Indirect treatment comparison of cenobamate to other ASMs for the treatment of uncontrolled focal seizures

Methods for Indirect Treatment Comparison: Results from a Systematic Literature Review

INTRODUCTION

Health technology assessment (HTA) agencies express a clear preference for randomized controlled trials when assessing the comparative efficacy of two or more treatments. However, an indirect treatment comparison (ITC) is often necessary where a direct comparison is unavailable or, in some cases, not possible. Numerous ITC techniques are described in the literature. A systematic literature review (SLR) was conducted to identify all the relevant literature on existing ITC techniques, provide a comprehensive description of each technique and evaluate their strengths and limitations from an HTA perspective in order to develop guidance on the most appropriate method to use in different scenarios.

METHODS

Electronic database searches of Embase and PubMed, as well as grey literature searches, were conducted on 15 November 2021. Eligible articles were peer-reviewed papers that specifically described the methods used for different ITC techniques and were written in English. The review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

A total of 73 articles were included in the SLR, reporting on seven different ITC techniques. All reported techniques were forms of adjusted ITC. Network meta-analysis (NMA) was the most frequently described technique (in 79.5% of the included articles), followed by matching-adjusted indirect comparison (MAIC) (30.1%), network meta-regression (24.7%), the Bucher method (23.3%), simulated treatment comparison (STC) (21.9%), propensity score matching (4.1%) and inverse probability of treatment weighting (4.1%). The appropriate choice of ITC technique is critical and should be based on the feasibility of a connected network, the evidence of heterogeneity between and within studies, the overall number of relevant studies and the availability of individual patient-level data (IPD). MAIC and STC were found to be common techniques in the case of single-arm studies, which are increasingly being conducted in oncology and rare diseases, whilst the Bucher method and NMA provide suitable options where no IPD is available.

CONCLUSION

ITCs can provide alternative evidence where direct comparative evidence may be missing. ITCs are currently considered by HTA agencies on a case-by-case basis; however, their acceptability remains low. Clearer international consensus and guidance on the methods to use for different ITC techniques is needed to improve the quality of ITCs submitted to HTA agencies. ITC techniques continue to evolve quickly, and more efficient techniques may become available in the future.

Efficacy and safety of adjunctive cenobamate based on patient etiology: Post-hoc analysis of YKP3089C017 randomized clinical trial

INTRODUCTION

Adjunctive cenobamate was effective and safe for the treatment of uncontrolled focal onset seizures in a randomized, double-blind, placebo-controlled, phase 2 study (YKP3089C017; NCT01866111). This post-hoc analysis assessed the efficacy of adjunctive cenobamate in the treatment of patients with different epileptic etiologies during the study.

METHODS

Adult patients with uncontrolled focal seizures who previously received 1 to 3 antiseizure medications (ASMs) were randomly assigned in a ratio of 1:1:1:1 to receive placebo or cenobamate 100, 200 or 400 mg/day. Patients were further stratified based on their etiologic causes as genetic/presumed genetic, unknown cause, structural cause, and not reported (NR) groups. The frequency per 28 days for an 18-week double-blind treatment period, responder rates (≥50 %, ≥75 %, ≥90 %, and 100 %) during the maintenance phase (12 weeks), and safety were assessed.

RESULTS

A total of 394 patients were categorized into the genetic/presumed genetic (n = 9; 2.28 %), unknown cause (n = 199; 50.51 %), structural cause (n = 177; 44.92 %), and NR (n = 13; 3.30 %) groups, with 4 patients were classified into either of the two etiological causes each. The baseline characteristics were comparable. The percentage of reduction in seizure frequency per 28 days was significantly higher in the cenobamate-treated structural (p = 0.01) and unknown cause (p = 0.0003) groups compared with the placebo group. Responder rates of ≥50 %, ≥75 %, ≥90 %, and 100 % were also higher with cenobamate therapy. Notably, no serious treatment-emergent adverse events (TEAEs) were observed in the genetic/presumed genetic group treated with cenobamate. The most common TEAEs (≥10 %) occurring in patients treated with cenobamate were nervous system disorders by system organ class, and somnolence was the most commonly reported TEAE.

CONCLUSION

Cenobamate reduces seizures in adult patients previously treated with ASMs, with high responder rates and acceptable safety, regardless of underlying causes.

A comparison of cenobamate with other newer antiseizure medications for adjunctive treatment of focal-onset seizures: A systematic review and network meta-analysis

PURPOSE

To compare the efficacy, safety, and tolerability of cenobamate with other newer anti-seizure medications (ASMs) including brivaracetam, eslicarbazepine, lacosamide, perampanel, and zonisamide, approved for adjunctive treatment of drug-resistant focal-onset seizures (FOS) in adults with epilepsy.

