Cenobamate (XCOPRI): Can preclinical and clinical evidence provide insight into its mechanism of action?

Neurotoxicity study of cenobamate-induced zebrafish early developmental stages

Cenobamate (CNB) is a novel anti-seizure medication with significant efficacy in treating epilepsy. However, in clinical trials, the most common adverse reactions observed in patients are central nervous system (CNS) symptoms. In animal studies, administration of CNB during pregnancy or lactation has been associated with adverse effects on neurodevelopment in offspring. To optimize the clinical use of CNB, we investigated the neurotoxicity of different concentrations of CNB (10, 20, 40, 80, and 160 μM) on zebrafish embryos. Following exposure, zebrafish embryos exhibited abnormal phenotypes such as shortened body length, impaired yolk sac absorption, and decreased heart rate. Behavioral experiments showed that CNB caused abnormal movements such as decreased spontaneous tail curling frequency, shortened total movement distance, and reduced average movement speed. We also found that CNB leads to increased acetylcholinesterase (AChE) activity levels in zebrafish embryos, along with differential expression of neurodevelopment-related genes such as nestin, gfap, synapsin IIa, and gap43. In summary, our research findings indicated that CNB may induce developmental and neurotoxic effects in zebrafish embryos by altering neurotransmitter systems and the expression of neurodevelopmental genes, thereby influencing behavior. This study will provide information for the clinical use of CNB, aiming to benefit more epilepsy patients through its appropriate administration.

Cenobamate, a New Promising Antiseizure Medication: Experimental and Clinical Aspects

About 40-50% of patients with drug-resistant epilepsy do not properly respond to pharmacological therapy with antiseizure medications (ASMs). Recently approved by the US Food and Drug Administration and European Medicines Agency as an add-on drug for focal seizures, cenobamate is an ASM sharing two basic mechanisms of action and exhibiting a promising profile of clinical efficacy. The drug preferably inhibits persistent sodium current and activates GABA-mediated events via extrasynaptic, non-benzodiazepine receptors. Thus, its antiseizure potential is dependent on both reducing excitation and enhancing inhibition in the central nervous system. In experimental seizure models, cenobamate exhibited a clear-cut activity in many of them with promising protective indexes, with only bicuculline-induced seizures being unaffected. Randomized clinical trials indicate that combinations of cenobamate, with already prescribed ASMs, resulted in significant percentages of seizure-free patients and patients with a significant reduction in seizure frequency, compared to other ASMs in the form of an add-on therapy. Its greater antiseizure efficacy was accompanied by adverse events comparable to other ASMs. Cenobamate has also been shown to possess neuroprotective activity, which may be of importance in affecting the process of epileptogenesis and, thus, modifying the course of epilepsy.

Efficacy of add-on Cenobamate treatment in refractory epilepsy due to Rasmussen's encephalitis

OBJECTIVE

To assess antiseizure effects of cenobamate, a new antiseizure medication with at least two mechanisms of action, in the rare, highly pharmacoresistant and progressive epilepsy syndrome related to Rasmussen's encephalitis.

METHODS

Three patients from the epilepsy centers in Freiburg, Kork, and Valencia are reported with focal epilepsy which had been pharmacoresistant to more than 10 prior treatment regimens. Assessment included at least 1 year of follow-up after cenobamate introduction and included seizure frequency, seizure severity (in particular status epilepticus) and changes in co-medication.

RESULTS

In the three patients, cenobamate add on treatment proved superior to all prior antiseizure and immunomodulatory treatments which had been individually applied. Not only were focal to bilateral tonic-clonic seizure completely controlled, but also focal motor status epilepticus no longer occurred. Co-medication could be reduced in all patients.

SIGNIFICANCE

This case series in a rare and highly pharmacoresistant epilepsy syndrome suggests high efficacy of cenobamate add-on treatment for seizure control. This may be a valuable information in epilepsy related to Rasmussen encephalitis and calls for further elucidation of the mechanism involved in superior seizure control also compared to prior treatments including sodium channel blockers and benzodiazepines.

PLAIN LANGUAGE SUMMARY

Rasmussen's encephalitis is a rare type of epilepsy that gets worse over time and doesn't respond well to most seizure medications. We describe three patients who tried many treatments without much success, but when they added cenobamate to their treatment, it worked better than the other medications. This also let them lower the overall amount of medication they were taking.

Cenobamate: real-world data from a retrospective multicenter study

BACKGROUND

Clinical trials have shown that cenobamate (CNB) is an efficacious and safe anti-seizure medication (ASM) for drug-resistant focal epilepsy. Here, we analyzed one of the largest real-world cohorts, covering the entire spectrum of epilepsy syndromes, the efficacy and safety of CNB, and resulting changes in concomitant ASMs.

METHODS

We conducted a retrospective observational study investigating CNB usage in two German tertiary referral centers between October 2020 and June 2023 with follow-up data up to 27 months of treatment. Our primary outcome was treatment response. Secondary outcomes comprised drug response after 12 and 18 months, seizure freedom rates, CNB dosage and retention, adverse drug reactions (ADRs), and changes in concomitant ASMs.

RESULTS

116 patients received CNB for at least two weeks. At 6 months, 98 patients were eligible for evaluation. Thereof 50% (49/98) were responders with no relevant change at 12 and 18 months. Seizure freedom was achieved in 18.4% (18/98) at 6 months, 16.7% (11/66), and 3.0% (1/33) at 12 and 18 months. The number of previous ASMs did not affect the seizure response rate. Overall, CNB was well-tolerated, however, in 7.7% (9/116), ADRs led to treatment discontinuation. The most frequent changes of concomitant ASMs included the discontinuation or reduction of sodium channel inhibitors, clobazam reduction, and perampanel discontinuation, while brivaracetam doses were usually left unchanged.

CONCLUSIONS

CNB proved to be a highly effective and generally well-tolerated ASM in patients with severe drug-resistant epilepsy, comprising a broad array of epilepsy syndromes beyond focal epilepsy.

Cenobamate suppresses seizures without inducing cell death in neonatal rats

GABA modulators such as phenobarbital (PB) and sodium channel blockers such as phenytoin (PHT) have long been the mainstay of pharmacotherapy for the epilepsies. In the context of neonatal seizures, both PB and PHT display incomplete clinical efficacy. Moreover, in animal models, neonatal exposure to these medications result in neurodegeneration raising concerns about safety. Cenobamate, a more recently approved medication, displays unique pharmacology as it is both a positive allosteric modulator of GABA-A receptors, and a voltage-gated sodium channel blocker. While cenobamate is approved for adult use, its efficacy and safety profile against neonatal seizures is poorly understood. To address this gap, we assessed the efficacy and safety of cenobamate in immature rodents. Postnatal day (P)7 rat pups were pretreated with cenobamate and challenged with the chemoconvulsant pentylenetetrazole (PTZ) to screen for anti-seizure effects. In a separate experiment, P7 rats were treated with cenobamate, and brains were processed to assess induction of cell death. Cenobamate displays dose-dependent anti-seizure efficacy in neonatal rats. Unlike PHB and PHT, it does not induce neurotoxicity in P7 rats. Thus, cenobamate may be effective at treating neonatal seizures while avoiding unwanted neurotoxic side effects such as cell death.

The cenobamate KORK study-A prospective monocenter observational study investigating cenobamate as an adjunctive therapy in refractory epilepsy, with comparisons to historical cohorts treated with add-on lacosamide, perampanel, and brivaracetam

OBJECTIVE

In Europe, cenobamate has been approved for use as an adjunctive therapy in adult patients with epilepsy (PWE) with focal-onset seizures (FOS) who have not responded satisfactorily to treatment with at least two antiseizure medications (ASMs). Pivotal trials and real-world observational studies have demonstrated a high efficacy of cenobamate, even in very difficult-to-treat epilepsies. Our aim was to investigate the efficacy of add-on cenobamate in adult PWE who were prospectively monitored. We compared these results with those previously obtained for add-on lacosamide, perampanel, and brivaracetam therapy.

METHODS

Patients were enrolled from the CENKORK study, which is a prospective, non-interventional, open-label, monocenter cohort study of adult PWE experiencing FOS. The titration of cenobamate was performed according to the guidelines outlined in the summary of product characteristics. The primary outcome measure was the retention rate at 6 months and 1 year. In addition, we assessed seizure-free rates, the proportion of patients achieving at least a 50% seizure reduction, adverse events, and the reasons for treatment discontinuation. These outcome measures were compared with historical controls treated with adjunctive lacosamide, perampanel, or brivaracetam at our center.

RESULTS

Between June 2021 and 2022, 172 PWE with ongoing FOS were included. 22 cases were lost to follow-up, leaving 150 cases for the 1-year assessment. The retention rates at 6 months and 1 year were 88.7% and 80%, respectively. Seizure freedom was achieved in 14% of patients at both the 6-month and 1-year marks, while the ≥50% responder rates were 50% and 61%, respectively. The 6-month retention rate was significantly higher in cenobamate than in other ASMs (p < 0.001 for each comparator). Adverse events were significantly more common with perampanel (p < 0.001).

