Extending the use of stiripentol to other epileptic syndromes: a case of PCDH19-related epilepsy

Use of Stiripentol in Patients with Dravet Syndrome: Common Practice Among Experts in Spain

BACKGROUND

Despite considerable evidence for the efficacy and safety of stiripentol in Dravet syndrome (DS), some aspects of stiripentol use remain challenging in clinical practice, such as dose titration and the adjustment of concomitant antiseizure medications (ASMs) to prevent potential adverse effects.

AIM

To (1) provide practical recommendations on the initiation of stiripentol treatment in patients with DS, (2) evaluate its effectiveness in the patient, and (3) guide the management of drug interactions and other aspects of treatment monitoring.

METHODS

Six Spanish neurologists (the authors) with expertise in the management of pediatric and adult patients with DS held a meeting in early 2024 to develop expert recommendations regarding the use of stiripentol in DS, based on a review of the literature and their common clinical experience.

RESULTS

According to these recommendations, stiripentol can be administered to patients with DS of any age, although its initiation and titration vary according to age group. Individualized adjustment of concomitant ASMs, such as valproic acid and clobazam or drugs specifically for DS (i.e., fenfluramine), at initiation and during stiripentol treatment, can mitigate drug interactions, thereby increasing the long-term tolerability of stiripentol treatment. In specific cases, stiripentol doses of > 50 mg/kg/day may be contemplated, and acute stiripentol administration may be considered to control refractory status epilepticus. Blood tests should be performed before starting stiripentol, at 3, 6, and 12 months after starting treatment, and then annually, except in the event of adverse effects, when additional testing may be necessary. Most adverse effects can be adequately managed by adjusting concomitant medications.

CONCLUSION

These practical recommendations may be easily adapted for use in different countries, and should increase physicians' confidence in the initiation and monitoring of stiripentol treatment, thus facilitating effective management of patients with DS and improving clinical outcomes.

[Epilepsy with PCDH19 mutation: polypharmacy as a consequence of the complexity and diversity of pathogenesis mechanisms]

Mutations in the human PCDH19 gene lead to epileptic encephalopathy of early childhood. It is characterized by the early onset of serial seizures, cognitive impairment and behavioral disorders (including autistic personality traits). In most cases, difficulties arise in selecting therapy due to pharmacoresistance. The pathogenesis of the disease is complex. The data available to us at the moment from numerous studies present the pathogenesis of «PCDH19 syndrome» as multi-level, affecting both the epigenetic support of cell life, and development of stem cells and progenitor cells in the process of neuroontogenesis, and the influence on the neurotransmitter mechanisms of the brain, and disruption of the formation of neural networks with an inevitable increase in the excitability of the cerebral cortex as a whole, and local changes in the highly labile regulatory structures of the hippocampal region. And it is not surprising that all these changes entail not only (and perhaps not so much) epileptization, but a profound disruption of the regulation of brain activity, accompanied by autism spectrum disorders, more profound disorders in the form of schizophrenia or cyclothymia, and the formation of delayed psychomotor development. A «side branch» of these pathogenetic processes can also be considered the participation of PCDH19 dysfunctions in certain variants of oncogenesis. The need for polypharmacy (in most cases) confirms the diversity of mechanisms involved in the pathogenesis of the disease and makes the prospects for the development of effective and rational treatment regimens very vague. Cautious optimism is caused only by attempts at relatively specific treatment with ganaxolone.

PCDH19-Related Epilepsies

Protocadherin-19 (PCDH19) is considered one of the most relevant genes related to epilepsy. To date, more than 150 mutations have been identified as causative for PCDH19-female epilepsy (also known as early infantile epileptic encephalopathy-9, EIEE9), which is characterized by early onset epilepsy, intellectual disabilities, and behavioral disturbances. More recently, mosaic-males (i.e., exhibiting the variants in less than 25% of their cells) have been described as affected by infant-onset epilepsy associated with intellectual disability, as well as compulsive or aggressive behavior and autistic features. Although little is known about the physiological role of PCDH19 protein and the pathogenic mechanisms that lead to EIEE9, many reports and clinical observation seem to suggest a relevant role of this protein in the development of cellular hyperexcitability. However, a genotype–phenotype correlation is difficult to establish. The main feature of EIEE9 consists in early onset of seizures, which generally occur in clusters lasting 1 to 5 minutes and repeating up to 10 times a day for several days. Seizures tend to present during febrile episodes, similarly to the first phases of Dravet syndrome and PCDH19 variants have been found in ∼25% of females who present with features of Dravet syndrome and testing negative for SCN1A variants. There is no “standardized” treatment for PCDH19-related epilepsy and most of the patients receiving a combination of several drugs. In this review, we focus on the latest researches on these aspects, with regard to protein expression, its known functions, and the mechanisms by which the protein acts. The clinical phenotypes related to PCDH19 mutations are also discussed.

