Perampanel: a selective AMPA antagonist for treating seizures

WRAPPER study: Real-world effectiveness and tolerability of adjunctive perampanel for people with drug-resistant epilepsy in Hong Kong

OBJECTIVE

The Prince of Wales Hospital (PWH) Real-world Analysis of People with Drug-Resistant Epilepsy (DRE) on PERampanel (WRAPPER) study assessed effectiveness and tolerability of adjunctive perampanel in people with DRE attending PWH.

METHODS

This was a prospective single-center real-world observational study involving 70 people with DRE between July 2016 and June 2021. A post hoc analysis after the initial study period of 16 weeks assessed outcomes for an extended period up to 52 weeks.

RESULTS

After 16 weeks, median dose of perampanel was 2 mg (IQR 24 mg). 50% responder rates were 40.0%, 41.5%, and 48.7% at 16, 26, and 52 weeks. Seizure freedom was 12.9%, 20.7%, and 25.6% at 16, 26, and 52 weeks. Monthly seizure frequency reduced from 3.0 (IQR 3.0-6.6) at baseline to 2.0 (IQR 2.0-6.0, p = 0.005) at 16 weeks; 2.0 (IQR 2.0-5.0, p = 0.01) at 26 weeks; and 2.0 (IQR 0.0-4.0, p = 0.018) at 52 weeks. Older age predicted 50% responders (OR 1.08, 95% CI 1.01-1.14, p = 0.048). At 16 weeks, 51.4% (36/70) had treatment-emergent adverse effects (TEAEs). Most common was seizure exacerbation at 35.7% (25/70) followed by fatigue at 15.7% (11/70). NPI-12 and ZBI scores indicated no increase in neuropsychiatric symptoms on perampanel.

SIGNIFICANCE

Low-dose 2-4 mg adjunctive perampanel for people with DRE conferred appreciable improvements in seizure reduction without significant neuropsychiatric adverse effects in the real-world setting at a tertiary center in Hong Kong and had better antiseizure effect with advancing age.

PLAIN LANGUAGE SUMMARY

This real-world study from Hong Kong found low-dose perampanel was effective and tolerable for people with drug-resistant epilepsy. Furthermore, perampanel was also potentially more effective with advancing age.

Effectiveness and safety of perampanel as adjunctive therapy among Chinese patients with focal-onset epilepsy: A real-world prospective observational study

OBJECTIVE

Perampanel (PER) has previously been shown to be effective and tolerable when used as an adjunctive therapy for patients with focal-onset seizures (FOS). This study aimed to evaluate the effect of PER as adjunctive therapy for patients with FOS in the Chinese population under real-world conditions for 1 year.

METHODS

A prospective, single-center, 1-year observational study was conducted at Huashan Hospital, enrolling both under age (≥4 years old) and adult patients with FOS. Response to PER was assessed at 3-, 6-, and 12-month checkpoints by analyzing the 50 % responder rate, the seizure-free rate, and reduction in seizure frequency.

RESULTS

One hundred and eight patients (mean age: 26.6 years, 56.5 % males) with FOS were included, with seventy-six patients finishing the 1-year follow-up (retention rate: 70.4 %, mean PER dose: 4.3 mg/day). The seizure frequency was reduced significantly at 3, 6, and 12 months relative to baseline (p < 0.001 for each seizure type). At 12 months, the responder rate was 65.8 %, and the seizure-free rate was 39.5 %. A significantly higher responder rate was found in patients with focal to bilateral tonic-clonic seizures (p = 0.024), among which the percentage of patients with sleep-related epilepsy was significantly high (p = 0.045). Responders had a lower number of concomitant anti-seizure medications (ASMs) than the non-responders (p = 0.009). Drug-related adverse events (AEs) were reported in 37 % of patients, mostly mild or moderate, and the patients who experienced AEs had a higher daily dose of PER than those who did not (p = 0.026).

