Pharmacological characterization of the 6 Hz psychomotor seizure model of partial epilepsy

Novel Alaninamide Derivatives with Drug-like Potential for Development as Antiseizure and Antinociceptive Therapies─In Vitro and In Vivo Characterization

In the present study, a series of original alaninamide derivatives have been designed applying a combinatorial chemistry approach, synthesized, and characterized in the in vivo and in vitro assays. The obtained molecules showed potent and broad-spectrum activity in basic seizure models, namely, the maximal electroshock (MES) test, the 6 Hz (32 mA) seizure model, and notably, the 6 Hz (44 mA) model of pharmacoresistant seizures. Most potent compounds 26 and 28 displayed the following pharmacological values: ED50 = 64.3 mg/kg (MES), ED50 = 15.6 mg/kg (6 Hz, 32 mA), ED50 = 29.9 mg/kg (6 Hz, 44 mA), and ED50 = 34.9 mg/kg (MES), ED50 = 12.1 mg/kg (6 Hz, 32 mA), ED50 = 29.5 mg/kg (6 Hz, 44 mA), respectively. Additionally, 26 and 28 were effective in the ivPTZ seizure threshold test and had no influence on the grip strength. Moreover, lead compound 28 was tested in the PTZ-induced kindling model, and then, its influence on glutamate and GABA levels in the hippocampus and cortex was evaluated by the high-performance liquid chromatography (HPLC) method. In addition, 28 revealed potent efficacy in formalin-induced tonic pain, capsaicin-induced pain, and oxaliplatin- and streptozotocin-induced peripheral neuropathy. Pharmacokinetic studies and in vitro ADME-Tox data proved favorable drug-like properties of 28. The patch-clamp recordings in rat cortical neurons showed that 28 at a concentration of 10 μM significantly inhibited fast sodium currents. Therefore, 28 seems to be an interesting candidate for future preclinical development in epilepsy and pain indications.

Characterization of the intrahippocampal kainic acid model in female mice with a special focus on seizure suppression by antiseizure medications

Despite special challenges in the medical treatment of women with epilepsy, in particular preclinical animal studies were focused on males for decades and females have only recently moved into the focus of scientific interest. The intrahippocampal kainic acid (IHKA) mouse model of temporal lobe epilepsy (TLE) is one of the most studied models in males reproducing electroencephalographic (EEG) and histopathological features of human TLE. Hippocampal paroxysmal discharges (HPDs) were described as drug resistant focal seizures in males. Here, we investigated the IHKA model in female mice, in particular drug-resistance of HPDs and the influence of antiseizure medications (ASMs) on the power spectrum. After injecting kainic acid (KA) unilaterally into the hippocampus of female mice, we monitored the development of epileptiform activity by local field potential (LFP) recordings. Subsequently, we evaluated the effect of the commonly prescribed ASMs lamotrigine (LTG), oxcarbazepine (OXC) and levetiracetam (LEV), as well as the benzodiazepine diazepam (DZP) with a focus on HPDs and power spectral analysis and assessed neuropathological alterations of the hippocampus. In the IHKA model, female mice replicated key features of human TLE as previously described in males. Importantly, HPDs in female mice did not respond to commonly prescribed ASMs in line with the drug-resistance in males, thus representing a suitable model of drug-resistant seizures. Intriguingly, we observed an increased occurrence of generalized seizures after LTG. Power spectral analysis revealed a pronounced increase in the delta frequency range after the higher dose of 30 mg/kg LTG. DZP abolished HPDs and caused a marked reduction over a wide frequency range (delta, theta, and alpha) of the power spectrum. By characterizing the IHKA model of TLE in female mice we address an important gap in basic research. Considering the special challenges complicating the therapeutic management of epilepsy in women, inclusion of females in preclinical studies is imperative. A well-characterized female model is a prerequisite for the development of novel therapeutic strategies tailored to sex-specific needs and for studies on the effect of epilepsy and ASMs during pregnancy.

Development of SV2A Ligands for Epilepsy Treatment: A Review of Levetiracetam, Brivaracetam, and Padsevonil

Epilepsy is a common neurological disorder that is primarily treated with antiseizure medications (ASMs). Although dozens of ASMs are available in the clinic, approximately 30% of epileptic patients have medically refractory seizures; other limitations in most traditional ASMs include poor tolerability and drug-drug interactions. Therefore, there is an urgent need to develop alternative ASMs. Levetiracetam (LEV) is a first-line ASM that is well tolerated, has promising efficacy, and has little drug-drug interaction. Although it is widely accepted that LEV acts through a unique therapeutic target synaptic vesicle protein (SV) 2A, the molecular basis of its action remains unknown. Even so, the next-generation SV2A ligands against epilepsy based on the structure of LEV have achieved clinical success. This review highlights the research and development (R&D) process of LEV and its analogs, brivaracetam and padsevonil, to provide ideas and experience for the R&D of novel ASMs.