SIGNIFICANCE

Add-on cenobamate proved to be particularly efficacious compared to our experience with other recently introduced ASMs.

PLAIN LANGUAGE SUMMARY

This observational study was carried out in 172 adult patients with difficult-to-treat epilepsy who were treated with adjunctive cenobamate. After 1 year, the data of 150 patients could be analyzed. Seizure freedom, in the preceding 3 months, was achieved in 14%. The rate of PWE continuing cenobamate was 80%. In our hands, cenobamate showed promising efficacy and tolerability even when compared to other recently introduced antiseizure medications.

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.

Efficacy and safety of add-on antiseizure medications for focal epilepsy: A network meta-analysis

OBJECTIVE

Several antiseizure medications (ASMs) have been approved for the treatment of focal epilepsy. However, there is a paucity of evidence on direct comparison of ASMs. We evaluated the comparative efficacy and safety of all approved add-on ASMs for the treatment of focal epilepsy using network meta-analysis.

METHODS

Data through extensive literature search was retrieved from PubMed, Embase, Cochrane, and ClinicalTrial.gov databases using predefined search terms from inception through March 2023. PRISMA reporting guidelines (CRD42023403450) were followed in this study. Efficacy outcomes assessed were ≥50%, ≥75%, and 100% responder rates. Patient retention rate and safety outcomes such as overall treatment-emergent adverse events (TEAEs) and individual TEAEs were assessed. "Gemtc" 4.0.4 package was used to perform Bayesian analysis. Outcomes are reported as relative risks (RRs) and 95% confidence interval (CI).

RESULTS

Literature search retrieved 5807 studies of which, 75 studies were included in the analysis. All ASMs showed significantly higher ≥50% responder rate compared with placebo. Except the ≥75% seizure frequency reduction for zonisamide (2.23; 95% CI: 1.00-5.70) and 100% for rufinamide (2.03; 95% CI: 0.54-11.00), all other interventions showed significantly higher ≥75% and 100% responder rates compared with placebo. Among treatments, significantly higher 100% responder rate was observed with cenobamate compared to eslicarbazepine (10.71; 95% CI: 1.56-323.9) and zonisamide (10.63; 95% CI: 1.37-261.2). All ASMs showed a lower patient retention rate compared to placebo, with the least significant value observed for oxcarbazepine (0.77; 95% CI: 0.7-0.84). Levetiracetam showed a lower risk of incidence (1.0; 95%CI: 0.94-1.1; SUCRA: 0.885067) for overall TEAE compared with other medications.

SIGNIFICANCE

All approved ASMs were effective as add-on treatment for focal epilepsy. Of the ASMs included, cenobamate had the greatest likelihood of allowing patients to attain seizure freedom.

PLAIN LANGUAGE SUMMARY

This article compares the efficacy and safety of antiseizure medications (ASMs) currently available to neurologists in the treatment of epileptic patients. Several newer generation ASMs that have been developed may be as effective or better than the older medications. We included 75 studies in the analysis. In comparison, all drugs improved ≥50%, ≥75% and 100% responder rates compared to control, except for Zonisamide and Rufinamide in the ≥75% and 100% responder rate categories. Retention of patients undergoing treatment was lower in drugs than placebo. All drugs were tolerated, the levetiracetam showed the best tolerability. Cenobamate more likely help completely to reduce seizures.

Preclinical efficacy profiles of the sigma-1 modulator E1R and of fenfluramine in two chronic mouse epilepsy models

OBJECTIVE

Given its key homeostatic role affecting mitochondria, ionotropic and metabotropic receptors, and voltage-gated ion channels, sigma-1 receptor (Sig1R) represents an interesting target for epilepsy management. Antiseizure effects of the positive allosteric modulator E1R have already been reported in acute seizure models. Although modulation of serotonergic neurotransmission is considered the main mechanism of action of fenfluramine, its interaction with Sig1R may be of additional relevance.

METHODS

To further explore the potential of Sig1R as a target, we assessed the efficacy and tolerability of E1R and fenfluramine in two chronic mouse models, including an amygdala kindling paradigm and the intrahippocampal kainate model. The relative contribution of the interaction with Sig1R was analyzed using combination experiments with the Sig1R antagonist NE-100.

RESULTS

Whereas E1R exerted pronounced dose-dependent antiseizure effects at well-tolerated doses in fully kindled mice, only limited effects were observed in response to fenfluramine, without a clear dose dependency. In the intrahippocampal kainate model, E1R failed to influence electrographic seizure activity. In contrast, fenfluramine significantly reduced the frequency of electrographic seizure events and their cumulative duration. Pretreatment with NE-100 reduced the effects of E1R and fenfluramine in the kindling model. Surprisingly, pre-exposure to NE-100 in the intrahippocampal kainate model rather enhanced and prolonged fenfluramine's antiseizure effects.

SIGNIFICANCE

In conclusion, the kindling data further support Sig1R as an interesting target for novel antiseizure medications. However, it is necessary to further explore the preclinical profile of E1R in chronic epilepsy models with spontaneous seizures. Despite the rather limited effects in the kindling paradigm, the findings from the intrahippocampal kainate model suggest that it is of interest to further assess a possible broad-spectrum potential of fenfluramine.

Therapeutic strategies during cenobamate treatment initiation: Delphi panel recommendations

The goal of epilepsy treatment is seizure freedom, typically with antiseizure medication (ASM). If patients fail to attain seizure control despite two trials of appropriately chosen ASMs at adequate doses, they are classified as having drug-resistant epilepsy (DRE). Adverse events (AEs) commonly occur in people with DRE because they are typically on ⩾2 ASMs, increasing the potential for drug-drug interactions. Early emerging AEs may impact adherence, decrease quality of life, and delay achieving optimal treatment dosages. Cenobamate is an oral ASM with a long half-life which has proven to be highly effective in clinical trials. An international Delphi panel of expert epileptologists experienced in the clinical use of cenobamate and other ASMs was convened to develop consensus best practices for managing patients during and after cenobamate titration, with consideration for its known pharmacokinetic and pharmacodynamic interactions, to allow patients to reach the most appropriate cenobamate dose while limiting tolerability issues. The modified Delphi process included one open-ended questionnaire and one virtual face-to-face meeting. Participants agreed that cenobamate can be prescribed for most patients experiencing focal-onset seizures. Patients initiating cenobamate therapy should have access to healthcare professionals as needed and their treatment response should be evaluated at the 100-mg dose. Patients with intellectual disabilities may need additional support to navigate the titration period. Proactive down-titration or withdrawal of sodium channel blockers (SCBs) is recommended when concomitant ASM regimens include ⩾2 SCBs. When applicable, maintaining a concomitant clobazam dose at ~5-10 mg may be beneficial. Patients taking oral contraceptives, newer oral anticoagulants, or HIV antiretroviral medications should be monitored for potential interactions. Because clinical evidence informing treatment decisions is limited, guidance regarding dose adjustments of non-ASM drugs was not developed beyond specific recommendations presented in the Summary of Product Characteristics.

Current challenges in focal epilepsy treatment: An Italian Delphi consensus

BACKGROUND

Epilepsy, a globally prevalent neurological condition, presents distinct challenges in management, particularly for focal-onset types. This study aimed at addressing the current challenges and perspectives in focal epilepsy management, with focus on the Italian reality.

METHODS

Using the Delphi methodology, this research collected and analyzed the level of consensus of a panel of Italian epilepsy experts on key aspects of focal epilepsy care. Areas of focus included patient flow, treatment pathways, controlled versus uncontrolled epilepsy, follow-up protocols, and the relevance of patient-reported outcomes (PROs). This method allowed for a comprehensive assessment of consensus and divergences in clinical opinions and practices.

RESULTS

The study achieved consensus on 23 out of 26 statements, with three items failing to reach a consensus. There was strong agreement on the importance of timely intervention, individualized treatment plans, regular follow-ups at Epilepsy Centers, and the role of PROs in clinical practice. In cases of uncontrolled focal epilepsy, there was a clear inclination to pursue alternative treatment options following the failure of two previous therapies. Divergent views were evident on the inclusion of epilepsy surgery in treatment for uncontrolled epilepsy and the routine necessity of EEG evaluations in follow-ups. Other key findings included concerns about the lack of pediatric-specific research limiting current therapeutic options in this patient population, insufficient attention to the transition from pediatric to adult care, and need for improved communication. The results highlighted the complexities in managing epilepsy, with broad consensus on patient care aspects, yet notable divergences in specific treatment and management approaches.

CONCLUSION

The study offered valuable insights into the current state and complexities of managing focal-onset epilepsy. It highlighted many deficiencies in the therapeutic pathway of focal-onset epilepsy in the Italian reality, while it also underscored the importance of patient-centric care, the necessity of early and appropriate intervention, and individualized treatment approaches. The findings also called for continued research, policy development, and healthcare system improvements to enhance epilepsy management, highlighting the ongoing need for tailored healthcare solutions in this evolving field.

Cenobamate Plasma Levels in Patients with Epilepsy: Correlation with Efficacy and Tolerability?