CONCLUSION

Perampanel, an add-on therapy for focal-onset seizures, was found to be effective and tolerable in Chinese patients at 12 months.

Perampanel-Induced Psychosis in a Young Woman: A Case Report

OBJECTIVES

A case of perampanel-induced psychosis in a young woman is reported, a side effect that has only rarely been reported in the literature.

METHODS

We describe a case of a young woman with epilepsy and no psychiatric history with perampanel-associated altered behavior and psychotic symptoms, requiring hospitalization in an acute psychiatry ward. We also provide a literature review on the possible neurobiological pathways implicated.

RESULTS

Perampanel is believed to block a small proportion of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor current, retarding epileptiform discharges while sparing most normal synaptic transmission. Most common adverse events are related to central nervous system (including dizziness, drowsiness, blurred vision and imbalance) and psychiatric symptoms have been reported.

CONCLUSIONS

The biological vulnerability to psychiatric and behavioral adverse reactions of antiepileptic drugs is multifactorial and different mechanisms and clinical predisposing factors may interact. For this reason, patients starting these antiseizure drugs need long-term and comprehensive clinical monitoring.

Clinical effects and outcomes of perampanel overdoses reported to U.S. poison centers

INTRODUCTION

Perampanel is indicated for partial onset seizures in children and adults. The mechanism is unique among antiepileptic agents as it inhibits glutamate activity on AMPA receptors. Currently, there are few published case reports describing overdose.

METHODS

This is a retrospective observational study of all single substance perampanel ingestions from January 2014 to December 2019 reported to the national poison data system (NPDS). The primary outcome is to describe the clinical effects of perampanel exposures. Secondary outcomes include evaluation of management and investigation of a dose-effect relationship for the purpose of triaging acute unintentional exposures.

RESULTS

A total of 138 exposures were reported to NPDS since the release of the agent. Median age was 20 years (IQR 10-38) with 68 (49.3%) males. The reason for exposure was most commonly therapeutic error (80, 58.0%), followed by exploratory ingestion (24, 17.4%), and suicidal ingestion (14, 10.1%). A total of six (4.3%) patients developed major effects, 20 (14.5%) moderate, 32 (23.2%) minor effects and 22 (15.9%) no effect. An additional 54 (39.1%) cases were not followed. Almost half of cases were managed at home. Of those that were in a healthcare facility (HCF) (n = 72), most were treated/evaluated and released (31, 43.1%), followed by admission to a non-critical care unit (20, 27.8%), and critical care unit (13, 18.1%). Most frequently reported symptoms were drowsiness (27, 19.6%), agitation (20, 14.5%), ataxia (13, 9.4%), and confusion (12, 8.7%). The most common therapies provided in a HCF were intravenous fluids (22,30.6%), followed by benzodiazepines (14, 19.4%), then other types of sedation (9, 12.5%). There were too few cases to determine a dose cut off for triaging.

CONCLUSIONS

While drowsiness, agitation, ataxia, and confusion were the most often reported symptoms, close to 19% developed moderate/major effects and almost 4% of patients received potentially life-saving interventions.

Insomnia is less prevalent and less severe, independent of depressive symptoms, in patients with epilepsy treated with perampanel as an adjuvant

PURPOSE

The potential benefit of perampanel for sleep disturbances is unknown. This study determined whether insomnia is less prevalent and less severe in patients with epilepsy (PWE) who take perampanel as an adjuvant.

METHODS

This cross-sectional study was conducted in adults with epilepsy. Insomnia in patients treated or not treated with perampanel was diagnosed according to the criteria of the International Classification of Sleep Disorders, the third edition (ICSD-3) and the Insomnia Severity Index (ISI). Patients were also scored on the Epworth Sleepiness Scale (ESS), Patient Health Questionnaire-9 (PHQ-9), and Generalized Anxiety Disorder-7 (GAD-7), and the groups were compared by stepwise linear or logistic regression analyses.