Alpha-2a adrenergic receptor activation in genetic absence epilepsy: An absence status model?

OBJECTIVE

The objective of the study was to propose a candidate animal model of absence status epilepticus induced by specific alpha-2a adrenergic receptor (α2AR) activation. We also aim to investigate the responsiveness of this model to classical anti-status or anti-absence medications.

METHODS

An α2AR agonist, dexmedetomidine (DEX), was injected intracerebroventricularly into adult rats with genetic absence epilepsy, and their electroencephalography (EEG) was recorded. The total duration, number, and mean duration of each spike-and-wave discharges (SWDs) were evaluated. The blocks of absence status events were classified as the initial and second sets of absence statuses. Ethosuximide (ETX) was administered as a pretreatment to another group of rats and later injected with 2.5 μg DEX. In addition, ETX, valproic acid (VPA), diazepam (DIAZ), and atipamezole (ATI) were administered after induced status-like events following DEX administration. Power spectral characteristics and coherence analysis were performed on the EEG to assess the absence status events and sleep.

RESULTS

The 2.5 μg dose of DEX increased the total SWD duration and induced continuous SWDs up to 26 min. Following the initial absence status event, sleep was induced; then, the second period of absence status-like activities were initiated. ETX pretreatment blocked the occurrence of absence status-like activities. Power spectral density analyses revealed that DEX-induced post-sleep activities had higher power in delta frequency band (1-4 Hz) and attenuated power of 7 Hz harmonics (14 and 21 Hz) than the pre-injection seizure. The mean duration of SWDs were decreased in all the groups, but occasional prolonged activities were seen in ETX or VPA-injected rats but not with DIAZ or ATI.

SIGNIFICANCE

This study presents an absence status epilepticus animal model that is activated by α2AR activation to investigate the pathophysiological role of absence status. Unlike other agents ATI switched off the second set of absence statuses to normal SWDs, without sedation or lethargy, can show it may preferentially block absence status-like activity.

THE PLAIN LANGUAGE SUMMARY

This study proposes a rat model for prolonged seizures, resembling absence status epilepticus. Activating the brain's alpha-2a adrenergic receptor with dexmedetomidine induced seizures lasting up to 26 minutes. Ethosuximide pretreatment and post-treatment with valproic acid, diazepam, and atipamezole decreased induced seizures. The findings suggest this model is valuable for studying absence status epilepticus. In addition, atipamezole normalized abnormal seizures without sedation, hinting at its potential for targeted treatment and further research.

Challenges and directions in epilepsy diagnostics and therapeutics: Proceedings of the 17th Epilepsy Therapies and Diagnostics Development conference

Substantial efforts are underway toward optimizing the diagnosis, monitoring, and treatment of seizures and epilepsy. We describe preclinical programs in place for screening investigational therapeutic candidates in animal models, with particular attention to identifying and eliminating drugs that might paradoxically aggravate seizure burden. After preclinical development, we discuss challenges and solutions in the design and regulatory logistics of clinical trial execution, and efforts to develop disease biomarkers and interventions that may be not only seizure-suppressing, but also disease-modifying. As disease-modifying treatments are designed, there is clear recognition that, although seizures represent one critical therapeutic target, targeting nonseizure outcomes like cognitive development or functional outcomes requires changes to traditional designs. This reflects our increasing understanding that epilepsy is a disease with profound impact on quality of life for the patient and caregivers due to both seizures themselves and other nonseizure factors. This review examines selected key challenges and future directions in epilepsy diagnostics and therapeutics, from drug discovery to translational application.

