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

A Sensitive and Selective LC-MS/MS-ESI Method for the Quantitation of Metabolites M9, M12, and M20 of Bexicaserin in Human Plasma and Urine Matrices

Bexicaserin is a highly selective 5HT2c receptor agonist being developed for the treatment of seizures associated with developmental and epileptic encephalopathies (DEEs). We report an LC-MS/MS method for the quantitative estimation of three pharmacologically inactive metabolites (M9, M12, and M20) of bexicaserin in human plasma/urine. Sample preparation involves the extraction of M9, M12, M20, and internal standards (ISs) from 25-μL plasma and 50-μL urine following protein precipitation. The chromatographic separation of analytes was achieved on a HSS T3-C18 column. The calibration curves ranged from 0.1 to 100 ng/mL for M9, 0.5-500 ng/mL for M12, and 1.0-1000 ng/mL for M20 in plasma and 2.0-2000 ng/mL for M9 and M12 and 10-10,000 ng/mL for M20 in urine. Intraday/interday precision and accuracy, linearity, matrix effect, extraction recovery, carry-over, dilution integrity, stability studies, and incurred sample reanalysis were performed in both plasma and urine. The intraday and interday accuracy and precision for metabolites met the stipulated regulatory guidelines. Stability studies in plasma and urine showed that analytes were stable at bench-top for > 23.5 h and in autosampler for > 69 h. Analytes were stable after five freeze-thaw cycles and > 552 days of long-term storage at -20°C and -80°C.

Navigating Uncertainty: Assessing Variants of Uncertain Significance in the CDKL5 Gene for Developmental and Epileptic Encephalopathy Using In Silico Prediction Tools and Computational Analysis

Mutations in the CDKL5 gene are associated with developmental and epileptic encephalopathy (DEE), a severe disorder characterized by developmental delay and epileptic activity. In genetic analyses of DEEs, variants classified as pathogenic confirm the diagnosis of the disease while Variants of Uncertain Significance (VUS) remain in a gray area due to insufficient evidence. This study aimed to optimize the interpretation of VUS in the CDKL5 gene by evaluating the performance of 22 in silico prediction tools using 186 known pathogenic or benign missense variants from the ClinVar database. The best-performing tools were then applied to analyze CDKL5 VUS variants, complemented by the evaluation of evolutionary conservation, structural analyses, and molecular dynamics simulations to assess their impact on protein structure and function. The results identified SNPred as the most reliable tool, achieving 100% accuracy, sensitivity, and specificity. Other high-performing tools, including ESM-1v, AlphaMissense, EVE, and ClinPred, demonstrated over 98% accuracy. Among 44 CDKL5 VUS variants evaluated, 20 were initially classified as pathogenic by these tools. However, further evaluation using stringent criteria-incorporating conservation scores, structural disruptions identified by Missense3D and PyMol, and molecular dynamics simulation results-led to the reclassification of 8 VUS variants as "potentially pathogenic" and the remaining 12 as "variants with conflicting data". This comprehensive approach provides a robust framework for the classification of VUS in the CDKL5 gene, offering critical insights for accurate diagnosis and treatment strategies in DEE. These findings will serve as a valuable resource for clinicians and geneticists in resolving the diagnostic ambiguity associated with VUS.