RESULTS

One hundred and twenty-six PWE were included in the study: 31 patients (24.6%) were taking perampanel. Insomnia was diagnosed in 15.9% and 20.6% of all patients according to the ICSD-3 and an ISI score of ≥15, respectively. Agreement between the two diagnostic methods was moderate (Cohen's kappa, 0.470). In a stepwise logistic regression model, insomnia diagnosed by either method was negatively associated with perampanel use (P<0.05) but positively correlated with depressive symptoms, anxiety, and duration of epilepsy. In a stepwise linear regression model, ISI scores correlated negatively with perampanel use (P=0.004) but positively with depressive symptoms (P<0.001) and anxiety (P=0.001).

CONCLUSIONS

Insomnia is less prevalent and less severe in PWE treated with perampanel independent of depressive symptoms, which will be helpful for treating PWE and comorbid sleep disturbances.

Dendritic structural plasticity and neuropsychiatric disease

The structure of neuronal circuits that subserve cognitive functions in the brain is shaped and refined throughout development and into adulthood. Evidence from human and animal studies suggests that the cellular and synaptic substrates of these circuits are atypical in neuropsychiatric disorders, indicating that altered structural plasticity may be an important part of the disease biology. Advances in genetics have redefined our understanding of neuropsychiatric disorders and have revealed a spectrum of risk factors that impact pathways known to influence structural plasticity. In this Review, we discuss the importance of recent genetic findings on the different mechanisms of structural plasticity and propose that these converge on shared pathways that can be targeted with novel therapeutics.

Perampanel Affects Up-Stream Regulatory Signaling Pathways of GluA1 Phosphorylation in Normal and Epileptic Rats

To elucidate the pharmacological properties of perampanel [2-(2-oxo-1-phenyl-5-pyridin-2-yl-1,2-dihydropyridin-3-yl)benzonitrile, a novel non-competitive antagonist of AMPA receptor], we investigated its effects on the up-stream regulatory pathways of GluA1 phosphorylation including protein kinase C (PKC), Ca²⁺-calmodulin-dependent protein kinase II (CAMKII), protein kinase A (PKA), extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), protein phosphatase (PP) 1, PP2A, and PP2B in normal and pilocarpine-induced epileptic rat model using Western blot analysis. In normal animals, perampanel affected GluA1 expression/phosphorylation, PKC, CAMKII, PKA, ERK1/2, JNK, and PPs activities. In epileptic rats, perampanel effectively inhibited spontaneous seizure activities. Perampanel enhanced phospho (p)-GluA1-S831 and -S845 ratios (phosphoprotein/total protein), while it reduced GluA1 expression. Perampanel also increased pCAMKII and pPKA ratios, which phosphorylate GluA1-S831 and -S845 site, respectively. Perampanel elevated pJNK and pPP2B ratios, which phosphorylates and dephosphorylates both GluA1-S831 and -S845 sits. Perampanel also increased pERK1/2 ratio in epileptic animals, while U0126 (an ERK1/2 inhibitor) did not affect pGluA1 ratios. Perampanel did not influence PKC, PP1, and PP2A expression levels and their phosphorylation ratios. In addition, perampanel did not have a detrimental impact on cognitive abilities of epileptic and normal rats in Morris water maze test. These findings suggest that perampanel may regulate AMPA receptor functionality via not only blockade of AMPA receptor but also the regulations of multiple molecules (CAMKII, PKA, JNK, and pPP2B)-mediated GluA1 phosphorylations without negative effects on cognition, although the effects of perampanel on PKC, PP1, and PP2A activities were different between normal and epileptic rats.

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.

Effect of adjunctive perampanel on the quality of sleep and daytime somnolence in patients with epilepsy

This prospective uncontrolled study evaluated the effect of low-dose adjunctive perampanel therapy (4 mg/day for 3 months) on the sleep-wake cycle and daytime somnolence in adult patients (n = 10) with focal seizures. A > 50% reduction in the number of seizures was reported in 80% of the study patients; treatment had no significant effect on any sleep parameters as evident by the Maintenance of Wakefulness Test, Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale scores. Two patients reported dizziness with treatment. In conclusion, low-dose perampanel may improve seizure control without affecting the sleep characteristics or daytime somnolence in patients with epilepsy.