Objective: Cenobamate is approved by the European Medicine Agency for the treatment of adult patients with epilepsy (PWEs) with ongoing focal-onset seizures despite appropriate treatment with at least two established antiseizure medications. Pivotal trials and post-marketing real-world observational studies suggest high efficacy with unusually high seizure-free rates. The authors sought to investigate the plasma levels of cenobamate under steady-state conditions in seizure-free versus non-responding PWEs, and in PWEs who experienced adverse events versus those who did not. Methods: Blood samples were collected from adult PWEs who were treated with adjunct cenobamate under steady-state conditions. Daily doses, concomitant medications, efficacy, and tolerability were assessed. The plasma cenobamate levels of seizure-free versus non-responding PWEs and between PWEs with and those without clinical adverse events were compared. Results: Samples from 101 PWEs were included. Thirty-six PWEs were seizure-free and 65 were non-responders. In 31 PWEs, adverse events were apparent, whereas in the remaining 70, no tolerability issues were reported. A linear correlation was found between the daily doses (range: 100 mg-400 mg) and the plasma levels (3.8 mg/L-54.6 mg/L). Neither the daily doses nor the plasma levels differed significantly between the investigated subgroups. The main reason for this result was that the individual therapeutic ranges varied widely: seizure freedom and adverse effects were observed alongside low doses and plasma levels in some PWEs. Conversely, there were examples of PWEs who did not respond or who reported no tolerability issues at high doses or plasma levels. Conclusions: To evaluate the individual therapeutic range and to better understand the influence of other drugs in cases where concomitant medications are used, the therapeutic drug monitoring of cenobamate may be useful. A general therapeutic range cannot be defined.

Current advances in rodent drug-resistant temporal lobe epilepsy models: Hints from laboratory studies

Anti-seizure drugs (ASDs) are the first choice for the treatment of epilepsy, but there is still one-third of patients with epilepsy (PWEs) who are resistant to two or more appropriately chosen ASDs, named drug-resistant epilepsy (DRE). Temporal lobe epilepsy (TLE), a common type of epilepsy usually associated with hippocampal sclerosis (HS), shares the highest proportion of drug resistance (approximately 70%). In view of the key role of the temporal lobe in memory, emotion, and other physiological functions, patients with drug-resistant temporal lobe epilepsy (DR-TLE) are often accompanied by serious complications, and surgical procedures also yield extra considerations. The exact mechanisms for the genesis of DR-TLE remain unillustrated, which makes it hard to manage patients with DR-TLE in clinical practice. Animal models of DR-TLE play an irreplaceable role in both understanding the mechanism and searching for new therapeutic strategies or drugs. In this review article, we systematically summarized different types of current DR-TLE models, and then recent advances in mechanism investigations obtained in these models were presented, especially with the development of advanced experimental techniques and tools. We are deeply encouraged that novel strategies show great therapeutic potential in those DR-TLE models. Based on the big steps reached from the bench, a new light has been shed on the precise management of DR-TLE.

Quantitative Analysis of Cenobamate and Concomitant Anti-Seizure Medications in Human Plasma via Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

Cenobamate (CNB) is a new anti-seizure medication (ASM) recently introduced in clinical practice after approval by the FDA and EMA for the add-on treatment of focal onset seizures in adult patients. Although its mechanism of action has not been fully understood, CNB showed promising clinical efficacy in patients treated with concomitant ASMs. The accessibility of CNB could pave a way for the treatment of refractory or drug-resistant epilepsies, which still affect at least one-third of the patients under pharmacological treatment. In this context, therapeutic drug monitoring (TDM) offers a massive opportunity for better management of epileptic patients, especially those undergoing combined therapy. Here, we describe the first fully validated ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the quantification of CNB and concomitant ASMs in human plasma, with samples extracted either manually or by means of a liquid handler. Our method was validated according to the most recent ICH International Guideline M10 for Bioanalytical Method Validation and Study Sample Analysis. The method proved to be selective for CNB and displayed a linear range from 0.8 to 80 mg/L; no matrix effect was found (98.2 ± 4.1%), while intra-day and inter-day accuracy and precision were within the acceptance range. Also, CNB short- and long-term stability in plasma under different conditions was assessed. Leftover human plasma samples were employed as study samples for method validation. Our method proved to be highly sensitive and selective to quantify CNB and concomitant ASMs in human plasma; therefore, this method can be employed for a routinely TDM-based approach to support physicians in the management of an epileptic patient.

The efficacy and safety of third-generation antiseizure medications and non-invasive brain stimulation to treat refractory epilepsy: a systematic review and network meta-analysis study

Background

The new antiseizure medications (ASMs) and non-invasive brain stimulation (NIBS) are controversial in controlling seizures. So, this network meta-analysis aimed to evaluate the efficacy and safety of five third-generation ASMs and two NIBS therapies for the treatment of refractory epilepsy.

Methods

We searched PubMed, EMBASE, Cochrane Library and Web of Science databases. Brivaracetam (BRV), cenobamate (CNB), eslicarbazepine acetate (ESL), lacosamide (LCM), perampanel (PER), repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS) were selected as additional treatments for refractory epilepsy in randomized controlled studies and other cohort studies. Randomized, double-blind, placebo-controlled, add-on studies that evaluated the efficacy or safety of medication and non-invasive brain stimulation and included patients with seizures were uncontrolled by one or more concomitant ASMs were identified. A random effects model was used to incorporate possible heterogeneity. The primary outcome was the change in seizure frequency from baseline, and secondary outcomes included the proportion of patients with ≥50% reduction in seizure frequency, and the rate of treatment-emergent adverse events.

Results

Forty-five studies were analyzed. The five ASMs and two NIBS decreased seizure frequency from baseline compared with placebo. The 50% responder rates of the five antiseizure drugs were significantly higher than that of placebo, and the ASMs were associated with fewer adverse events than placebo (p < 0.05). The surface under the cumulative ranking analysis revealed that ESL was most effective in decreasing the seizure frequency from baseline, whereas CNB provided the best 50% responder rate. BRV was the best tolerated. No significant publication bias was identified for each outcome index.

Conclusion

The five third-generation ASMs were more effective in controlling seizures than placebo, among which CNB, ESL, and LCM were most effective, and BRV exhibited better safety. Although rTMS and tDCS did not reduce seizure frequency as effectively as the five drugs, their safety was confirmed.

Systematic review registration

PROSPERO, https://www.crd.york.ac.uk/prospero/ (CRD42023441097).

Cenobamate enhances the anticonvulsant effect of other antiseizure medications in the DBA/2 mouse model of reflex epilepsy

Clinical studies documented that cenobamate (CNB) has a marked efficacy compared to other antiseizure medications (ASMs) in reducing focal seizures. To date, different aspects of CNB need to be clarified, including its efficacy against generalized seizures. Similarly, the pattern of drug-drug interactions between CNB and other ASMs also compels further investigation. This study aimed to detect the role of CNB on generalized seizures using the DBA/2 mouse model. We have also studied the effects of an adjunctive CNB treatment on the antiseizure properties of some ASMs against reflex seizures. The effects of this adjunctive treatment on motor performance, body temperature, and brain levels of ASMs were also evaluated. CNB was able to antagonize seizures in DBA/2 mice. CNB, at 5 mg/kg, enhanced the antiseizure activity of ASMs, such as diazepam, clobazam, levetiracetam, perampanel, phenobarbital, topiramate, and valproate. No synergistic effects were observed when CNB was co-administered with some Na+ channel blockers. The increase in antiseizure activity was associated with a comparable intensification in motor impairment; however, the therapeutic index of combined treatment of ASMs with CNB was more favorable than the combination with vehicle except for carbamazepine, phenytoin, and oxcarbazepine. Since CNB did not significantly influence the brain levels of the ASMs studied, we suggest that pharmacokinetic interactions seem not probable. Overall, this study shows the ability of CNB to counteract generalized reflex seizures in mice. Moreover, our data documented an evident synergistic antiseizure effect for the combination of CNB with ASMs including phenobarbital, benzodiazepines, valproate, perampanel, topiramate, and levetiracetam.

Cenobamate in refractory epilepsy: Overview of treatment options and practical considerations

Management of drug resistant epilepsy (DRE) represents a challenge to the treating clinician. This manuscript addresses DRE and provides an overview of treatment options, medical, surgical, and dietary. It addresses treatment strategies in polytherapy, then focuses on the role cenobamate (CNB) may play in reducing the burden of DRE while providing practical advice for its introduction. CNB is a recently approved, third generation, anti-seizure medication (ASM), a tetrazole-derived carbamate, thought to have a dual mechanism of action, through its effect on sodium channels as well as on GABAA receptors at a non-benzodiazepine site. CNB, having a long half-life, is an effective add-on ASM in refractory focal epilepsy with a higher response rate and a higher seizure-freedom rate than is usually seen in regulatory clinical trials. Experience post-licensing, though still limited, supports the findings of clinical trials and is encouraging. Its spectrum of action in relation to generalized epilepsies and seizures remains to be established, and there are no data on its efficacy in monotherapy. At the time of writing, CNB has been prescribed for some 50 000 individuals with DRE and focal epilepsy. A larger number is needed to fully establish its safety profile. It should at all times be introduced slowly to minimize the risk of serious allergic drug reactions. It has clinically meaningful interactions which must be anticipated and managed to maximize tolerability and likelihood of successful treatment. Despite the above, it may well prove to be of major benefit in the treatment of many patients with drug resistant epilepsy.