Treatment of Seizures in People with Intellectual Disability

There is a synergistic relationship between epilepsy and intellectual disability (ID), and the approach to managing people with these conditions needs to be holistic. Epilepsy is the main co-morbidity associated with ID, and clinical presentation tends to be complex, associated with higher rates of treatment resistance, multi-morbidity and premature mortality. Despite this relationship, there is limited level 1 evidence to inform treatment choice for this vulnerable population. This review updates the current evidence base for anti-seizure medication (ASM) prescribing for people with ID. Recommendations are made on the basis of evidence and expert clinical opinion and summarised into a Traffic Light System for accessibility. This review builds on work developed through UK's Royal College of Psychiatrists, Faculty of Intellectual Disability Psychiatry and includes newer pragmatic data from the Cornwall UK Ep-ID Research Register, a national research register for England and Wales that has been in existence for the last 10 years. The Register acts as a source for an in-depth exploration of the evidence base for prescribing 'newer' (third generation, specifically post-2004) ASMs. Its findings are discussed and compared. A practical approach to prescribing and choosing ASMs is recommended on the based evidence. This approach considers the drug profile, including adverse effects and clinical characteristics. The review also details newer specialist ASMs restricted to certain epilepsy syndromes, and potential future ASMs that may be available soon. For completeness, we also explore non-pharmacological interventions, including surgeries, to support epilepsy management.

A Highly Sensitive Triple Quad LC-MS/MS Method Development and Validation for the Determination of Bexicaserin (LP352) in Human Plasma and Urine Matrices

Bexicaserin is a highly selective agonist at the 5-HT2c receptor in clinical development for the treatment of seizures associated with developmental and epileptic encephalopathies (DEEs). We report an LC-MS/MS method for the quantitative estimation of bexicaserin in human plasma and urine. The sample preparation involves the extraction of bexicaserin and internal standard (13CD2-bexicaserin; IS) from 150 μL plasma and 50 μL urine using a solid phase extraction method. The chromatographic separation of bexicaserin and IS was achieved on a Poroshell EC-C18 column using 5 min gradient program. The calibration curve ranged from 0.1 to 100 ng/mL in plasma and 1.0 to 1000 ng/mL in urine. Intraday and interday precision and accuracy, linearity, matrix effect, extraction recovery, carry-over, dilution integrity, a battery of stability studies, and incurred sample reanalysis were performed for bexicaserin in both plasma and urine. The intraday and interday accuracy and precision were well within the acceptable limits in both plasma and urine matrices. Stability studies in plasma and urine showed that bexicaserin was stable on bench for 24 h, in autosampler over 54 h, five freeze-thaw cycles, and long-term storage at -20°C and -80°C for > 368 days. The validated methods were successfully applied in clinical study.

Refining management strategies for Lennox-Gastaut syndrome: Updated algorithms and practical approaches

Lennox-Gastaut syndrome (LGS) is a severe developmental and epileptic encephalopathy (DEE) characterized by multiple types of drug-resistant seizures (which must include tonic seizures) with classical onset before 8 years (although some cases with later onset have also been described), abnormal electroencephalographic features, and cognitive and behavioral impairments. Management and treatment of LGS are challenging, due to associated comorbidities and the treatment resistance of seizures. A panel of five epileptologists reconvened to provide updated guidance and treatment algorithms for LGS, incorporating recent advancements in antiseizure medications (ASMs) and understanding of DEEs. The resulting consensus document is based on current evidence from clinical trials and clinical practice and the panel's expert opinion, focusing on new ASMs with novel mechanisms of action, such as highly purified cannabidiol and fenfluramine. For a patient presenting with newly diagnosed LGS or suspected LGS, the recommended first-line treatment continues to be valproate. If this is ineffective as monotherapy, adjunctive therapy with, firstly, lamotrigine and secondly, rufinamide, is recommended. If seizure control remains suboptimal, subsequent adjunctive ASM treatment options include (alphabetically) cannabidiol, clobazam, felbamate, fenfluramine, and topiramate, although evidence for these is more limited. Whenever possible, no more than two ASMs should be used together. Nonpharmacological treatment approaches should be used in conjunction with ASM therapy and include ketogenic diet therapies, vagus nerve stimulation, and corpus callosotomy. Patients with LGS that has evolved from another type of epilepsy who are not already being treated with valproate should be transitioned to valproate and then managed using the same algorithm as for newly diagnosed LGS. Older patients with established LGS should be reviewed at least annually by a suitably experienced neurologist. The revised guidance aims to improve seizure control and quality of life for patients with LGS through personalized, evidence-based treatment strategies while addressing the challenges of accurate diagnosis and management in a rapidly evolving therapeutic landscape. PLAIN LANGUAGE SUMMARY: Lennox-Gastaut syndrome (LGS) is a severe type of epilepsy that usually starts in childhood but continues into adulthood. It is characterized by a variety of different types of seizures (abnormal electrical activity in the brain), which are difficult to treat and often cause people with the condition to fall and injure themselves. Most people with LGS have learning difficulties and need a lot of support, often in residential care. The authors are experts in treating people with LGS and this article provides up-to-date guidance and advice on how best to care for those with the condition.

