Fenfluramine HCl (Fintepla® ) provides long-term clinically meaningful reduction in seizure frequency: Analysis of an ongoing open-label extension study

Practical considerations for the use of fenfluramine to manage patients with Dravet syndrome or Lennox-Gastaut syndrome in clinical practice

Fenfluramine (FFA), an antiseizure medication (ASM) with serotonergic and sigma-1 receptor activity, is used to manage patients with developmental and epileptic encephalopathies (DEEs). It is approved in the US for treating seizures associated with Dravet syndrome (DS) and Lennox-Gastaut syndrome (LGS) in patients ≥2 years old and as add-on therapy for seizures associated with DS and LGS in the EU, UK, and Japan in similarly aged patients. Consensus guidelines for treatment of DS have recommended FFA to be an early-line ASM, and it has also shown efficacy in managing seizures associated with LGS. DS and LGS are DEEs associated with a range of seizure types, developmental impairments, and multiple comorbidities. Here we provide case vignettes describing 4 patients (3 DS and 1 LGS) aged 4-29 years old in whom up to 14 ASMs had previously failed, to illustrate real-world practice issues encountered by neurologists. This review provides guidance on the use of FFA in the context of ASM polytherapy and drug-drug interactions (DDIs), behavioral issues, dose titration, and adverse events. Along with data from the clinical trial program, these case vignettes emphasize the low risk of DDIs, a generally well-tolerated safety profile, and other seizure and nonseizure benefits (eg, improved cognition and sleep) associated with the use of FFA in DS or LGS. PLAIN LANGUAGE SUMMARY: Fenfluramine is used to treat seizures in individuals with Dravet syndrome and Lennox-Gastaut syndrome, but there are a range of issues that clinicians may face when treating patients. This review highlights four patients from the authors' everyday clinical work and offers guidance and practical considerations by neurologists with expertise in managing these complex conditions related to drug interactions, dosing, and side effects associated with fenfluramine.

Cost Effectiveness of Adding Fenfluramine to Standard of Care for Patients with Dravet Syndrome in Sweden

OBJECTIVE

This study evaluated, in a Swedish setting, the cost effectiveness of fenfluramine (FFA) as an add-on to standard of care (SoC) for reducing seizure frequency in Dravet syndrome, a severe developmental epileptic encephalopathy.

METHODS

Cost effectiveness of FFA+SoC compared with SoC only was evaluated using a patient-level simulation model with a lifetime horizon. Patient characteristics and treatment effects, including convulsive seizures, seizure-free days and mortality, were derived from FFA clinical trials. Resource use and costs included cost of drug acquisition, routine care and monitoring, as well as ongoing and emergency resources. Quality of life (QoL) estimates for patients and their caregivers were derived from clinical trial data. Robustness was evaluated by one-way sensitivity analysis, probabilistic sensitivity analysis and scenario analyses.

RESULTS

Lifetime cost of FFA+SoC was ~3 million SEK per patient compared with ~1.5 million SEK for SoC only. FFA+SoC generated 15% more QALYs than SoC only (21.2 vs 18.5 over a lifetime), resulting in an incremental cost-effectiveness ratio (ICER) of ~540,000 SEK. Moreover, FFA+SoC had a higher probability of being cost effective than SoC only from a willingness-to-pay threshold of 710,000 SEK. Results remained generally consistent across scenario analyses, with only few exceptions (exclusions of carer utility or FFA effect on sudden unexpected death in epilepsy).

CONCLUSION

Due to better seizure control, FFA is a clinically meaningful add-on therapy and was estimated to be a cost-effective addition to current SoC for patients with this rare disease in Sweden at a willingness-to-pay threshold of 1,000,000 SEK.

Evaluating bexicaserin for the treatment of developmental epileptic encephalopathies

INTRODUCTION

Developmental epileptic encephalopathies (DEEs) pose significant challenges due to their refractory nature and limited treatment options. Despite advancements in genetic understanding, effective therapies targeting underlying pathophysiology are lacking. Serotoninergic dysfunction has been implicated in epilepsy, sparking interest in serotonin as a therapeutic target.

AREA COVERED

This article explores the potential of bexicaserin, a selective 5-HT2C receptor agonist, as an adjunctive antiseizure medication in DEEs. Bexicaserin is thought to modulate GABAergic neurotransmission, suppressing central hyperexcitability. Preclinical studies demonstrate its efficacy across various seizure models. Clinical trials, including the Pacific Study, reveal promising results in reducing motor seizures. However, challenges such as adverse effects and treatment discontinuation underscore the need for further investigation.

EXPERT OPINION

The efficacy of 5-HT2C serotoninergic agonists, validated in preclinical and clinical studies, highlights serotonin's role in DEEs. Bexicaserin offers new therapeutic possibilities, potentially synergizing with existing antiseizure medications. Polypharmacotherapy, targeting distinct pathways, may enhance therapeutic outcomes. Monitoring pharmacological interactions and addressing central nervous system comorbidities are crucial for optimizing treatment strategies. Further research is needed to elucidate bexicaserin's mechanisms and potential antiepileptogenic effects.

What have we learned from the real-world efficacy of FFA in DS and LGS? A post-marketing study in clinical practice

OBJECTIVE

To evaluate the effectiveness and tolerability of fenfluramine (FFA) in routine clinical practice treating real-world populations with Dravet syndrome (DS) and Lennox-Gastaut syndrome (LGS).

METHODS

This was a retrospective analysis of patients with DS or LGS who initiated FFA treatment from 2018 to 2022 at a single center. Patient demographics, medical history, seizure characteristics, and treatment outcomes were collected from electronic medical records. Duration of FFA treatment, dosage regimens, seizure frequency, seizure severity, improvements in cognitive, social, and motor outcomes, and adverse events were extracted and analyzed. Effectiveness was assessed using ≥50 % sustained reduction in monthly seizure frequency vs baseline for ≥2 consecutive months at 12 months; seizure freedom was a secondary measure.

RESULTS

Seizure frequency data was available for 56 of 68 patients included in the study. At 12 months, 50 patients (89.3 %) remained on FFA treatment; 58 % of these patients achieved a ≥50 % sustained response and 10 % experienced seizure freedom. Cognitive, motor, and social improvement were noted in 70.7 %, 36.2 %, and 27.6 % of patients, respectively. The total number of concomitant antiseizure medications was reduced by ≥1 in 29.4 % of patients. No differences were found between DS and LGS patients in these outcomes; age at start of FFA and age at the 12-month timepoint did not have an effect. At least one AE was experienced by 59.7% of patients; in 86.5% of the cases, AEs were plausibly related to treatment. While 70.3% of AEs were self-resolving and 81.8% of the remaining patients experienced mild AEs, 1 patient experienced a serious AE unrelated to FFA which resulted in the patient's death. There were no cases of pulmonary arterial hypertension or ventricular heart disease.

SIGNIFICANCE

The effectiveness and tolerability of FFA treatment in patients with DS or LGS in this retrospective analysis of real-world data were consistent with those seen in randomized clinical trials.

Fenfluramine increases survival and reduces markers of neurodegeneration in a mouse model of Dravet syndrome

OBJECTIVE

In patients with Dravet syndrome (DS), fenfluramine reduced convulsive seizure frequency and provided clinical benefit in nonseizure endpoints (e.g., executive function, survival). In zebrafish mutant scn1 DS models, chronic fenfluramine treatment preserved neuronal cytoarchitecture prior to seizure onset and prevented gliosis; here, we extend these findings to a mammalian model of DS (Scn1a+/- mice) by evaluating the effects of fenfluramine on neuroinflammation (degenerated myelin, activated microglia) and survival.

METHODS

Scn1a+/- DS mice were treated subcutaneously once daily with fenfluramine (15 mg/kg) or vehicle from postnatal day (PND) 7 until 35-37. Sagittal brain sections were processed for immunohistochemistry using antibodies to degraded myelin basic protein (D-MBP) for degenerated myelin, or CD11b for activated (inflammatory) microglia; sections were scored semi-quantitatively. Apoptotic nuclei were quantified by TUNEL assay. Statistical significance was evaluated by 1-way ANOVA with post-hoc Dunnett's test (D-MBP, CD11b, and TUNEL) or Logrank Mantel-Cox (survival).

RESULTS

Quantitation of D-MBP immunostaining per 0.1 mm2 unit area of the parietal cortex and hippocampus CA3 yielded significantly higher spheroidal and punctate myelin debris counts in vehicle-treated DS mice than in wild-type mice. Fenfluramine treatment in DS mice significantly reduced these counts. Activated CD11b + microglia were more abundant in DS mouse corpus callosum and hippocampus than in wild-type controls. Fenfluramine treatment of DS mice resulted in significantly fewer activated CD11b + microglia than vehicle-treated DS mice in these brain regions. TUNEL staining in corpus callosum was increased in DS mice relative to wild-type controls. Fenfluramine treatment in DS mice lowered TUNEL staining relative to vehicle-treated DS mice. By PND 35-37, 55% of control DS mice had died, compared with 24% of DS mice receiving fenfluramine treatment (P = 0.0291).

