Innovative LC-MS/MS method for therapeutic drug monitoring of fenfluramine and cannabidiol in the plasma of pediatric patients with epilepsy

We present a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantifying fenfluramine (FFA), its active metabolite norfenfluramine (norFFA), and Epidyolex®, a pure cannabidiol (CBD) oral solution in plasma. Recently approved by the EMA for the adjunctive treatment of refractory seizures in patients with Dravet and Lennox-Gastaut syndromes aged above 2 years, FFA and CBD still do not have established therapeutic blood ranges, and thus need careful drug monitoring to manage potential pharmacokinetic and pharmacodynamic interactions. Our method, validated by ICH guidelines M10, utilizes a rapid extraction protocol from 100 µL of human plasma and a reversed-phase C-18 HPLC column, with deuterated internal standards. The Thermofisher Quantiva triple-quadrupole MS coupled with an Ultimate 3000 UHPLC allowed multiple reaction monitoring detection, ensuring precise analyte quantification. The assay exhibited linear responses across a broad spectrum of concentrations: ranging from 1.64 to 1000 ng/mL for both FFA and CBD, and from 0.82 to 500 ng/mL for norFFA. The method proves accurate and reproducible, free from matrix effect. Additionally, FFA stability in plasma at 4 °C and -20 °C for up to 7 days bolsters its clinical applicability. Plasma concentrations detected in patients samples, expressed as mean ± standard deviation, were 0.36 ± 0.09 ng/mL for FFA, 19.67 ± 1.22 ng/mL for norFFA. This method stands as a robust tool for therapeutic drug monitoring (TDM) of FFA and CBD, offering significant utility in assessing drug-drug interactions in co-treated patients, thus contributing to optimized patient care in complex therapeutic scenarios.

Efficacy of pharmacological treatments for Dravet syndrome: Systematic review and network meta-analysis

BACKGROUND

Numerous anti-seizure medications (ASMs) have been developed to treat Dravet syndrome (DS). This network meta-analysis aimed to comprehensively analyse the efficacy of ASMs in DS patients, especially in non-seizure-free patients after treatment.

METHODS

PubMed, EMBASE, Cochrane Library, and Chinese National Knowledge Infrastructure databases were searched. The treatment efficacy was assessed by the percentage reduction in monthly convulsive seizure frequency (MCSF) from baseline or individuals who achieved at least a 50 % or 75 % reduction from baseline in convulsive seizure frequency (CSF).

RESULTS

Six randomised controlled trials with 633 participants and seven regimens based on four add-on ASMs-fenfluramine (FFA), stiripentol (STP), cannabidiol (CBD), and soticlestat-were included. All drug regimens were superior to the placebo at achieving at least 50 % and 75 % reductions in CSF, but only STP, 0.4 mg/kg/d FFA (FFA0.4), and 0.7 mg/kg/d FFA (FFA0.7) reduced MCSF. STP (50 mg/kg/d) had the highest correlation with reducing MCSF and achieving at least a 50 % reduction from baseline in CSF, followed by FFA0.4 and FFA0.7. Soticlestat and CBD may also be effective in reducing seizures in DS patients.

CONCLUSION

STP can be recommended as the first choice among the included drug regimens for reducing seizures in DS patients, while FFA0.4 may be considered the second choice. Other drug regimens can be used as alternative treatments. STP, FFA0.4, and FFA0.7 may consistently present favourable efficacy in most DS patients, while other regimens may present prominent inter-individual variability. Appropriate dose selection and intense monitoring are necessary when treating DS using these drugs.

Evaluating fenfluramine hydrochloride as an oral solution for the treatment of seizures associated with Lennox-Gastaut syndrome

INTRODUCTION

Lennox-Gastaut syndrome (LGS) is a severe childhood-onset developmental and epileptic encephalopathy characterized by treatment-refractory seizures, including tonic/atonic 'drop' seizures, and intellectual impairment and slow spike-wave discharges on the electroencephalogram. Fenfluramine, previously prescribed as a weight-loss drug but then withdrawn, has recently been approved in the US, EU, and UK for the adjunct treatment of seizures associated with LGS.

AREAS COVERED

The authors review the efficacy and safety findings from clinical trials of fenfluramine in LGS. The authors then discuss the evidence for adverse effects that may be of particular concern to fenfluramine, namely cardiac abnormalities, and weight loss, in the context of the use of fenfluramine for the treatment of the refractory seizures in LGS.

EXPERT OPINION

Fenfluramine has demonstrated efficacy in reducing the frequency of seizures in LGS, notably drop seizures, in short-term and long-term clinical trials. Valvular heart disease and pulmonary hypertension have not been reported at the low doses (≤26 mg/day) used in these studies, however, data are limited. Due to its novel mechanism of action, fenfluramine may be of benefit in LGS which has not responded adequately to other antiseizure medications. However, none of these medications, including fenfluramine, achieves the ultimate goal of seizure freedom in most cases.

Efficacy and safety of six new antiseizure medications for adjunctive treatment of focal epilepsy and epileptic syndrome: A systematic review and network meta-analysis

OBJECTIVE

This study aimed to evaluate the efficacy and safety of six new antiseizure medications (ASMs) for adjunctive treatment in adult patients with focal epilepsy and adolescents with Dravet syndrome (DS), Lennox-Gastaut syndrome (LGS), or tuberous sclerosis complex (TSC).