Pharmacological approaches in drug-resistant pediatric epilepsies caused by pathogenic variants in potassium channel genes

Variants in genes encoding for voltage-gated K+ (Kv) channels are frequent cause of drug-resistant pediatric epilepsies. Obtaining a molecular diagnosis gives the opportunity to assess the efficacy of pharmacological strategies based on in vitro features of mutant channels. In this retrospective observational study, we selected patients with drug-resistant pediatric epilepsies caused by variants in potassium channel encoding genes, followed at the Fondazione IRCCS Istituto Neurologico Carlo Besta of Milan, Italy. After the experimental characterization of variants' functional properties in transiently transfected Chinese Hamster Ovary (CHO) cells, we identified drugs to be used as pharmacological approaches. We recruited six patients carrying different missense variants in four Kv channels (Kv7.2, Kv7.3, Kv3.1, and KNa1.1). In vitro experiments demonstrated that variants in Kv7 channels induced loss-of-function (LoF) effects, while those affecting Kv3.1 or KNa1.1 led to gain-of-function (GoF). Moreover, we found that the Kv7 channels activator gabapentin was able to revert the LoF effects caused by Kv7.2/Kv7.3 variants, and the potassium channel-blocker fluoxetine counteracted the GoF effects in Kv3.1 or KNa1.1 variants. According to experimental data, patients carrying Kv7 variants were treated with gabapentin. While this treatment resulted successful in two patients (#1, Kv7.2 G310S variant; #3, Kv7.3 V359L + Kv7.3 D542N), it resulted detrimental in the remaining case (#2, Kv7.2 D535E), requiring drug withdrawal. The application in vivo of fluoxetine to counteract GoF effects induced by Kv3.1 or KNa1.1 variants determined a significant reduction of both seizure frequency and behavior disturbances in patient #4 (Kv3.1 V425M), and in both subjects carrying KNa1.1 variants (#5, S937G and #6, R262Q). However, for the latter case, this drug was halted due to severe behavioral side effects. For most of the patients herein reported, pharmacological strategies, selected according to the in vitro functional properties of Kv-channels pathogenic variants, resulted in a significant improvement of both epileptic and cognitive features.

Perampanel reduces seizure frequency in patients with developmental and epileptic encephalopathy for a long term

Seizures in patients with developmental and epileptic encephalopathies (DEEs) are often highly resistant to various antiseizure medications. Perampanel (PER) is a novel antiseizure medication that non-competitively inhibits the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor and is expected to reduce seizure frequency not only for focal seizures and generalized tonic-clonic seizures (GTCS) but also for other seizure types. This study aimed to clarify the long-term therapeutic efficacy and tolerability of PER in patients with DEEs. We analyzed data regarding patients' background characteristics, medication retention, trends in seizure frequency, and adverse events obtained from 24 patients with DEEs who had been on PER treatment for 60 months. The retention rates were 62.5% and 46.9% at 12 and 60 months, respectively. At 60 months after PER initiation, the rate of patients with > 50% seizure reduction was 33.3%, 33.3%, 38.5%, 54.5%, 54.5%, and 36.4% among patients with atypical absence seizures, tonic seizures, focal seizures, GTCS, myoclonic seizures, and atonic seizures, respectively. The frequency of adverse events was 70.8%. PER showed long-term efficacy in various seizure types. PER is a promising treatment option for patients with DEEs.