Azoles display promising anticonvulsant effects through possible PPAR-α activation

Azoles such as nafimidone, denzimol and loreclezole are known for their clinical efficacy against epilepsy, and loreclezole acts by potentiating γ-aminobutyric acid (GABA)-ergic currents. In the current study, we report a series of azole derivatives in alcohol ester and oxime ester structure showing promising anticonvulsant effects in 6 Hz and maximal electro shock (MES) models with minimal toxicity. The most promising of the series, 5f, was active in both 6 Hz and MES tests with a median effective dose (ED50) of 118.92 mg/kg in 6 Hz test and a median toxic dose (TD50) twice as high in mice. The compounds were predicted druglike and blood-brain barrier (BBB) penetrant in silico. Contrary to what was expected, the compounds showed no in vitro affinity to GABAA receptors (GABAARs) in radioligand binding assays; however, they were found structurally similar to peroxisome proliferator-activated receptors alpha (PPAR-α) agonists and predicted to show high affinity and agonist-like binding to PPAR-α in molecular docking studies. As a result, 5f emerged as a safe azole anticonvulsant with a wide therapeutic window and possible action through PPAR-α activation.

A comprehensive assessment of palmatine as anticonvulsant agent - In vivo and in silico studies

Previously, we demonstrated that palmatine (PALM) - an isoquinoline alkaloid from Berberis sibrica radix, exerted antiseizure activity in the pentylenetetrazole (PTZ)-induced seizure assay in larval zebrafish. The aim of the present study was to more precisely characterize PALM as a potential anticonvulsant drug candidate. A range of zebrafish and mouse seizure/epilepsy models were applied in the investigation. Immunostaining analysis was conducted to assess the changes in mouse brains, while in silico molecular modelling was performed to determine potential targets for PALM. Accordingly, PALM had anticonvulsant effect in ethyl 2-ketopent-4-enoate (EKP)-induced seizure assay in zebrafish larvae as well as in the 6 Hz-induced psychomotor seizure threshold and timed infusion PTZ tests in mice. The protective effect in the EKP-induced seizure assay was confirmed in the local field potential recordings. PALM did not affect seizures in the gabra1a knockout line of zebrafish larvae. In the scn1Lab-/- zebrafish line, pretreatment with PALM potentiated seizure-like behaviour of larvae. Repetitive treatment with PALM, however, did not reduce development of PTZ-induced seizure activity nor prevent the loss of parvalbumin-interneurons in the hippocampus of the PTZ kindled mice. In silico molecular modelling revealed that the noted anticonvulsant effect of PALM in EKP-induced seizure assay might result from its interactions with glutamic acid decarboxylase and/or via AMPA receptor non-competitive antagonism. Our study has demonstrated the anticonvulsant activity of PALM in some experimental models of seizures, including a model of pharmacoresistant seizures induced by EKP. These results indicate that PALM might be a suitable new drug candidate but the precise mechanism of its anticonvulsant activity has to be determined.

Current advances in rodent drug-resistant temporal lobe epilepsy models: Hints from laboratory studies

Anti-seizure drugs (ASDs) are the first choice for the treatment of epilepsy, but there is still one-third of patients with epilepsy (PWEs) who are resistant to two or more appropriately chosen ASDs, named drug-resistant epilepsy (DRE). Temporal lobe epilepsy (TLE), a common type of epilepsy usually associated with hippocampal sclerosis (HS), shares the highest proportion of drug resistance (approximately 70%). In view of the key role of the temporal lobe in memory, emotion, and other physiological functions, patients with drug-resistant temporal lobe epilepsy (DR-TLE) are often accompanied by serious complications, and surgical procedures also yield extra considerations. The exact mechanisms for the genesis of DR-TLE remain unillustrated, which makes it hard to manage patients with DR-TLE in clinical practice. Animal models of DR-TLE play an irreplaceable role in both understanding the mechanism and searching for new therapeutic strategies or drugs. In this review article, we systematically summarized different types of current DR-TLE models, and then recent advances in mechanism investigations obtained in these models were presented, especially with the development of advanced experimental techniques and tools. We are deeply encouraged that novel strategies show great therapeutic potential in those DR-TLE models. Based on the big steps reached from the bench, a new light has been shed on the precise management of DR-TLE.

Effect of dietary supplementation with Lactobacillus helveticus R0052 on seizure thresholds and antiseizure potency of sodium valproate in mice

OBJECTIVE

Both animal and human studies, though limited, showed that multi-strain probiotic supplementation may reduce the number of seizures and/or seizure severity. Here, we evaluated the effect of a single strain probiotic supplementation on seizure susceptibility, antiseizure efficacy of sodium valproate, and several behavioral parameters in mice.

