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

Presurgical Use of Cenobamate for Adult and Pediatric Patients Referred for Epilepsy Surgery: Expert Panel Recommendations

Cenobamate has demonstrated efficacy in patients with treatment-resistant epilepsy, including patients who continued to have seizures after epilepsy surgery. This article provides recommendations for cenobamate use in patients referred for epilepsy surgery evaluation. A panel of six senior epileptologists from the United States and Europe with experience in presurgical evaluation of patients with epilepsy and in the use of antiseizure medications (ASMs) was convened to provide consensus recommendations for the use of cenobamate in patients referred for epilepsy surgery evaluation. Many patients referred for surgical evaluation may benefit from ASM optimization; both ASM and surgical treatment should be individualized. Based on previous clinical studies and the authors' clinical experience with cenobamate, a substantial proportion of patients with treatment-resistant epilepsy can become seizure-free with cenobamate. We recommend a cenobamate trial and ASM optimization in parallel with presurgical evaluations. Cenobamate can be started before phase two monitoring, especially in patients who are found to be suboptimal surgery candidates. As neurostimulation therapies are generally palliative, we recommend trying cenobamate before vagus nerve stimulation (VNS), deep brain stimulation, or responsive neurostimulation (RNS). In surgically remediable cases (mesial temporal sclerosis, benign discrete lesion in non-eloquent cortex, cavernous angioma, etc.), cenobamate use should not delay imminent surgery; however, a patient may decide to defer or even cancel surgery should they achieve sustained seizure freedom with cenobamate. This decision should be made on an individual, case-by-case basis based on seizure etiology, patient preferences, potential surgical risks (mortality and morbidity), and likely surgical outcome. The addition of cenobamate after unsuccessful surgery or palliative neuromodulation may also be associated with better outcomes.

Adjunctive cenobamate in people with focal onset seizures: Insights from the Italian Expanded Access Program

OBJECTIVE

This study was undertaken to assess the effectiveness/tolerability of adjunctive cenobamate, variations in the load of concomitant antiseizure medications (ASMs) and predictors of clinical response in people with focal epilepsy.

METHODS

This was a retrospective study at 21 centers participating in the Italian Expanded Access Program. Effectiveness outcomes included retention and responder rates (≥50% and 100% reduction in baseline seizure frequency). Tolerability/safety outcomes included the rate of treatment discontinuation due to adverse events (AEs) and their incidence. Total drug load was quantified as the number of concomitant ASMs and total defined daily dose (DDD). Concomitant ASMs were also classified according to their mechanism of action and pharmacokinetic interactions to perform explorative subgroup analyses.

RESULTS

A total of 236 subjects with a median age of 38 (Q1-Q3 = 27-49) years were included. At 12 months, cenobamate retention rate was 78.8% and responders were 57.5%. The seizure freedom rates during the preceding 3 months were 9.8%, 12.2%, 16.3%, and 14.0% at 3, 6, 9, and 12 months. A higher percentage of responders was observed among subjects treated with clobazam, although the difference was not statistically significant. A total of 223 AEs were recorded in 133 of 236 participants, leading to cenobamate discontinuation in 8.5% cases. At 12 months, a reduction of one or two concomitant ASMs occurred in 42.6% and 4.3% of the subjects. The median total DDD of all concomitant ASMs decreased from 3.34 (Q1-Q3 = 2.50-4.47) at baseline to 2.50 (Q1-Q3 = 1.67-3.50) at 12 months (p < .001, median percentage reduction = 22.2%). The highest rates of cotreatment withdrawal and reductions in the DDD were observed for sodium channel blockers and γ-aminobutyric acidergic modulators (above all for those linked to pharmacokinetic interactions), and perampanel.

SIGNIFICANCE

Adjunctive cenobamate was associated with a reduction in seizure frequency and in the burden of concomitant ASMs in adults with difficult-to-treat focal epilepsy. The type of ASM associated did not influence effectiveness except for a favorable trend with clobazam.

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.

