

The Effect of Plasma Protein Binding on the Therapeutic Monitoring of Antiseizure Medications

Epilepsy is a widely diffused neurological disorder including a heterogeneous range of syndromes with different aetiology, severity and prognosis. Pharmacological treatments are based on the use, either in mono- or in polytherapy, of antiseizure medications (ASMs), which act at different synaptic levels, generally modifying the excitatory and/or inhibitory response through different action mechanisms. To reduce the risk of adverse effects and drug interactions, ASMs levels should be closely evaluated in biological fluids performing an appropriate Therapeutic Drug Monitoring (TDM). However, many decisions in TDM are based on the determination of the total drug concentration although measurement of the free fraction, which is not bound to plasma proteins, is becoming of ever-increasing importance since it correlates better with pharmacological and toxicological effects. Aim of this work has been to review methodological aspects concerning the evaluation of the free plasmatic fraction of some ASMs, focusing on the effect and the clinical significance that drug-protein binding has in the case of widely used drugs such as valproic acid, phenytoin, perampanel and carbamazepine. Although several validated methodologies are currently available which are effective in separating and quantifying the different forms of a drug, prospective validation studies are undoubtedly needed to better correlate, in real-world clinical contexts, pharmacokinetic monitoring to clinical outcomes.

Dysregulation of Ambient Glutamate and Glutamate Receptors in Epilepsy: An Astrocytic Perspective

Given the important functions that glutamate serves in excitatory neurotransmission, understanding the regulation of glutamate in physiological and pathological states is critical to devising novel therapies to treat epilepsy. Exclusive expression of pyruvate carboxylase and glutamine synthetase in astrocytes positions astrocytes as essential regulators of glutamate in the central nervous system (CNS). Additionally, astrocytes can significantly alter the volume of the extracellular space (ECS) in the CNS due to their expression of the bi-directional water channel, aquaporin-4, which are enriched at perivascular endfeet. Rapid ECS shrinkage has been observed following epileptiform activity and can inherently concentrate ions and neurotransmitters including glutamate. This review highlights our emerging knowledge on the various potential contributions of astrocytes to epilepsy, particularly supporting the notion that astrocytes may be involved in seizure initiation via failure of homeostatic responses that lead to increased ambient glutamate. We also review the mechanisms whereby ambient glutamate can influence neuronal excitability, including via generation of the glutamate receptor subunit GluN2B-mediated slow inward currents, as well as indirectly affect neuronal excitability via actions on metabotropic glutamate receptors that can potentiate GluN2B currents and influence neuronal glutamate release probabilities. Additionally, we discuss evidence for upregulation of System x c - , a cystine/glutamate antiporter expressed on astrocytes, in epileptic tissue and changes in expression patterns of glutamate receptors.

Adenosine Signaling and Clathrin-Mediated Endocytosis of Glutamate AMPA Receptors in Delayed Hypoxic Injury in Rat Hippocampus: Role of Casein Kinase 2

Chronic adenosine A1R stimulation in hypoxia leads to persistent hippocampal synaptic depression, while unopposed adenosine A2AR receptor stimulation during hypoxia/reperfusion triggers adenosine-induced post-hypoxia synaptic potentiation (APSP) and increased neuronal death. Still, the mechanisms responsible for this adenosine-mediated neuronal damage following hypoxia need to be fully elucidated. We tested the hypothesis that A1R and A2AR regulation by protein kinase casein kinase 2 (CK2) and clathrin-dependent endocytosis of AMPARs both contribute to APSPs and neuronal damage. The APSPs following a 20-min hypoxia recorded from CA1 layer of rat hippocampal slices were abolished by A1R and A2AR antagonists and by broad-spectrum AMPAR antagonists. The inhibitor of GluA2 clathrin-mediated endocytosis Tat-GluA2-3Y peptide and the dynamin-dependent endocytosis inhibitor dynasore both significantly inhibited APSPs. The CK2 antagonist DRB also inhibited APSPs and, like hypoxic treatment, caused opposite regulation of A1R and A2AR surface expression. APSPs were abolished when calcium-permeable AMPAR (CP-AMPAR) antagonist (IEM or philanthotoxin) or non-competitive AMPAR antagonist perampanel was applied 5 min after hypoxia. In contrast, perampanel, but not CP-AMPAR antagonists, abolished APSPs when applied during hypoxia/reperfusion. To test for neuronal viability after hypoxia, propidium iodide staining revealed significant neuroprotection of hippocampal CA1 pyramidal neurons when pretreated with Tat-GluA2-3Y peptide, CK2 inhibitors, dynamin inhibitor, CP-AMPAR antagonists (applied 5 min after hypoxia), and perampanel (either at 5 min hypoxia onset or during APSP). These results suggest that the A1R-CK2-A2AR signaling pathway in hypoxia/reperfusion injury model mediates increased hippocampal synaptic transmission and neuronal damage via calcium-permeable AMPARs that can be targeted by perampanel for neuroprotective stroke therapy.