METHODS

A comprehensive literature search was performed using PubMed, Medline, Embase, and Cochrane library databases from inception to October 13, 2023. We included published studies for a systematic review and a network meta-analysis (NMA). The efficacy and safety were reported in terms of a 50% response rate and dropout rate along with serious adverse events (SAEs). The outcomes were ranked with the surface under the cumulative ranking curve (SUCRA).

RESULTS

Twenty eligible trials with 5516 patients and 21 interventions, including placebo, contributed to the analysis. Included ASMs were brivaracetam (BRV), cenobamate (CBM), cannabidiol (CBD), fenfluramine (FFM), everolimus (ELM), and soticlestat (SLT). The six new ASMs were compared in four different epilepsy subtypes. In focal epilepsy treatment, BRV seemed to be safe [vs placebo, risk ratio (RR) = 0.69, 95 % confidence interval (CI): 0.25-1.91] and effective (vs placebo, RR = 2.18, 95 % CI: 1.25-3.81). In treating focal epilepsy, CBM 300 mg was more effective at a 50 % response rate (SUCRA 91.8 %) compared with BRV and CBD. However, with the increase in dosage, more SAEs (SUCRA 85.6 %) appeared compared with other ASMs. CBD had good efficacy on LGS (SUCRA 88.4) and DS (SUCRA 66.2), but the effect on adult focal epilepsy was not better than that of placebo [vs placebo, RR = 0.83 (0.36-1.93)]. The NMA indicated that the likelihood of the most appropriate intervention (SUCRA 91.2 %) with minimum side effects（SUCRA 12.5 %）for the DS was FFM. Compared with CBD, high exposure to ELM demonstrated a more effective treatment of TSC (SUCRA 89.7 %). More high-quality SLT studies are needed to further evaluate the efficacy and safety. The comparison-adjusted funnel plots of annualized relapse rate and side effects in the included studies revealed no significant funnel plot asymmetry.

CONCLUSIONS

This NMA indicated that the most effective treatment strategy for focal epilepsy, DS, Lennox-Gastaut syndrome, and TSC, respectively, included CBM 300 mg, FFM, CBD, and ELM. However, the aforementioned findings need further confirmation.

Determining the Relationship Between Seizure-Free Days and Other Predictors of Quality of Life in Patients with Dravet Syndrome and Their Carers from FFA Registration Studies

INTRODUCTION

Dravet syndrome (DS) is a rare, lifelong epileptic encephalopathy characterised by frequent and severe seizures associated with premature mortality. Typically diagnosed in infancy, patients also experience progressive behavioural, motor-function and cognitive decline. Twenty percent of patients do not reach adulthood. Quality of life (QoL) is impaired for both patients and their carers. Reducing convulsive seizure frequency, increasing convulsive seizure-free days (SFDs) and improving patient/carer QoL are primary treatment goals in DS. This study explored the relationship between SFDs and patients' and carers' QoL to inform a cost-utility analysis of fenfluramine (FFA).

METHODS

In FFA registration studies, patients (or their carer proxies) completed the Paediatric QoL inventory (PedsQL). These data were mapped to EuroQol-5 Dimensions Youth version (EQ-5D-Y) to provide patient utilities. Carer utilities were collected using EQ-5D-5L and mapped to EQ-5D-3L to align patient and carer QoL on the same scale. Linear mixed-effects and panel regression models were tested and Hausman tests identified the most appropriate approach for each group. On this basis, a linear mixed-effects regression model was used to examine the relationships between patient EQ-5D-Y and clinically relevant variables (age, frequency of SFDs per 28 days, motor impairments and treatment dose). A linear panel regression model examined the relationship between SFDs and carer QoL.

RESULTS

After adjustment for age and underlying comorbidities, the patient regression model showed that SFDs per 28 days was a significant predictor of QoL. Each additional patient-SFD increased utility by 0.005 (p < 0.001). The carer linear panel model also showed that increasing SFDs per 28 days was a significant predictor of improved QoL. Each additional SFD increased carer utility by 0.014 (p < 0.001).

CONCLUSION

This regression framework highlights that SFDs are significantly correlated with both patients' and carers' QoL. Treatment with effective antiseizure medications that increase SFDs directly improves QoL for patients and their carers.

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 treatment for Dravet syndrome: Caregiver- and clinician-reported benefits on the quality of life of patients, caregivers, and families living in Germany, Spain, Italy, and the United Kingdom

OBJECTIVE

Clinical trial data and prior preliminary research indicate that fenfluramine (FFA) provides meaningful improvements in seizure-related and quality of life (QOL) outcomes for individuals with Dravet syndrome (DS), their caregivers, and their families. This study sought to replicate and extend these preliminary findings in a new sample of individuals with DS and their families who live in European countries.

METHODS

Study participants were European clinicians and parents caring for individuals with DS who had participated in an EU FFA Early Access Program. Participants completed one-on-one semi-structured interviews and were asked the extent to which they noticed changes in a number of the child's seizure- and non-seizure-related QOL domains after starting FFA treatment. Participants were also asked about the benefits of FFA treatment to the caregivers' lives and for the family unit.