Cenobamate and Clobazam Combination as Personalized Medicine in Autoimmune-Associated Epilepsy With Anti-Gad65 Antibodies

BACKGROUND AND OBJECTIVES

Autoimmune-associated epilepsy (AAE) with antiglutamic acid decarboxylase 65 (GAD65) antibodies is considered a T-cell-mediated encephalitis that evolves to drug-resistant epilepsy. We do not have an effective therapeutic strategy for these patients. Because the GAD enzyme is primarily responsible for the conversion of glutamate to GABA, the mechanism of epileptogenesis in this condition predicts decreased levels of GABA content in synaptic vesicles. Cenobamate (CNB) acts as a positive allosteric modulator at synaptic and extra synaptic GABAA receptors, producing increased inhibitory neurotransmission in the brain. This mechanism could be especially beneficial in AAE with anti-GAD65 antibodies because it would be able to correct the imbalance due to the GABAergic stimulation deficit in postsynaptic neurons.

METHODS

We recruit a retrospective multicentric consecutive case series of AAE with anti-GAD65 antibodies from 5 epilepsy units in Spain who have received treatment with CNB.

RESULTS

A total of 8 patients were recruited. This cohort of highly refractory patients have failed a mean of 9.50 (SD = 3.20) ASM without control of seizures for sustained periods of time. The average number of seizures per month during the previous 3 months before CNB treatment was 19.63 (SD = 17.03). After the introduction of CNB improvement was achieved in all our patients, with a median reduction in the number of seizures of 92.22% (interquartile range [IQR]: 57.25-98.75). The mean follow-up was 156.75 days (SD = 68.23). In patients with concomitant treatment with clobazam (CLB), the median percentage of seizure reduction was higher than those not taking CLB: 94.72% (IQR: 87.25-100) vs 41.50% (p = 0.044) and also higher than the control group of patients with refractory epilepsy not related to anti-GAD65 treated with the same combination: 94.72% (IQR: 87.25-100) vs 45.00% (IQR: 25.00-87.00) (p = 0.019).

DISCUSSION

Treatment with the combination CNB + CLB could be a type of personalized medicine in patients with AAE with anti-GAD65. Our preliminary data will need to be endorsed with new prospective and controlled studies.

New GABA-Targeting Therapies for the Treatment of Seizures and Epilepsy: I. Role of GABA as a Modulator of Seizure Activity and Recently Approved Medications Acting on the GABA System

γ-Aminobutyric acid (GABA) is the most prevalent inhibitory neurotransmitter in the mammalian brain and has been found to play an important role in the pathogenesis or the expression of many neurological diseases, including epilepsy. Although GABA can act on different receptor subtypes, the component of the GABA system that is most critical to modulation of seizure activity is the GABAA-receptor-chloride (Cl-) channel complex, which controls the movement of Cl- ions across the neuronal membrane. In the mature brain, binding of GABA to GABAA receptors evokes a hyperpolarising (anticonvulsant) response, which is mediated by influx of Cl- into the cell driven by its concentration gradient between extracellular and intracellular fluid. However, in the immature brain and under certain pathological conditions, GABA can exert a paradoxical depolarising (proconvulsant) effect as a result of an efflux of chloride from high intracellular to lower extracellular Cl- levels. Extensive preclinical and clinical evidence indicates that alterations in GABAergic inhibition caused by drugs, toxins, gene defects or other disease states (including seizures themselves) play a causative or contributing role in facilitating or maintaning seizure activity. Conversely, enhancement of GABAergic transmission through pharmacological modulation of the GABA system is a major mechanism by which different antiseizure medications exert their therapeutic effect. In this article, we review the pharmacology and function of the GABA system and its perturbation in seizure disorders, and highlight how improved understanding of this system offers opportunities to develop more efficacious and better tolerated antiseizure medications. We also review the available data for the two most recently approved antiseizure medications that act, at least in part, through GABAergic mechanisms, namely cenobamate and ganaxolone. Differences in the mode of drug discovery, pharmacological profile, pharmacokinetic properties, drug-drug interaction potential, and clinical efficacy and tolerability of these agents are discussed.

Anticonvulsant effects of cenobamate in chemically and electrically induced seizure models in rodents

Background

Cenobamate is an antiseizure medication used to treat partial-onset (focal) seizures. It is a molecule with one chiral center and a unique dual mechanism of action: enhancement of fast and slow inactivation of sodium channels with preferential inhibition of the persistent current and positive allosteric modulation of GABAA receptor-mediated ion channels.

Aims/Methods

Anticonvulsant effects of cenobamate (YKP3089; R-enantiomer), YKP3090 (S-enantiomer), and YKP1983 (racemate) were evaluated in chemically and electrically induced focal and generalized seizure models in rodents. The Genetic Absence Epilepsy Rat from Strasbourg (GAERS) model examined the effect of cenobamate on spike-wave seizures. Motor coordination was assessed with rotarod tests and minimal motor impairment exams.

Results

Early in development, cenobamate was found to have activity in focal and generalized seizure models in animals and was selected for continued development. Cenobamate prevented seizures in a dose-dependent manner, prevented seizure spread, and increased seizure threshold without potentiating seizure initiation or the development of tolerance to its anticonvulsant effects. In contrast, YKP3090 and YKP1983 were only effective against generalized tonic-clonic seizures. Cenobamate also protected mice from 6 Hz psychomotor-induced seizures. Cenobamate showed significant dose-dependent reductions in the number and cumulative duration of spike-and-wave discharges in the GAERS model.

Discussion

Cenobamate showed efficacy or efficacy signals in all animal models of epilepsy tested with a favorable risk-versus-benefit ratio, supporting its clinical use in the treatment of partial-onset (focal) seizures in adults and warranting further clinical research in generalized seizures and absence seizures.

Loss of normal Alzheimer's disease-associated Presenilin 2 function alters antiseizure medicine potency and tolerability in the 6-Hz focal seizure model

Introduction

Patients with early-onset Alzheimer's disease (EOAD) experience seizures and subclinical epileptiform activity, which may accelerate cognitive and functional decline. Antiseizure medicines (ASMs) may be a tractable disease-modifying strategy; numerous ASMs are marketed with well-established safety. However, little information is available to guide ASM selection as few studies have rigorously quantified ASM potency and tolerability in traditional seizure models in rodents with EOAD-associated risk factors. Presenilin 2 (PSEN2) variants evoke EOAD, and these patients experience seizures. This study thus established the anticonvulsant profile of mechanistically distinct ASMs in the frontline 6-Hz limbic seizure test evoked in PSEN2-knockout (KO) mice to better inform seizure management in EOAD.

Methods

The median effective dose (ED50) of prototype ASMs was quantified in the 6-Hz test in male and female PSEN2-KO and wild-type (WT) C57BL/6J mice (3-4 months old). Minimal motor impairment (MMI) was assessed to estimate a protective index (PI). Immunohistological detection of cFos established the extent to which 6-Hz stimulation activates discrete brain regions in KO vs. WT mice.

Results

There were significant genotype-related differences in the potency and tolerability of several ASMs. Valproic acid and levetiracetam were significantly more potent in male KO than in WT mice. Additionally, high doses of valproic acid significantly worsened MMI in KO mice. Conversely, carbamazepine was significantly less potent in female KO vs. WT mice. In both male and female KO mice vs. WTs, perampanel and lamotrigine were equally potent. However, there were marked genotype-related shifts in PI of both carbamazepine and perampanel, with KO mice exhibiting less MMI at the highest doses tested. Gabapentin was ineffective against 6-Hz seizures in KO mice vs. WTs without MMI changes. Neuronal activation 90 min following 6-Hz stimulation was significantly increased in the posterior parietal association cortex overlying CA1 and in the piriform cortex of WT mice, while stimulation-induced increases in cFos immunoreactivity were absent in KO mice.

Discussion

Acute ASM potency and tolerability in the high-throughput 6-Hz test may be significantly altered with loss of normal PSEN2 function. Seizures in discrete EOAD populations may benefit from precisely selected medicines optimized for primary ASM pharmacological mechanisms.