SIGNIFICANCE

This is the first report of anti-neuroinflammation and pro-survival after fenfluramine treatment in a mammalian DS model. These results corroborate prior data in humans and animal models and suggest important pharmacological activities for fenfluramine beyond seizure reduction.

PLAIN LANGUAGE SUMMARY

Dravet syndrome is a severe epilepsy disorder that impairs learning and causes premature death. Clinical studies in patients with Dravet syndrome show that fenfluramine reduces convulsive seizures. Additional studies suggest that fenfluramine may have benefits beyond seizures, including promoting survival and improving control over emotions and behavior. Our study is the first to use a Dravet mouse model to investigate nonseizure outcomes of fenfluramine. Results showed that fenfluramine treatment of Dravet mice reduced neuroinflammation significantly more than saline treatment. Fenfluramine-treated Dravet mice also lived longer than saline-treated mice. These results support clinical observations that fenfluramine may have benefits beyond seizures.

Targeted Molecular Strategies for Genetic Neurodevelopmental Disorders: Emerging Lessons from Dravet Syndrome

Dravet syndrome is a severe developmental and epileptic encephalopathy mostly caused by heterozygous mutation of the SCN1A gene encoding the voltage-gated sodium channel α subunit Nav1.1. Multiple seizure types, cognitive deterioration, behavioral disturbances, ataxia, and sudden unexpected death associated with epilepsy are a hallmark of the disease. Recently approved antiseizure medications such as fenfluramine and cannabidiol have been shown to reduce seizure burden. However, patients with Dravet syndrome are still medically refractory in the majority of cases, and there is a high demand for new therapies aiming to improve behavioral and cognitive outcome. Drug-repurposing approaches for SCN1A-related Dravet syndrome are currently under investigation (i.e., lorcaserin, clemizole, and ataluren). New therapeutic concepts also arise from the field of precision medicine by upregulating functional SCN1A or by activating Nav1.1. These include antisense nucleotides directed against the nonproductive transcript of SCN1A with the poison exon 20N and against an inhibitory noncoding antisense RNA of SCN1A. Gene therapy approaches such as adeno-associated virus-based upregulation of SCN1A using a transcriptional activator (ETX101) or CRISPR/dCas technologies show promising results in preclinical studies. Although these new treatment concepts still need further clinical research, they offer great potential for precise and disease modifying treatment of Dravet syndrome.

The Psychedelic N,N-Dipropyltryptamine Prevents Seizures in a Mouse Model of Fragile X Syndrome via a Mechanism that Appears Independent of Serotonin and Sigma1 Receptors

The serotonergic psychedelic psilocybin shows efficacy in treating neuropsychiatric disorders, though the mechanism(s) underlying its therapeutic effects remain unclear. We show that a similar psychedelic tryptamine, N,N-dipropyltryptamine (DPT), completely prevents audiogenic seizures (AGS) in an Fmr1 knockout mouse model of fragile X syndrome at a 10 mg/kg dose but not at lower doses (3 or 5.6 mg/kg). Despite showing in vitro that DPT is a serotonin 5-HT2A, 5-HT1B, and 5-HT1A receptor agonist (with that rank order of functional potency, determined with TRUPATH Gα/βγ biosensors), pretreatment with selective inhibitors of 5-HT2A/2C, 5-HT1B, or 5-HT1A receptors did not block DPT's antiepileptic effects; a pan-serotonin receptor antagonist was also ineffective. Because 5-HT1A receptor activation blocks AGS in Fmr1 knockout mice, we performed a dose-response experiment to evaluate DPT's engagement of 5-HT1A receptors in vivo. DPT elicited 5-HT1A-dependent effects only at doses greater than 10 mg/kg, further supporting that DPT's antiepileptic effects were not 5-HT1A-mediated. We also observed that the selective sigma1 receptor antagonist, NE-100, did not impact DPT's antiepileptic effects, suggesting DPT engagement of sigma1 receptors was not a crucial mechanism. Separately, we observed that DPT and NE-100 at high doses caused convulsions on their own that were qualitatively distinct from AGS. In conclusion, DPT dose-dependently blocked AGS in Fmr1 knockout mice, but neither serotonin nor sigma1 receptor antagonists prevented this action. Thus, DPT might have neurotherapeutic effects independent of its serotonergic psychedelic properties. However, DPT also caused seizures at high doses, showing that DPT has complex dose-dependent in vivo polypharmacology.

Fenfluramine in the treatment of Dravet syndrome: Results of a third randomized, placebo-controlled clinical trial

OBJECTIVE

This study was undertaken to assess the safety and efficacy of fenfluramine in the treatment of convulsive seizures in patients with Dravet syndrome.

METHODS

This multicenter, randomized, double-blind, placebo-controlled, parallel-group, phase 3 clinical trial enrolled patients with Dravet syndrome, aged 2-18 years with poorly controlled convulsive seizures, provided they were not also receiving stiripentol. Eligible patients who had ≥6 convulsive seizures during the 6-week baseline period were randomized to placebo, fenfluramine .2 mg/kg/day, or fenfluramine .7 mg/kg/day (1:1:1 ratio) administered orally (maximum dose = 26 mg/day). Doses were titrated over 2 weeks and maintained for an additional 12 weeks. The primary endpoint was a comparison of the monthly convulsive seizure frequency (MCSF) during baseline and during the combined titration-maintenance period in patients given fenfluramine .7 mg/kg/day versus patients given placebo.

RESULTS

A total of 169 patients were screened, and 143 were randomized to treatment. Mean age was 9.3 ± 4.7 years (±SD), 51% were male, and median baseline MCSF in the three groups ranged 12.7-18.0 per 28 days. Patients treated with fenfluramine .7 mg/kg/day demonstrated a 64.8% (95% confidence interval = 51.8%-74.2%) greater reduction in MCSF compared with placebo (p < .0001). Following fenfluramine .7 mg/kg/day, 72.9% of patients had a ≥50% reduction in MCSF compared with 6.3% in the placebo group (p < .0001). The median longest seizure-free interval was 30 days in the fenfluramine .7 mg/kg/day group compared with 10 days in the placebo group (p < .0001). The most common adverse events (>15% in any group) were decreased appetite, somnolence, pyrexia, and decreased blood glucose. All occurred in higher frequency in fenfluramine groups than placebo. No evidence of valvular heart disease or pulmonary artery hypertension was detected.

SIGNIFICANCE

The results of this third phase 3 clinical trial provide further evidence of the magnitude and durability of the antiseizure response of fenfluramine in children with Dravet syndrome.

Reintroducing Fenfluramine as a Treatment for Seizures: Current Knowledge, Recommendations and Gaps in Understanding

Despite the introduction of new anti-seizure medications in recent years, approximately one-third of the epileptic population continues to experience seizures. Recently, the anti-obesity medication fenfluramine (FFA) has been successfully repurposed, and it has received approval from various regulatory agencies for the treatment of seizures associated with Dravet syndrome and Lennox-Gastaut syndrome. The potential antiseizure effects of FFA were initially observed in patients with photosensitive epilepsy in the 1980s but it was not rigorously explored as a treatment option until 30 years later. This narrative review aims to provide an overview of the historical progression of FFA's use, starting from initial clinical observations to preclinical studies and, ultimately, successful clinical trials in the field of epilepsy.

Pharmacological diversity amongst approved and emerging antiseizure medications for the treatment of developmental and epileptic encephalopathies

Developmental and epileptic encephalopathies (DEEs) are rare neurodevelopmental disorders characterised by early-onset and often intractable seizures and developmental delay/regression, and include Dravet syndrome and Lennox-Gastaut syndrome (LGS). Rufinamide, fenfluramine, stiripentol, cannabidiol and ganaxolone are antiseizure medications (ASMs) with diverse mechanisms of action that have been approved for treating specific DEEs. Rufinamide is thought to suppress neuronal hyperexcitability by preventing the functional recycling of voltage-gated sodium channels from the inactivated to resting state. It is licensed for adjunctive treatment of seizures associated with LGS. Fenfluramine increases extracellular serotonin levels and may reduce seizures via activation of specific serotonin receptors and positive modulation of the sigma-1 receptor. Fenfluramine is licensed for adjunctive treatment of seizures associated with Dravet syndrome and LGS. Stiripentol is a positive allosteric modulator of type-A gamma-aminobutyric acid (GABAA) receptors. As a broad-spectrum inhibitor of cytochrome P450 enzymes, its antiseizure effects may additionally arise through pharmacokinetic interactions with co-administered ASMs. Stiripentol is licensed for treating seizures associated with Dravet syndrome in patients taking clobazam and/or valproate. The mechanism(s) of action of cannabidiol remains largely unclear although multiple targets have been proposed, including transient receptor potential vanilloid 1, G protein-coupled receptor 55 and equilibrative nucleoside transporter 1. Cannabidiol is licensed as adjunctive treatment in conjunction with clobazam for seizures associated with Dravet syndrome and LGS, and as adjunctive treatment of seizures associated with tuberous sclerosis complex. Like stiripentol, ganaxolone is a positive allosteric modulator at GABAA receptors. It has recently been licensed in the USA for the treatment of seizures associated with cyclin-dependent kinase-like 5 deficiency disorder. Greater understanding of the causes of DEEs has driven research into the potential use of other novel and repurposed agents. Putative ASMs currently in clinical development for use in DEEs include soticlestat, carisbamate, verapamil, radiprodil, clemizole and lorcaserin.