METHODS

Lactobacillus helveticus R0052 was given orally for 28 days. Its influence on seizure thresholds was evaluated in the ivPTZ- and electrically-induced seizure tests. The effect on the antiseizure potency of valproate was assessed in the scPTZ test. We also investigated the effects of probiotic supplementation on anxiety-related behavior (in the elevated plus maze and light/dark box tests), motor coordination (in the accelerating rotarod test), neuromuscular strength (in the grip-strength test), and spontaneous locomotor activity. Serum and brain concentrations of valproate as well as cecal contents of SCFAs and lactate were determined using HPLC method.

RESULTS

L. helveticus R0052 significantly increased the threshold for the 6 Hz-induced psychomotor seizure. There was also a slight increase in the threshold for myoclonic and clonic seizure in the ivPTZ test. L. helveticus R0052 did not affect the threshold for tonic seizures both in the maximal electroshock- and ivPTZ-induced seizure tests. No changes in the antiseizure potency of valproate against the PTZ-induced seizures were reported. Interestingly, L. helveticus R0052 increased valproate concentration in serum, but not in the brain. Moreover, L. helveticus R0052 did not produce any significant effects on anxiety-related behavior, motor coordination, neuromuscular strength, and locomotor activity. L. helveticus R0052 supplementation resulted in increased concentrations of total SCFAs, acetate, and butyrate.

CONCLUSIONS

Altogether, this study shows that a single-strain probiotic - L. helveticus R0052 may decrease seizure susceptibility and this effect can be mediated, at least in part, by increased production of SCFAs. In addition, L. helveticus R0052 may affect bioavailability of valproate, which warrants further investigations.

Ketogenic diet therapy for pediatric epilepsy is associated with alterations in the human gut microbiome that confer seizure resistance in mice

The gut microbiome modulates seizure susceptibility and the anti-seizure effects of the ketogenic diet (KD) in animal models, but whether these relationships translate to KD therapies for human epilepsy is unclear. We find that the clinical KD alters gut microbial function in children with refractory epilepsy. Colonizing mice with KD-associated microbes promotes seizure resistance relative to matched pre-treatment controls. Select metagenomic and metabolomic features, including those related to anaplerosis, fatty acid β-oxidation, and amino acid metabolism, are seen with human KD therapy and preserved upon microbiome transfer to mice. Mice colonized with KD-associated gut microbes exhibit altered hippocampal transcriptomes, including pathways related to ATP synthesis, glutathione metabolism, and oxidative phosphorylation, and are linked to susceptibility genes identified in human epilepsy. Our findings reveal key microbial functions that are altered by KD therapies for pediatric epilepsy and linked to microbiome-induced alterations in brain gene expression and seizure protection in mice.

Natural product-derived therapies for treating drug-resistant epilepsies: From ethnopharmacology to evidence-based medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Epilepsy is one of the most prevalent neurological human diseases, affecting 1% of the population in all age groups. Despite the availability of over 25 anti-seizure medications (ASMs), which are approved in most industrialized countries, approximately 30% of epilepsy patients still experience seizures that are resistant to these drugs. Since ASMs target only limited number of neurochemical mechanisms, drug-resistant epilepsy (DRE) is not only an unmet medical need, but also a formidable challenge in drug discovery.

AIM

In this review, we examine recently approved epilepsy drugs based on natural product (NP) such as cannabidiol (CBD) and rapamycin, as well as NP-based epilepsy drug candidates still in clinical development, such as huperzine A. We also critically evaluate the therapeutic potential of botanical drugs as polytherapy or adjunct therapy specifically for DRE.

METHODS

Articles related to ethnopharmacological anti-epileptic medicines and NPs in treating all forms of epilepsy were collected from PubMed and Scopus using keywords related to epilepsy, DRE, herbal medicines, and NPs. The database clinicaltrials.gov was used to find ongoing, terminated and planned clinical trials using herbal medicines or NPs in epilepsy treatment.

RESULTS

A comprehensive review on anti-epileptic herbal drugs and natural products from the ethnomedical literature is provided. We discuss the ethnomedical context of recently approved drugs and drug candidates derived from NPs, including CBD, rapamycin, and huperzine A. Recently published studies on natural products with preclinical efficacy in animal models of DRE are summarized. Moreover, we highlight that natural products capable of pharmacologically activating the vagus nerve (VN), such as CBD, may be therapeutically useful to treat DRE.

CONCLUSIONS

The review highlights that herbal drugs utilized in traditional medicine offer a valuable source of potential anti-epileptic drug candidates with novel mechanisms of action, and with clinical promise for the treatment of drug-resistant epilepsy (DRE). Moreover, recently developed NP-based anti-seizure medications (ASMs) indicate the translational potential of metabolites of plant, microbial, fungal and animal origin.