Cenobamate (YKP3089) and Drug-Resistant Epilepsy: A Review of the Literature

Cenobamate (CNB), ([(R)-1-(2-chlorophenyl)-2-(2H-tetrazol-2-yl)ethyl], is a novel tetrazole alkyl carbamate derivative. In November 2019, the Food and Drug Administration approved Xcopri®, marketed by SK Life Science Inc., (Paramus, NJ, USA) for adult focal seizures. The European Medicines Agency approved Ontozry® by Arvelle Therapeutics Netherlands B.V.(Amsterdam, The Neatherlands) in March 2021. Cenobamate is a medication that could potentially change the perspectives regarding the management and prognosis of refractory epilepsy. In this way, this study aims to review the literature on CNB's pharmacological properties, pharmacokinetics, efficacy, and safety. CNB is a highly effective drug in managing focal onset seizures, with more than twenty percent of individuals with drug-resistant epilepsy achieving seizure freedom. This finding is remarkable in the antiseizure medication literature. The mechanism of action of CNB is still poorly understood, but it is associated with transient and persistent sodium currents and GABAergic neurotransmission. In animal studies, CNB showed sustained efficacy and potency in the 6 Hz test regardless of the stimulus intensity. CNB was revealed to be the most cost-effective drug among different third-generation antiseizure medications. Also, CNB could have neuroprotective effects. However, there are still concerns regarding its potential for abuse and suicidality risk, which future studies should clearly assess, after which protocols should be changed. The major drawback of CNB therapy is the slow and complex titration and maintenance phases preventing the wide use of this new agent in clinical practice.

Adjunctive cenobamate in highly active and ultra-refractory focal epilepsy: A "real-world" retrospective study

OBJECTIVE

Recent clinical trials have shown that cenobamate substantially improves seizure control in focal-onset drug-resistant epilepsy (DRE). However, little is known about cenobamate's performance in highly active (≥20 seizures/month) and ultra-refractory focal epilepsy (≥6 failed epilepsy treatments, including antiseizure medications [ASMs], epilepsy surgery, and vagus nerve stimulation). Here, we studied cenobamate's efficacy and tolerability in a "real-world" severe DRE cohort.

METHODS

We conducted a single-center retrospective analysis of consecutive adults treated with cenobamate between October 2020 and September 2022. All patients received cenobamate through an Early Access Program. Cenobamate retention, seizure outcomes, treatment-emergent adverse events, and adjustments to concomitant ASMs were analyzed.

RESULTS

Fifty-seven patients received cenobamate for at least 3 months (median duration, 11 months). The median cenobamate dose was 250 mg/day (range 75-350 mg). Baseline demographics were consistent with highly active (median seizure frequency, 60/month) and ultra-refractory epilepsy (median previously failed ASMs, nine). Most (87.8%) had prior epilepsy surgery and/or vagus nerve stimulation. Six patients stopped cenobamate due to lack of efficacy and/or adverse events. One patient died from factors unrelated to cenobamate. Among patients who continued cenobamate, three achieved seizure freedom (5.3% of cohort), 24 had a 75%-99% reduction in seizures (42.1% of cohort), and 16 had a 50%-74% reduction (28.1% of cohort). Cenobamate led to abolition of focal to bilateral tonic-clonic seizures in 55.6% (20/36) of patients. Among treatment responders, 67.4% (29/43) were treated with cenobamate doses of ≥250 mg/day. Three-fourths of patients reported at least one side-effect, most commonly fatigue and somnolence. Adverse events most commonly emerged at cenobamate doses of ≥250 mg/day. Side-effects were partially manageable by reducing the overall ASM burden, most often clobazam, eslicarbazepine, and perampanel.

SIGNIFICANCE

Patients with highly active and ultra-refractory focal epilepsy experienced meaningful seizure outcomes on cenobamate. Emergence of adverse events at doses above 250 mg/day may limit the potential for further improvements in seizure control at higher cenobamate doses.

Animal Models of Drug-Resistant Epilepsy as Tools for Deciphering the Cellular and Molecular Mechanisms of Pharmacoresistance and Discovering More Effective Treatments

In the last 30 years, over 20 new anti-seizure medicines (ASMs) have been introduced into the market for the treatment of epilepsy using well-established preclinical seizure and epilepsy models. Despite this success, approximately 20-30% of patients with epilepsy have drug-resistant epilepsy (DRE). The current approach to ASM discovery for DRE relies largely on drug testing in various preclinical model systems that display varying degrees of ASM drug resistance. In recent years, attempts have been made to include more etiologically relevant models in the preclinical evaluation of a new investigational drug. Such models have played an important role in advancing a greater understanding of DRE at a mechanistic level and for hypothesis testing as new experimental evidence becomes available. This review provides a critical discussion of the pharmacology of models of adult focal epilepsy that allow for the selection of ASM responders and nonresponders and those models that display a pharmacoresistance per se to two or more ASMs. In addition, the pharmacology of animal models of major genetic epilepsies is discussed. Importantly, in addition to testing chemical compounds, several of the models discussed here can be used to evaluate other potential therapies for epilepsy such as neurostimulation, dietary treatments, gene therapy, or cell transplantation. This review also discusses the challenges associated with identifying novel therapies in the absence of a greater understanding of the mechanisms that contribute to DRE. Finally, this review discusses the lessons learned from the profile of the recently approved highly efficacious and broad-spectrum ASM cenobamate.

Recent advances in pharmacotherapy for epilepsy

PURPOSE OF REVIEW

Epilepsy affects 70 million people worldwide and is a significant cause of morbidity and early mortality. The mainstay of therapy is oral medications. Epilepsy drug development is escalating, driven by continued drug resistance in up to a third of epilepsy patients. Treatment development now focuses on discovery of novel mechanisms of action and syndrome-specific therapies.

RECENT FINDINGS

Difficult-to-treat epilepsy related to conditions including tuberous sclerosis complex (TSC), Lennox Gastaut syndrome (LGS) and Dravet syndrome (DS) have been the target of recent developments. Disease-modifying therapy for epilepsy related to TSC with vigabatrin at onset of first electroencephalographic epileptiform changes, rather than after first clinical seizure, has demonstrated strongly positive seizure and developmental outcomes. Fenfluramine, approved for DS and, more recently, LGS, has robust data supporting efficacy, safety/tolerability, as well as mortality, quality of life and cognitive function. Rescue therapy has expanded to include better tolerated benzodiazepines in the form of nasal midazolam and valium. Cenobamate, a first-in-class inactivator of the persistent voltage-gated sodium channel and approved for adult partial onset epilepsy, has exceptional efficacy and tolerability and will be expanded to children and to generalized onset epilepsy in adults.

SUMMARY

The repertoire of available and developmental therapies for epilepsy is rapidly expanding, and now includes disease-modifying vigabatrin in TSC and agents with extraordinary efficacy, fenfluramine and cenobamate.

Treatment with Cenobamate in Adult Patients with Lennox-Gastaut Syndrome: A Case Series

Background. Lennox-Gastaut syndrome (LGS) is a developmental and epileptic encephalopathy (DEE) in which drug resistance to antiepileptic drugs (AEDs) is common. Focal-onset seizures (FOS) are among the seizure types characterizing LGS. Cenobamate (CNB) is a new AED indicated for the treatment of FOS and it has shown promising results in terms of seizure frequency reduction in both clinical trials and real-world experience. To date, the use of CNB in patients with DEEs is limited to Dravet syndrome. Methods: This was a retrospective study aimed to determine the 12-month effectiveness and tolerability of CNB in patients with LGS following real-world practice. Results: Four patients with LGS receiving CNB treatment were identified. At 12 months from starting CNB, the reduction in baseline seizure frequency ranged from 25 to 74%, with two patients achieving ≥50% seizure reduction. CNB was generally well tolerated and adjustments in doses of concomitant AEDs were required. Conclusions: CNB may represent a promising therapeutic option in patients with drug-resistant epilepsy associated with LGS. Further research is needed to confirm this preliminary evidence.

Use of cenobamate for the treatment of focal epilepsy: an Italian expert opinion paper

INTRODUCTION

Cenobamate is a new antiseizure medication (ASM) recently introduced in the USA for the treatment of adults with focal-onset seizures. In March 2021, the European Commission authorized its use for the adjunctive treatment of focal-onset seizures with or without secondary generalization (focal seizures with or without progression to bilateral tonic-clonic seizures, according to current ILAE terminology) in adults with epilepsy not adequately controlled despite the treatment with at least two ASMs.

AREAS COVERED

This review summarizes the mechanism of action, efficacy, and safety of Cenobamate. The authors provide their expert opinions on the use of this drug.

EXPERT OPINION

The aim of this paper is to report on the Italian preliminary experience with the use of cenobamate, focusing on treatment goals, optimal dosing and titration schedules, strategies to minimize adverse effects, and identification of suitable candidates for treatment. There was agreement that slow titration may improve tolerability, and that clinically significant benefit can be achieved in many patients at relatively low doses. A favorable response to relatively low doses of cenobamate could be an early predictor of ultimate responsiveness. Overall, cenobamate is a welcome new treatment for adults with focal seizures resistant to conventional ASMs.