RESULTS

25 parent caregivers and 16 clinicians participated. The caregivers and clinicians reported improvements in both seizure-related (i.e., reductions in seizure activity, improvements in the frequency or type of seizure triggers and post-ictal recovery times, and improved post-seizure function) and non-seizure-related (e.g., cognition, focus, alertness, speech, academic performance, behavior, sleep, motor function) QOL domains after FFA treatment in individuals with DS. Caregivers also reported improved mood and more time for things they enjoyed, felt less overwhelmed, reported better sleep quality, and had less personal and family stress; clinicians corroborated most of these reports. All clinicians (100%) and most (96%) caregivers said they would "very likely" or "quite likely" recommend FFA to others with DS.

CONCLUSIONS

Real-world experience in Europe with FFA treatment is associated with meaningful improvements in many QOL domains for individuals with DS and their families; replicating findings from a previous study of DS patients and their families from the USA. Caregivers and clinicians provided specific examples of the benefits of FFA for people with DS, caregivers, and their families and are very likely to recommend FFA to others with DS.

Cannabidiol reveals a disruptive strategy for 21st century epilepsy drug discovery

Over 30 antiseizure medicines (ASMs) have been uncovered in a diversity of preclinical seizure and epilepsy models, with several critical inflection points in the 20th century fundamentally transforming ASM discovery. This commentary aims to review the historical relevance of cannabidiol's (CBD; Epidiolex) approval for epilepsy in the context of other ASMs brought to market. Further, we highlight how CBD's approval may represent an inflection point for 21st century ASM discovery. CBD is one of the main phytocannabinoids of Cannabis sativa. Unlike its related phytocannabinoid, Δ9-tetrahydrocannabinol, CBD does not exert any euphorigenic, tolerance, or withdrawal effects at anticonvulsant doses. CBD also possess marked anti-inflammatory effects, offering the tantalizing potential of a new pharmacological approach in epilepsy. For decades, hints of the anticonvulsant profile of CBD had been suggested with a small handful of studies in rodent seizure models, yet difficulties in formulation, compounded by the social and regulatory pressures related to medical use of cannabis plant-derived agents constrained any clinical implementation. Nonetheless, CBD possesses a broad antiseizure profile in preclinical seizure and epilepsy models, but the transformative impact of CBD'-s approval came because of studies in a rodent model of the orphan disease Dravet syndrome (DS). DS is a pediatric developmental epileptic encephalopathy with high mortality, frequent spontaneous recurrent seizures, and marked resistance to conventional ASMs, such as phenytoin and carbamazepine. CBD was approved for DS by the US Food and Drug Administration in 2018 after convincing efficacy was established in randomized, placebo-controlled trials in children. Because of the clinical approval of CBD as a novel, cannabis plantderived ASM for DS, CBD has revealed a new strategy in ASM discovery to reignite 21st century therapeutic development for epilepsy. In this commentary, we review the major preclinical and clinical milestones of the late 20th century that made CBD, a compound historically subjected to regulatory restrictions, a key driver of a new discovery strategy for epilepsy in the 21st century.

Fenfluramine treatment is associated with improvement in everyday executive function in preschool-aged children (<5 years) with Dravet syndrome: A critical period for early neurodevelopment

OBJECTIVE

To evaluate whether fenfluramine (FFA) is associated with improvement in everyday executive function (EF)-self-regulation-in preschool-aged children with Dravet syndrome (DS).

METHODS

Children with DS received placebo or FFA in one of two phase III studies (first study: placebo, FFA 0.2 mg/kg/day, or FFA 0.7 mg/kg/day added to stiripentol-free standard-of-care regimens; second study: placebo or FFA 0.4 mg/kg/day added to stiripentol-inclusive regimens). Everyday EF was evaluated at baseline and Week 14-15 for children aged 2-4 years with parent ratings on the Behavior Rating Inventory of Executive Function®-Preschool (BRIEF®-P); raw scores were transformed to T-scores and summarized in Inhibitory Self-Control Index (ISCI), Flexibility Index (FI), Emergent Metacognition Index (EMI), and Global Executive Composite (GEC). Clinically meaningful improvement and worsening were defined using RCI ≥ 90% and RCI ≥ 80% certainty, respectively. The associations between placebo vs FFA combined (0.2, 0.4, and 0.7 mg/kg/day) or individual treatment groups and the likelihood of clinically meaningful change in BRIEF®-P indexes/composite T-scores were evaluated using Somers'd; pairwise comparisons were calculated by 2-sided Fisher's Exact tests (p ≤ 0.05) and Cramér's V.