Fenfluramine: A Review in Dravet and Lennox-Gastaut Syndromes

Fenfluramine (Fintepla®) is an oral anti-seizure medication (ASM) with a novel mechanism of action consisting of activity in the serotonergic system coupled with positive allosteric modulation effects at sigma-1 receptors. Originally approved for use at high doses as an appetite suppressant, it was subsequently withdrawn after being linked to valvular heart disease (VHD) and pulmonary arterial hypertension (PAH), before being investigated for use at low doses as an adjunctive ASM in patients with developmental epileptic encephalopathies, including Dravet syndrome (DS) and Lennox-Gastaut syndrome (LGS) who have pharmacoresistant seizures. In clinical trials, treatment with adjunctive fenfluramine markedly reduced convulsive seizure frequency in patients with DS that were sustained for up to 3 years, and reduced drop seizure frequency in patients with LGS that were sustained for up to 1 year. Notably, fenfluramine was also associated with clinically meaningful improvements in aspects of everyday executive functioning (EF) not entirely explainable by seizure reduction alone. Furthermore, it was generally well tolerated with, importantly, no reports of VHD or PAH. Thus, adjunctive fenfluramine is a novel and effective treatment for pharmacoresistant seizures associated with DS and LGS that may also improve aspects of everyday EF in some patients.

Failure to use new breakthrough treatments for epilepsy

Despite the approval of ~20 additional antiseizure medications (ASMs) since the 1980s, one-third of epilepsy patients experience seizures despite therapy. Drug-resistant epilepsy (DRE) is associated with cognitive and psychiatric comorbidities, socioeconomic impairment, injuries, and a 9.3-13.4 times higher mortality rate than in seizure-free patients. Improved seizure control can reduce morbidity and mortality. Two new ASMs were launched in the United States in 2020: cenobamate for focal epilepsy in adults and fenfluramine for Dravet syndrome (DS). They offer markedly improved efficacy. Cenobamate achieved 21% seizure freedom with the highest dose and decreased tonic-clonic seizures by 93% during maintenance treatment in a randomized clinical trial (RCT). In long-term, open-label studies, 10%-36% of patients were seizure-free for a median duration of ~30-45 months. Fenfluramine treatment in DS reduced convulsive seizure frequency by 56% over placebo at the highest dose, with 8% of patients free of convulsive seizures, and 25% with only one convulsive seizure over 14 weeks. These results were sustained for up to 3 years in open-label extension studies. Mortality was reduced 5-fold. These results are superior to all other approved ASMs, placing these two drugs among the most effective antiseizure therapies. The adverse event profiles resemble those of other ASMs. Despite greater efficacy and similar toxicity, these medications are infrequently used. Two years after US market entry, < 5% of either adults with focal DRE or patients with DS were treated with either cenobamate or fenfluramine. We believe this is a failure of our medical system, resulting from limited knowledge about these drugs stemming partly from the separation of academia from industry; restrictions to access created by health care payors, hospitals, and regulatory agencies; and insufficient post-launch information about the efficacy and safety of these ASMs.

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.

Efficacy and Safety of Fenfluramine in Epilepsy: A Systematic Review and Meta-analysis

INTRODUCTION

Fenfluramine (FFA) is an amphetamine derivative that promotes the release and blocks the neuronal reuptake of serotonin. Initially introduced as an appetite suppressant, FFA also showed antiseizure properties. This systematic review aimed to assess the efficacy and safety of FFA for the treatment of seizures in patients with epilepsy.

METHODS

We systematically searched (in week 3 of June 2022) MEDLINE, the Cochrane Central Register of Controlled Trials, and the US National Institutes of Health Clinical Trials Registry. Randomized, double- or single-blinded, placebo-controlled studies of FFA in patients with epilepsy and uncontrolled seizures were identified. Efficacy outcomes included the proportions of patients with ≥ 50% and 100% reductions in baseline seizure frequency during the treatment period. Tolerability outcomes included the proportions of patients who withdrew from treatment for any reason and suffered adverse events (AEs). The risk of bias in the included studies was assessed according to the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions. The risk ratio (RR) along with the 95% confidence interval (CI) were estimated for each outcome.

RESULTS

Three trials were identified and a total of 469 Dravet syndrome (DS) and Lennox-Gastaut syndrome (LGS) subjects were randomized. All three trials were judged to be at low risk of biases. In patients with DS, the RRs for ≥ 50% and 100% reductions in convulsive seizure frequency for the FFA group compared to placebo were 5.61 (95% CI 2.73-11.54) and 4.71 (95% CI 0.57-39.30), respectively. In patients with LGS, the corresponding RRs for ≥ 50% and 100% reductions in drop seizure frequency were 2.58 (95% CI 1.33-5.02) and 0.50 (95% CI 0.031-7.81), respectively. The drug was withdrawn for any reason in 10.1% and 5.8% of patients receiving FFA and placebo, respectively (RR 1.79, 95% CI 0.89-3.59). Treatment discontinuation due to AEs occurred in 5.4% and 1.2% of FFA- and placebo-treated patients, respectively (RR 3.63, 95% CI 0.93-14.16). Decreased appetite, diarrhoea, fatigue, and weight loss were AEs associated with FFA treatment.

CONCLUSION

Fenfluramine reduces the frequency of seizures in patients with DS and LGS. Decreased appetite, diarrhoea, fatigue, and weight loss are non-cardiovascular AEs associated with FFA.

Fenfluramine provides clinically meaningful reduction in frequency of drop seizures in patients with Lennox-Gastaut syndrome: Interim analysis of an open-label extension study

OBJECTIVE

This study was undertaken to evaluate the long-term safety and effectiveness of fenfluramine in patients with Lennox-Gastaut syndrome (LGS).

METHODS

Eligible patients with LGS who completed a 14-week phase 3 randomized clinical trial enrolled in an open-label extension (OLE; NCT03355209). All patients were initially started on .2 mg/kg/day fenfluramine and after 1 month were titrated by effectiveness and tolerability, which were assessed at 3-month intervals. The protocol-specified treatment duration was 12 months, but COVID-19-related delays resulted in 142 patients completing their final visit after 12 months.

RESULTS

As of October 19, 2020, 247 patients were enrolled in the OLE. Mean age was 14.3 ± 7.6 years (79 [32%] adults) and median fenfluramine treatment duration was 364 days; 88.3% of patients received 2-4 concomitant antiseizure medications. Median percentage change in monthly drop seizure frequency was -28.6% over the entire OLE (n = 241) and -50.5% at Month 15 (n = 142, p < .0001); 75 of 241 patients (31.1%) experienced ≥50% reduction in drop seizure frequency. Median percentage change in nondrop seizure frequency was -45.9% (n = 192, p = .0038). Generalized tonic-clonic seizures (GTCS) and tonic seizures were most responsive to treatment, with median reductions over the entire OLE of 48.8% (p < .0001, n = 106) and 35.8% (p < .0001, n = 186), respectively. A total of 37.6% (95% confidence interval [CI] = 31.4%-44.1%, n = 237) of investigators and 35.2% of caregivers (95% CI = 29.1%-41.8%, n = 230) rated patients as Much Improved/Very Much Improved on the Clinical Global Impression of Improvement scale. The most frequent treatment-emergent adverse events were decreased appetite (16.2%) and fatigue (13.4%). No cases of valvular heart disease (VHD) or pulmonary arterial hypertension (PAH) were observed.

SIGNIFICANCE

Patients with LGS experienced sustained reductions in drop seizure frequency on fenfluramine treatment, with a particularly robust reduction in frequency of GTCS, the key risk factor for sudden unexpected death in epilepsy. Fenfluramine was generally well tolerated; VHD or PAH was not observed long-term. Fenfluramine may provide an important long-term treatment option for LGS.