Efficacy and tolerability of perampanel as a first add-on therapy with different anti-seizure drugs

PURPOSE

To investigate the efficacy and tolerability of perampanel (PER) when administered as a first add-on therapy to patients with focal epilepsy or idiopathic generalized epilepsy (IGE) taking one other antiseizure drug (ASD).

METHODS

This multicentre, retrospective, one-year observational study collected data from patients (≥12 years) who initiated treatment with PER as first add-on therapy. Patients had to be experiencing inadequate seizure control on ASD monotherapy and tried ≤3 ASD monotherapies before initiating PER. Multivariate logistic regression analyses were performed, adjusted for the number and type of previous seizures, duration and aetiology of epilepsy.

RESULTS

Of the 149 patients included in the study (mean age 41 years; 54.4 % male), 118 (79.2 %) were still receiving PER as first add-on treatment after 12 months. Mean PER dose was 6.2 mg/day. At 12 months, 45.6 % were seizure-free and 84.6 % responders. A significant difference in seizure freedom rate was found between patients with IGE and patients with focal epilepsy, but not in responders. Reduced seizure control was observed when PER was administered with strong enzyme-inducing ASDs; conversely, increased seizure control was seen when the same dose of PER was combined with enzyme-inhibiting ASDs. The most frequent adverse events were dizziness (15.4 %), irritability (14.1 %) and drowsiness (14.1 %); no differences in tolerance were observed among different combinations.

CONCLUSION

PER demonstrated a good efficacy and safety profile when used as a first add-on therapy in patients who did not respond to monotherapy. PER dose adjustments may optimize seizure control when combined with strong enzyme-inducing or enzyme-inhibiting ASDs.

Thiazole-Bearing 4-Thiazolidinones as New Anticonvulsant Agents

Here, we describe the synthesis and anticonvulsant activity of thiazole-bearing hybrids based on 2-imino-4-thiazolidinone and 2,4-dioxothiazolidine-5-carboxylic acid cores. The structure of target compounds was based on the following: (i) A combination of two thiazole cores; (ii) similarity to ralitolin’s structure; (iii) the compliance with structural requirements for the new anticonvulsants. Target compounds were synthesized via known approaches based on Knoenavegel reaction, alkylation reaction, and one-pot three-component reaction. Anticonvulsant properties of compounds were evaluated in two different models—pentylenetetrazole-induced seizures and maximal electroshock seizure tests. Among the tested compounds 5Z-(3-nitrobenzylidene)-2-(thiazol-2-ylimino)-thiazolidin-4-one Ib, 2-[2,4-dioxo-5-(thiazol-2- ylcarbamoylmethyl)-thiazolidin-3-yl]-N-(2-trifluoromethylphenyl)acetamide IId and (2,4-dioxo-5- (thiazol-2-ylcarbamoylmethylene)-thiazolidin-3-yl)acetic acid ethyl ester IIj showed excellent anticonvulsant activity in both models. The directions of compounds modification based on SAR aspects were discussed. The results of the study provide a basis for further study of the anticonvulsant properties of selected thiazole-thiazolidinones.