RESULTS

Data were analyzed for 61 evaluable children of median age 3 years (placebo, n = 22; FFA 0.2 mg/kg/day, n = 15; 0.4 mg/kg/day [with stiripentol], n = 10; 0.7 mg/kg/day, n = 14 [total FFA, n = 39]). Elevated or problematic T-scores (T ≥ 65) were reported in 55% to 86% of patients at baseline for ISCI, EMI, and GEC, and in ∼33% for FI. Seventeen of the 61 children (28%) showed reliable, clinically meaningful improvement (RCI ≥ 90% certainty) in at least one BRIEF®-P index/composite, including a majority of the children in the FFA 0.7 mg/kg/day group (9/14, 64%). Only 53% of these children (9/17) also experienced clinically meaningful reduction (≥50%) in monthly convulsive seizure frequency, including 6/14 patients in the FFA 0.7 mg/kg/day group. Overall, there were positive associations between the four individual treatment groups and the likelihood of reliable, clinically meaningful improvement in all BRIEF®-P indexes/composite (ISCI, p = 0.001; FI, p = 0.005; EMI, p = 0.040; GEC, p = 0.002). The FFA 0.7 mg/kg/day group showed a greater likelihood of reliable, clinically meaningful improvement than placebo in ISCI (50% vs 5%; p = 0.003), FI (36% vs 0%; p = 0.005), and GEC (36% vs 0%; p = 0.005). For EMI, the FFA 0.7 mg/kg/day group showed a greater likelihood of reliable, clinically meaningful improvement than the FFA 0.2 mg/kg/day group (29% vs 0%; p = 0.040), but did not meet the significance threshold compared with placebo (29% vs 5%; p = 0.064). There were no significant associations between treatment and the likelihood of reliable, clinically meaningful worsening (p > 0.05).

SIGNIFICANCE

In this preschool-aged DS population with high baseline everyday EF impairment, FFA treatment for 14-15 weeks was associated with dose-dependent, clinically meaningful improvements in regulating behavior, emotion, cognition, and overall everyday EF. These clinically meaningful improvements in everyday EF were not entirely due to seizure frequency reduction, suggesting that FFA may have direct effects on everyday EF during the early formative years of neurodevelopment.

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.

Long-term cardiovascular safety of fenfluramine in patients with Dravet syndrome treated for up to 3 years: Findings from serial echocardiographic assessments

OBJECTIVE

To assess the cardiovascular safety of fenfluramine when used to treat children and young adults with Dravet syndrome.

METHODS

Patients with Dravet syndrome who completed one of three phase 3 clinical trials of fenfluramine could enroll in the open-label extension (OLE) study (NCT02823145). All patients started fenfluramine treatment at an oral dose of 0.2 mg/kg/day. The dose was titrated based on efficacy and tolerability to a maximum of 0.7 mg/kg/day (absolute maximum 26 mg/day) or 0.4 mg/kg/day (absolute maximum 17 mg/day) in patients concomitantly receiving stiripentol. Serial transthoracic echocardiography was performed using standardized methods and blinded readings at OLE entry, after 4-6 weeks, and every 3 months thereafter. Valvular heart disease (VHD) was defined as ≥ moderate mitral regurgitation or ≥ mild aortic regurgitation combined with physical signs or symptoms attributable to valve dysfunction. Pulmonary artery hypertension (PAH) was defined as systolic pulmonary artery pressure >35 mmHg.

RESULTS

A total of 327 patients (median age, 9.0 years; range, 2-19 years) have enrolled in the OLE and received ≥1 dose of fenfluramine. The median duration of treatment was 23.9 months (range, 0.2-42.6 months) and the median dose of fenfluramine was 0.44 mg/kg/day. No patient demonstrated VHD or PAH at any time during the OLE.

SIGNIFICANCE/INTERPRETATION

This study, which represents the largest, longest, and most rigorous examination of cardiovascular safety of fenfluramine yet reported, found no cases of VHD or PAH. These results, combined with fenfluramine's substantial antiseizure efficacy, support a strong positive benefit-risk profile for fenfluramine in the treatment of Dravet syndrome.

Fenfluramine modulates the anti-amnesic effects induced by sigma-1 receptor agonists and neuro(active)steroids in vivo

Fenfluramine (N-ethyl-α-methl-3-(trifluoromethyl)phenethylamine) is an anti-seizure medication (ASM) particularly effective in patients with Dravet syndrome, a severe treatment-resistant epileptic encephalopathy. Fenfluramine acts not only as neuronal serotonin (5-HT) releaser but also as a positive modulator of the sigma-1 receptor (S1R). We here examined the modulatory activity of Fenfluramine on the S1R-mediated anti-amnesic response in mice using combination analyses. Fenfluramine and Norfenfluramine, racemate and isomers, were combined with either the S1R agonist (PRE-084) or the S1R-acting neuro(active)steroids, pregnenolone sulfate (PREGS), Dehydroepiandrosterone sulfate (DHEAS), or progesterone. We report that Fenfluramine racemate or (+)-Fenfluramine, in the 0.1-1 mg/kg dose range, attenuated the dizocilpine-induced learning deficits in spontaneous alternation and passive avoidance, and showed low-dose synergies in combination with PRE-084. These effects were blocked by the S1R antagonist NE-100. Dehydroepiandrosterone sulfate or PREGS attenuated dizocilpine-induced learning deficits in the 5-20 mg/kg dose range. Co-treatments at low dose between steroids and Fenfluramine or (+)-Fenfluramine were synergistic. Progesterone blocked Fenfluramine effect. Finally, Fenfluramine and (+)-Fenfluramine effects were prevented by the 5-HT1A receptor antagonist WAY-100635 or 5-HT2A antagonist RS-127445, but not by the 5-HT1B/1D antagonist GR 127935 or the 5-HT2C antagonist SB 242084, confirming a 5-HT1A and 5-HT2A receptor involvement in the drug effect on memory. We therefore confirmed the positive modulation of Fenfluramine racemate or dextroisomer on S1R and showed that, in physiological conditions, the drug potentiated the low dose effects of neuro(active)steroids, endogenous S1R modulators. The latter are potent modulators of the excitatory/inhibitory balance in the brain, and their levels must be considered in the antiepileptic action of Fenfluramine.