Adjuvant Treatment for Protocadherin 19 (PCDH19) Syndrome

Protocadherin 19 (PCDH19) syndrome is inherited as an X-linked pattern and affects mainly females. This syndrome is caused by a mutation in the PCDH19 gene encoding for the protocadherin protein. It is characterized by refractory seizures during febrile episodes with neuropsychiatric manifestations. There is no consensus on the treatment of PCDH19. We conducted a literature review to investigate the main drugs used for this syndrome, and to evaluate the best possible course of adjuvant treatment for these patients. We used an advanced PubMed search strategy with the following inclusion criteria: a) full-text papers, b) English Language, and c) studies conducted in humans. Exclusion criteria: a) literature reviews, b) systematic reviews, and c) metanalysis. We gathered 26 observational papers to conduct this literature review on clobazam and bromide which have been shown to reduce seizures by 50%. Corticosteroids improved neurological symptoms during the episodes in a few patients. Nevertheless, they recurred after a few months. Preliminary results of ganaxolone, which is still under study, demonstrated a reduction of 60% in seizure episodes. A ketogenic diet has been studied to treat several refractory epilepsies, including PCDH19; it has promising results as effective adjuvant therapy in the resolution of status epilepticus, suggesting it could be used as part of the treatment in early childhood. Stiripentol was given as adjuvant therapy in a patient with PCDH19 epilepsy resulting in the most extended period of seizure-free episodes, but more studies must be performed to assess its efficacy.

A Review of Targeted Therapies for Monogenic Epilepsy Syndromes

Genetic sequencing technologies have led to an increase in the identification and characterization of monogenic epilepsy syndromes. This increase has, in turn, generated strong interest in developing “precision therapies” based on the unique molecular genetics of a given monogenic epilepsy syndrome. These therapies include diets, vitamins, cell-signaling regulators, ion channel modulators, repurposed medications, molecular chaperones, and gene therapies. In this review, we evaluate these therapies from the perspective of their clinical validity and discuss the future of these therapies for individual syndromes.

The Broad Clinical Spectrum of Epilepsies Associated With Protocadherin 19 Gene Mutation

Protocadherin 19 (PCDH19) gene is one of the most common genes involved in epilepsy syndromes. According to literature data PCDH19 is among the 6 genes most involved in genetic epilepsies. PCDH19 is located on chromosome Xq22.1 and is involved in neuronal connections and signal transduction. The most frequent clinical expression of PCDH19 mutation is epilepsy and mental retardation limited to female (EFMR) characterized by epileptic and non-epileptic symptoms affecting mainly females. However, the phenotypic spectrum of these mutations is considerably variable from genetic epilepsy with febrile seizure plus to epileptic encephalopathies. The peculiar exclusive involvement of females seems to be caused by a cellular interference in heterozygosity, however, affected mosaic-males have been reported. Seizure types range from focal seizure to generalized tonic-clonic, tonic, atonic, absences, and myoclonic jerks. Treatment of PCDH19-related epilepsy is limited by drug resistance and by the absence of specific treatment indications. However, seizures become less severe with adolescence and some patients may even become seizure-free. Non-epileptic symptoms represent the main disabilities of adult patients with PCDH19 mutation. This review aims to analyze the highly variable phenotypic expression of PCDH19 gene mutation associated with epilepsy.

Next-generation sequencing in childhood-onset epilepsies: Diagnostic yield and impact on neuronal ceroid lipofuscinosis type 2 (CLN2) disease diagnosis

Epilepsy is one of the most common childhood-onset neurological conditions with a genetic etiology. Genetic diagnosis provides potential for etiologically-based management and treatment. Existing research has focused on early-onset (<24 months) epilepsies; data regarding later-onset epilepsies is limited. The goal of this study was to determine the diagnostic yield of a clinically available epilepsy panel in a selected pediatric epilepsy cohort with epilepsy onset between 24-60 months of life and evaluate whether this approach decreases the age of diagnosis of neuronal ceroid lipofuscinosis type 2 (CLN2). Next-generation sequencing (NGS)-based epilepsy panels, including genes associated with epileptic encephalopathies and inborn errors of metabolism (IEMs) that present with epilepsy, were used. Copy-number variant (CNV) detection from NGS data was included. Variant interpretation was performed per American College of Medical Genetics and Genomics (ACMG) guidelines. Results are reported from 211 consecutive patients with the following inclusion criteria: 24-60 months of age at the time of enrollment, first unprovoked seizure at/after 24 months, and at least one additional finding such as EEG/MRI abnormalities, speech delay, or motor symptoms. Median age was 42 months at testing and 30 months at first seizure onset; the mean delay from first seizure to comprehensive genetic testing was 10.3 months. A genetic diagnosis was established in 43 patients (20.4%). CNVs were reported in 25.6% diagnosed patients; 27.3% of CNVs identified were intragenic. Within the diagnosed cohort, 11 (25.6%) patients were diagnosed with an IEM. The predominant molecular diagnosis was CLN2 (14% of diagnosed patients). For these patients, diagnosis was achieved 12-24 months earlier than reported by natural history of the disease. This study supports comprehensive genetic testing for patients whose first seizure occurs ≥ 24 months of age. It also supports early application of testing in this age group, as the identified diagnoses can have significant impact on patient management and outcome.