Treatment simplification to optimize cenobamate effectiveness and tolerability: A real-world retrospective study in Spain

OBJECTIVE

This study aimed to explore the impact of co-antiseizure medication (co-ASM) optimization on the effectiveness and tolerability of adjunctive cenobamate (CNB) in patients with drug-resistant epilepsy in a real-world setting.

METHODS

This unicentric, retrospective, observational study included adults with focal-onset seizures who had received ≥2 previous ASMs. The main effectiveness endpoints included responder rates and seizure frequency reduction at 3, 6, and 12-month visits. The number of co-ASMs and defined daily dose (DDD) were analyzed at every visit. Safety endpoints included adverse drug reactions (ADRs).

RESULTS

Thirty-four patients with a median epilepsy duration of 22 years and a median of 15.5 seizures/month were analyzed. The median number of prior ASMs was 12, and the mean number of co-ASMs was 2.9 (SD 1). There was a reduction in seizure frequency/month from baseline to the last visit (p < 0.0001). Between baseline and the end of the study, the mean number of co-ASMs in the per-protocol (PP) population was reduced from 2.9 to 1.6 (p < 0.0001), and DDD was reduced from 3.6 to 1.4 (p < 0.0001). Sodium channel blockers (carbamazepine and lacosamide) and GABAergic drugs (clobazam) were the agents with the most significant reductions in DDD after 12 months. The percentage of patients in the PP population with ≥3 co-ASMs was reduced from 61.8% at baseline to 14.3% at 12 months; 1 patient was receiving CNB as monotherapy at the last visit. At the last visit, 85.7% of the PP population were ≥50% responders, and 33.3% were seizure-free. The percentage of patients with ADRs in the PP population was 71.9% at 3 months and 52.3% at 12 months.

SIGNIFICANCE

Following rational polytherapy, optimization of co-ASM management during CNB treatment allowed high seizure freedom rates despite meaningful reductions in co-medication, while also achieving both good tolerability and patient satisfaction scores in a highly drug-resistant population.

PLAIN LANGUAGE SUMMARY

Many patients with epilepsy still have seizures, even after being treated with several different epilepsy drugs. In this study of 34 patients from a Spanish clinic, we show that the epilepsy drug cenobamate can reduce the number of seizures in these patients, even after many other epilepsy drugs have failed. We also show that patients treated with cenobamate can reduce the dose or even stop taking certain other epilepsy drugs. This allows them to simplify their treatment and reduce adverse effects while still keeping control of their epilepsy.

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.

Spanish consensus on the management of concomitant antiseizure medications when using cenobamate in adults with drug-resistant focal seizures

OBJECTIVE

Cenobamate is an antiseizure medication (ASM) associated with high rates of seizure freedom and acceptable tolerability in patients with focal seizures. To achieve the optimal cenobamate dose for maximal potential effectiveness while avoiding or minimizing drug-related adverse events (AEs), the administration of cenobamate with other ASMs must be managed through concomitant ASM load reduction. A panel of Spanish epilepsy experts aimed to provide a Spanish consensus on how to adjust the dose of concomitant ASMs in patients with drug-resistant epilepsy (DRE) in order to improve the effectiveness and tolerability of adjunctive cenobamate.

METHODS

A three-stage modified Delphi consensus process was undertaken, including six Spanish epileptologists with extensive experience using cenobamate. Based on current literature and their own expert opinion, the expert panel reached a consensus on when and how to adjust the dosage of concomitant ASMs during cenobamate titration.

RESULTS

The expert panel agreed that tailored titration and close follow-up are required to achieve the best efficacy and tolerability when initiating cenobamate in patients receiving concomitant ASMs. When concomitant clobazam, phenytoin, phenobarbital, and sodium channel blockers are taken at high dosages, or when the patient is receiving two or more sodium channel blockers, dosages should be proactively lowered during the cenobamate titration period. Other concomitant ASMs should be reduced only if the patient reports a moderate/severe AE at any stage of the titration period.