Mechanochemical synthesis and anticonvulsant activity of 3-aminopyrrolidine-2,5-dione derivatives

A series of 3-aminopyrrolidine-2,5-dione derivatives was synthesized and tested for anticonvulsant activity. Succinimide derivatives were obtained from a simple solvent-based reaction and a mechanochemical aza-Michael reaction of maleimide or its N-substituted derivatives with selected amines. The structure of the compounds was confirmed by spectroscopic methods (NMR, FT-IR, HPLC, ESI-MS, EA and XRD for four compounds). The cytotoxic activity of the succinimide derivatives was evaluated using HepG2 cells for hepatocytotoxicity and SH-SY5Y cells for neurocytotoxicity. None of the studied compounds showed hepatocytotoxicity and two showed neurocytotoxicity. Initial anticonvulsant screening was performed in mice using the psychomotor seizure test (6 Hz, 32 mA). The selected compounds were evaluated in the following acute models of epilepsy: the maximal electroshock test, psychomotor seizure test (6 Hz, 44 mA), subcutaneous pentylenetetrazole seizure test, and acute neurotoxicity (rotarod test). The most active compound 3-((4-chlorophenyl)amino)pyrrolidine-2,5-dione revealed antiseizure activity in all seizure models (including pharmacoresistant seizures) and showed better median effective doses (ED50) and protective index values than the reference compound, ethosuximide. Furthermore, 3-(benzylamino)pyrrolidine-2,5-dione and 3-(phenylamino)pyrrolidine-2,5-dione exhibited antiseizure activity in the 6 Hz and MES tests, and 3-(butylamino)-1-phenylpyrrolidine-2,5-dione and 3-(benzylamino)-1-phenylpyrrolidine-2,5-dione exhibited antiseizure activity in the 6 Hz test. All active compounds demonstrated low in vivo neurotoxicity in the rotarod test and yielded favourable protective indices.

Revisiting the concept of drug-resistant epilepsy: A TASK1 report of the ILAE/AES Joint Translational Task Force

Despite progress in the development of anti-seizure medications (ASMs), one third of people with epilepsy have drug-resistant epilepsy (DRE). The working definition of DRE, proposed by the International League Against Epilepsy (ILAE) in 2010, helped identify individuals who might benefit from presurgical evaluation early on. As the incidence of DRE remains high, the TASK1 workgroup on DRE of the ILAE/American Epilepsy Society (AES) Joint Translational Task Force discussed the heterogeneity and complexity of its presentation and mechanisms, the confounders in drawing mechanistic insights when testing treatment responses, and barriers in modeling DRE across the lifespan and translating across species. We propose that it is necessary to revisit the current definition of DRE, in order to transform the preclinical and clinical research of mechanisms and biomarkers, to identify novel, effective, precise, pharmacologic treatments, allowing for earlier recognition of drug resistance and individualized therapies.

Additive Anticonvulsant Profile and Molecular Docking Analysis of 5,5'-Diphenylhydantoin Schiff Bases and Phenytoin

Four 5,5'-diphenylhydantoin Schiff bases possessing different aromatic species (SB1-SB4) were recently synthesized and characterized using spectroscopic and electrochemical tools. The present study aimed to ascertain the anticonvulsant activity of the novel phenytoin derivatives SB1-Ph, SB2-Ph, SB3-Ph, and SB4-Ph, containing different electron-donor and electron-acceptor groups, and their possible mechanism of action. The SB2-Ph exhibited the highest potency to suppress the seizure spread with ED50 = 8.29 mg/kg, comparable to phenytoin (ED50 = 5.96 mg/kg). While SB2-Ph did not produce neurotoxicity and sedation, it decreased locomotion and stereotypy compared to control. When administered in combination, the four Schiff bases decreased the phenytoin ED50 by more than 2× and raised the protective index by more than 7× (phenytoin+SB2-Ph). The strongest correlation between in-vivo and docking study results was found for ligands' interaction energies with kappa and delta receptors. These data, combined with the worst interaction energies of our ligands with the mu receptor, suggest that the primary mechanism of their action involves the kappa and delta receptors, where the selectivity to the kappa receptor leads to higher biological effects. Our findings suggest that the four Schiff bases might be promising candidates with potential applications as a safe and effective adjuvant in epilepsy.