Clinical applications of small-molecule GABAAR modulators for neurological disorders

Gamma-aminobutyric acid type A receptor (GABAAR) modulators are crucial in treating neurological and psychiatric disorders, including epilepsy, anxiety, insomnia, and depression. This review examines the synthetic approaches and clinical applications of representative small-molecule GABAAR modulators. Benzodiazepines, such as Diazepam, are well-known positive allosteric modulators (PAMs) that enhance GABAAR function, providing therapeutic effects but also associated with side effects like sedation and dependence. Non-benzodiazepine modulators, including Z-drugs like Zolpidem and Zaleplon, offer improved selectivity for the α1 subunit of GABAAR, reducing some of these side effects. Neurosteroids such as allopregnanolone and its synthetic analogs, including Brexanolone, have emerged as potent GABAAR modulators with applications in conditions like postpartum depression and refractory epilepsy. Advances in molecular biology and pharmacology have facilitated the development of isoform-specific modulators, potentially reducing off-target effects and enhancing therapeutic profiles. Additionally, combining GABAAR modulators with other therapeutic agents has shown promise in enhancing efficacy and minimizing side effects. This review highlights the design strategies, pharmacodynamics, clinical efficacy, and safety profiles of these compounds, emphasizing the opportunities for developing novel GABAAR modulators with improved therapeutic outcomes.

The expanding field of genetic developmental and epileptic encephalopathies: current understanding and future perspectives

Recent advances in genetic testing technologies have revolutionised the identification of genetic abnormalities in early onset developmental and epileptic encephalopathies (DEEs). In this Review, we provide an update on the expanding landscape of genetic factors contributing to DEEs, encompassing over 800 reported genes. We focus on the cellular and molecular mechanisms driving epileptogenesis, with an emphasis on emerging therapeutic strategies and effective treatment options. We explore noteworthy, novel genes linked to DEE phenotypes, such as gBRAT-1 and GNAO1, and gene families such as GRIN and HCN. Understanding the network-level effects of gene variants will pave the way for potential gene therapy applications. Given the diverse comorbidities associated with DEEs, a multidisciplinary team approach is essential. Despite ongoing efforts and improved genetic testing, DEEs lack a cure, and treatment complexities persist. This Review underscores the necessity for larger international prospective studies focusing on both seizure outcomes and developmental trajectories.

Next-generation sequencing in pediatric-onset epilepsies: Analysis with target panels and personalized therapeutic approach

OBJECTIVE

The objective of this study is to report the results of the genetic analysis in a large and well-characterized population with pediatric-onset epilepsies and to identify those who could benefit from precision medicine treatments.

METHODS

In this retrospective observational study, we consecutively recruited patients with pediatric-onset epilepsy observed at a tertiary neurological center over a time span of 7 years, collecting clinical and laboratory findings. Following in-depth diagnostic process to exclude possible structural and metabolic causes of the disease, patients with a suspected genetically determined etiology underwent next-generation sequencing (NGS) screening with panels for the analysis of target genes causative of epilepsy.

RESULTS

We detected likely pathogenic or pathogenic variants (classes IV and V) in 24% of the 562 patients who underwent genetic investigations. By the evaluation of patients' data, we observed that some features (onset of epilepsy before one year old, presence of neurological deficits, psychomotor delay/cognitive disability, and malformative aspects at brain MRI) were significantly associated with class IV or V variants. Moreover, statistical analysis showed that the diagnostic yield resulted higher for patients affected by Progressive Myoclonic Epilepsy (PME) and with early onset developmental and epileptic encephalopathies (DEE), compared with focal epilepsies, genetic generalized epilepsies, DEE with onset at/after 1 y.o., and unclassified epileptic syndromes. According to the results of the genetic screening, up to 33% of patients carrying class IV or V variants resulted potentially eligible for precision medicine treatments.