Insights into the FDA 2018 New Drug Approvals

OBJECTIVE

The Center of Drug Evaluation and Research (CDER) in the food and drug administration (FDA) approves new drugs every year. This review discusses the novel drugs of the FDA in 2018, with emphasis on the breakthrough drugs, the milestones in the approved list, and drugs with the highest expected sales in 2024.

METHODS

The following scientific search engines were surveyed for the clinical trials of the drugs approved by the FDA in 2018: Pubmed, Springer link, ScienceDirect, Scopus, Wiley online library, Taylor and Francis, and Google Scholar. The total forecast sales were compared based on information from the Cortellis database, EvaluatePharma, and Nature Biobusiness Briefs.

RESULTS

The 2018 year was full of good news for the drug market in the USA, with 59 new drug approvals by the FDA, which is the highest number of approvals in the last twenty years. The oncology and the antimicrobial drugs represent almost 50% of the new list, which gives hope to cancer patients and subjects with infectious diseases. In the 2018 FDA list, a number of drugs are expected to exceed 1$ billion dollars of sales by 2024.

CONCLUSION

The new drugs approved by the FDA in 2018 have been reviewed. This year showed the highest number of new drug approvals in the last two decades. Among the 59 drugs approved in 2018, 14 drugs are considered breakthroughs, which revive hope for many poorly managed diseases. The list also contains 19 drugs that are first in class and 43 that were given priority reviews.

Novel and de novo mutation of PCDH19 in Girls Clustering Epilepsy

BACKGROUND

PCDH19 has become the second most relevant gene in epilepsy after SCN1A. Seizures often provoked by fever.

METHODS

We screened 152 children with fever-sensitive epilepsy for gene detection. Their clinical information was followed up.

RESULTS

We found eight PCDH19 point mutations (four novel and four reported) and one whole gene deletion in 10 female probands (seven sporadic cases and three family cases) who also had cluster seizures. The common clinical features of 16 patients in 10 families included fever-sensitive and cluster seizures, mainly focal or tonic-clonic seizures, and absence of status epilepticus, normal intelligence, or mild-to-moderate cognitive impairment, the onset age ranges from 5 months to 20 years. Only four patients had multiple or focal transient discharges in interictal EEG. Focal seizures originating in the frontal region were recorded in four patients, two from the parietal region, and one from the occipital region.

CONCLUSION

PCDH19 mutation can be inherited or de novo. The clinical spectrum of PCDH19 mutation includes PCDH19 Girls Clustering Epilepsy with or without mental retardation, psychosis, and asymptomatic male. The onset age of PCDH19 Girls Clustering Epilepsy can range from infancy to adulthood. Sisters in the same family may be sensitive to the same antiepileptic drugs. And our report expands the mutation spectrum of PCDH19 Girls Clustering Epilepsy.

Genomic testing in pediatric epilepsy

Genomic testing has become routine in the diagnosis and management of pediatric patients with epilepsy. In a single test, hundreds to thousands of genes are examined for DNA changes that may not only explain the etiology of the patient's condition but may also inform management and seizure control. Clinical genomic testing has been in clinical practice for less than a decade, and because of this short period of time, the appropriate clinical use and interpretation of genomic testing is still evolving. Compared to the previous era of single-gene testing in epilepsy, which yielded a diagnosis in <5% of cases, many clinical genomic studies of epilepsy have demonstrated a clinically significant diagnosis in 30% or more of patients tested. This review will examine key studies of the past decade and indicate the clinical scenarios in which genomic testing should be considered standard of care.

Extending the use of stiripentol to SLC13A5-related epileptic encephalopathy

INTRODUCTION

SLC13A5-related epileptic encephalopathy is a recently described autosomal recessive disorder that is characterized by infantile epilepsy and developmental delay. Seizures are markedly drug resistant and often induced by fever; they mainly occur in clusters, sometimes evolving into status epilepticus.