Development and Validation of a UHPLC-MS/MS-Based Method to Quantify Cenobamate in Human Plasma Samples

Cenobamate (CNB) is the newest antiseizure medication (ASM) approved by the FDA in 2019 to reduce uncontrolled partial-onset seizures in adult patients. Marketed as Xcopri in the USA or Ontozry in the EU (tablets), its mechanism of action has not been fully understood yet; however, it is known that it inhibits voltage-gated sodium channels and positively modulates the aminobutyric acid (GABA) ion channel. CNB shows 88% of oral bioavailability and is responsible for modifying the plasma concentrations of other co-administered ASMs, such as lamotrigine, carbamazepine, phenytoin, phenobarbital and the active metabolite of clobazam. It also interferes with CYP2B6 and CYP3A substrates. Nowadays, few methods are reported in the literature to quantify CNB in human plasma. The aim of this study was to develop and validate, according to the most recent guidelines, an analytical method using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) to evaluate CNB dosage in plasma samples. Furthermore, we provided a preliminary clinical application of our methodology by evaluating the pharmacokinetic parameters of CNB in two non-adult patients. Plasma levels were monitored for two months. Preliminary data showed a linear increase in plasma CNB concentrations, in both patients, in agreement with the increase in CNB dosage. A seizure-free state was reported for both patients at the dose of 150 mg per day.

Current and future pharmacotherapy options for drug-resistant epilepsy

INTRODUCTION

Epilepsy is one of the most common and serious neurological conditions, affecting over 70 million individuals worldwide and despite advances in treatment, the proportion of drug-resistant patients has remained largely unchanged.

AREAS COVERED

The present paper reviews current and future (under preclinical and clinical development) pharmacotherapy options for the treatment of drug-resistant focal and generalized epilepsies.

EXPERT OPINION

Current pharmacotherapy options for drug-resistant epilepsy include perampanel, brivaracetam and the newly approved cenobamate for focal epilepsies; cannabidiol (Epidiolex) for Lennox-Gastaut Syndrome (LGS), Dravet and Tuberous Sclerosis Complex (TSC); fenfluramine for Dravet syndrome and ganaxolone for seizures in Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder. Many compounds are under clinical development and may hold promise for future pharmacotherapies. For adult focal epilepsies, padsevonil and carisbamate are at a more advanced Phase III stage of clinical development followed by compounds at Phase II like selurampanel, XEN1101 and JNJ-40411813. For specific epilepsy syndromes, XEN 496 is under Phase III development for potassium voltage-gated channel subfamily Q member 2 developmental and epileptic encephalopathy (KCNQ2-DEE), carisbamate is under Phase III development for LGS and Ganaxolone under Phase III development for TSC. Finally, in preclinical models several molecular targets including inhibition of glycolysis, neuroinflammation and sodium channel inhibition have been identified in animal models although further data in animal and later human studies are needed.

Dose Adjustment of Concomitant Antiseizure Medications During Cenobamate Treatment: Expert Opinion Consensus Recommendations

INTRODUCTION

Our objective was to provide expert consensus recommendations to improve treatment tolerability through dose adjustments of concomitant antiseizure medications (ASMs) during addition of cenobamate to existing ASM therapy in adult patients with uncontrolled focal seizures.

METHODS

A panel of seven epileptologists experienced in the use of ASMs, including cenobamate, used a modified Delphi process to reach consensus. The panelists discussed tolerability issues with concomitant ASMs during cenobamate titration and practical strategies for dose adjustments that may prevent or mitigate adverse effects. The resulting recommendations consider concomitant ASM dose level and specify proactive (prior to report of an adverse effect) and reactive (in response to report of an adverse effect) dose adjustment suggestions based on concomitant ASM pharmacokinetic and pharmacodynamic interactions with cenobamate. Specific dose adjustment recommendations are provided.

RESULTS

We recommend proactively lowering the dose of clobazam, phenytoin, and phenobarbital due to their known drug-drug interactions with cenobamate, and lacosamide due to a pharmacodynamic interaction with cenobamate, to prevent adverse effects during cenobamate titration. Reactive lowering of a concomitant ASM dose is sufficient for other ASMs at standard dosing owing to quick resolution of adverse effects. For carbamazepine and lamotrigine doses exceeding the upper end of standard dosing (e.g., carbamazepine, greater than 1200 mg/day; lamotrigine, greater than 500 mg/day), we encourage consideration of proactive dose reduction at cenobamate 200 mg/day to prevent potential adverse effects. All dose reductions for adverse effects can be repeated every 2 weeks as dictated by the adverse effects. At cenobamate 200 mg/day, we recommend that patients be evaluated for marked improvement of seizures and further dose reductions be considered to reduce potentially unnecessary polypharmacy.

CONCLUSION

The primary goal of the recommended dose reductions of concomitant ASMs is to prevent or resolve adverse effects, thereby allowing cenobamate to reach the optimal dose to achieve the maximal potential of improving seizure control.

New evidence in adjunctive treatment of focal-onset seizures in adults: a critical appraisal

Anti-seizure medications (ASMs) represent the pillar of the treatment of epilepsy. The rate of drug-resistant epilepsy remained substantially unchanged over time and there is still the need for new and more effective treatment options. Brivaracetam, cenobamate, eslicarbazepine acetate, lacosamide and perampanel are 'third-generation' ASMs. The aim of this article is to summarize the currently available evidence about the relative efficacy and tolerability of the 'third-generation' ASMs as adjunctive treatment of focal-onset seizures in adults. So far, no randomized controlled study directly compared these ASMs, and their comparative efficacy and tolerability have been indirectly evaluated by one network meta-analysis. Sixteen trials were included in the network meta-analysis. The efficacy endpoints were the rates of seizure response and seizure freedom, defined as ≥ 50% and 100% reduction in baseline monthly seizure frequency. The tolerability endpoints were the rate of patients who developed any treatment emergent adverse events (TEAEs) and any TEAE leading to drug discontinuation. Cenobamate had the greatest likelihood of being the best option for the ≥ 50% and 100% seizure frequency reduction. Brivaracetam and lacosamide had the greatest likelihood to rank as the best-tolerated treatments for the occurrence of any TEAE and TEAE leading to discontinuation. Although network meta-analyses are not substitutes of direct comparisons, they can provide valuable evidence about the hierarchy of interventions. Additional real-world data can be useful complement to characterize the clinical profile and therapeutic potentialities of third-generation ASMs.

Current Principles in the Management of Drug-Resistant Epilepsy

Drug-resistant epilepsy is associated with poor health outcomes and increased economic burden. In the last three decades, various new antiseizure medications have been developed, but the proportion of people with drug-resistant epilepsy remains relatively unchanged. Developing strategies to address drug-resistant epilepsy is essential. Here, we define drug-resistant epilepsy and emphasize its relationship to the conceptualization of epilepsy as a symptom complex, delineate clinical risk factors, and characterize mechanisms based on current knowledge. We address the importance of ruling out pseudoresistance and consider the impact of nonadherence on determining whether an individual has drug-resistant epilepsy. We then review the principles of epilepsy drug therapy and briefly touch upon newly approved and experimental antiseizure medications.

Update on Antiseizure Medications 2022

EDITORS NOTE

The article "Update on Antiseizure Medications 2022" by Dr Abou-Khalil was first published in the February 2016 Epilepsy issue of Continuum: Lifelong Learning in Neurology as "Antiepileptic Drugs," and at the request of the Editor-in-Chief was updated by Dr Abou-Khalil for the 2019 issue and again for this issue.

The novel dual-mechanism Kv7 potassium channel/TSPO receptor activator GRT-X is more effective than the Kv7 channel opener retigabine in the 6-Hz refractory seizure mouse model

Epilepsy, one of the most common and most disabling neurological disorders, is characterized by spontaneous recurrent seizures, often associated with structural brain alterations and cognitive and psychiatric comorbidities. In about 30% of patients, the seizures are resistant to current treatments; so more effective treatments are urgently needed. Among the ∼30 clinically approved antiseizure drugs, retigabine (ezogabine) is the only drug that acts as a positive allosteric modulator (or opener) of voltage-gated Kv7 potassium channels, which is particularly interesting for some genetic forms of epilepsy. Here we describe a novel dual-mode-of-action compound, GRT-X (N-[(3-fluorophenyl)-methyl]-1-(2-methoxyethyl)-4-methyl-2-oxo-(7-trifluoromethyl)-1H-quinoline-3-carboxylic acid amide) that activates both Kv7 potassium channels and the mitochondrial translocator protein 18 kDa (TSPO), leading to increased synthesis of brain neurosteroids. TSPO activators are known to exert anti-inflammatory, neuroprotective, anxiolytic, and antidepressive effects, which, together with an antiseizure effect (mediated by Kv7 channels), would be highly relevant for the treatment of epilepsy. This prompted us to compare the antiseizure efficacy of retigabine and GRT-X in six mouse and rat models of epileptic seizures, including the 6-Hz model of difficult-to-treat focal seizures. Furthermore, the tolerability of the two compounds was compared in mice and rats. Potency comparisons were based on both doses and peak plasma concentrations. Overall, GRT-X was more effective than retigabine in three of the six seizure models used here, the most important difference being the high efficacy in the 6-Hz (32 mA) seizure model in mice. Based on drug plasma levels, GRT-X was at least 30 times more potent than retigabine in the latter model. These data indicate that GRT-X is a highly interesting novel anti-seizure drug with a unique (first-in-class) dual-mode mechanism of action.