Gliotransmission: A Novel Target for the Development of Antiseizure Drugs

For more than a century, epilepsy has remained an incapacitating neurological disorder with a high incidence worldwide. Mesial temporal lobe epilepsy (TLE) is a common type of epilepsy without an effective pharmacological treatment. An increase in excitability and hypersynchrony of electrical neuronal activity during development are typically associated with an excitatory/inhibitory imbalance in the neuronal network. Astrocytes release gliotransmitters, which can regulate neuronal excitability and synaptic transmission; therefore, the classical neurocentric vision of the cellular basis of epileptogenesis has begun to change. Growing evidence suggests that the key contribution of astrocyte-to-neuron signaling in the mechanisms underlies the initiation, propagation, and recurrence of seizure activity. The aim of this review was to summarize current evidence obtained from experimental models that suggest how alterations in astroglial modulation of synaptic transmission and neuronal activity contribute to the development of this brain disease. In this article, we will summarize the main pharmacological, Ca²⁺-imaging, and electrophysiological findings in the gliotransmitter-mediated modulation of neuronal activity and their possible regulation as a novel cellular target for the development of pharmacological strategies for treating refractory epilepsies.

Open-label, uncontrolled retrospective study of perampanel in adults with Lennox-Gastaut syndrome

PURPOSE

Perampanel (PER) was added to the anticonvulsant regimen of 71 patients with Lennox-Gastaut Syndrome (LGS) to evaluate its efficacy against seizures and its tolerability.

METHOD

We evaluated at 3-month intervals 62 with pure LGS and 9 with LGS-like epileptic encephalopathy (28 females, 43 males, mean age 40.1 ± 11.5 yrs, median 38, range 20-71) in whom PER was introduced by 2 mg steps at 2- to 4-week intervals up to 6 mg/day, with possible dose reduction or increases after that. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines were followed.

RESULTS

Mean PER exposure was 538.9 days ± 425 (median 429), with 44 patients (62 %) on PER at last follow-up. About 2/3 of patients were responders, including 35.2 % that had a ≥75 % decrease in their seizures. Among these 16.9 % had a ≥90 % decrease. No improvement was seen in 14 patients; 5 had a less than 50 % response, and 6 had seizure aggravation. Therefore, 25 (35.2 %) were considered non-responders. Half of the patients developed at least one side-effect. Significant negative changes in behavior were noted in 1/3 of the cases, including irritability (8.5 %) and aggressivity (7 %). Contrastingly, 4 patients reported positive behavioral and psychological well-being side-effects.

CONCLUSIONS

This retrospective, open-label study provides evidence that PER may significantly help in LGS. PER should be tried in LGS patients who are not satisfactorily controlled. Its use may be limited in some patients due to behavioral side-effects occurring, particularly at doses ≥ 6 mg/d.

Perampanel attenuates myoclonus in a patient with neuronal ceroid lipofuscinoses type 2 disease

Neuronal ceroid lipofuscinoses type 2 disease (CLN2) is a very rare, autosomal recessive neurodegerative disease caused by deficient activity of the enzyme tripeptidyl peptidase 1 (TPP1). The seizures in CLN2 are polymorphic and resistant to antiepileptic drugs. In particular, myoclonus (epileptic and non-epileptic) predominant as the disease progresses. Herein, we present a child of CLN2 disease, who had near-continuous myoclonus, and was subsequently attenuated by administration of Perampanel. This girl had initially presented with language delay and generalized tonic clonic seizure at 3 years of age. The diagnosis of CLN2 was made via genetic study, which showed compound heterozygous mutation on TPP1 gene (c.622 C > T and partial gene deletion including at least exons 1-3). Currently, at the age of 8 years, there was near-continuous myoclonus (epileptic and non-epileptic), which worsen during acute illness. Eventually, she was given Perampanel with starting dose of 1 mg/day and slowly titrated upto 6 mg/day in 4 weeks. There was significant attenuation of myoclonus (>50% seizure reduction). To our knowledge, this is the first case in the literature describing the efficacy of perampanel in treating myoclonus in CLN2 disease.