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.

Improved everyday executive functioning following profound reduction in seizure frequency with fenfluramine: Analysis from a phase 3 long-term extension study in children/young adults with Dravet syndrome

OBJECTIVE

Individuals with Dravet syndrome (DS) experience frequent pharmacoresistant seizures beginning in infancy. Most exhibit poor neurodevelopmental outcomes including motor function difficulties, behavior problems, and cognitive impairment. Cognitive deficits in children with DS have been associated with seizure frequency and antiseizure medication (ASM) use. Recent research in children and young adults with DS has begun to examine the role of executive functions (EFs), as these include higher-order cognitive functions and may mediate the relationship between risk factors and cognitive impairment. Current conceptualizations, however, of EFs involve the broader self-regulation of cognitive, behavioral, and emotional domains. We explored relationships between reduction in convulsive seizure frequency and everyday EFs in a subset of children and young adults with DS treated with adjunctive fenfluramine for 1 year.

METHODS

This is a post-hoc analysis of data from children and young adults with Dravet syndrome aged 5-18 years who participated in a phase 3 randomized, placebo-controlled clinical trial (core study) followed by completion of at least 1 year of fenfluramine treatment in an open-label extension (OLE) study. Eligible children and young adults started the OLE study at 0.2 mg/kg/day fenfluramine and were titrated to optimal seizure control and tolerability (maximum daily dose: 26 mg/day). Parents/caregivers documented convulsive seizure frequency per 28 days (i.e., monthly convulsive seizure frequency [MCSF]) by electronic diary. A parent/caregiver for each child also completed the Behavior Rating Inventory of Executive Function (BRIEF®) parent form, a questionnaire capturing parents'/caregivers' perceptions of everyday EF that was included as a safety measure to assess treatment-related adverse effects on EF during the trial. Ratings on BRIEF® were mapped to the current edition, the BRIEF®2 parent form, and were used to calculate T-scores for the Behavior Regulation Index (BRI), Emotion Regulation Index (ERI), Cognitive Regulation Index (CRI), and Global Executive Composite (GEC). Change in BRIEF®2 T-scores from baseline in the core study to Year 1 of the OLE study was calculated. Spearman's rho correlation coefficients assessed associations between change in BRIEF®2 indexes/composite T-scores and percentage change in MCSF. Children and young adults were divided into 2 groups based on percentage of MCSF reduction achieved from pre-randomization baseline in the core study to Year 1 of the OLE study: <50% and ≥50% MCSF reduction. Changes in the distribution of BRIEF®2 indexes/composite T-scores were compared between MCSF reduction groups using Mann-Whitney U tests. The proportions of children and young adults in these groups who showed clinically meaningful improvement in everyday EF, defined as Reliable Change Index (RCI) values ≥95% certainty relative to a reference population of neurotypically developing healthy volunteers, were then assessed by cross-tabulations and Somers' D tests (p ≤ 0.05). When there was a significant meaningful improvement in an index score, post-hoc analyses using the same statistical methods were conducted to evaluate the individual BRIEF®2 scales composing that index. Supplemental analyses examined the proportions of patients in MCSF reduction groups <25% and ≥75% who achieved clinically meaningful improvement or worsening in everyday EF using RCI values ≥95% certainty and ≥80% certainty, respectively, relative to the reference population.

RESULTS

At the time of analysis, 58 children and young adults (mean age: 11 ± 4 years) had reached OLE Year 1 of fenfluramine treatment with a 75% median percentage reduction in seizure frequency from pre-randomization baseline. Overall, there was a significant correlation between change in MCSF and change in BRIEF®2 T-scores for ERI (p = 0.008), but not for BRI, CRI, or GEC (p > 0.05). At OLE Year 1, 78% (n = 45) of total children/young adults had ≥50% MCSF reduction (50% [n = 29] achieved ≥75% MCSF reduction) and 22% (n = 13) of total children/young adults had <50% MCSF reduction (12% [n = 7] showed <25% MCSF reduction). The ≥50% MCSF reduction group was significantly more likely to achieve clinically meaningful improvement (RCI ≥ 95% certainty) in ERI (p = 0.002) and in CRI (p = 0.001) than the <50% MCSF reduction group. There were no significant differences in the proportions of children and young adults in the 2 MCSF reduction groups showing clinically meaningful worsening (RCI ≥ 80% certainty) on the BRIEF®2 indexes/composite.

SIGNIFICANCE

In children and young adults with DS, the magnitude of reduction in MCSF after long-term treatment with adjunctive fenfluramine was associated with clinically meaningful levels of improvement in everyday EF. Seventy-eight percent (78%) of children and young adults treated with adjunctive fenfluramine for 1 year in the OLE study achieved ≥50% reduction in MCSF, for a magnitude of efficacy associated with a significantly greater likelihood of experiencing clinically meaningful improvement in emotion regulation and cognitive regulation.