SIGNIFICANCE

Cenobamate is an effective ASM with a dose-dependent effect. To maximize effectiveness while maintaining the best tolerability profile, co-medication management is needed. The recommendations included herein provide practical guidance for proactive and reactive management of co-medication in cenobamate-treated patients with DRE and a high drug load.

PLAIN LANGUAGE SUMMARY

Patients with epilepsy may continue to have seizures even after treatment with several different antiseizure medications (ASMs). Cenobamate is an ASM that can reduce seizures in these patients. In this study, six Spanish experts in epilepsy discussed the best way to use cenobamate in drug-resistant epilepsy. They provide practical guidance on when and how the dose of other ASMs might be adjusted to reduce side effects and optimize the use of cenobamate.

Safety and Efficacy of Cenobamate for the Treatment of Focal Seizures in Older Patients: Post Hoc Analysis of a Phase III, Multicenter, Open-Label Study

BACKGROUND

Cenobamate is an antiseizure medication (ASM) approved in the US and Europe for the treatment of uncontrolled focal seizures.

OBJECTIVE

This post hoc analysis of a phase III, open-label safety study assessed the safety and efficacy of adjunctive cenobamate in older adults versus the overall study population.

METHODS

Adults aged 18-70 years with uncontrolled focal seizures taking stable doses of one to three ASMs were enrolled in the phase III, open-label safety study; adults aged 65-70 years from that study were included in our safety analysis. Discontinuations due to adverse events and treatment-emergent adverse events (TEAEs) were assessed throughout the study in all patients who received one or more doses of cenobamate (safety study population). Efficacy was assessed post hoc in patients who had adequate seizure data available (post hoc efficacy population); we assessed patients aged 65-70 years from that population. Overall, 100% responder rates were assessed in the post hoc efficacy maintenance-phase population in 3-month intervals. Concomitant ASM drug load changes were also measured. For each ASM, drug load was defined as the ratio of actual drug dose/day to the World Health Organization defined daily dose (DDD).

RESULTS

Of 1340 patients (mean age 39.7 years) in the safety study population, 42 were ≥ 65 years of age (mean age 67.0 years, 52.4% female). Median duration of exposure was 36.1 and 36.9 months for overall patients and older patients, respectively, and mean epilepsy duration was 22.9 and 38.5 years, respectively. At 1, 2, and 3 years, 80%, 72%, and 68% of patients overall, and 76%, 71%, and 69% of older patients, respectively, remained on cenobamate. Common TEAEs (≥ 20%) were somnolence and dizziness in overall patients, and somnolence, dizziness, fall, fatigue, balance disorder, and upper respiratory tract infection in older patients. Falls in older patients occurred after a mean 452.1 days of adjunctive cenobamate treatment (mean dose 262.5 mg/day; mean concomitant ASM drug load 2.46). Of 240 patients in the post hoc efficacy population, 18 were ≥ 65 years of age. Mean seizure frequency at baseline was 18.1 seizures/28 days for the efficacy population and 3.1 seizures/28 days for older patients. Rates of 100% seizure reduction within 3-month intervals during the maintenance phase increased over time for the overall population (n = 214) and older adults (n = 15), reaching 51.9% and 78.6%, respectively, by 24 months. Mean percentage change in concomitant ASM drug load, not including cenobamate, was reduced in the overall efficacy population (31.8%) and older patients (36.3%) after 24 months of treatment.

CONCLUSIONS

Results from this post hoc analysis showed notable rates of efficacy in older patients taking adjunctive cenobamate. Rates of several individual TEAEs occurred more frequently in older patients. Further reductions in concomitant ASMs may be needed in older patients when starting cenobamate to avoid adverse effects such as somnolence, dizziness, and falls.

CLINICAL TRIALS REGISTRATION

ClinicalTrials.gov NCT02535091.

Reductions in concomitant antiseizure medication drug load during adjunctive cenobamate therapy: Post-hoc analysis of a subset of patients from a phase 3, multicenter, open-label study

OBJECTIVE

Many patients with epilepsy require polytherapy, which increases their antiseizure medication (ASM) drug load, a measure that considers the doses of all ASMs a patient is taking. Changes in concomitant ASM drug load after adding cenobamate were evaluated post-hoc in a subset of the open-label, phase 3 study.