Discovery of E2730, a novel selective uncompetitive GAT1 inhibitor, as a candidate for anti-seizure medication

OBJECTIVE

As of 2022, 36 anti-seizure medications (ASMs) have been licensed for the treatment of epilepsy, however, adverse effects (AEs) are commonly reported. Therefore, ASMs with a wide margin between therapeutic effects and AEs are preferred over ASMs that are associated with a narrow margin between efficacy and risk of AEs. E2730 was discovered using in vivo phenotypic screening and characterized as an uncompetitive, yet selective, inhibitor of γ-aminobutyric acid (GABA) transporter 1 (GAT1). Here, we describe the preclinical characteristics of E2730.

METHODS

Anti-seizure effects of E2730 were evaluated in several animal models of epilepsy: corneal kindling, 6 Hz-44 mA psychomotor seizure, amygdala kindling, Fragile X syndrome, and Dravet syndrome models. Effects of E2730 on motor coordination were assessed in accelerating rotarod tests. The mechanism of action of E2730 was explored by [3 H]E2730 binding assay. The GAT1-selectivity over other GABA transporters was examined by GABA uptake assay of GAT1, GAT2, GAT3, or betaine/GABA transporter 1 (BGT-1) stably expressing HEK293 cells. To further investigate the mechanism for E2730-mediated inhibition of GAT1, in vivo microdialysis and in vitro GABA uptake assays were conducted under conditions of different GABA concentrations.

RESULTS

E2730 showed anti-seizure effects in the assessed animal models with an approximately >20-‍fold margin between efficacy and motor incoordination. [3 H]E2730 binding on brain synaptosomal membrane was abolished in GAT1-deficient mice, and E2730 selectively inhibited GAT1-mediated GABA uptake over other GABA transporters. In addition, results of GABA uptake assays showed that E2730-mediated inhibition of GAT1 positively correlated to the level of ambient GABA in vitro. E2730 also increased extracellular GABA concentration in hyperactivated conditions but not under basal levels in vivo.

SIGNIFICANCE

E2730 is a novel, selective, uncompetitive GAT1 inhibitor, which acts selectively under the condition of increasing synaptic activity, contributing to a wide margin between therapeutic effect and motor incoordination.

Toward the use of novel alternative methods in epilepsy modeling and drug discovery

Epilepsy is a chronic brain disease and, considering the amount of people affected of all ages worldwide, one of the most common neurological disorders. Over 20 novel antiseizure medications (ASMs) have been released since 1993, yet despite substantial advancements in our understanding of the molecular mechanisms behind epileptogenesis, over one-third of patients continue to be resistant to available therapies. This is partially explained by the fact that the majority of existing medicines only address seizure suppression rather than underlying processes. Understanding the origin of this neurological illness requires conducting human neurological and genetic studies. However, the limitation of sample sizes, ethical concerns, and the requirement for appropriate controls (many patients have already had anti-epileptic medication exposure) in human clinical trials underscore the requirement for supplemental models. So far, mammalian models of epilepsy have helped to shed light on the underlying causes of the condition, but the high costs related to breeding of the animals, low throughput, and regulatory restrictions on their research limit their usefulness in drug screening. Here, we present an overview of the state of art in epilepsy modeling describing gold standard animal models used up to date and review the possible alternatives for this research field. Our focus will be mainly on ex vivo, in vitro, and in vivo larval zebrafish models contributing to the 3R in epilepsy modeling and drug screening. We provide a description of pharmacological and genetic methods currently available but also on the possibilities offered by the continued development in gene editing methodologies, especially CRISPR/Cas9-based, for high-throughput disease modeling and anti-epileptic drugs testing.

Identification of New Antiseizure Medication Candidates in Preclinical Animal Studies

Epilepsy is a multifactorial neurologic disease that often leads to many devastating disabilities and an enormous burden on the healthcare system. Until now, drug-resistant epilepsy has presented a major challenge for approximately 30% of the epileptic population. The present article summarizes the validated rodent models of seizures employed in pharmacological researches and comprehensively reviews updated advances of novel antiseizure candidates in the preclinical phase. Newly discovered compounds that demonstrate antiseizure efficacy in preclinical trials will be discussed in the review. It is inspiring that several candidates exert promising antiseizure activities in drug-resistant seizure models. The representative compounds consist of derivatives of hybrid compounds that integrate multiple approved antiseizure medications, novel positive allosteric modulators targeting subtype-selective γ-Aminobutyric acid type A receptors, and a derivative of cinnamamide. Although the precise molecular mechanism, pharmacokinetic properties, and safety are not yet fully clear in every novel antiseizure candidate, the adapted approaches to design novel antiseizure medications provide new insights to overcome drug-resistant epilepsy.