Dravet Syndrome as an Example of Precision Medicine in Epilepsy

Dravet syndrome (DS) is a drug-resistant, early-onset, developmental and epileptic encephalopathy where there have been many recently approved therapies with many more in development. With the availability of more syndrome specific treatment options coupled with an earlier diagnosis, DS is well-positioned to be an example of how a precise syndromic diagnosis can guide treatment choices and improve overall outcomes and also allow for the development of potential disease modifying therapies to address more than just seizures. In this review we summarize the current state of DS approved therapies and those that are in various stages of development.

Current and promising therapeutic options for Dravet syndrome

INTRODUCTION

Dravet Syndrome (DS) is a developmental and epileptic encephalopathy carrying high-level psychobehavioral burdens. Although the disease has been known for almost 4 decades, and despite significant progress in the understanding of its physiopathology and natural course, the pharmacological treatment leaves patients and caregivers with significant unmet needs. This review provides a summary of the current and promising therapeutic options for DS.

AREAS COVERED

PubMed and ClinicalTrials.gov were screened using 'Dravet Syndrome' OR 'DS,' AND 'pharmacotherapy,' AND 'treatments.' Randomized clinical trials, structured reviews, and meta-analyses were selected for in-human application of well-known anti-seizure medications; while in-vivo experiments on models of DS were selected to evaluate the potential of new therapeutic strategies.

EXPERT OPINION

The search for new pharmacological treatment options is led by the need for care and defeat of the natural course of the disease, an aspect still largely neglected by the available therapeutic strategies. Yet, the last 6 years have led to a climate of increased interest and availability of clinical trials. Particularly, gene therapy could hopefully prevent DS evolution by directly relieving the specific genetic defect, although the possibility of off-target editing, and the uneasy administration route have still largely prevented its use.

Efficacy and safety of adjunctive antiseizure medications for dravet syndrome: A systematic review and network meta-analysis

Purpose: Recently, the U.S. Food and Drug Administration (FDA) approved stiripentol, cannabidiol, and fenfluramine to treat patients with Dravet syndrome (DS). Moreover, soticlestat was determined as a promising new drug for the treatment of DS as it has good efficacy and safety. However, the efficacy and safety of these drugs have not yet been evaluated in "head-to-head" trials. This study aimed to compare and evaluate the efficacy and safety of these adjunctive antiseizure medications in the treatment of DS. Methods: We searched in PubMed, Embase, Cochrane Library, and Web of Science databases for randomized controlled trials (RCTs) and open-label extension (OLE) studies in patients with DS. We performed a random-effect meta-analysis of OLE studies and a network meta-analysis for RCTs to evaluate the efficacy and safety of antiseizure medications in the treatment of DS. Primary efficacy outcomes were defined as a ≥50% reduction in seizure frequency compared with baseline. Furthermore, safety evaluation indicators were defined as the incidence of adverse events (AEs) and serious adverse events (SAEs) during treatment. Relative ranking was assessed using the surface under the cumulative ranking curve (SUCRA) probabilities. Results: Seven RCTs involving four antiseizure medications (stiripentol, cannabidiol, fenfluramine, and soticlestat) and a total of 634 patients were included in the analysis. According to the SUCRA results, all four drugs significantly reduced the frequency of seizures compared with the placebo. Soticlestat was the most likely to reduce seizure frequency by ≥50% compared to the baseline [risk ratio (RR): 19.32; 95% confidence interval (CI): 1.20-311.40], followed by stiripentol and fenfluramine. Stiripentol was ranked highest for the near percentage reduction in the seizure rate from baseline [RR: 12.33; 95% CI: 1.71-89.17] and the occurrence of any treatment-emergent adverse events [RR: 3.73; 95% CI: 1.65-8.43] and serious adverse events [RR: 4.76; 95% CI: 0.61-37.28]. A total of ten OLE studies containing 1,121 patients were included in our study. According to the results of the meta-analysis, the order of probability of reducing seizure frequency by ≥50% was fenfluramine (0.715, 95% CI: 0.621-0.808), stiripentol (0.604, 95% CI: 0.502-0.706), cannabidiol (0.448, 95% CI: 0.403-0.493). And the probability of occurrence of AEs is ranked as fenfluramine(0.832, 95% CI: 0.795-0.869), cannabidiol (0.825, 95% CI:0.701-0.950), stiripentol (0.823, 95% CI: 0.707-0.938), soticlestat (0.688, 95% CI: 0.413-0.890). Conclusion: According to the results of indirect comparison of efficacy and safety, cannabidiol is slightly inferior to the other three antiseizure medications in terms of efficacy and safety. Soticlestat, fenfluramine, and stripentol may have little difference in efficacy, but soticlestat and fenfluramine are safer. Soticlestat is probably the best adjunctive antiseizure medication, followed by fenfluramine. This conclusion is consistent with the comparison of long-term efficacy and safety.

An examination of the efficacy and safety of fenfluramine in adults, children, and adolescents with Dravet syndrome in a real-world practice setting: A report from the Fenfluramine European Early Access Program

OBJECTIVE

To examine the efficacy and safety of fenfluramine in patients with Dravet syndrome (DS) in three age groups: <6, 6-17, and ≥18 years old, treated in a real-world setting.

METHODS

Patients with DS were treated with fenfluramine in the European Union Early Access Program (EAP). Following a 28-day baseline period to establish the pretreatment monthly convulsive seizure frequency (MCSF), fenfluramine was started at a dose chosen by the treating physician and gradually titrated based on efficacy and tolerability up to a maximum of 0.7 mg/kg/day. Seizure incidence was recorded in a written diary, and adverse events (AEs) were reported at each patient visit. Cardiovascular safety was assessed by transthoracic echocardiography before treatment started and at least every 6 months thereafter.

RESULTS

A total of 149 patients have enrolled in the EAP and 63 were <6 years old, 62 were 6-17 years old, and 24 were ≥18 years old. After 3 months of treatment 62%, 53%, and 50% of patients demonstrated ≥75% reduction in MCSF in the <6, 6-17, and ≥18-year-old groups, respectively. This pattern of response was sustained through 12 months of treatment with 55%, 46%, and 80% of the <6, 6-17, and ≥18-year-old groups, respectively, experiencing a ≥75% reduction in MCSF. Most common AEs were loss of appetite (21%) and somnolence (16%). No valvular heart disease or pulmonary artery hypertension was observed.

SIGNIFICANCE

The magnitude, consistency, and durability of the response to add-on fenfluramine is consistent across age groups in patients with Dravet syndrome.

Fenfluramine: A Review of Pharmacology, Clinical Efficacy, and Safety in Epilepsy

Despite the availability of more than 30 antiseizure medications (ASMs), the proportion of patients who remain refractory to ASMs remains static. Refractory seizures are almost universal in patients with epileptic encephalopathies. Since many of these patients are not candidates for curative surgery, there is always a need for newer ASMs with better efficacy and safety profile. Recently, the anti-obesity medication fenfluramine (FFA) has been successfully repurposed, and various regulatory agencies approved it for seizures associated with Dravet and Lennox–Gastaut syndromes. However, there is a limited in-depth critical review of FFA to facilitate its optimal use in a clinical context. This narrative review discusses and summarizes the antiseizure mechanism of action of FFA, clinical pharmacology, and clinical studies related to epilepsy, focusing on efficacy and adverse effects.

Fenfluramine treatment for dravet syndrome: Real-world benefits on quality of life from the caregiver perspective

OBJECTIVE

Prior research has demonstrated durable and profound reductions in seizure frequency and improvements in executive functions in individuals with Dravet syndrome (DS) who are treated with fenfluramine (FFA). This study aimed to understand the benefits of FFA from the perspective of the patients' caregivers.

METHODS

Caregivers for a child with DS participated in semi-structured interviews to discuss the benefits of FFA treatment on the child with DS, the caregiver, and the family.

RESULTS

65 caregivers participated. Patients were between 2 and 33 years old and had been treated with FFA for an average of 22.7 months. The most commonly reported seizure-related benefits (> 50 % of participants) of FFA treatment included a reduction in seizure activity, fewer seizure triggers, and shorter post-ictal recovery. The most common quality of life (QOL) benefits in patients included improvements in cognitive function, alertness, and academic performance. In addition, the caregivers reported improvements in their sleep quality (74 %) and that they felt less overwhelmed (72 %) and stressed (69 %) after their children began FFA treatment. Many caregivers also reported improved relationships between the child with DS and their siblings (52 %).

CONCLUSIONS

The study found that FFA treatment is associated with meaningful improvement in a large number of QOL domains both for the people with DS who received FFA and their families.