METHODS

A systematic literature review (SLR) was conducted to obtain relevant efficacy, safety, and tolerability data for ASMs for the treatment of drug-resistant FOS. All studies were thoroughly assessed for potential sources of heterogeneity and analysed via Bayesian network meta-analyses (NMAs). Efficacy outcomes were ≥50 % responder rate and seizure freedom during the maintenance period, which were modelled simultaneously using a multinomial Bayesian NMA. Safety and tolerability outcomes were the proportion of patients who experienced at least one treatment-emergent adverse event (TEAE) and the proportion who experienced at least one TEAE leading to discontinuation.

RESULTS

The SLR identified 76 studies, of which 23 were included in the Bayesian NMAs. Cenobamate was associated with statistically significant higher rates for the ≥50 % responder rate and seizure freedom outcomes compared with all ASMs analysed. The point estimates indicated that cenobamate was associated with higher rates of experiencing at least one TEAE and at least one TEAE leading to discontinuation compared with brivaracetam, lacosamide, and zonisamide; however, no results were statistically significant.

CONCLUSION

Cenobamate was associated with increased efficacy compared with all ASMs analysed. There were no statistically significant differences in the safety and tolerability outcomes. The results presented corroborate the conclusions drawn from previous published NMAs, which also highlight the notable efficacy of cenobamate in comparison with other ASMs.

Add-on treatment with cenobamate is already effective at low doses in refractory focal epilepsy: A prospective observational study

OBJECTIVE

Cenobamate, a novel antiseizure medication with a dual mechanism of action, has been shown in pivotal trials to significantly improve seizure control in treatment-resistant focal epilepsy. We aimed to evaluate whether these promising results could be confirmed in a real-world setting with a follow-up period of up to 12 months.

METHODS

Patients from a tertiary epilepsy center who received cenobamate add-on between June 2021 and October 2023 were followed up prospectively at 3, 6, and 12 months after treatment initiation for assessment of seizure outcomes and treatment-related adverse events.

RESULTS

The clinical cohort included 112 adult patients with 30% nonlesional cases and a wide spectrum of epileptogenic lesions underlying refractory focal epilepsy. We observed a significant reduction in monthly seizure frequency of all seizure types already after 3 months of treatment at a median cenobamate dose of 100 mg/day. Forty-six percent of patients were responders with a ≥50% seizure reduction, 26% had a ≥75% seizure reduction, and 9% became seizure-free. Among the 74 patients with available follow-up of 12 months, the responder rates reached 55%, 35%, and 19% for ≥50%, ≥75%, and 100% seizure reduction, respectively. After 3 months of treatment, 38% of patients reported adverse effects, mainly (84%) mild to moderate in intensity. Adjustment of comedication allowed successful management of adverse effects in 32% of patients. At a group level, there was no correlation between the cenobamate daily dose and the incidence of adverse events.

SIGNIFICANCE

We found a clinically relevant response to cenobamate already at a low daily dose of 100 mg also in a patient cohort with a higher degree of drug resistance than in pivotal trials. Our prospectively collected data provide real-world evidence for high efficacy and good tolerability of the drug, although no standardized treatment protocol or comparison with a control group was applied.

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).

The Acceptance of Indirect Treatment Comparison Methods in Oncology by Health Technology Assessment Agencies in England, France, Germany, Italy, and Spain

INTRODUCTION

Randomized controlled trials (RCTs) are the gold standard when comparing treatment effectiveness, and Health Technology Assessment (HTA) agencies state a clear preference for such direct comparisons. When these are not available, an indirect treatment comparison (ITC) is an alternative option. The objective of this study was to assess the acceptance of ITC methods by HTA agencies across England, France, Germany, Italy, and Spain, using oncology cases for a homogeneous sample of HTA evaluations.

METHODS

The study was conducted on the PrismAccess database in May 2021 to retrieve HTA evaluation reports for oncology treatments for solid tumors, in which an ITC was presented. The analysis was restricted to HTA evaluation reports published between April 2018 and April 2021 in England, France, Germany, Italy, and Spain. Identified HTA evaluation reports were screened and reviewed by two independent reviewers. For each ITC presented, the methodology and its acceptance by the HTA agency were analyzed.