Anticonvulsant effects of cenobamate in chemically and electrically induced seizure models in rodents

Background

Cenobamate is an antiseizure medication used to treat partial-onset (focal) seizures. It is a molecule with one chiral center and a unique dual mechanism of action: enhancement of fast and slow inactivation of sodium channels with preferential inhibition of the persistent current and positive allosteric modulation of GABAA receptor-mediated ion channels.

Aims/Methods

Anticonvulsant effects of cenobamate (YKP3089; R-enantiomer), YKP3090 (S-enantiomer), and YKP1983 (racemate) were evaluated in chemically and electrically induced focal and generalized seizure models in rodents. The Genetic Absence Epilepsy Rat from Strasbourg (GAERS) model examined the effect of cenobamate on spike-wave seizures. Motor coordination was assessed with rotarod tests and minimal motor impairment exams.

Results

Early in development, cenobamate was found to have activity in focal and generalized seizure models in animals and was selected for continued development. Cenobamate prevented seizures in a dose-dependent manner, prevented seizure spread, and increased seizure threshold without potentiating seizure initiation or the development of tolerance to its anticonvulsant effects. In contrast, YKP3090 and YKP1983 were only effective against generalized tonic-clonic seizures. Cenobamate also protected mice from 6 Hz psychomotor-induced seizures. Cenobamate showed significant dose-dependent reductions in the number and cumulative duration of spike-and-wave discharges in the GAERS model.

Discussion

Cenobamate showed efficacy or efficacy signals in all animal models of epilepsy tested with a favorable risk-versus-benefit ratio, supporting its clinical use in the treatment of partial-onset (focal) seizures in adults and warranting further clinical research in generalized seizures and absence seizures.

Loss of normal Alzheimer's disease-associated Presenilin 2 function alters antiseizure medicine potency and tolerability in the 6-Hz focal seizure model

Introduction

Patients with early-onset Alzheimer's disease (EOAD) experience seizures and subclinical epileptiform activity, which may accelerate cognitive and functional decline. Antiseizure medicines (ASMs) may be a tractable disease-modifying strategy; numerous ASMs are marketed with well-established safety. However, little information is available to guide ASM selection as few studies have rigorously quantified ASM potency and tolerability in traditional seizure models in rodents with EOAD-associated risk factors. Presenilin 2 (PSEN2) variants evoke EOAD, and these patients experience seizures. This study thus established the anticonvulsant profile of mechanistically distinct ASMs in the frontline 6-Hz limbic seizure test evoked in PSEN2-knockout (KO) mice to better inform seizure management in EOAD.

Methods

The median effective dose (ED50) of prototype ASMs was quantified in the 6-Hz test in male and female PSEN2-KO and wild-type (WT) C57BL/6J mice (3-4 months old). Minimal motor impairment (MMI) was assessed to estimate a protective index (PI). Immunohistological detection of cFos established the extent to which 6-Hz stimulation activates discrete brain regions in KO vs. WT mice.

Results

There were significant genotype-related differences in the potency and tolerability of several ASMs. Valproic acid and levetiracetam were significantly more potent in male KO than in WT mice. Additionally, high doses of valproic acid significantly worsened MMI in KO mice. Conversely, carbamazepine was significantly less potent in female KO vs. WT mice. In both male and female KO mice vs. WTs, perampanel and lamotrigine were equally potent. However, there were marked genotype-related shifts in PI of both carbamazepine and perampanel, with KO mice exhibiting less MMI at the highest doses tested. Gabapentin was ineffective against 6-Hz seizures in KO mice vs. WTs without MMI changes. Neuronal activation 90 min following 6-Hz stimulation was significantly increased in the posterior parietal association cortex overlying CA1 and in the piriform cortex of WT mice, while stimulation-induced increases in cFos immunoreactivity were absent in KO mice.

Discussion

Acute ASM potency and tolerability in the high-throughput 6-Hz test may be significantly altered with loss of normal PSEN2 function. Seizures in discrete EOAD populations may benefit from precisely selected medicines optimized for primary ASM pharmacological mechanisms.