The contribution of fenfluramine to the treatment of Dravet syndrome in Spain through Multi-Criteria Decision Analysis

INTRODUCTION

Dravet Syndrome (DS) is a severe, developmental epileptic encephalopathy (DEE) that begins in infancy and is characterized by pharmaco-resistant epilepsy and neurodevelopmental delay. Despite available antiseizure medications (ASMs), there is a need for new therapeutic options with greater efficacy in reducing seizure frequency and with adequate safety and tolerability profiles. Fenfluramine is a new ASM for the treatment of seizures associated with DS as add-on therapy to other ASMs for patients aged 2 years and older. Fenfluramine decreases seizure frequency, prolongs periods of seizure freedom potentially helping to reduce risk of Sudden Unexpected Death in Epilepsy (SUDEP) and improves patient cognitive abilities positively impacting on patients' Quality of Life (QoL). Reflective Multi-Criteria Decision Analysis (MCDA) methodology allows to determine what represents value in a given indication considering all relevant criteria for healthcare decision-making in a transparent and systematic manner from the perspective of relevant stakeholders. The aim of this study was to determine the relative value contribution of fenfluramine for the treatment of DS in Spain using MCDA.

METHOD

A literature review was performed to populate an adapted a MCDA framework for orphan-drug evaluation in Spain. A panel of ten Spanish experts, including neurologists, hospital pharmacists, patient representatives and decision-makers, scored four comparative evidence matrices. Results were analyzed and discussed in a group meeting through reflective MCDA discussion methodology.

RESULTS

Dravet syndrome is considered a severe, rare disease with significant unmet needs. Fenfluramine is perceived to have a higher efficacy profile than all available alternatives, with a better safety profile than stiripentol and topiramate and to provide improved QoL versus studied alternatives. Fenfluramine results in lower other medical costs in comparison with stiripentol and clobazam. Participants perceived that fenfluramine could lead to indirect costs savings compared to available alternatives due to its efficacy in controlling seizures. Overall, fenfluramine's therapeutic impact on patients with DS is considered high and supported by high-quality evidence.

CONCLUSIONS

Based on reflective MCDA, fenfluramine is considered to add greater benefit in terms of efficacy, safety and QoL when compared with available ASMs.

Impact of Genetic Testing on Therapeutic Decision-Making in Childhood-Onset Epilepsies-a Study in a Tertiary Epilepsy Center

We assessed the frequency of pediatric monogenic epilepsies and precision therapies at a tertiary epilepsy center. We analyzed medical records of children, born in 2006-2011 and followed at the Danish Epilepsy Center from January to December 2015; 357 patients were identified, of whom 27 without epilepsy and 35 with acquired brain damage were excluded. Of the remaining 295 children, 188 were consented for study inclusion and genetic testing. At inclusion, 86/188 had a preexisting genetic diagnosis and did not undergo further genetic testing. The 102 genetically unsolved patients underwent WES, which identified a (likely) pathogenic variant in eight patients and a highly relevant variant of unknown significance (VUS) in seven additional patients. Single nucleotide polymorphism array was performed in the remaining 87 patients and revealed no (likely) pathogenic copy number variants (CNVs). Patients with a genetic diagnosis had a significantly lower median age at seizure onset and more often had febrile seizures, status epilepticus, or neurodevelopmental impairment compared to those who remained genetically unsolved. Most common epilepsies were focal or multifocal epilepsies and developmental and epileptic encephalopathies (DDEs). Fifty-three patients, with a putative genetic diagnosis, were potentially eligible for precision therapy approaches. Indeed, genetic diagnosis enabled treatment adjustment in 32/53 (60%); 30/32 (93%) patients experienced at least a 50% reduction in seizure burden while only 4/32 (12.5%) became seizure-free. In summary, a genetic diagnosis was achieved in approximately 50% of patients with non-acquired epilepsy enabling precision therapy approaches in half of the patients, a strategy that results in > 50% reduction in seizure burden, in the majority of the treated patients.

CDKL5 deficiency disorder: clinical features, diagnosis, and management

CDKL5 deficiency disorder (CDD) was first identified as a cause of human disease in 2004. Although initially considered a variant of Rett syndrome, CDD is now recognised as an independent disorder and classified as a developmental epileptic encephalopathy. It is characterised by early-onset (generally within the first 2 months of life) seizures that are usually refractory to polypharmacy. Development is severely impaired in patients with CDD, with only a quarter of girls and a smaller proportion of boys achieving independent walking; however, there is clinical variability, which is probably genetically determined. Gastrointestinal, sleep, and musculoskeletal problems are common in CDD, as in other developmental epileptic encephalopathies, but the prevalence of cerebral visual impairment appears higher in CDD. Clinicians diagnosing infants with CDD need to be familiar with the complexities of this disorder to provide appropriate counselling to the patients' families. Despite some benefit from ketogenic diets and vagal nerve stimulation, there has been little evidence that conventional antiseizure medications or their combinations are helpful in CDD, but further treatment trials are finally underway.

Improving Therapy of Pharmacoresistant Epilepsies: The Role of Fenfluramine

Epilepsy is among the most common neurological chronic disorders, with a prevalence of 0.5-1%. Despite the introduction of new antiepileptic drugs during recent years, about one third of the epileptic population remain drug-resistant. Hence, especially in the pediatric population limited by different pharmacokinetics and pharmacodynamics and by ethical and regulatory issues it is needed to identify new therapeutic resources. New molecules initially used with other therapeutic indications, such as fenfluramine, are being considered for the treatment of pharmacoresistant epilepsies, including Dravet Syndrome (DS) and Lennox-Gastaut Syndrome (LGS). Drug-refractory seizures are a hallmark of both these conditions and their treatment remains a major challenge. Fenfluramine is an amphetamine derivative that was previously approved as a weight loss drug and later withdrawn when major cardiac adverse events were reported. However, a new role of fenfluramine has emerged in recent years. Indeed, fenfluramine has proved to be a promising antiepileptic drug with a favorable risk-benefit profile for the treatment of DS, LGS and possibly other drug-resistant epileptic syndromes. The mechanism by which fenfluramine provide an antiepileptic action is not fully understood but it seems to go beyond its pro-serotoninergic activity. This review aims to provide a comprehensive analysis of the literature, including ongoing trials, regarding the efficacy and safety of fenfluramine as adjunctive treatment of pharmacoresistant epilepsies.

Up to What Extent Does Dravet Syndrome Benefit From Neurostimulation Techniques?

Background

Dravet syndrome (DS) is a refractory developmental and epileptic encephalopathy (EE) with a variety of comorbidities, including cognitive impairment, autism-like behavior, speech dysfunction, and ataxia, which can seriously affect the quality of life of patients and impose a great burden on society and their families. Currently, the pharmacological therapy is patient dependent and may work or not. Neuromodulation techniques, including vagus nerve stimulation (VNS), deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), responsive neurostimulation (RNS), and chronic subthreshold cortical stimulation (CSCS), have become common adjuvant therapies for neurological diseases, but their efficacy in the treatment of DS is unknown.

Methods

We searched Web of Science, PubMed, and SpringerLink for all published cases related to the neuromodulation techniques of DS until January 15, 2022. The systematic review was supplemented with relevant articles from the references. The results reported by each study were summarized narratively.

Results

The Web of science, PubMed and SpringerLink search yielded 258 items. A total of 16 studies published between 2016 and 2021 met the final inclusion criteria. Overall, 16 articles (109 cases) were included in this study, among which fifteen (107 patients) were involved VNS, and one (2 patients) was involved DBS. After VNS implantation, seizures were reduced to ≥50% in 60 cases (56%), seizure free were found in 8 cases (7.5%). Only two DS patients received DBS treatment, and the initial outcomes of DBS implantation were unsatisfactory. The seizures significantly improved over time for both DBS patients after the addition of antiepileptic drugs.

Conclusion

More than half of the DS patients benefited from VNS, and VNS may be effective in the treatment of DS. However, it is important to note that VNS does not guarantee improvement of seizures, and there is a risk of infection and subsequent device failure. Although DBS is a safe and effective strategy for the treatment of refractory epilepsy, the role of DBS in DS needs further study, as the sample size was small. Thus far, there is no strong evidence for the role of DBS in DS.

A review of fenfluramine for the treatment of Dravet syndrome patients

Introduction

Dravet Syndrome (DS) is a rare epileptiform disorder typically presenting within the first year of life of a normally developing infant. It is characterized by several prolonged seizures that are often resistant to current anti-epileptic drug (AED) regimens. This paper outlines the history and clinical trials of the drug fenfluramine, a drug that when used in addition to AED regimens may provide hope to children affected by DS.

Body

Fenfluramine (3-trifulormethyl-N-ethylamphetamine) is an amphetamine derivative that primarily affects serotonin neurotransmitter levels. It was initially prescribed in the 1960s as an appetite suppressant marketed as a weight loss drug. However, it was removed from the markets due to its association with cardiac valvopathies. It continued to by studied in epilepsy by Gastaut in the 1980s in children with self-induced syncope and irretractable epilepsy. In 2012, Ceulemans et al. studied the use of fenfluramine in patients with DS. Following the success of that retrospective case study, Nabbout et al. and Legae et al. conducted two randomized control trials leading to the FDA approval of fenfluramine under its trade name Fintepla in 2020.