METHODS

Patients 18-70 years old with uncontrolled focal seizures taking 1-3 ASMs were enrolled. Total concomitant ASM drug load (not including cenobamate) was calculated by dividing the patient's prescribed dose for each ASM by its defined daily dose, per the World Health Organization, then summing the ratios. Changes in concomitant ASM drug load were measured from baseline in 3-month intervals up to 24 months by both total and class-specific ASM drug load. Subgroups of interest included: older adults (65-70 years), prior epilepsy-related surgery vs none, and baseline seizure frequency < 3 vs ≥ 3 seizures/28 days.

RESULTS

Data from 240 patients were available (mean age 41.8 years, mean baseline drug load 3.57). Following cenobamate initiation, the mean concomitant ASM drug load was reduced by 29.4 % at Month 12 % and 31.8 % at Month 24. Reductions occurred in all assessed ASM drug classes, with the largest reduction in benzodiazepines (55.2 % at Month 24). Each assessed subgroup exceeded a 30 % reduction in concomitant ASM drug load at Month 24. Over 24 months, maintenance of ≥ 50 % response occurred in 89.3 %, 86.4 %, and 90.6 % of patients with low (-0.25 to <0), moderate (-0.59 to -0.25), or high (-3.3 to -0.59) numerical reductions in concomitant ASM drug load from baseline, respectively, compared with 86.0 % in patients with no change in drug load; maintenance of 100 % response occurred in 80.7 %, 84.3 %, and 70.0 % of patients with low, moderate, or high numerical reductions in concomitant ASM drug load, compared with 82.0 % in patients with no change.

CONCLUSIONS

Adding cenobamate led to reduced mean concomitant ASM drug loads during 1 and 2 years of treatment. Reductions occurred regardless of ASM drug class, patient age, or epilepsy disease characteristics and did not impact maintenance of response rates.

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.

Dose reduction and discontinuation of concomitant antiseizure medications after initiating cenobamate: A retrospective review

This retrospective chart review examined dose reductions and discontinuations of concomitant antiseizure medications (ASMs) following cenobamate initiation and maintenance in patients with epilepsy treated at MetroHealth (Cleveland, OH) between 9/1/2020-9/26/2022. Concomitant ASM dose adjustments and treatment-emergent adverse events (TEAEs) were assessed. Efficacy (100 % seizure reduction) was examined among patients who received cenobamate for ≥ 3 months at data cutoff (including titration). As of 9/26/2022, 95 patients received cenobamate (mean age, 45.9 years; 48.4 % female, median exposure 7.5 months). Five patients (5.3 %) discontinued (n = 1 withdrawal by patient; n = 1 noncompliance; n = 3 adverse event). Among the 90 patients taking cenobamate at data cutoff, 50 % (45/90) discontinued ≥ 1 concomitant ASM, most commonly clobazam (n = 18), levetiracetam (n = 10), and phenytoin (n = 7); 21 patients (23.3 %) had additional concomitant ASM dose reductions, most commonly phenytoin (n = 6) and clobazam (n = 4). Sixteen patients received cenobamate monotherapy. Among 79 patients who received cenobamate for ≥ 3 months at data cutoff, 51.9 % (41/79) were seizure-free for ≥ 3 months. Of the 41 seizure-free patients, 58.5 % (24/41) were taking 100 mg/day of cenobamate. Sixteen of the 95 cenobamate-treated patients (16.8 %) reported 22 TEAEs. The most common TEAE was fatigue (n = 7). These data suggest that cenobamate therapy may allow reduction or elimination of polytherapy in some patients.

Sustainability of seizure reduction and seizure control with adjunctive cenobamate: Post hoc analysis of a phase 3, open-label study

OBJECTIVE

In this post hoc analysis of a subset of patients from a long-term, open-label phase 3 study, we assessed ≥50%, ≥75%, ≥90%, and 100% seizure reduction and sustainability of these responses with cenobamate using a time-to-event analytical approach.