Fenfluramine for treatment-resistant epilepsy in Dravet syndrome and other genetically mediated epilepsies

Fenfluramine hydrochloride, initially utilized as a weight loss drug in the 1970s and later removed from the market for adverse cardiopulmonary side effects, has since been repurposed as an antiseizure medicine (ASM). The potential antiseizure effects of fenfluramine were first identified in patients with photosensitive epilepsy in the 1980s but it was not rigorously explored as a treatment option until 30 years later. Compared with other ASMs, fenfluramine offers a novel mechanism by acting on serotonin and σ1 receptors, demonstrated in vitro and in vivo in animal models of Dravet syndrome. Results from a large double-blind, placebo-controlled trial demonstrated robust efficacy for seizure reduction in patients with Dravet syndrome, and met its primary endpoint with the 0.7 mg/kg/day fenfluramine treatment group experiencing a 62.3% or greater reduction in mean monthly convulsive seizure frequency (MCSF) compared with placebo. Here we provide a comprehensive review of the preclinical and clinical activity of fenfluramine, a recently approved drug for treatment of epilepsy in patients with Dravet syndrome.

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

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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.

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

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

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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.

Efficacy of Fenfluramine and Norfenfluramine Enantiomers and Various Antiepileptic Drugs in a Zebrafish Model of Dravet Syndrome

Dravet syndrome (DS) is a rare genetic encephalopathy that is characterized by severe seizures and highly resistant to commonly used antiepileptic drugs (AEDs). In 2020, FDA has approved fenfluramine (FFA) for treatment of seizures associated with DS. However, the clinically used FFA is a racemic mixture (i.e. (±)-FFA), that is substantially metabolized to norfenfluramine (norFFA), and it is presently not known whether the efficacy of FFA is due to a single enantiomer of FFA, or to both, and whether the norFFA enantiomers also contribute significantly. In this study, the antiepileptic activity of enantiomers of FFA (i.e. (+)-FFA and (−)-FFA) and norFFA (i.e. (+)-norFFA and (−)-norFFA) was explored using the zebrafish scn1Lab^−/− mutant model of DS. To validate the experimental conditions used, we assessed the activity of various AEDs typically used in the fight against DS, including combination therapy. Overall, our results are highly consistent with the treatment algorithm proposed by the updated current practice in the clinical management of DS. Our results show that (+)-FFA, (−)-FFA and (+)-norFFA displayed significant antiepileptic effects in the preclinical model, and thus can be considered as compounds actively contributing to the clinical efficacy of FFA. In case of (−)-norFFA, the results were less conclusive. We also investigated the uptake kinetics of the enantiomers of FFA and norFFA in larval zebrafish heads. The data show that the total uptake of each compound increased in a time-dependent fashion. A somewhat similar uptake was observed for the (+)-norFFA and (−)-norFFA, implying that the levo/dextrotation of the structure did not dramatically affect the uptake. Significantly, when comparing (+)-FFA with the less lipophilic (+)-norFFA, the data clearly show that the nor-metabolite of FFA is taken up less than the parent compound.

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.

New and Emerging Medications for Treatment of Pediatric Epilepsy

BACKGROUND

Multiple medications have recently been approved or are nearing US Food and Drug Administration approval for treatment of pediatric epilepsy, while a number of other compounds are in development. Many of these therapies are seeking indications in rare epilepsy syndromes and present novel mechanisms of action for the treatment of epilepsy.

METHODS

Data related to drugs in development or under study were accessed following literature search via PubMed or author knowledge of publically available data.

RESULTS

Several new compounds are recently approved or under study for epilepsy in children.

CONCLUSIONS

The following is a brief overview of the new and emerging medications for the treatment of pediatric epilepsy.

Fenfluramine acts as a positive modulator of sigma-1 receptors

OBJECTIVE

Adjunctive fenfluramine hydrochloride, classically described as acting pharmacologically through a serotonergic mechanism, has demonstrated a unique and robust clinical response profile with regard to its magnitude, consistency, and durability of effect on seizure activity in patients with pharmacoresistant Dravet syndrome. Recent findings also support long-term improvements in executive functions (behavior, emotion, cognition) in these patients. The observed clinical profile is inconsistent with serotonergic activity alone, as other serotonergic medications have not been demonstrated to have these clinical effects. This study investigated a potential role for σ1 receptor activity in complementing fenfluramine's serotonergic pharmacology.

METHODS

Radioligand binding assays tested the affinity of fenfluramine for 47 receptors associated with seizures in the literature, including σ receptors. Cellular function assays tested fenfluramine and norfenfluramine (its major metabolite) activity at various receptors, including adrenergic, muscarinic, and serotonergic receptors. The σ1 receptor activity was assessed by the mouse vas deferens isometric twitch and by an assay of dissociation of the σ1 receptor from the endoplasmic reticulum stress protein binding immunoglobulin protein (BiP). In vivo mouse models assessed fenfluramine activity at σ1 receptors in ameliorating dizocilpine-induced learning deficits in spatial and nonspatial memory tasks, alone or in combination with the reference σ1 receptor agonist PRE-084.