Pharmacokinetic and pharmacodynamic considerations for the clinical efficacy of perampanel in focal onset seizures

INTRODUCTION

Medical therapy is the mainstay of management of epilepsy. Despite the increasing number of available antiepileptic drugs (AEDs), approximately one-third of epileptic patients do not have adequate control of seizures. There is still a need for the development of new AEDs with enhanced effectiveness and tolerability. Areas covered: The present manuscript is based on an Internet and PubMed search (January 2005 to August 2018). It is focused on pharmacokinetic and clinical data of perampanel (PER) for the treatment of epilepsy. Expert opinion: PER has a novel mechanism of action, which opens up new options for a rational combination therapy. Phase III trials have demonstrated the efficacy and safety of PER as adjunctive therapy for the treatment of partial-onset seizures (POS) and primary generalized tonic-clonic seizures in patients aged ≥12 years. PER is also approved by FDA as monotherapy for the treatment of POS. A clinical trial is ongoing to verify the efficacy and safety of PER monotherapy in untreated patients with POS. In the future, head-to-head comparisons are needed to determine the exact position of PER relative to other AEDs. Moreover, further studies are needed to evaluate the efficacy and safety of PER in patients aged <12 years.

ABBREVIATIONS

4βOHC: 4β-hydroxycholesterol; AUC: area under the curve; CBZ: Carbamazepine; CLCr: creatinine clearance; Cmax: maximum plasma concentration; CYP: cytochrome P; EIAED: enzyme-inducing antiepileptic drug; EMA: European Medicines Agency; FDA: Food and Drug Administration; GI: gastrointestinal; OXC: oxcarbazepine; PER: perampanel; PGTC: primary generalized tonic-clonic; PHT: phenytoin; POS: partial-onset seizures; QD: once-daily; TEAE: treatment-emergent adverse event; Tmax: median time to reach peak concentration; UGT: uridine diphosphoglucose-glucuronosyltransferase; VPA: valproic acid.

Perampanel and decanoic acid show synergistic action against AMPA receptors and seizures

Perampanel is an adjunctive treatment for epilepsy that works through the direct inhibition of AMPA receptors. The same molecular mechanism has recently been shown for a fatty acid, decanoic acid, prescribed in the medium chain triglyceride ketogenic diet for the treatment of patients with drug-resistant epilepsy. Because each compound has been proposed to act through a distinct AMPA receptor binding site, we predicted that perampanel and decanoic acid would act synergistically against AMPA receptors and, consequently, seizures. Here, we show a synergistic interaction between perampanel and decanoic acid in direct AMPA receptor inhibition, in an ex vivo model of seizure activity, and against seizure-induced activity in human brain slices. These data support a potential role for combination treatment using perampanel and dietary decanoic acid to provide enhanced seizure control.

"Market withdrawals" of medicines in Germany after AMNOG: a comparison of HTA ratings and clinical guideline recommendations

BACKGROUND

According to the AMNOG act, the German Federal Joint Committee (G-BA) determines the additional benefit of new medicines as a basis for subsequent price negotiations. Pharmaceutical companies may withdraw their medications from the market at any time during the process. This analysis aims to compare recommendations in clinical guidelines and HTA appraisals of medicines that were withdrawn from the German market since the introduction of AMNOG in 2011.

METHODS

Medications withdrawn from the German market between January 2011 and June 2016 following benefit assessment were categorized as opt-outs (max. 2 weeks after start of price negotiations) or supply terminations (during or after further price negotiations). Related guidelines were systematically analyzed. For all withdrawals, therapeutic area, additional benefit rating and recommendation status in relevant clinical guidelines were assessed.

RESULTS

Among 139 medications, 10 opt-outs and 12 supply terminations were identified. Twenty-one out of 22 withdrawn medicines (95%) received 'no additional benefit' appraisal by the G-BA (average 'no additional benefit' rating for all AMNOG products: 47%). Of the 22 medicines, 15 (68%) were recommended by at least one guideline at the time of benefit assessment and 18 (82%) on 1 June 2016. Heterogeneity among guidelines was high. Acceptance of clinical trial endpoints was different between G-BA appraisals and clinical guidelines.

CONCLUSION

Our analysis revealed considerable differences across clinical guidelines as well as between clinical guidelines and HTA appraisals of the medicines that were withdrawn from the German market. Better alignment of the clinical perspective and close collaboration between all involved parties is required to achieve and maintain optimization of patient care.