Third-Generation Antiseizure Medications for Adjunctive Treatment of Focal-Onset Seizures in Adults: A Systematic Review and Network Meta-analysis

Background

Brivaracetam (BRV), cenobamate (CNB), eslicarbazepine acetate (ESL), lacosamide (LCM) and perampanel (PER) are antiseizure medications (ASMs) approved for adjunctive treatment of focal-onset seizures. So far, no randomised controlled trial directly compared the efficacy and safety of these drugs.

Objective

We estimated the comparative efficacy and safety of these ASMs for the treatment of focal-onset seizures in adults with epilepsy using a network meta-analysis (NMA).

Methods

We systematically searched (June week 4, 2021) MEDLINE (accessed by PubMed), the Cochrane Central Register of Controlled Trials (CENTRAL), and the US National Institutes of Health Clinical Trials Registry (http://www.clinicaltrials.gov). There were no date limitations or language restrictions. Randomised, double-blinded, controlled, parallel-group, add-on studies that compared oral BRV, CNB, ESL, LCM, and PER versus any comparator over maintenance periods of at least 12 weeks and included adult patients with focal seizures uncontrolled by concomitant ASMs were identified. The efficacy outcomes were the proportions of patients with ≥ 50% and 100% reduction in baseline seizure frequency during the maintenance period. The tolerability outcomes were the proportions of participants who experienced at least one treatment-emergent adverse event (TEAE) and experienced at least one TEAE leading to discontinuation. Effect sizes were estimated by network meta-analyses within a frequentist framework. The hierarchy of competing interventions was established using the surface under the cumulative ranking curve (SUCRA).

Results

Sixteen trials (BRV: n = 3, CNB: n = 1, ESL: n = 4, LCM: n = 4, PER: n = 4) were included, overall enrolling 4507 patients randomised to add-on active treatments (BRV = 803, CNB = 221, ESL =9 90, LCM = 1104, and PER = 1389) and 2246 to add-on placebo. Cenobamate was associated with a higher rate of ≥ 50% seizure frequency reduction than BRV [odds ratio (OR) 2.02, 95% confidence interval (CI) 1.11–3.66], ESL (OR 1.93, 95% CI 1.07–3.48), LCM (OR 1.86, 95% CI 1.04–3.32), and PER (OR 2.07, 95% CI 1.16–3.70). There was a not statistically significant trend favouring CNB over ESL, LCM and PER for the seizure freedom outcome. Brivaracetam (OR 0.61, 95% CI 0.44–0.86) and LCM (OR 0.60, 95% CI 0.40–0.88) were associated with a lower proportion of participants experiencing TEAEs compared to ESL, and patients treated with PER were associated with a higher risk to experience at least one TEAE (OR 1.42, 95% CI 1.02–1.96) than BRV. According to SUCRA, CNB had the greatest likelihood of being the best option for the ≥ 50% and 100% seizure frequency reduction, and BRV and LCM had the highest probabilities of being the best-tolerated treatments.

Conclusions

Cenobamate ranked best for efficacy, and BRV and LCM were best tolerated over the other comparators. Although NMAs cannot replace direct comparisons, they may support physicians in clinical decision making.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40265-021-01661-4.

Post hoc analysis of a phase 3, multicenter, open-label study of cenobamate for treatment of uncontrolled focal seizures: Effects of dose adjustments of concomitant antiseizure medications

Objective

To report post hoc results on how adjustments to baseline antiseizure medications (ASMs) in a subset of study sites (10 US sites) from a long‐term, open‐label phase 3 study of adjunctive cenobamate affected tolerability, efficacy, and retention.

Methods

Patients with uncontrolled focal seizures taking stable doses of one to three ASMs were administered increasing doses of cenobamate (12.5, 25, 50, 100, 150, 200 mg/day) over 12 weeks at 2‐week intervals (target dose = 200 mg/day). Further increases to 400 mg/day by 50 mg/day biweekly increments were allowed during maintenance phase. Dose adjustments of cenobamate and concomitant ASMs were allowed. Data were assessed until last visit, at data cut‐off, on or after September 1, 2019.

Results

A total of 240 patients meeting eligibility criteria were assessed (median [max] exposure 30.2 [43.0] months), with 177 patients continuing cenobamate at data cut‐off. Most common baseline concomitant ASMs were lacosamide, levetiracetam, lamotrigine, zonisamide, and clobazam. For most baseline concomitant ASMs, ~70% of patients taking that ASM were continuing cenobamate at data cut‐off. Patients continuing cenobamate had greater mean ASM dose reductions and percent dose changes from baseline vs those who discontinued. Of patients continuing cenobamate, 24.6% discontinued one or more concomitant ASMs completely. Dose decreases for all concomitant ASMs generally occurred during titration or early maintenance phases and were mostly due to central nervous system (CNS)–related adverse events such as somnolence, dizziness, unsteady gait, and fatigue. Responder rates from ≥50% through 100% for patients continuing cenobamate were generally similar regardless of concomitant ASMs (of those most commonly taken), with ~81% being ≥50% responders and ~12% achieving 100% seizure reduction in the maintenance phase, which lasted up to 40.2 (median = 29.5) months.

Significance

Concomitant ASM dose reductions were associated with more patients remaining on cenobamate. This is likely due to efficacy and improved tolerability, with overall reduced concomitant drug burden in patients with uncontrolled seizures despite taking one to three baseline concomitant ASMs.

Practical guidance for the management of adults receiving adjunctive cenobamate for the treatment of focal epilepsy-expert opinion

Clinical trial results have demonstrated that adjunctive cenobamate (CNB) substantially decreases seizure frequency in adults with uncontrolled focal onset seizures with an acceptable and well-identified safety profile. This manuscript summarizes an expert panel's recommendations regarding optimized CNB treatment of epilepsies with focal onset seizures. Cenobamate, when slowly titrated to the target maintenance dose, represents an effective new antiseizure medication (ASM) with a comparatively high rate of seizure freedom relative to existing treatment options. This paper reviews selection of suitable CNB treatment candidates, realistic treatment expectations and goals, appropriate CNB target doses, and methods to mitigate or avoid potential adverse events. Cenobamate can be a promising therapeutic choice for adult people with epilepsy with focal onset seizures who do not reach adequate seizure control despite treatment with conventional ASMs.

Is Cenobamate the Breakthrough We Have Been Wishing for?

Close to one-third of patients with epilepsies are refractory to current anti-seizure medications; however, trials with cenobamate suggest effectiveness in such patients with focal onset seizures. We searched for data published or otherwise reported on cenobamate and outlined these here. Despite being marketed in the USA, few studies are yet published in full, and trials are ongoing. Nevertheless, cenobamate showed potential for a high degree of efficacy in reducing seizures with an unprecedented seizure-free rate of up to 28%. Rare cases of hypersensitivity reactions seen in early trials seem to be avoided by the current recommended titration schedule. Other adverse events were rated mild-to-moderate and most commonly included dizziness, drowsiness, and headache. If data are confirmed in further published trials, cenobamate will be a welcome new treatment and further analyses may identify those that will benefit the most.

Long-term safety of adjunctive cenobamate in patients with uncontrolled focal seizures: Open-label extension of a randomized clinical study

Objective

This study was undertaken to examine long‐term (up to 7.8 years) retention rate, safety, and tolerability of the antiseizure medication (ASM) cenobamate as adjunctive treatment in the open‐label extension (OLE) of study YKP3089C013 (C013; ClinicalTrials.gov: NCT01397968).

Methods

Patients who completed the 12‐week, multicenter, multinational, double‐blind, randomized, placebo‐controlled C013 study, which examined adjunctive cenobamate treatment of adults with uncontrolled focal seizures, were eligible to enroll in the OLE. During the OLE, dose adjustments of cenobamate and concomitant ASMs were allowed. Safety assessments included frequency of treatment‐emergent adverse events (TEAEs) and serious TEAEs, TEAE severity, and TEAEs leading to discontinuation. Probability of patient continuation in the OLE was examined using a Kaplan–Meier analysis.

Results

One hundred forty‐nine patients entered the OLE (median duration of cenobamate treatment = 6.25 years). As of the data cutoff, 57% of patients (85/149) remained in the OLE (median treatment duration = 6.8 years, range = 6.4–7.8 years). The median modal daily cenobamate dose was 200 mg (range = 50–400 mg). The probability of treatment continuation at 1–6 years of cenobamate treatment was 73%, 67%, 63%, 61%, 60%, and 59%, respectively. Among patients who continued at 1 year (n = 107), the probability of continuing at Years 2–5 was 92%, 87%, 83%, and 82%. The most common discontinuation reasons were patient withdrawal (19.5%, 29/149), adverse event (10.1%, 15/149), and lack of efficacy (5.4%, 8/149). TEAEs leading to discontinuation in 1% or more of patients were fatigue (1.3%, 2/149), ataxia (1.3%, 2/149), and memory impairment or amnesia (1.3%, 2/149). Dizziness (32.9%, 49/149), headache (26.8%, 40/149), and somnolence (21.5%, 32/149) were the most frequently reported TEAEs and were primarily mild or moderate in severity.