RESULTS

Fenfluramine and norfenfluramine bound ≥30% to β2-adrenergic, muscarinic M1, serotonergic 5-HT1A, and σ receptors, as well as sodium channels, with a Ki between 266 nM (σ receptors) and 17.5 μM (β-adrenergic receptors). However, only σ1 receptor isometric twitch assays showed a positive functional response, with weak stimulation by fenfluramine and inhibition by norfenfluramine. Fenfluramine, but not the 5-HT2C agonist lorcaserin, showed a positive modulation of the PRE-084-induced dissociation of σ1 protein from BiP. Fenfluramine also showed dose-dependent antiamnesic effects against dizocilpine-induced learning deficits in spontaneous alternation and passive avoidance responses, which are models of σ1 activation. Moreover, low doses of fenfluramine synergistically potentiated the low-dose effect of PRE-084, confirming a positive modulatory effect at the σ1 receptor. Finally, all in vivo effects were blocked by the σ1 receptor antagonist NE-100.

SIGNIFICANCE

Fenfluramine demonstrated modulatory activity at σ1 receptors in vitro and in vivo in addition to its known serotonergic activity. These studies identify a possible new σ1 receptor mechanism underpinning fenfluramine's central nervous system effects, which may contribute to its antiseizure activity in Dravet syndrome and positive effects observed on executive functions in clinical studies.

Fenfluramine: New Treatment for Seizures in Dravet Syndrome

Investigators for the FAiRE DS Study Group assessed the efficacy and safety of Fenfluramine for treating seizures in patients less than 18 y.o. with Dravet Syndrome in an international double-blind, placebo-controlled clinical trial. A total of 119 patients (mean age 9.0 y, 54% male) were enrolled in the study.

Effects of repeated treatment with methcathinone, mephedrone, and fenfluramine on intracranial self-stimulation in rats

RATIONALE

Synthetic cathinones constitute a class of abused drugs that can act at dopamine, norepinephrine, and serotonin transporters (DAT, NET, and SERT, respectively). Intracranial self-stimulation (ICSS) is a preclinical procedure that can be used to evaluate abuse potential of drugs, and prior studies have indicated that abuse-related ICSS effects of monoamine-transporter substrates, including some synthetic cathinones, are positively correlated with drug selectivity for DAT vs. SERT. Abuse potential of drugs can also be influenced by regimens of repeated drug exposure, but the role of repeated exposure on abuse-related ICSS effects of synthetic cathinones has not been examined.

OBJECTIVES

This study used ICSS to evaluate effects of repeated treatment with the DAT>SERT substrate methcathinone, the DAT<SERT substrate fenfluramine, and the DAT≈SERT substrate mephedrone.

METHODS

Male Sprague-Dawley rats were trained in a frequency-rate ICSS procedure, and different groups were used to evaluate effects of methcathinone, mephedrone, and fenfluramine before, during, and after regimens of repeated treatment with the designated drug.

RESULTS

Before repeated treatment, methcathinone produced dose-dependent and abuse-related ICSS facilitation, fenfluramine produced dose-dependent ICSS depression, and mephedrone produced mixed effects that included both facilitation and depression. Chronic treatment produced no change in effects of methcathinone, but complete tolerance to effects of fenfluramine. For mephedrone, chronic treatment produced partial tolerance to ICSS depression and enhanced expression of ICSS facilitation.

CONCLUSIONS

Repeated exposure to mixed-action DAT≈SERT substrates such as mephedrone can result in increased abuse potential due to sustained expression of DAT-mediated abuse-related effects and tolerance to SERT-mediated abuse-limiting effects.

Individualized treatment approaches: Fenfluramine, a novel antiepileptic medication for the treatment of seizures in Dravet syndrome

Dravet syndrome is a rare and severe encephalopathy that first presents in infancy with seizures refractory to conventional antiepileptic drugs. Forty-five percent of patients report four or more tonic-clonic seizures per month despite multidrug regimens. Fenfluramine, an amphetamine derivative, was initially developed as an appetite suppressant with a serotonergic mechanism of action. Clinical observation of a potential antiepileptic activity in a small homogeneous cohort of patients combined with a genetic workup of these patients led to the hypothesis of fenfluramine as a treatment for seizures in Dravet syndrome. This concept was successfully evaluated in a zebrafish model and led to a Phase 3 trial of fenfluramine to treat seizures in children with Dravet syndrome. Preliminary results of the trial suggest that fenfluramine may be a highly effective, well-tolerated treatment for patients with Dravet syndrome. This short review summarizes the history of use of fenfluramine from the initial clinical observations followed by preclinical studies and subsequent successful clinical trial. This article is part of the Special Issue "Individualized Epilepsy Management: Medicines, Surgery and Beyond."

Current Treatment Strategies and Future Treatment Options for Dravet Syndrome

PURPOSE OF REVIEW

Dravet syndrome is a rare but severe genetic epilepsy that has unique treatment challenges. This is a review of current and future potential treatment options.