Two-year real-world experience with perampanel in patients with refractory focal epilepsy: Austrian data

BACKGROUND

The aim of this study was to analyse registry data of seizure outcome and adverse events (AEs) for perampanel as add-on therapy in patients with focal epilepsy since its approval in 2012 for adjunctive treatment of focal epilepsy in patients ⩾12 years.

METHOD

A retrospective 2-year chart review of all patients receiving perampanel was carried out.

RESULTS

A total of 122 patients received perampanel [median treatment length: 20.1 (range: 3.4-26.8) months]; 71 (58%) remained on treatment at last follow up. Overall, 33 patients (27%) were seizure-free for ⩾3 months at last follow up; of these, eight were seizure free for ⩾3 times the longest interictal interval before perampanel therapy; 18 (15%) had reduced seizure frequency ⩾50%. A total of 58 (47%) had an AE and 34 (28%) withdrew from treatment because of AEs. AEs included dizziness (33%), fatigue (12%), psychiatric symptoms (8%), cognitive deficits (7%), speech problems (5%), nausea (4%) and gait problems (4%). AEs subsided in 17/18 patients (94%) following a 2 mg dose reduction. A total of 43 (35%) took a concomitant enzyme inducer. Patients not taking enzyme inducers were more likely to be seizure free (p = 0.002); there were no other between-group differences.

CONCLUSIONS

Perampanel was well tolerated and improved seizure control in 42% of patients (50- 100% reduction), with higher rates in those not receiving a concomitant enzyme inducer. AEs, particularly dizziness, were common but often disappeared with a slight dose reduction. The results are consistent with those from randomized controlled trials.

Mechanisms of glutamate toxicity in multiple sclerosis: biomarker and therapeutic opportunities

Research advances support the idea that excessive activation of the glutamatergic pathway plays an important part in the pathophysiology of multiple sclerosis. Beyond the well established direct toxic effects on neurons, additional sites of glutamate-induced cell damage have been described, including effects in oligodendrocytes, astrocytes, endothelial cells, and immune cells. Such toxic effects could provide a link between various pathological aspects of multiple sclerosis, such as axonal damage, oligodendrocyte cell death, demyelination, autoimmunity, and blood-brain barrier dysfunction. Understanding of the mechanisms underlying glutamate toxicity in multiple sclerosis could help in the development of new approaches for diagnosis, treatment, and follow-up in patients with this debilitating disease. While several clinical trials of glutamatergic modulators have had disappointing results, our growing understanding suggests that there is reason to remain optimistic about the therapeutic potential of these drugs.

Perampanel inhibition of AMPA receptor currents in cultured hippocampal neurons

Perampanel is an aryl substituted 2-pyridone AMPA receptor antagonist that was recently approved as a treatment for epilepsy. The drug potently inhibits AMPA receptor responses but the mode of block has not been characterized. Here the action of perampanel on AMPA receptors was investigated by whole-cell voltage-clamp recording in cultured rat hippocampal neurons. Perampanel caused a slow (τ∼1 s at 3 µM), concentration-dependent inhibition of AMPA receptor currents evoked by AMPA and kainate. The rates of block and unblock of AMPA receptor currents were 1.5×105 M-1 s-1 and 0.58 s-1, respectively. Perampanel did not affect NMDA receptor currents. The extent of block of non-desensitizing kainate-evoked currents (IC50, 0.56 µM) was similar at all kainate concentrations (3-100 µM), demonstrating a noncompetitive blocking action. Parampanel did not alter the trajectory of AMPA evoked currents indicating that it does not influence AMPA receptor desensitization. Perampanel is a selective negative allosteric AMPA receptor antagonist of high-affinity and slow blocking kinetics.