Significance

Long‐term retention in the C013 OLE study demonstrated sustained safety and tolerability of adjunctive cenobamate treatment up to 7.8 years in adults with treatment‐resistant focal seizures taking one to three ASMs.

Pharmacology of Cenobamate: Mechanism of Action, Pharmacokinetics, Drug-Drug Interactions and Tolerability

Cenobamate is one of the latest antiseizure medications (ASMs) developed for the treatment of focal onset seizures in adult patients. The recommended starting dose is 12.5 mg/day, titrated gradually to the target daily dose of 200 mg, which may be increased to a maximum of 400 mg/day based on clinical response. Although the high rate of seizure freedom observed in randomized, placebo-controlled clinical trials has resulted in exciting expectations, further clinical studies are needed to better define its clinical profile. Cenobamate is characterized by a peculiar pharmacology regarding both pharmacodynamics and pharmacokinetics. The mechanism of action has only partly been described, with the drug acting on voltage-gated sodium channels through a pronounced action on persistent rather than transient currents. Cenobamate also acts as a positive allosteric modulator of GABA_A receptors independently from the benzodiazepine binding site. The bioavailability of cenobamate is not influenced by other drugs, except phenytoin; it can inhibit cytochrome P450 (CYP) 2C19 and induce CYP3A4 and 2B6, and hence can potentially interact with many drugs (e.g. dose adjustments may be required for lamotrigine, carbamazepine and clobazam). The pharmacokinetics of cenobamate are not linear and dosage increases imply a disproportional increase in plasma levels, particularly at doses higher than 300 mg. The most common and dose-related adverse effects associated with cenobamate include central nervous system-related symptoms, mainly somnolence, dizziness, diplopia, and disturbances in gait and coordination. A somewhat higher incidence of adverse events has been observed in patients concomitantly treated with sodium channel blockers. The most relevant safety issues are currently represented by the risk of severe skin reactions (apparently avoidable by a slow titration) and QT shortening (the drug is contraindicated in patients with familial short QT syndrome or taking QT-shortening drugs). Overall, cenobamate is a promising ASM with an intriguing and not fully understood mechanism of action; pharmacokinetic issues need to be considered in clinical practice.

The ups and downs of alkyl-carbamates in epilepsy therapy: How does cenobamate differ?

Since 1955, several alkyl-carbamates have been developed for the treatment of anxiety and epilepsy, including meprobamate, flupirtine, felbamate, retigabine, carisbamate, and cenobamate. They have each enjoyed varying levels of success as antiseizure drugs; however, they have all been plagued by the emergence of serious and sometimes life-threatening adverse events. In this review, we compare and contrast their predominant molecular mechanisms of action, their antiseizure profile, and where possible, their clinical efficacy. The preclinical, clinical, and mechanistic profile of the prototypical γ-aminobutyric acidergic (GABAergic) modulator phenobarbital is included for comparison. Like phenobarbital, all of the clinically approved alkyl-carbamates share an ability to enhance inhibitory neurotransmission through modulation of the GABA_A receptor, although the specific mechanism of interaction differs among the different drugs discussed. In addition, several alkyl-carbamates have been shown to interact with voltage-gated ion channels. Flupirtine and retigabine share an ability to activate K⁺ currents mediated by KCNQ (Kv7) K⁺ channels, and felbamate, carisbamate, and cenobamate have been shown to block Na⁺ channels. In contrast to other alkyl-carbamates, cenobamate seems to be unique in its ability to preferentially attenuate the persistent rather than transient Na⁺ current. Results from recent randomized controlled clinical trials with cenobamate suggest that this newest antiseizure alkyl-carbamate possesses a degree of efficacy not witnessed since felbamate was approved in 1993. Given that ceno-bamate's mechanistic profile is unique among the alkyl-carbamates, it is not clear whether this impressive efficacy reflects an as yet undescribed mechanism of action or whether it possesses a unique synergy between its actions at the GABA_A receptor and on persistent Na⁺ currents. The high efficacy of cenobamate is, however, tempered by the risk of serious rash and low tolerability at higher doses, meaning that further safety studies and clinical experience are needed to determine the true clinical value of cenobamate.

Cenobamate tablets as a treatment for focal-onset seizures in adults

Introduction: Despite the introduction of numerous new antiseizure medications (ASMs) still about one-third of epilepsies remain drug-resistant. Therefore, new compounds with advanced efficacy are urgently needed. Cenobamate (CNB) is a new ASM that has been recently introduced in the United States for the treatment of adults with focal-onset seizures. The approval in Europe is under way.Areas covered: This review covers the pharmacological profile of CNB, the proof-of-concept trial, the two double-blind, placebo-controlled phase 2 trials investigating adjunct CNB in adults with focal-onset seizures, one open-label safety trial, and a variety of published abstract material that provided additional post hoc data.Expert opinion: In two placebo-controlled randomized multicenter phase 2 trials adjunct CNB showed unusually high efficacy with rates of seizure-free people with epilepsy (PWE) partially beyond 20%. However, during the clinical program cases of drug-related reactions with eosinophilia and systemic symptoms (DRESS syndrome) occurred. Therefore, an open-label safety study was performed in more than 1300 PWE with particularly slower titration schedules which did not add more cases with similar reactions. Taking into consideration the promising efficacy and the safety experience from the open-label trial, CNB applied according to the meanwhile recommended titration strategy, might offer a new prospect.

Critical Appraisal of Cenobamate as Adjunctive Treatment of Focal Seizures in Adults

Cenobamate (CNB) is the latest antiseizure medication (ASM) authorized for the treatment of focal-onset seizures in adults. Although the precise mechanism of action of CNB is not yet fully understood, this drug inhibits the persistent, rather than transient, voltage-gated sodium channel currents and is a positive allosteric modulator of synaptic and extrasynaptic GABA_A receptors, differently from benzodiazepines. CNB has a non-linear pharmacokinetic with a terminal half-life range of about 50/60 hours within the therapeutic dose range, which allows once daily administration. Cenobamate inhibits cytochrome P450 (CYP) 2C19 and induces CYP3A4 and 2B6, and hence can potentially interact with ASMs (eg, phenytoin, carbamazepine and clobazam) and no-ASMs drugs. In two randomized, double-blind, placebo-controlled trials in patients with focal epilepsies, CNB has shown a particularly good efficacy with a rate of seizure freedom of about 20% during the maintenance period in participants treated with the dose of 400 mg/day. The most common treatment-emergent adverse effects include central nervous system-related symptoms, like dizziness, diplopia, somnolence, and gait disturbances. Safety issues of particular interest are severe skin reactions (drug reaction with eosinophilia and systemic symptoms) and QT shortening, which contraindicates its use in subjects with familial short QT syndrome or in combination with other QT-shortening drugs. The recommended starting dose is 12.5 mg/day, which can be gradually titrated to the target dose (200 mg/day) and further increased up to 400 mg/day. There are several aspects of CNB that need to be still addressed, including the long-term efficacy and the efficacy in patients with generalized seizures. Ongoing studies will clarify these issues. The clinical relevance of the peculiar pharmacokinetics and the pattern of drug-drug interactions also require further investigation.

The Pharmacology and Clinical Efficacy of Antiseizure Medications: From Bromide Salts to Cenobamate and Beyond

Epilepsy is one of the most common and disabling chronic neurological disorders. Antiseizure medications (ASMs), previously referred to as anticonvulsant or antiepileptic drugs, are the mainstay of symptomatic epilepsy treatment. Epilepsy is a multifaceted complex disease and so is its treatment. Currently, about 30 ASMs are available for epilepsy therapy. Furthermore, several ASMs are approved therapies in nonepileptic conditions, including neuropathic pain, migraine, bipolar disorder, and generalized anxiety disorder. Because of this wide spectrum of therapeutic activity, ASMs are among the most often prescribed centrally active agents. Most ASMs act by modulation of voltage-gated ion channels; by enhancement of gamma aminobutyric acid-mediated inhibition; through interactions with elements of the synaptic release machinery; by blockade of ionotropic glutamate receptors; or by combinations of these mechanisms. Because of differences in their mechanisms of action, most ASMs do not suppress all types of seizures, so appropriate treatment choices are important. The goal of epilepsy therapy is the complete elimination of seizures; however, this is not achievable in about one-third of patients. Both in vivo and in vitro models of seizures and epilepsy are used to discover ASMs that are more effective in patients with continued drug-resistant seizures. Furthermore, therapies that are specific to epilepsy etiology are being developed. Currently, ~ 30 new compounds with diverse antiseizure mechanisms are in the preclinical or clinical drug development pipeline. Moreover, therapies with potential antiepileptogenic or disease-modifying effects are in preclinical and clinical development. Overall, the world of epilepsy therapy development is changing and evolving in many exciting and important ways. However, while new epilepsy therapies are developed, knowledge of the pharmacokinetics, antiseizure efficacy and spectrum, and adverse effect profiles of currently used ASMs is an essential component of treating epilepsy successfully and maintaining a high quality of life for every patient, particularly those receiving polypharmacy for drug-resistant seizures.