METHODS

Of 240 patients with uncontrolled focal seizures who had adequate seizure data available, 214 completed the 12-week titration phase and received ≥1 dose of cenobamate in the maintenance phase (max dose 400 mg/day) and were included in this post hoc analysis. Among patients who met an initial given seizure-reduction level (≥50%, ≥75%, ≥90%, or 100%), sustainability of that response was measured using a time-to-event methodology. An event was defined as the occurrence of a study visit at which the seizure frequency during the interval since the prior study visit exceeded the initially attained reduction level. Study visits during the maintenance phase occurred at 3-month intervals.

RESULTS

Of the 214 patients analyzed, 188 (88%), 177 (83%), 160 (75%), and 145 (68%) met ≥50%, ≥75%, ≥90%, and 100% seizure-reduction responses, respectively, for at least one study visit interval during the maintenance phase. The median (95% confidence interval [CI]) time to first visit without a ≥50% seizure reduction was not reached by 30 months of follow-up (53% of patients maintained their initial ≥50% seizure reduction). Median (95% CI) time to first visit without sustaining the initial ≥75%, ≥90%, or 100% seizure reduction was 13.0 (7.5-21.9) months, 7.5 (5.4-11.6) months, and 7.0 (5.3-10.4) months, respectively. Among the 145 patients who had 100% seizure reduction during at least one study visit, 22% remained seizure-free for at least 30 months and 63% had ≤3 study visits with seizures.

SIGNIFICANCE

Adjunctive treatment with cenobamate led to sustained seizure reductions during the maintenance phase of the phase 3 safety study.

Real-world safety and effectiveness of cenobamate in patients with focal onset seizures: Outcomes from an Expanded Access Program

OBJECTIVE

This study investigated early, real-world outcomes with cenobamate (CNB) in a large series of patients with highly drug-resistant epilepsy within a Spanish Expanded Access Program (EAP).

METHOD

This was a multicenter, retrospective, observational study in 14 hospitals. Inclusion criteria were age ≥18 years, focal seizures, and EAP authorization. Data were sourced from patient clinical records. Primary effectiveness endpoints included reductions (100%, ≥90%, ≥75%, and ≥50%) or worsening in seizure frequency at 3-, 6-, and 12-month visits and at the last visit. Safety endpoints included rates of adverse events (AEs) and AEs leading to discontinuation.

RESULTS

The study included 170 patients. At baseline, median epilepsy duration was 26 years and median number of seizures/month was 11.3. The median number of prior antiseizure medications (ASMs) and concomitant ASMs were 12 and 3, respectively. Mean CNB dosages/day were 176 mg, 200 mg, and 250 mg at 3, 6, and 12 months. Retention rates were 98.2%, 94.5%, and 87% at 3, 6, and 12 months. At last available visit, the rate of seizure freedom was 13.3%; ≥90%, ≥75%, and ≥50% responder rates were 27.9%, 45.5%, and 63%, respectively. There was a significant reduction in the number of seizures per month (mean: 44.6%; median: 66.7%) between baseline and the last visit (P < 0.001). Responses were maintained regardless of the number of prior or concomitant ASMs. The number of concomitant ASMs was reduced in 44.7% of patients. The cumulative percentage of patients with AEs and AEs leading to discontinuation were 68.2% and 3.5% at 3 months, 74.1% and 4.1% at 6 months, and 74.1% and 4.1% at 12 months. The most frequent AEs were somnolence and dizziness.

SIGNIFICANCE

In this highly refractory population, CNB showed a high response regardless of prior and concomitant ASMs. AEs were frequent but mostly mild-to-moderate, and few led to discontinuation.

Pharmacokinetics of cenobamate as monotherapy compared with adjunctive therapy

OBJECTIVE

Cenobamate was approved by the US Food and Drug Administration (FDA) based on studies of adjunctive therapy in patients with focal epilepsy. To support the use of cenobamate monotherapy, this pharmacokinetic (PK)-based simulation analysis evaluated the predicted PK exposure of cenobamate when used as monotherapy versus adjunctive therapy.