METHODS AND RESULTS

We report the use of stiripentol as an adjunctive therapy in three siblings with drug-resistant SLC13A5-related epilepsy. The three patients showed remarkable improvement in the severity and frequency of seizures, status epilepticus, emergency department visits, and alertness.

CONCLUSION

These observations extend the use of stiripentol beyond the classical Dravet syndrome, and further studies on the use of this drug in drug-resistant epilepsy, mainly of genetic origin, are warranted.

Stiripentol and vigabatrin current roles in the treatment of epilepsy

INTRODUCTION

Stiripentol and vigabatrin are the two anticonvulsant drugs currently approved in severe infantile-onset epilepsies, respectively Dravet syndrome and infantile spasms.

AREAS COVERED

For both, the indication was discovered by chance thanks to an exploratory study. Both demonstrated indisputable efficacy through randomized-controlled trials. Stiripentol as adjunctive therapy to clobazam and valproate performed better than placebo, and vigabatrin as first-line monotherapy better than the reference steroid therapy in spasms due to tuberous sclerosis. At one-year treatment vigabatrin and steroids were equally efficient in the other etiologies of spasms. However, it took more than 20 years for both drugs to be approved world-wide.

EXPERT OPINION

Stiripentol suffered from pharmacokinetic potentiation of clobazam, thus raising the question whether it was efficient per se. Finally, animal models and pharmacogenetic data on CYP2C19 confirmed its specific anticonvulsant effect. Stiripentol (in comedication with clobazam and valproate) is therefore to be recommended for Dravet patients. Vigabatrin was found to have a frequent and irreversible retinal toxicity, which required an alternative visual testing to be detected in young children. Today the benefit/risk ratio of vigabatrin as first-line is considered to be positive in infantile spasms, given the severity of this epilepsy and the lack of a safer alternative therapy.

Pharmacological considerations in the use of stiripentol for the treatment of epilepsy

INTRODUCTION

Despite the fact that more than 20 antiepileptic drugs (AEDs) are currently available, about one-third of patients still present drug resistance. Further efforts are required to develop novel and more efficacious therapeutic strategies, especially for refractory epileptic syndromes showing few and anecdotic therapeutic options.

AREAS COVERED

Stiripentol (STP) is a second generation AED that shows GABAergic activity, with immature brain selectivity, and an indirect metabolic action on co-administered AEDs. Two pivotal studies demonstrated STP efficacy in patients with Dravet syndrome with refractory partial seizures, and marketing authorization in Europe, Canada and Japan was granted thereafter. Post-marketing surveys reported a good efficacy and tolerability profile. In addition, interesting data is currently emerging regarding off-label experimentation of STP in other forms of epilepsy.

EXPERT OPINION

STP is an important addition to the limited treatment options available for patients resistant to common AEDs. The possibility to inhibit seizures through the metabolic pathway of lactate dehydrogenase and the inhibitory effects on the entry of Na(+) and Ca(2+) are the most recent findings to emerge about STP and could be proof of its neuroprotective action. Moreover, its positive effects on cognitive function, its good safety and tolerability profile and the increasing data about STP efficacy on other refractory epileptic syndromes may prove to be fertile grounds for further investigation.

Effectiveness of antiepileptic therapy in patients with PCDH19 mutations

PURPOSE

PCDH19 mutations cause epilepsy and mental retardation limited to females (EFMR) or Dravet-like syndromes. Especially in the first years of life, epilepsy is known to be highly pharmacoresistant. The aim of our study was to evaluate the effectiveness of antiepileptic therapy in patients with PCDH19 mutations.

METHODS

We report a retrospective multicenter study of antiepileptic therapy in 58 female patients with PCDH19 mutations and epilepsy aged 2-27 years (mean age 10.6 years).

RESULTS

The most effective drugs after 3 months were clobazam and bromide, with a responder rate of 68% and 67%, respectively, where response was defined as seizure reduction of at least 50%. Defining long-term response as the proportion of responders after 12 months of treatment with a given drug in relation to the number of patients treated for at least 3 months, the most effective drugs after 12 months were again bromide and clobazam, with a long-term response of 50% and 43%, respectively. Seventy-four percent of the patients became seizure-free for at least 3 months, 47% for at least one year.

SIGNIFICANCE

The most effective drugs in patients with PCDH19 mutations were bromide and clobazam. Although epilepsy in PCDH19 mutations is often pharmacoresistant, three quarters of the patients became seizure-free for at least for 3 months and half of them for at least one year. However, assessing the effectiveness of the drugs is difficult because a possible age-dependent spontaneous seizure remission must be considered.