RESULTS

Five hundred and forty-three HTA evaluation reports were identified, of which 120 (22%) presented an ITC. This proportion was the highest in England (51%) and lowest in France (6%). The overall acceptance rate of ITC methods was 30%, with the highest in England (47%) and lowest in France (0%). Network meta-analysis (NMA; 23%) was the most commonly used ITC technique, with a 39% acceptance rate overall, followed by Bucher ITC (19%; 43% acceptance rate) and matching-adjusted indirect comparison (13%; 33% acceptance rate). The most common criticisms of the ITC methods from HTA agencies related to data limitations (heterogeneity and lack of data; 48% and 43%, respectively) and the statistical methods used (41%).

CONCLUSIONS

The generally low acceptance rate of ITC methods by HTA agencies in oncology suggests that, whilst in the absence of a direct comparison ITCs may provide relevant evidence, this evidence is not widely considered sufficient for the purpose of HTA evaluations. The perception of ITC methods for the purpose of HTA evaluations varies substantially between countries. There is a need for further clarity on the properties of ITC techniques and the assessment of their results as ITC methods continue to evolve quickly and further techniques may become available in the future.

Cenobamate: Real-World Experience Matches Clinical Trials

Adjunctive Cenobamate in Highly Active and Ultra-Refractory Focal Epilepsy: A “Real-World” Retrospective Study Pena-Ceballos J, Moloney PB, Munteanu T, Doyle M, Colleran N, Liggan B, Breen A, Murphy S, El-Naggar H, Widdess-Walsh P, Delanty N. Epilepsia . 2023;64(5):1225-1235. doi:10.1111/epi.17549 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.

Cenobamate in patients with highly refractory focal epilepsy: A retrospective real-world study

PURPOSE

To determine the effectiveness and safety outcomes of cenobamate in a cohort of patients with highly refractory focal epilepsy in routine clinical practice.

METHODS

Observational, retrospective, phase 4 study on subjects receiving cenobamate in three Spanish centers. The primary endpoint was the retention rate at the last follow-up. The main secondary endpoints were the 50%-responder  and seizure-free rates at three months and the last follow-up. Other secondary endpoints were Global Clinical Impressions-Improvement (CGI-I) scores and treatment-emergent adverse events (TEAEs).

RESULTS

Fifty-one patients with highly refractory focal epilepsy with 24.7 years of disease evolution, ten previously tried ASM, and a 23.5% of previous epilepsy surgery were included. The retention rate at the last follow-up was 80.4%. The 50% responder rate in focal seizures at three months was 56.5% (median reduction per month 51%, 0-74.6; p < 0.0001) and in focal to bilateral tonic-clonic seizures was 63.6% (median reduction per month 89%, 0-100; p = 0.022). A total of 54.3% of subjects reported a reduction in the intensity of focal seizures, and 66% manifested clinically significant satisfaction. Cenobamate allowed a significant decrease in concomitant ASM, especially sodium channel blockers. TEAEs were reported in 43.1% of individuals, 85% of whom resolved or improved, with no new safety findings.

CONCLUSION

In this analysis of patients with highly refractory focal epilepsy treated with cenobamate according to standard clinical practice, there was evidence of a high reduction in both seizure frequency and intensity, with a manageable safety profile.

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.

Determination of the economically justifiable price of cenobamate in the treatment of focal-onset seizures in adult patients with drug-resistant epilepsy in Spain

OBJECTIVE

To determine the economically justifiable price (EJP) of cenobamate to become a cost-effective alternative compared with third-generation anti-seizure medications in the treatment of focal-onset seizures (FOS) in adult patients with drug-resistant epilepsy (DRE) in Spain.

METHODS

Cost-effectiveness analysis comparing cenobamate with brivaracetam, perampanel, eslicarbazepine acetate and lacosamide. Markov model simulation of treatment pathway over a 60-year time horizon. Determination of effectiveness and quality-adjusted life-years (QALYs) of each health status, and disutilities associated with treatment-related adverse events. Acquisition costs and use of medical resources were obtained from published literature and expert opinion. Base-case of cenobamate's EJP calculated applying a willingness-to-pay (WTP) threshold of €21,000/QALY. Analyses performed at different thresholds, including dominant price scenario. Results robustness were assessed through sensitivity analyses.

RESULTS

Base-case shows that cenobamate's daily EJP of €7.30 is cost-effective for a threshold of €21,000/QALY. At a daily price of €5.45, cenobamate becomes dominant over all treatment alternatives producing cost-savings for the national health system (NHS). Sensitivity analyses supported the robustness of base-case findings.

CONCLUSIONS

Treatment with cenobamate produces incremental clinical benefit over third generation ASMs and at the base-case EJP could represent a cost-effective option for the adjunctive treatment of FOS in adult patients with DRE in Spain.

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.