Efficacy and tolerability of perampanel in ten patients with Lafora disease

Perampanel in routine clinical use in idiopathic generalized epilepsy: The 12-month GENERAL study

OBJECTIVE

To analyze the effectiveness and tolerability of perampanel across different seizure types in routine clinical care of patients with idiopathic generalized epilepsy (IGE).

METHODS

This multicenter, retrospective, 1-year observational study collected data from patient records at 21 specialist epilepsy units in Spain. All patients who were aged ≥12 years, prescribed perampanel before December 2016, and had a confirmed diagnosis of IGE were included.

RESULTS

The population comprised 149 patients with IGE (60 with juvenile myoclonic epilepsy, 51 generalized tonic-clonic seizures [GTCS] only, 21 juvenile absence epilepsy, 10 childhood absence epilepsy, 6 adulthood absence epilepsy, and one Jeavons syndrome). Mean age was 36 years. The retention rate at 12 months was 83% (124/149), and 4 mg was the most common dose. At 12 months, the seizure-free rate was 59% for all seizures (88/149); 63% for GTCS (72/115), 65% for myoclonic seizures (31/48), and 51% for absence seizures (24/47). Seizure frequency was reduced significantly at 12 months relative to baseline for GTCS (78%), myoclonic (65%), and absence seizures (48%). Increase from baseline seizure frequency was seen in 5.2% of patients with GTCS seizures, 6.3% with myoclonic, and 4.3% with absence seizures. Perampanel was effective regardless of epilepsy syndrome, concomitant antiepileptic drugs (AEDs), and prior AEDs, but retention and seizure freedom were significantly higher when used as early add-on (after ≤2 prior AEDs) than late (≥3 prior AEDs). Adverse events were reported in 50% of patients over 12 months, mostly mild or moderate, and irritability (23%), somnolence (15%), and dizziness (14%) were most frequent.

SIGNIFICANCE

In routine clinical care of patients with IGE, perampanel improved seizure outcomes for GTCS, myoclonic seizures, and absence seizures, with few discontinuations due to adverse events. This is the first real-world evidence with perampanel across different seizure types in IGE.

Lafora Disease: A Ubiquitination-Related Pathology

Lafora disease (LD, OMIM254780) is a rare and fatal form of progressive myoclonus epilepsy (PME). Among PMEs, LD is unique because of the rapid neurological deterioration of the patients and the appearance in brain and peripheral tissues of insoluble glycogen-like (polyglucosan) inclusions, named Lafora bodies (LBs). LD is caused by mutations in the EPM2A gene, encoding the dual phosphatase laforin, or the EPM2B gene, encoding the E3-ubiquitin ligase malin. Laforin and malin form a functional complex that is involved in the regulation of glycogen synthesis. Thus, in the absence of a functional complex glycogen accumulates in LBs. In addition, it has been suggested that the laforin-malin complex participates in alternative physiological pathways, such as intracellular protein degradation, oxidative stress, and the endoplasmic reticulum unfolded protein response. In this work we review the possible cellular functions of laforin and malin with a special focus on their role in the ubiquitination of specific substrates. We also discuss here the pathological consequences of defects in laforin or malin functions, as well as the therapeutic strategies that are being explored for LD.

Lafora disease: from genotype to phenotype

The progressive myoclonic epilepsy of Lafora or Lafora disease (LD) is a neurodegenerative disorder characterized by recurrent seizures and cognitive deficits. With typical onset in the late childhood or early adolescence, the patients show progressive worsening of the disease symptoms, leading to death in about 10 years. It is an autosomal recessive disorder caused by the loss-of-function mutations in the EPM2A gene, coding for a protein phosphatase (laforin) or the NHLRC1 gene coding for an E3 ubiquitin ligase (malin). LD is characterized by the presence of abnormally branched water insoluble glycogen inclusions known as Lafora bodies in the neurons and other tissues, suggesting a role for laforin and malin in glycogen metabolic pathways. Mouse models of LD, developed by targeted disruption of the Epm2a or Nhlrc1 gene, recapitulated most of the symptoms and pathological features as seen in humans, and have offered insight into the pathomechanisms. Besides the formation of Lafora bodies in the neurons in the presymptomatic stage, the animal models have also demonstrated perturbations in the proteolytic pathways, such as ubiquitin proteasome system and autophagy, and inflammatory response. This review attempts to provide a comprehensive coverage on the genetic defects leading to the LD in humans, on the functional properties of the laforin and malin proteins, and on how defects in any one of these two proteins result in a clinically similar phenotype. We also discuss the disease pathologies as revealed by the studies on the animal models and, finally, on the progress with therapeutic attempts albeit in the animal models.

Perampanel: Does it have broad-spectrum potential?