RECENT FINDINGS

Treatment for Dravet syndrome should encompass many aspects of the syndrome such as gait, behavior, and nutrition, as well as focus on seizure control. Many sodium channel blockers should be avoided as they are likely to exacerbate seizures. Current options for treatment include valproic acid, clobazam, stiripentol, and ketogenic diet. Testing is underway for several new treatment options with unique mechanisms of action and therapeutic targets, including the serotonin system and genetic modulation. Accurate and early diagnosis of Dravet syndrome will lead to avoidance of medications that may exacerbate seizures. Additionally, a multi-disciplinary approach and careful planning for management of episodes of status epilepticus may lead to improved outcomes. Ongoing research for novel approaches to treatment creates optimism for future improvement in outcomes.

Fenfluramine-induced PVAT-dependent contraction depends on norepinephrine and not serotonin

Perivascular adipose tissue (PVAT) modulates vascular tone and altered PVAT function is observed in vascular diseases such as hypertension and atherosclerosis. We discovered that the PVAT surrounding rat thoracic aorta (RA) and the superior mesenteric artery (SMA) contain significant amounts of 5-hydroxytryptamine (5-HT). We hypothesized that the 5-HT contained within the PVAT is functional and vasoactive. Isolated tissue baths were used for isometric contractility studies and high performance liquid chromatography was used to quantitatively measure amines in the PVAT and release studies. The 5-HT releaser fenfluramine (10 nM-100 μM) was tested for its ability to contract arteries with and without PVAT. Contraction was reported as a percentage of the initial contraction to 10 μM phenylephrine. The RA with PVAT contracted to fenfluramine to a greater maximum (98 ± 10%) than RA without PVAT (24 ± 4%), while no difference in contraction of SMA to maximum fenfluramine with (78 ± 2%) and without (75 ± 6%) PVAT was observed. Contradicting our hypothesis, the maximum contraction of RA with PVAT to fenfluramine was diminished by the alpha-1 adrenoreceptor antagonist prazosin (100 nM; vehicle: 71 ± 4%, prazosin: 24 ± 2%) and the norepinephrine transporter (NET) inhibitor nisoxetine (1 μM; vehicle: 71 ± 4%, nisoxetine: 25 ± 4%) but not the 5-HT_2A/2C receptor antagonist ketanserin (10 nM) or serotonin specific reuptake inhibitor fluoxetine (10 μM). To test if fenfluramine caused release of 5-HT or NE from PVAT, PVAT from RA was incubated with vehicle or fenfluramine (10 μM-10 mM), and amines released into the incubating buffer were quantified. A pronounced concentration-dependent NE-release (more than 5-HT) was observed. Collectively, this research illustrates the pharmacology of fenfluramine to primarily stimulate NE release (better than 5-HT) in a NET-dependent manner, leading to vasoconstriction. This adds additional support to PVAT as being an important reservoir of amines.

Five-year extended follow-up status of 10 patients with Dravet syndrome treated with fenfluramine

Dravet syndrome (DS) is a rare and therapy-resistant epilepsy syndrome. A retrospective analysis of add-on fenfluramine treatment in 12 patients with DS was published in 2012 and provided evidence of a meaningful long-term response. Herein we present the results of a subsequent 5-year prospective observation of this original cohort. Ten patients with a mean current age of 24 years were followed prospectively from 2010 until 2014. The mean current dose of fenfluramine was 0.27 mg/kg/day, with a mean treatment duration of 16.1 years. Seizure frequency was derived from a seizure diary. Cardiac examinations and assessments of clinical effectiveness and adverse events were performed at least annually. Three patients were seizure-free for the entire 5 years, and an additional four patients experienced seizure-free intervals of at least 2 years. Fenfluramine was generally well-tolerated. Two patients had mild (stable) valve thickening on the last echocardiography that was deemed clinically insignificant. No patient had any clinical or echocardiographic signs of pulmonary hypertension. These findings support the long-term control of convulsive seizures by low-dose fenfluramine while being well tolerated in this cohort of patients with DS. After up to 27 years of treatment, no patient has developed any clinical signs or symptoms of cardiac valvulopathy or pulmonary hypertension.

Systemic treatment with D-fenfluramine, but not sibutramine, blocks cue-induced reinstatement of food-seeking behavior in the rat

Individuals struggling with obesity often have difficulty maintaining dietary regimens. One source of dietary relapse is the reinstatement of previous feeding behaviors following the presentation of cues indicating the availability of palatable but highly caloric food reward. The drugs fenfluramine and sibutramine have previously been prescribed because they enhance satiety mechanisms and decrease meal size. However, it is unclear whether these anorectic agents are also effective in blocking the cue-induced reinstatement of food-seeking behaviors. In these three experiments, we compared the effects of systemic treatment of d-fenfluramine (3mg/kg; N=10) and sibutramine (3mg/kg; N=11) with that of the D1 antagonist SCH 23390 (6μg/kg; N=11) at a dose that has previously been shown to attenuate cue-induced reinstatement. d-Fenfluramine treatment blocked the cue's ability to reinstate lever pressing as compared to the saline injection day. In contrast, sibutramine had no effect on cue-induced reinstatement; all animals reinstated their lever pressing during the first reinstatement test, and this was unaffected by sibutramine treatment. SCH 23390 treatment did not significantly reduce cue-induced reinstatement in this set of experiments. The results suggest that the motivational effects of d-fenfluramine is not limited to the promotion of satiety once a meal has been initiated, and demonstrate that some anorectic treatments may inhibit the effectiveness of conditioned cues to elicit relapse of food-seeking behavior.