Discussion

The success of the randomized control trials suggests the addition of fenfluramine to current AED regimens may lead to better control of seizures in patients with DS. The side effects of fenfluramine prove to be manageable and the concern for valvopathies has not been reproducible with low dose fenfluramine.

New Trends and Most Promising Therapeutic Strategies for Epilepsy Treatment

Background: Despite the wide availability of novel anti-seizure medications (ASMs), 30% of patients with epilepsy retain persistent seizures with a significant burden in comorbidity and an increased risk of premature death. This review aims to discuss the therapeutic strategies, both pharmacological and non-, which are currently in the pipeline.

Methods: PubMed, Scopus, and EMBASE databases were screened for experimental and clinical studies, meta-analysis, and structured reviews published between January 2018 and September 2021. The terms “epilepsy,” “treatment” or “therapy,” and “novel” were used to filter the results.

Conclusions: The common feature linking all the novel therapeutic approaches is the spasmodic rush toward precision medicine, aiming at holistically evaluating patients, and treating them accordingly as a whole. Toward this goal, different forms of intervention may be embraced, starting from the choice of the most suitable drug according to the type of epilepsy of an individual or expected adverse effects, to the outstanding field of gene therapy. Moreover, innovative insights come from in-vitro and in-vivo studies on the role of inflammation and stem cells in the brain. Further studies on both efficacy and safety are needed, with the challenge to mature evidence into reliable assets, ameliorating the symptoms of patients, and answering the challenges of this disease.

Impact of fenfluramine on the expected SUDEP mortality rates in patients with Dravet syndrome

PURPOSE

To assess the impact of fenfluramine (FFA) on the expected mortality incidence, including sudden unexpected death in epilepsy (SUDEP), in persons with Dravet syndrome (DS).

METHODS

In this pooled analysis, total time of exposure for persons with DS who were treated with FFA in phase 3 clinical trials, in United States and European Early Access Programs, and in two long-term open-label observational studies in Belgium was calculated. Literature was searched for reports of SUDEP mortality in DS, which were utilized as a comparison. Mortality rates were expressed per 1000 person-years.

RESULTS

A total of 732 persons with DS were treated with FFA, representing a total of 1185.3 person-years of exposure. Three deaths occurred, all in the phase 3 program: one during placebo treatment (probable SUDEP) and two during treatment with FFA (one probable SUDEP and one definite SUDEP). The all-cause and SUDEP mortality rates during treatment with FFA was 1.7 per 1000 person-years (95% CI, 0.4 to 6.7), a value lower than the all-cause estimate of 15.8 per 1000 person-years (95% CI, 9.9 to 25.4) and SUDEP estimate of 9.3 (95% CI, 5.0 to 17.3) reported by Cooper et al. (Epilepsy Res 2016;128:43-7) for persons with DS receiving standard-of-care.

CONCLUSION

All-cause and SUDEP mortality rates in DS patients treated with FFA were substantially lower than in literature reports. Further studies are warranted to confirm that FFA reduces SUDEP risk in DS patients and to better understand the potential mechanism(s) by which FFA lowers SUDEP risk.

CLINICAL TRIAL REGISTRATION

NCT02926898, NCT02682927, NCT02826863, NCT02823145, NCT03780127.

Treatment with fenfluramine in patients with Dravet syndrome has no long-term effects on weight and growth

OBJECTIVE

Appetite disturbance and growth abnormalities are commonly reported in children with Dravet syndrome (DS). Fenfluramine (Fintepla) has demonstrated profound reduction in convulsive seizure frequency in DS and was recently approved for use in DS in the US and EU. Prior to its use in epilepsy, fenfluramine was approved to suppress appetite in obese adults. Here, we evaluated the impact of fenfluramine on weight and growth in patients with DS treated for ≥12 months or ≥24 months and compared the results with growth curves in normative reference populations and published historical controls among patients with DS.

METHODS

Historical control data from a recent study of 68 patients with DS show decreases in height and weight Z-scores of ∼0.1 standard deviation (SD) for every 12-month increase in age (Eschbach K. Seizure. 2017;52:117-22). Anthropometric data for fenfluramine were extracted from an open-label extension (OLE) study of eligible patients with DS (2-18 y/o; fenfluramine dose: 0.2-0.7 mg/kg/day). Z-score analyses were based on the Boston Children's Hospital algorithm and assessed potential impact of fenfluramine on growth at OLE baseline, at Month 12, and at Month 24. A mixed-effect model for repeated measures (MMRM) estimated changes in height and weight over time. Height and weight Z-scores were also analyzed by dose group (0.2-<0.3 mg/kg/day, 0.3-<0.5 mg/kg/day, and 0.5-0.7 mg/kg/day), averaged over time.

RESULTS

At the time of analysis, 279 patients were treated with fenfluramine for ≥12 months; 128 were treated for ≥24 months. Relative to the reference population with DS, fenfluramine treatment for ≥12 months or for ≥24 months had minimal impact on height or weight over time as assessed by Z-score analyses. No substantial dose-dependent changes from baseline were observed at Month 12 nor at Month 24. MMRM showed that patients treated with fenfluramine for ≥12 months (N = 262) had an estimated change in Z-score per year of -0.056 for height and -0.166 for weight. For patients with data from all three time points (baseline, 12 months, and 24 months; N = 110), estimated changes in Z-scores per year were -0.025 for height and -0.188 for weight. MMRM projections based on normative reference growth curves were comparable to growth data from historical control populations with DS.

SIGNIFICANCE/CONCLUSION

Long-term treatment with fenfluramine had minimal impact on the growth of patients with DS as demonstrated by differences in Z-scores for height and weight at 12 months and at 24 months. Changes in Z-scores for height and weight were consistent with published reports on patients with DS.

Efficacy, tolerability, and retention of fenfluramine for the treatment of seizures in patients with Dravet syndrome: Compassionate use program in Germany

OBJECTIVE

Dravet syndrome (DS) is a rare but severe drug-resistant epilepsy. Before the approval of fenfluramine (FFA) for the treatment of seizures in DS, patients in Germany could receive treatment under a compassionate use program (CUP).

METHODS

We conducted a multicenter, retrospective, observational study to describe the efficacy, tolerability, and retention of FFA within the CUP. Patients received add-on therapy with oral FFA gradually titrated to a target dose between .13 and .7 mg/kg/day.

RESULTS

Overall, 78 patients with DS (median age = 8.0 years, range = 2.1-46.0; 53% female, median concomitant antiseizure medications [ASMs] = 3) were treated with FFA for a median duration of 255.5 days (range = 31-572). Responder rates (a ≥50% reduction; n = 78) and seizure-freedom rates at 3 months were 68% and 14% for total seizures, respectively, and 67% and 23% for generalized tonic-clonic seizures. Responder rates were consistent at 6 and 12 months (n = 66 and n = 43, respectively). Median seizure days per month significantly decreased from 10.0 (range = .5-30) to 3.0 (range = 0-30) in the 3-month period before and after FFA treatment (p < .001). Significantly fewer patients reported at least one episode of status epilepticus (28% vs. 14% patients before and after FFA initiation, p = .005). During FFA treatment, 35 (45%) patients were able to discontinue a concomitant ASM. At the last follow-up date, 66 (85%) patients remained on treatment with FFA. The most common adverse events were somnolence (36%), decreased appetite (22%), and ataxia (8%). Forty-eight (62%) patients were reported as having a meaningful global clinical improvement.

SIGNIFICANCE

In a large cohort of patients, FFA demonstrated efficacy across a range of outcomes including clinically significant reductions in convulsive seizures, and was well tolerated, providing valuable information for real-world practice.

An Emerging Role for Sigma-1 Receptors in the Treatment of Developmental and Epileptic Encephalopathies

Developmental and epileptic encephalopathies (DEEs) are complex conditions characterized primarily by seizures associated with neurodevelopmental and motor deficits. Recent evidence supports sigma-1 receptor modulation in both neuroprotection and antiseizure activity, suggesting that sigma-1 receptors may play a role in the pathogenesis of DEEs, and that targeting this receptor has the potential to positively impact both seizures and non-seizure outcomes in these disorders. Recent studies have demonstrated that the antiseizure medication fenfluramine, a serotonin-releasing drug that also acts as a positive modulator of sigma-1 receptors, reduces seizures and improves everyday executive functions (behavior, emotions, cognition) in patients with Dravet syndrome and Lennox-Gastaut syndrome. Here, we review the evidence for sigma-1 activity in reducing seizure frequency and promoting neuroprotection in the context of DEE pathophysiology and clinical presentation, using fenfluramine as a case example. Challenges and opportunities for future research include developing appropriate models for evaluating sigma-1 receptors in these syndromic epileptic conditions with multisystem involvement and complex clinical presentation.