This article reviews the profile of perampanel, a novel noncompetitive α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor antagonist, and its role as a potential broad-spectrum antiepileptic drug in the treatment of epilepsy. For this narrative review, data were collected using specified search criteria. Articles reporting the evidence for perampanel's efficacy from preclinical models, phase 3 clinical studies, observational studies, and descriptive evidence were included. AMPA receptors play a key role in mediating the action of glutamate at the excitatory synapse. Preclinical research showed the AMPA receptor blockade to constitute a promising target for antiepileptic drug therapy. In animal models, perampanel proved to be protective against seizures and reduce seizure severity and duration. Four phase-3 randomized controlled trials (3 in patients with focal seizures and one in primary generalized tonic-clonic seizures in idiopathic generalized epilepsy) have been completed. In focal (partial) onset seizures, perampanel (4, 8, and 12 mg) significantly reduced seizure frequency per 28 days (23.3%-28.8% vs 12.8%; P < .01) and responder rates (≥50% reduction in seizures) (28.5%-35.3% vs 19.3%; P < .05) compared with placebo. In primary generalized tonic-clonic seizures, perampanel 8 mg resulted in greater reduction in seizure frequency per 28 days (-76.5% vs -38.4%; P < .0001) and responder rate (64.2% vs 39.5%; P = .0019) than placebo. The efficacy, safety, and tolerability of perampanel have been reproduced in real-world clinical practice, and the agent has been shown to be effective in other epilepsy syndromes. Perampanel is a potentially broad-spectrum antiepileptic drug with a novel mechanism of action that may be a useful addition for patients with epilepsy with various seizure types. The availability of novel antiepileptic drugs for epilepsy treatment enables more individualized treatment for these patients.

Extraneurological sparing in long-lived typical Lafora disease

Lafora disease (LD) clinically appears in previously healthy teenagers as progressively worsening seizures, myoclonus, dementia, and ultimately a vegetative state leading to death within a decade of its onset. Here we present a typical case of LD in which the patient survived until the age of 40. Although the patient's brain was severely affected, other organs remained functional until her death. The field of LD research is approaching potentially curative therapies (eg, with antisense oligonucleotides or gene replacement) targeting only the central nervous system (CNS). Our case provides anecdotal evidence suggesting that a patient with typical LD can retain full bodily health aside from the effects of neurological damage.

Perampanel, an AMPA receptor antagonist: From clinical research to practice in clinical settings

Epileptic seizures are refractory to treatment in approximately one-third of patients despite the recent introduction of many newer antiepileptic drugs (AEDs). Development of novel AEDs therefore remains a high priority. Perampanel is a first-in-class non-competitive selective AMPA receptor antagonist with a unique mechanism of action. Clinical efficacy and safety of perampanel as adjunctive treatment for focal seizures with/without secondary generalization (±SG) and primary generalized tonic-clonic (PGTC) seizures have been established in five phase 3 randomized controlled trials (RCTs), and a long-term extension study, and perampanel is approved as monotherapy for focal seizures ±SG in the USA. In patients with focal seizures ±SG, add-on perampanel resulted in median percent reduction in seizure frequency 23.3%-34.5% and ≥50% responder rate 28.5%-37.6%; in PGTC seizures, these results were 76.5% and 64.2%, respectively. Efficacy among adolescents (reduction in seizure frequency 34.8%-35.6%; ≥50% responder rate 40.9%-45.0%) and elderly people (reduction in seizure frequency 12.5%-16.9%; ≥50% responder rate 22.2%-42.9%) is similar to those in adults, and results remain comparable between Asian (reduction in seizure frequency 17.3%-38.0%) and global populations. Perampanel has been extensively studied in real-world clinical practice, with similar efficacy and safety results to the RCTs (≥50% responder rate 12.8%-75.0%; adverse events of somnolence/sedation, dizziness, ataxia, and behavioral changes). Real-world observational studies suggest that perampanel tolerability can be improved by slow titration (2 mg every 2-4 weeks), and bedtime administration can mitigate somnolence and dizziness. Counseling about the potential for behavioral changes and close monitoring are recommended.

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.

Efficacy of perampanel in a patient with epilepsia partialis continua

Perampanel is the first-in-class selective and noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist. It is authorized in the U.S. and Europe as an add-on antiepileptic drug for partial-onset seizures, and for primary generalized tonic–clonic seizures. Single reports have also indicated a potential efficacy for myoclonic jerks. Here, we report a patient whose drug-resistant epilepsia partialis continua completely resolved after adding perampanel. She has remained seizure-free in an eighteen-month follow-up period. Epilepsia partialis continua reemerged transiently after perampanel was temporarily discontinued, with no recurrence after its reintroduction. Therefore, this effect was reproducible, and suggests that it might be worth trying perampanel in similar settings.

AMPA receptors and perampanel behind selected epilepsies: current evidence and future perspectives

INTRODUCTION

The alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors are the major mediators of glutamate-mediated excitatory neurotransmission, and are critical for synchronization and spread of epileptic activity. Areas covered: AMPA receptor antagonists have been also developed as antiepileptic drugs and perampanel (PER) is the first highly selective, non-competitive AMPA-type glutamate receptor antagonist that is available on the market. It is approved as adjunctive therapy for the treatment of partial-onset seizures with or without secondary generalization, and for primary generalized tonic-clonic seizures in idiopathic generalized epilepsy, in patients aged ≥ 12 years. This article reviews the role of AMPA receptors in the neuronal hyperexcitability underlying epilepsy, the mechanism of action and clinical experience on the anti-seizure activity of PER. Moreover, the rationale for targeting AMPA receptor in specific epileptic disorders, including brain tumor-related epilepsy, mesial temporal lobe epilepsy with/without hippocampal sclerosis, and status epilepticus is evaluated. Finally, the pharmacological rationale for the development of AMPA receptor antagonists in other neurological disorders beyond epilepsy is considered. Expert opinion: Further research aimed at better understanding the pharmacology and blocking mechanism of PER and other AMPA receptor antagonists will drive future development of therapeutic agents that target epilepsy and other neurological diseases.