SIGNIFICANCE

The large-scale application of NGS multigene panels of analysis is a useful tool for the molecular diagnosis of patients with pediatric-onset epilepsies, allowing the identification of those who could benefit from a personalized therapeutic approach.

PLAIN LANGUAGE SUMMARY

The analysis of patients with pediatric-onset epilepsy using advanced technologies for the screening of all the implicated genes allows the identification of the cause of diseases in an ever-increasing number of cases. Understanding the pathogenic mechanisms could, in some cases, guide the selection and optimization of appropriate treatment approaches for patients.

Is there a biochemical basis for purinergic P2X3 and P2X4 receptor antagonists to be considered as anti-seizure medications?

Patients with epilepsy require improved medications. Purinergic receptors were identified as late as 1976 and are slowly emerging as potential drug targets for the discovery of antiseizure medications. While compounds interacting with these receptors have been approved for use as medicines (e.g., gefapixant for cough) and continue to be explored for a number of diseases (e.g., pain, cancer), there have been no purinergic receptor antagonists that have been advanced for epilepsy. There are very few studies on the channel conducting receptors, P2X3 and P2X4, that suggest their possible role in seizure generation or control. However, the limited data available provides some compelling reasons to believe that they could be valuable antiseizure medication drug targets. The data implicating P2X3 and P2X4 receptors in epilepsy includes the role played by ATP in neuronal excitability and seizures, receptor localization, increased receptor expression in epileptic brain, the involvement of these receptors in seizure-associated inflammation, crosstalk between these purinergic receptors and neuronal processes involved in seizures (GABAergic and glutamatergic neurotransmission), and the significant attenuation of seizures and seizure-like activity with P2X receptor blockade. The discovery of new and selective antagonists for P2X3 and P2X4 receptors is ongoing, armed with new structural data to guide rational design. The availability of safe, brain-penetrant compounds will likely encourage the clinical exploration of epilepsy as a disease entity.

Respiratory Dysfunction in Epileptic Encephalopathies: Insights and Challenges

Epileptic encephalopathies constitute a group of severe epileptic disorders characterized by intractable seizures and cognitive regression. Beyond the hallmark neurological manifestations, these disorders frequently exhibit associated respiratory dysfunction, which is increasingly recognized as a critical aspect of their pathophysiology. Respiratory abnormalities in epileptic encephalopathies encompass a spectrum of manifestations, ranging from subtle alterations in breathing patterns to life-threatening events such as apneas and hypoventilation. These respiratory disturbances often occur during seizures, the interictal period, or even persist chronically, leading to significant morbidity and mortality. We explore the varied clinical presentations and their implications on patient outcomes, emphasizing the need for heightened awareness among clinicians. This review unravels the intricate mechanisms linking epilepsy and respiratory dysfunction. GABAergic and glutamatergic imbalances, alterations in central respiratory centers, and abnormal autonomic control are among the key factors contributing to respiratory disturbances in these patients. We elucidate the neurobiological intricacies that underlie these processes and their relevance to therapeutic interventions. Accurate diagnosis of respiratory dysfunction in epileptic encephalopathies is often hindered by its diverse clinical phenotypes and the absence of routine screening protocols. We scrutinize the diagnostic hurdles, highlighting the necessity of comprehensive respiratory assessments in managing these patients. Timely recognition of respiratory issues may guide treatment decisions and mitigate complications. Management of respiratory dysfunction in epileptic encephalopathies is complex and necessitates a multidisciplinary approach. We explore various therapeutic modalities, including antiepileptic drugs (AEDs), ventilatory support, and novel interventions like neuromodulation techniques. The review emphasizes the individualized nature of treatment strategies tailored to each patient's specific needs. In conclusion, this narrative review offers a comprehensive overview of respiratory dysfunction in epileptic encephalopathies, shedding light on its clinical importance, underlying mechanisms, diagnostic challenges, and therapeutic considerations. By addressing these insights and challenges, we hope to inspire further research and innovation to enhance the care and outcomes of patients with epileptic encephalopathies.