Natural History Studies and Clinical Trial Readiness for Genetic Developmental and Epileptic Encephalopathies

The developmental and epileptic encephalopathies (DEEs) are the most severe group of epilepsies. They usually begin in infancy or childhood with drug-resistant seizures, epileptiform EEG patterns, developmental slowing or regression, and cognitive impairment. DEEs have a high mortality and profound morbidity; comorbidities are common including autism spectrum disorders. With advances in genetic sequencing, over 400 genes have been implicated in DEEs, with a genetic cause now identified in over 50% patients. Each genetic DEE typically has a broad genotypic-phenotypic spectrum, based on the underlying pathophysiology. There is a pressing need to improve health outcomes by developing novel targeted therapies for specific genetic DEE phenotypes that not only improve seizure control, but also developmental outcomes and comorbidities. Clinical trial readiness relies firstly on a deep understanding of phenotype-genotype correlation and evolution of a condition over time, in order to select appropriate patients for clinical trials. Understanding the natural history of the disorder informs assessment of treatment efficacy in terms of both clinical outcome and biomarker utility. Natural history studies (NHS) provide a high quality, integrated, comprehensive approach to understanding a complex disease and underpin clinical trial design for novel therapies. NHS are pre-planned observational studies designed to track the course of a disease and identify demographic, genetic, environmental, and other variables, including biomarkers, that correlate with the disease's evolution and outcomes. Due to the rarity of individual genetic DEEs, appropriately funded high-quality DEE NHS will be required, with sustainable frameworks and equitable access to affected individuals globally.

Comparative short-term efficacy and safety of add-on anti-seizure medications in Dravet syndrome: An indirect treatment comparison

PURPOSE

Although cannabidiol and fenfluramine have been recently approved by the US Food and Drug Administration (FDA) for seizures in children with Dravet syndrome (DS), the comparative efficacy and safety of these and stiripentol as an add-on therapy for DS has not been evaluated in head-to-head trials. The current study aimed to assess the comparative efficacy and safety of add-on anti-seizure medications in DS.

METHODS

PubMed and EMBASE database search and a manual search was done using keywords; "antiepileptic", "Dravet syndrome" and "antiseizure". The primary efficacy outcome was ≥50% reduction in convulsive seizure frequency from baseline while the safety outcome was treatment-emergent adverse events (TEAEs). Frequentist approach were used for combining direct and indirect evidence and network plots prepared. The drugs were ranked based on p-scores obtained using the surface under the cumulative ranking (SUCRA). Heterogeneity across studies was calculated by I² statistic and Q test.

RESULTS

Five randomized controlled trials (RCTs) with 565 patients with DS (2-20 years) who received placebo or any of the three active interventions (stiripentol, cannabidiol, and fenfluramine) were included. Compared with placebo, all the three drugs were associated with a significant reduction in convulsive seizure frequency from baseline. Stiripentol had the highest probability ranking for ≥50% reduction in convulsive seizure frequency from baseline [OR: 20.2; 95% CI: 2.1-198.0] and for occurrence of any treatment emergent adverse events (TEAEs) [OR:53.9; 95% CI: 1.4 to 2079.8] followed by fenfluramine and cannabidiol. However, for serious TEAEs, the ranking order was stiripentol followed by cannabidiol and fenfluramine. The trial on stiripentol had limited sample size explaining the wide confidence intervals for the comparative outcomes.

CONCLUSION

In this indirect comparison, fenfluramine and stiripentol hadd comparable efficacy but fenfluramine appeareded to be safer in terms of less frequent serious TEAEs. Cannabidiol had relatively lower efficacy and was associated with serious TEAEs. A head-to-head trial between stiripentol, cannabidiol and fenfluramine is the need of the hour.

Fenfluramine in the successful treatment of super-refractory status epilepticus in a patient with Dravet syndrome

•

Dravet syndrome (DS) patient in super-refractory status epilepticus (SRSE) for 5 weeks.

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Add-on fenfluramine (FFA) successfully treated SRSE in DS.

•

Most effective dose of FFA was 0.7 mg/kg/day.

•

Long-term FFA provided >90% reduction in seizures and prevented status epilepticus.

•

FFA maintenance also resulted in improvement of neurocognitive function.

A 20-year-old woman with Dravet syndrome and multiple prior episodes of status epilepticus presented to our hospital in November 2018 in super-refractory status epilepticus. After 5 weeks of unsuccessful continuous treatment with anesthetics, including pentobarbital and ketamine, we sought and were granted an emergency approval by the United States Food and Drug Administration to administer fenfluramine, an investigational new drug, to this patient. One week of treatment with fenfluramine at 0.4 mg/kg/day was ineffective. The dose of fenfluramine was titrated to 0.7 mg/kg/day, and after 1 week, electrographic seizures ceased. One week later, the patient was seizure-free and off all anesthetic agents. Add-on treatment with fenfluramine was continued with no further episodes of status epilepticus and >90% reduction in tonic-clonic seizures. This case report illustrates the potential for fenfluramine to prevent reoccurrence of status epilepticus and to manage super-refractory status epilepticus in patients with Dravet syndrome.

Effect of fenfluramine on convulsive seizures in CDKL5 deficiency disorder

CDKL5 deficiency disorder (CDD) is an X-linked pharmacoresistant neurogenetic disorder characterized by global developmental delays and uncontrolled seizures. Fenfluramine (FFA), an antiseizure medication (ASM) indicated for treating convulsive seizures in Dravet syndrome, was assessed in six patients (five female; 83%) with CDD whose seizures had failed 5-12 ASMs or therapies. Median age at enrollment was 6.5 years (range: 2-26 years). Mean FFA treatment duration was 5.3 months (range: 2-9 months) at 0.4 mg/kg/day (n = 2) or 0.7 mg/kg/day (n = 4; maximum: 26 mg/day). One patient had valproate added for myoclonic seizures. The ASM regimens of all other patients were stable. Among five patients with tonic-clonic seizures, FFA treatment resulted in a median 90% reduction in frequency (range: 86%-100%). Tonic seizure frequency was reduced by 50%-60% in two patients with this seizure type. One patient experienced fewer myoclonic seizures; one patient first developed myoclonic seizures on FFA, which were controlled with valproate. Adverse events were reported in two patients. The patient with added valproate experienced lethargy; one patient had decreased appetite and flatus. No patient developed valvular heart disease or pulmonary arterial hypertension. Our preliminary results suggest that FFA may be a promising ASM for CDD. Randomized clinical trials are warranted.

Fenfluramine repurposing from weight loss to epilepsy: What we do and do not know

In 2020, racemic-fenfluramine was approved in the U.S. and Europe for the treatment of seizures associated with Dravet syndrome, through a restricted/controlled access program aimed at minimizing safety risks. Fenfluramine had been used extensively in the past as an appetite suppressant, but it was withdrawn from the market in 1997 when it was found to cause cardiac valvulopathy. Available evidence indicates that appetite suppression and cardiac valvulopathy are mediated by different serotonergic mechanisms. In particular, appetite suppression can be ascribed mainly to the enantiomers d-fenfluramine and d-norfenfluramine, the primary metabolite of d-fenfluramine, whereas cardiac valvulopathy can be ascribed mainly to d-norfenfluramine. Because of early observations of markedly improved seizure control in some forms of epilepsy, fenfluramine remained available in Belgium through a Royal Decree after 1997 for use in a clinical trial in patients with Dravet syndrome at average dosages lower than those generally prescribed for appetite suppression. More recently, double-blind placebo-controlled trials established its efficacy in the treatment of convulsive seizures associated with Dravet syndrome and of drop seizures associated with Lennox-Gastaut syndrome, at doses up to 0.7 mg/kg/day (maximum 26 mg/day). Although no cardiovascular toxicity has been associated with the use of fenfluramine in epilepsy, the number of patients exposed to date has been limited and only few patients had duration of exposure longer than 3 years. This article analyzes available evidence on the mechanisms involved in fenfluramine-induced appetite suppression, antiseizure effects and cardiovascular toxicity. Despite evidence that stimulation of 5-HT_2B receptors (the main mechanism leading to cardiac valvulopathy) is not required for antiseizure activity, there are many critical gaps in understanding fenfluramine's properties which are relevant to its use in epilepsy. Particular emphasis is placed on the remarkable lack of publicly accessible information about the comparative activity of the individual enantiomers of fenfluramine and norfenfluramine in experimental models of seizures and epilepsy, and on receptors systems considered to be involved in antiseizure effects. Preliminary data suggest that l-fenfluramine retains prominent antiseizure effects in a genetic zebrafish model of Dravet syndrome. If these findings are confirmed and extended to other seizure/epilepsy models, there would be an incentive for a chiral switch from racemic-fenfluramine to l-fenfluramine, which could minimize the risk of cardiovascular toxicity and reduce the incidence of adverse effects such as loss of appetite and weight loss.