METHODS

A population pharmacokinetic (PopPK) model of cenobamate was developed using pooled human data from eight phase 1 studies in healthy subjects or special populations, and three phase 2 and 3 studies in patients with focal seizures (N = 960). Concomitant antiseizure medications (ASMs) with a statistically significant effect on the apparent systemic clearance (CL/F) of cenobamate in the PopPK model were used to compare simulated patient plasma exposures (area under the plasma concentration vs time curve [AUC]) following monotherapy versus adjunctive therapy. Treatment equivalence between monotherapy and adjunctive therapy was concluded if the 90% confidence interval (CI) of the geometric mean AUC ratio was within 0.8-1.25.

RESULTS

In the PopPK model, statistically significant effects on cenobamate CL/F were shown for clobazam (decreased cenobamate CL/F by 19%) and carbamazepine (increased cenobamate CL/F by 15%); these differences were not considered clinically meaningful. Other ASMs (lacosamide, lamotrigine, levetiracetam, oxcarbazepine, topiramate, and valproate) when coadministered with cenobamate did not have significant effects on the disposition (ie, PK or efficacy) of cenobamate. The geometric mean ratio (90% CIs) of cenobamate AUC for adjunctive therapy/monotherapy was 0.87 (0.816-0.925) for adjunctive carbamazepine and 1.24 (1.147-1.339) for adjunctive clobazam. The 90% CI was within the no-effect limits (90% CIs 0.8-1.25) for adjunctive carbamazepine and partially exceeding no-effect limits for adjunctive clobazam.

CONCLUSIONS

Based on the results from this PopPK analysis, cenobamate monotherapy can be expected to result in comparable exposures to those that have been demonstrated to be safe and effective when used as adjunctive therapy for the treatment of focal seizures, supporting the use of cenobamate as monotherapy in these patients.

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.

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.

The cenobamate-clobazam interaction- evidence of synergy in addition to pharmacokinetic interaction

OBJECTIVES

Report insights into the pharmacokinetic and pharmacodynamic interaction between cenobamate (CNB) and clobazam (CLB), derived from data in patients enrolled at our center in a global multicenter open-label safety study of CNB.

MATERIALS & METHODS

Patients in this study either took CLB at baseline (n = 6) or had CLB added after CNB titration to maximal dose (n = 5) in addition to other antiseizure medications. Clobazam was always administered as a single bedtime dose. Random serum concentrations of CLB and N-desmethylclobazam (N-CLB) were obtained.

RESULTS

Baseline daily CLB doses were 20-50 mg. Sedation began in the six baseline CLB patients at CNB doses of 25-100 mg. The N-CLB/ CLB ratio increased proportionally to the CNB dose. CLB was stopped in all six patients, five of whom were ≥50% responders. Seizure control deteriorated after stopping CLB, with only one remaining responder. Clobazam was restarted at 5 mg/d in five of the six patients. At the last follow-up, four of these patients were continuing CLB; two were seizure-free and 2 were ≥50% responders. Among the five patients that added 5 mg/d CLB de novo, three were responders. All patients were still on CNB at the end of the study.

DISCUSSION

Data suggest starting CLB dose reduction at CNB doses of 25-100 mg/d. Due to possible synergy, the addition of low-dose CLB could be considered in patients with incomplete response to CNB.

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.

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.

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.

Onset of efficacy and adverse events during Cenobamate titration period

OBJECTIVES

Cenobamate is an antiseizure medication (ASM) approved in Europe as adjunctive therapy for adults with inadequately controlled focal seizures. This post hoc analysis reports onset of efficacy and characterizes time to onset, duration, and severity of the most common treatment-emergent adverse events (TEAEs) during cenobamate titration.

MATERIALS & METHODS

Adult patients with uncontrolled focal seizures taking 1 to 3 concomitant ASMs were randomized to receive adjunctive cenobamate or placebo (double-blind studies C013 and C017) or cenobamate (open-label study C021). Outcome assessments included efficacy (median percentage change in seizure frequency and onset [studies C013 and C017]) and safety (onset, duration, and severity of TEAEs [all studies]).