Seizure remission and improvement of neurological function in sialidosis with perampanel therapy

A 15-year-old boy experienced myoclonic seizures for 3 years. He initially had occasional myoclonus, gradually progressive ataxia, tremors, and psychomotor and speech regression developed. Eventually, he exhibited nearly continuous myoclonus. He received treatment of sodium valproate, levetiracetam, clobazam, and phenobarbital, without efficacy. A ketogenic diet also proved ineffective. Adjunctive therapy with 4 mg/day of perampanel was started and was gradually titrated to 10 mg/day. The remission of myoclonic seizures was achieved within one month. The patient's neurological and cognitive functions improved to a certain degree during the following 20 months. Sialidosis was confirmed by the mutations of NEU1 gene.

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A case of sialidosis I with compound mutations of c.544A > G and c.619C > T in NEU1 gene presented with drug-resistant seizures.

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Seizures associated with sialidosis eventually resolved on adjunctive perampanel therapy titrated to 10 mg/day.

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Our patient with sialidosis was drug-resistant to anti-seizure medication before responding to perampanel.

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Perampanel might be a potentially effective treatment for sialidosis in patients with Progressive Myoclonus Epilepsy.

Recent advances in epilepsy management

PURPOSE OF REVIEW

Recent advances in our understanding of seizure generation have resulted in modified recommendations for when seizure treatment should be initiated, revisions to our definition of status epilepticus, and new pharmacological and neuromodulatory therapies. The goal of this review is to provide the anesthesiologist with an overview of the advancements they are most likely to encounter while providing clinical care.

RECENT FINDINGS

There have been recent modifications to seizure definitions and treatment recommendations. These include the idea that treatment with antiepileptic therapy should be initiated after the first unprovoked seizure in individuals who are at high risk for another seizure, and that the idea that status epilepticus should be thought of as a two-phase process, related to an initial phase after which intervention should be started, and a second phase after which time risk of long-term sequelae is increased. Additionally, several new therapies have become available that have novel mechanisms of action, which are more efficacious and have fewer side-effects.

SUMMARY

As knowledge about mechanisms of seizure generation has improved, there has been a concurrent evolution in our thinking about seizure-related definitions, and indications for initiation of treatment. Several next generation drug therapies with more specific targets have also become available. Taken together, there have been significant improvements in care options.

Adenosine A1 and A2A Receptors in the Brain: Current Research and Their Role in Neurodegeneration

The inhibitory adenosine A1 receptor (A1R) and excitatory A2A receptor (A2AR) are predominantly expressed in the brain. Whereas the A2AR has been implicated in normal aging and enhancing neurotoxicity in multiple neurodegenerative diseases, the inhibitory A1R has traditionally been ascribed to have a neuroprotective function in various brain insults. This review provides a summary of the emerging role of prolonged A1R signaling and its potential cross-talk with A2AR in the cellular basis for increased neurotoxicity in neurodegenerative disorders. This A1R signaling enhances A2AR-mediated neurodegeneration, and provides a platform for future development of neuroprotective agents in stroke, Parkinson’s disease and epilepsy.

Perampanel (Fycompa): A Review of Clinical Efficacy and Safety in Epilepsy

Perampanel (Fycompa): a review of clinical efficacy and safety in epilepsy.

Practical Use of Newer Antiepileptic Drugs as Adjunctive Therapy in Focal Epilepsy

This article lays the background for, and discusses the practical issues surrounding, the adjunctive use of the last four antiepileptic drugs (AEDs) to be licensed for the treatment of pharmacoresistant focal seizures in the UK and elsewhere. More than 30% of adolescent and adult patients will not be fully controlled on the currently available therapeutic armamentarium. After not responding to their first three AED schedules, only a handful of patients attained seizure freedom on subsequent regimens. To optimise the response to any new AED in this setting, it is often necessary to reduce the existing drug burden. The pharmacology, tolerability and safety, and everyday use of lacosamide, eslicarbazepine acetate, retigabine (ezogabine) and perampanel will be reviewed and discussed. This will be accompanied by data from prospective audits with each drug undertaken at the Western Infirmary in Glasgow, Scotland, and a report of their successful introduction in an illustrative case. Overall, there is a large variation in the course of refractory epilepsy and the effect of AED therapy on this process seems minimal. Nevertheless, a number of patients will benefit from the introduction of each new AED, with some becoming seizure-free.