Fenfluramine responder analyses and numbers needed to treat: Translating epilepsy trial data into clinical practice

OBJECTIVE

Clinical trials typically report antiepileptic drug efficacy by evaluating reduction in monthly convulsive seizure frequency (MCSF) through group response (active versus placebo). Although useful for regulatory purposes, population statistics do not easily translate into clinical practice, where treatment decisions are made on an individual-patient basis. Responder analyses help bridge this gap by showing proportions of patients who achieved various MCSF improvement levels. Deriving numbers needed to treat (NNTs) to achieve clinically desirable response levels can further inform individual decision-making. We calculated the NNT with fenfluramine to achieve "clinically meaningful" (≥50%) or "profound" (≥75%) MCSF reductions in patients with Dravet syndrome (DS).

METHODS

NNT to achieve ≥50% or ≥75% MCSF reduction was assessed using longitudinal data from two phase 3 studies for adjunctive fenfluramine in DS patients aged 2-18 years. NNT was calculated: 1/((Experimental-Responder Rate)-(Control-Responder Rate)).

RESULTS

In Study 1, NNTs to achieve ≥50% and ≥75% MCSF reduction were 1.8 and 2.1 at 0.7 mg/kg/day fenfluramine. In Study 2, these NNTs were 2.0 and 3.1, respectively. These results were seen as early as Weeks 6-7 and were sustained through Weeks 14-15.

INTERPRETATION

For every two to three patients with DS treated with fenfluramine in these trials, one patient achieved ≥50% or ≥75% MCSF reduction, respectively, compared with placebo (large treatment effect size; Cohen's d≈0.8). Responder analyses and NNTs can aid in clinical decision-making by offering clinically important information that is complementary to the population mean data on the chance of an individual patient achieving meaningful levels of MCSF improvement. (NCT02682927/NCT02826863, NCT02926898).

The role of new medical treatments for the management of developmental and epileptic encephalopathies: Novel concepts and results

Developmental and epileptic encephalopathies (DEEs) are among the most challenging of all epilepsies to manage, given the exceedingly frequent and often severe seizure types, pharmacoresistance to conventional antiseizure medications, and numerous comorbidities. During the past decade, efforts have focused on development of new treatment options for DEEs, with several recently approved in the United States or Europe, including cannabidiol as an orphan drug in Dravet and Lennox-Gastaut syndromes and everolimus as a possible antiepileptogenic and precision drug for tuberous sclerosis complex, with its impact on the mammalian target of rapamycin pathway. Furthermore, fenfluramine, an old drug, was repurposed as a novel therapy in the treatment of Dravet syndrome. The evolution of new insights into pathophysiological processes of various DEEs provides possibilities to investigate novel and repurposed drugs and to place them into the context of their role in future management of these patients. The purpose of this review is to provide an overview of these new medical treatment options for the DEEs and to discuss the clinical implications of these results for improved treatment.

A critical evaluation of fenfluramine hydrochloride for the treatment of Dravet syndrome

Introduction: Dravet Syndrome (DS) is a severe developmental and epileptic encephalopathy. Fenfluramine recently demonstrated to be a highly efficacious and safe treatment option for DS patients. Fenfluramine has been recently approved by the FDA and EMA and is marketed as Fintepla®.Areas covered: DS and the need for additional anticonvulsive treatment options is discussed. The results of three placebo-controlled phase III studies (1 with and 2 without stiripentol) and 2 open label (extension) studies are reviewed. All studies demonstrate a consistent and impressive seizure reduction, confirming the results of two smaller investigator-initiated trials. The mechanism of action of fenfluramine is discussed. Finally, the place of fenfluramine in the future treatment of DS is outlined.Expert opinion: Fenfluramine has a potent anticonvulsive effect in DS. Although not yet fully elucidated, the anticonvulsive mechanism of fenfluramine seems to be mainly serotonergic. Fenfluramine is generally well tolerated. A dose reduction is necessary in combination with stiripentol. Considering new competitors, efficacy seems lower for cannabidiol and is comparable with stiripentol. Preclinical studies indicate a disease specific action and possible disease modification in DS. The latter would support the use of fenfluramine above its anticonvulsive effect and needs to be further elaborated.

A systematic review of adults with Dravet syndrome

Dravet Syndrome (DS) is a rare and severe infantile-onset epileptic encephalopathy. DS research focuses mainly on children. We did a systematic review, completed on January 18^th, 2021, examining the number of clinical DS studies. We show that there are 208 studies on children exclusively, 28 studies on adults exclusively, and 116 studies involving adults and children combined. This 7:1 ratio of children to adult studies exclusively shows the dearth of research that addresses long-term natural history of DS into adulthood. Through this systematic review, we examine the most up-to-date information in DS adults as it pertains to seizures, electroencephalogram, imaging, treatment, motor abnormalities, cognitive and social behavior outcomes, cardiac abnormalities, sleep disturbances, diagnosis in adults, and mortality. Overall, the frequency of seizures increases in the first decade of life and then myoclonic, atypical absences and focal seizures with impaired awareness tend to decrease in frequency or even disappear in adulthood. Adults tend to have a notable reduction in status epilepticus, especially after 30 years of age. Parkinsonian features were seen in patients as young as 19 years old and are more severe in older patients, suggesting a progression of the parkinsonian symptoms. In adulthood, patients continue to present with behavior problems, associated with a lower health-related quality of life. The leading reported cause of death in DS adults is Sudden Unexpected Death in Epilepsy (SUDEP). Further studies in older adults are needed to understand the long-term outcomes of patients with DS.

Advances in the design and discovery of novel small molecule drugs for the treatment of Dravet Syndrome

Introduction: Dravet syndrome (severe myoclonic epilepsy in infancy) begins in the first year of life characterized by generalized or unilateral clonic seizures that are frequently triggered by high fever. A subsequent worsening stage occurs (in years 1-4 of life) and seizure activity is accompanied by disturbed psychomotor development. The third stage of the disease, known as the 'stabilization phase,' is associated with seizures and intellectual impairment. Of note, a mutation in the voltage-gated sodium-channel gene α 1 subunit (SCN1A) has been found in around 85% of patients with Dravet syndrome.Areas covered: The authors review the current treatment strategies as well as potential drugs in the initial stages of clinical evaluation. The authors also review drugs with protective activity in mice models of Dravet syndrome.Expert opinion: Experimental data and results from initial clinical studies have brought attention to several drugs with various mechanisms of action including: ataluren (a suppressant of premature stop codons; under clinical evaluation), EPX-100, EPX-200, fenfluramine (serotonin modulators), soticlestat (an 24-hydroxylase cholesterol enzyme inhibitor), SPN-817 (an inhibitor of acetylcholinesterase), verapamil (a voltage-dependent calcium channel inhibitor) and STK-001 (an antisense oligonucleotide). The latter is scheduled for clinical evaluation.

Fenfluramine HCl (Fintepla® ) provides long-term clinically meaningful reduction in seizure frequency: Analysis of an ongoing open-label extension study

OBJECTIVE

Fenfluramine has been shown to provide clinically meaningful and statistically significant reductions in convulsive seizure frequency in children and adolescents (aged 2-18 years) with Dravet syndrome in two randomized, placebo-controlled clinical trials. The objective of this analysis was to assess longer-term safety and efficacy of fenfluramine in patients who completed one of the double-blind studies and entered an open-label extension (OLE) study.

METHODS

Patients enrolling in the OLE study initiated fenfluramine at 0.2 mg/kg/d regardless of their treatment assignment in the double-blind study. After 4 weeks, the fenfluramine dose could be titrated based on efficacy and tolerability to maximum of 0.7 mg/kg/d (absolute maximum 27 mg/d) or maximum of 0.4 mg/kg/d (absolute maximum 17 mg/d) in patients receiving concomitant stiripentol. The number and type of seizures were recorded daily in an electronic diary, and safety, including echocardiography, was assessed at Months 1, 2, and 3, and at 3-month intervals thereafter.

RESULTS

A total of 232 patients were enrolled as of March 13, 2018. During this analysis period, patients were treated for a median 256 days (range = 46-634 days). Over the entire OLE analysis period, the median decrease in convulsive seizure frequency compared to baseline in the double-blind studies was -66.8% (range = -100% to 234.9%; P < .001). The median reduction in seizure frequency was similar in patients <6 (-75.7%) and ≥6 years old (-64.7%). The most commonly reported adverse events included pyrexia (21.6%), nasopharyngitis (19.4%), and decreased appetite (-15.9%). No valvular heart disease (VHD) or pulmonary arterial hypertension (PAH) was observed.

SIGNIFICANCE

Study results demonstrate that fenfluramine provides clinically meaningful (≥50%) seizure frequency reduction over an extended period in patients with Dravet syndrome. No patient developed VHD or PAH, and fenfluramine was generally well tolerated.