RESULTS

Onset of efficacy was observed by Weeks 1 to 4 of titration in studies C013 and C017 which used a faster titration schedule than study CO21. In study C013, the median percentage seizure frequency reduction was 36.7% in patients receiving cenobamate versus 16.3% in those taking placebo (p = .002); in study C017, significant differences in seizure frequency emerged in Week 1 and continued throughout titration between all cenobamate groups and placebo (p < .001). The most commonly reported TEAEs were somnolence, dizziness, fatigue, and headache, with first onset of each reported as early as Week 1; however, the majority resolved.

CONCLUSIONS

Reductions in seizure frequency occurred during titration with initial efficacy observed prior to reaching the target dose. These reductions were regarded as clinically meaningful because they may indicate early efficacy at lower doses than previously expected and had a considerable impact on patient quality of life. Long-term treatment with adjunctive cenobamate was generally safe and well-tolerated.

Adjunctive use of cenobamate for pediatric refractory focal-onset epilepsy: A single-center retrospective study

OBJECTIVE

We explored the efficacy and safety profile of cenobamate as an adjunctive therapy in patients with refractory focal-onset epilepsy in the pediatric population.

METHODS

This was a retrospective, single-center study of cenobamate used as an adjunctive medication in pediatric patients with refractory focal-onset epilepsy . We measured seizure reduction, median reduction in seizure frequency, median dose, responder rate, and treatment-emergent adverse events.

RESULTS

We studied the efficacy and safety profile of cenobamate in 21 pediatric patients (mean age 15.9). Cenobamate was up titrated using the prescribed starter pack with final doses ranging from 100 mg to 400 mg daily. The mean and median dose of cenobamate was 209.8 mg (±98.87 mg) and 200 mg (175-275), respectively. For patients weighing less than 50 kg, mean and median dose was 4.0 mg/kg/day (3.20-4.63) and 4.32 mg/kg/day, respectively. Mean and median baseline seizure frequency per month in this cohort was 15.38 and 16, respectively, prior to the introduction of cenobamate. After the adjunctive use of cenobamate, mean and median seizure frequency per month reduced to 7.29 and 1, respectively; median reduction in seizure frequency was 93.7%. Seizure reduction of at least 50% (responder rate) was noted in 13 (62.5%) patients and a seizure reduction of at least 75% noted in 11 (52.4%) patients, similar to that seen in adults. Four patients (19%) achieved seizure freedom. Of the 21 pediatric patients, 9 (42.8%) patients had treatment-emergent adverse events (TEAE) with the most commonly reported symptom being ataxia (5, 23.8%) and sedation (2, 9.5%). Three (14.3%) patients discontinued early due to these side effects. No children developed drug rash with eosinophilia and systemic symptoms (DRESS).

CONCLUSION

Cenobamate demonstrates similar efficacy rates and safety profile within the pediatric population when compared to the published adult data, making it an effective, safe, and tolerable adjunctive medication for children with refractory focal-onset epilepsy, even at the maximum daily dose.

The importance of drug titration in the management of patients with epilepsy

The variable response to antiseizure medication (ASM) treatment and the numerous drug- and patient-related factors that must be considered when initiating therapy make drug titration to an optimal and tolerable dose an essential component in the pharmacologic treatment of patients with epilepsy. When initiating a new ASM, a "start low, go slow" titration approach is generally recommended and has been shown to reduce the risk of severe idiosyncratic reactions with certain medications and improve tolerability with regard to many frequently occurring central nervous system-related adverse effects (e.g., somnolence, dizziness). Many patients with epilepsy will require medication changes due to lack of efficacy or intolerability of the initial regimen. When this occurs, patients may be switched from one monotherapy to another or receive adjunctive therapy. When transitioning a patient from one ASM to another (referred to as monotherapy conversion or transitional polytherapy), there are several strategies for tapering the baseline ASM depending on the clinical scenario. Regardless of the particular strategy, the goal should be to discontinue the baseline ASM in order to prevent increased toxicity due to drug load. When adding on ASM therapy, flexible titration of the new ASM and adjustment of concomitant ASMs to achieve disease control with the lowest possible drug load (lowest numbers and lowest doses) may help improve tolerability of the add-on therapy. Communication with patients during the initiation of a new therapy may help patients adhere to the titration schedule, allowing them to reach their optimal maintenance dose.