Current role of perampanel in pediatric epilepsy

Perampanel is among the latest AEDs approved, indicated for the treatment of partial-onset seizures with or without secondary generalization, and for primary generalized tonic-clonic seizures, in patients aged 12 years and older. This paper summarizes the clinical recommendations on the current role of perampanel in the treatment of pediatric epilepsies and future directions for research. The optimal dosage should be comprised between 4 and 12 mg/day, with 8 mg/day being the most common dosage used. The rate and severity of adverse events, including psychiatric symptoms, can be decreased by starting at low doses, and titrating slowly. Overall, perampanel presents an acceptable risk/benefit ratio, but special caution should be made to the risk of seizure aggravation and behavioral problems. The favorable cognitive profile, the ease of use of the titration scheme and the once-daily formulation offer advantage over other AEDs and make this drug particularly suitable for adolescent population. Perampanel is a welcome addition to the armamentarium of the existing AEDs, as it represents a new approach in the management of epilepsy, with a novel mechanism of action and a potential to have a considerable impact on the treatment of adolescents with epilepsy.

Efficacy of perampanel for controlling seizures and improving neurological dysfunction in a patient with dentatorubral-pallidoluysian atrophy (DRPLA)

We administered perampanel (PER) to a bedridden 13-year-old male patient with dentatorubral-pallidoluysian atrophy (DRPLA). The DRPLA diagnosis was based on the presence of a CAG trinucleotide repeat in the ATN1 gene. The patient experienced continuous myoclonic seizures and weekly generalized tonic–clonic seizures (GTCs). PER stopped the patient's myoclonic seizures and reduced the GTCs to fragmented clonic seizures. The patient recovered his intellectual abilities and began to walk again with assistance. We suggest that PER be considered as one of the key drugs used to treat patients with DRPLA.

Perampanel in 12 patients with Unverricht-Lundborg disease

OBJECTIVE

Perampanel (PER) was used in 12 patients with Unverricht-Lundborg disease (ULD) to evaluate its efficacy against myoclonus and seizures.

METHODS

We treated 11 patients with EPM1 mutations (6 F, 5 M, aged 13-62 years) and a 43-year-old man with de novo KCNC1 mutation. PER was introduced by 2 mg steps at 2-4 week intervals until 6 mg/day, with a possible dose reduction or dose increase.

RESULTS

Ten patients had a clear clinical response of myoclonus, and five were able to reduce concomitant therapy. Improvement was noted sometimes as soon as with 2 mg/day. Epileptic seizures stopped on PER in the six patients who still had experienced generalized tonic-clonic or myoclonic seizures (100%). Some abatement of efficacy on myoclonus was seen in two patients who still retained some benefit. Weight gain was reported in six patients (50%). Psychological and behavioral side-effects were observed in six patients (50%) and led to withdrawal of PER in three cases and dose reduction in three, with abatement of the problems.

SIGNIFICANCE

This study provides evidence that for ULD patients, PER may show marked efficacy even in severe cases, particularly against myoclonus, but also against seizures. PER should thus be tried in ULD patients whose seizures are not satisfactorily controlled. Its use is limited because of psychological and behavioral side effects, with higher doses of approximately 6 mg/day or greater likely risk factors.

Update on pharmacotherapy of myoclonic seizures

INTRODUCTION

Myoclonic seizures are brief, involuntary muscular jerks arising from the central nervous system that can occur in different epilepsy syndromes, including idiopathic generalized epilepsies or the most severe group of epileptic encephalopathies. Valproate is commonly the first choice alone or in combination with some benzodiazepines or levetiracetam. However, more treatment options exist today as there is emerging evidence to support the efficacy of some newer antiepileptic drugs. In addition, of major importance remains avoidance of medications (e.g., carbamazepine, phenytoin) that may aggravate myoclonic seizures. This is an updated review on the available therapeutic options for treatment of myoclonic seizures. Areas covered: Key efficacy, tolerability and efficacy data are showed for different antiepileptic drugs with antimyoclonic effect, alone and/or in combination. Expert opinion: Pharmacological treatment of myoclonic seizures is based on clinical experience with little evidence from randomized clinical trials. Valproate, levetiracetam, and some benzodiazepines, are widely used. There is still insufficient evidence for the use of other antiseizure drugs, such as topiramate or zonisamide as monotherapy. Better understanding of pathophysiologic mechanisms of myoclonic epilepsies could yield great improvement in the treatment and quality of life of patients.