Effectiveness and safety of adjunctive cenobamate for focal seizures in adults with developmental disability treated in clinical practice

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92.9% (26/28 patients) continued cenobamate through 6 months, showing high retention.

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High responder rates/substantial focal seizure reduction occurred with cenobamate.

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100% seizure reduction occurred in 48.2% of patients at 6 months.

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Adverse effects were often mitigated by concomitant antiseizure medication reduction.

Effectiveness and tolerability of adjunctive cenobamate for uncontrolled focal seizures in adults living with a developmental disability are not defined. Retrospective medical record review included adults ≥18 years old living with a developmental disability, either in a group home or with parents, and experiencing uncontrolled focal seizures despite stable doses of ≥1 antiseizure medication (ASM). Effectiveness was examined as percentage change in focal seizure frequency per month from the 2-month average before cenobamate to the average of months 5 and 6 while receiving cenobamate. Percentages of patients achieving responder rates in focal seizure frequency at 6 months of cenobamate treatment were examined. Adverse effects and concomitant ASM dosage adjustments were assessed. Of the 28 included patients, 26 (92.9%) continued cenobamate beyond 6 months. The responder rate of 100% seizure reduction (seizure-free) occurred in 48.2% of the patients who continued cenobamate for 6 months. Ten adverse effects were reported in 9 patients (32.1%), and 80% (8/10) were resolved by reducing concomitant ASM dosages. Two patients (7.1%) discontinued cenobamate due to adverse effects. Cenobamate resulted in substantial reduction in focal seizure frequency and was well tolerated.

Efficacy of cenobamate for uncontrolled focal seizures: Post hoc analysis of a Phase 3, multicenter, open-label study

Objective

To report long‐term post hoc efficacy and safety data from 10 US study sites from an open‐label Phase 3 study of adjunctive cenobamate (NCT02535091).

Methods

Patients with uncontrolled focal seizures taking stable doses of 1–3 antiseizure medications (ASMs) were administered increasing daily 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 increments biweekly were allowed during the maintenance phase. Dose adjustments of cenobamate and concomitant ASMs were allowed. Data were assessed until the last clinic visit on or after September 1, 2019.

Results

Of 255 patients, 240 with focal aware motor, focal impaired awareness, or focal to bilateral tonic–clonic seizure data while on treatment were evaluated (median [maximum] exposure = 30.2 [43.0] months across the entire study). Median baseline seizure frequency/28 days was 2.8 (mean = 18.1). Of the 240 patients, 177 (73.8%) were continuing cenobamate treatment at data cutoff. The ≥50% responder rate for the total treatment duration was 71.7% (172/240). During titration, the ≥50% responder rates were 48.1% during Weeks 1–4 (12.5–25 mg/day cenobamate) and 61.7% during Weeks 5–8 (50–100 mg/day cenobamate). Among all patients who received a dose of cenobamate in the maintenance phase (n = 214), 13.1% (28/214) and 40.2% (86/214) achieved 100% and ≥90% seizure reduction during their entire maintenance treatment duration (median = 29.5 months). Among all patients, 87 (36.3%) had any consecutive ≥12‐month duration of 100% seizure reduction. Common treatment‐emergent adverse events among all 240 patients included fatigue (34.6%), dizziness (32.1%), and somnolence (29.6%).

Significance

This post hoc analysis of a subset of patients from the long‐term open‐label study showed high rates of sustained 100% and ≥90% seizure reduction, with many achieving response early during titration. These findings suggest durable seizure frequency reduction with cenobamate in adults with uncontrolled focal seizures.