Development of Antiepileptic Drugs throughout History: From Serendipity to Artificial Intelligence

This article provides a comprehensive narrative review of the history of antiepileptic drugs (AEDs) and their development over time. Firstly, it explores the significant role of serendipity in the discovery of essential AEDs that continue to be used today, such as phenobarbital and valproic acid. Subsequently, it delves into the historical progression of crucial preclinical models employed in the development of novel AEDs, including the maximal electroshock stimulation test, pentylenetetrazol-induced test, kindling models, and other animal models. Moving forward, a concise overview of the clinical advancement of major AEDs is provided, highlighting the initial milestones and the subsequent refinement of this process in recent decades, in line with the emergence of evidence-based medicine and the implementation of increasingly rigorous controlled clinical trials. Lastly, the article explores the contributions of artificial intelligence, while also offering recommendations and discussing future perspectives for the development of new AEDs.

Caffeine impairs anticonvulsant effects of levetiracetam in the maximal electroshock seizure threshold test in mice

OBJECTIVES

Caffeine is the most widely used psychoactive substance in the world. Animal studies indicate that acute caffeine exposure at high doses may induce seizures and diminish the anticonvulsant activity of antiepileptic drugs (AEDs) at much lower doses. The aim of the current study was to assess the effect of caffeine on the anticonvulsant action of levetiracetam (LEV) and vigabatrin (VGB).

METHODS

The anticonvulsant activity of LEV and VGB was examined in the maximal electroshock seizure threshold test in mice (MEST test). All drugs were administered intraperitoneally by single injections, and caffeine was applied at doses capable of interfering with AEDs. Effects of caffeine exposure on AEDs were also investigated in tests of memory and motor performance.

RESULTS

Caffeine reduced the protective effect of LEV against electroconvulsions. Total brain concentration of LEV was unaffected by caffeine as well as inversely; LEV had no significant impact on the brain caffeine concentration, suggesting a pharmacodynamic nature of the interaction between LEV and caffeine in the MEST test. VGB at applied doses did not affect the convulsive threshold. Administration of VGB, but not LEV, alone or in combination with caffeine, impaired memory retention. In the chimney test, the combined treatment with AEDs and caffeine did not cause motor coordination impairment.

CONCLUSIONS

It is suggested that caffeine may negatively affect the anticonvulsant action of LEV in patients with epilepsy.

Anticonvulsant Profile of Selected Medium-Chain Fatty Acids (MCFAs) Co-Administered with Metformin in Mice in Acute and Chronic Treatment

In contrast to the other components of the medium-chain triglycerides ketogenic diet (MCT KD), i.e., caprylic acid (CA8), a comprehensive evaluation of caproic (CA6) and lauric acids' (CA12) properties in standard chemical and electrical seizure tests in mice has not yet been performed. We investigated their effects in maximal electroshock seizure threshold (MEST), 6 Hz seizure threshold and intravenous (i.v.) pentylenetetrazole (PTZ) seizure tests. Since ketone body production can be regulated by the activation of 5'AMP-activated protein kinase (AMPK), we hypothesized that metformin (an AMPK activator) enhance ketogenesis and would act synergistically with the fatty acids to inhibit convulsions. We assessed the effects of acute and chronic co-treatment with metformin and CA6/CA8 on seizures. CA6 and CA12 (p.o.) increased seizure threshold in the 6 Hz seizure test. CA6 at the highest tested dose (30 mmol/kg) developed toxicity in several mice, impaired motor performance and induced ketoacidosis. Acute and chronic co-treatment with metformin and CA6/CA8 did not affect seizure thresholds. Moreover, we observed the pro-convulsive effect of the acute co-administration of CA8 (5 mmol/kg) and metformin (100 mg/kg). Since this co-treatment was pro-convulsive, the safety profile and risk/benefit ratio of MCT KD and metformin concomitant therapy in epileptic patients should be further evaluated.

Animal Models of Drug-Resistant Epilepsy as Tools for Deciphering the Cellular and Molecular Mechanisms of Pharmacoresistance and Discovering More Effective Treatments

In the last 30 years, over 20 new anti-seizure medicines (ASMs) have been introduced into the market for the treatment of epilepsy using well-established preclinical seizure and epilepsy models. Despite this success, approximately 20-30% of patients with epilepsy have drug-resistant epilepsy (DRE). The current approach to ASM discovery for DRE relies largely on drug testing in various preclinical model systems that display varying degrees of ASM drug resistance. In recent years, attempts have been made to include more etiologically relevant models in the preclinical evaluation of a new investigational drug. Such models have played an important role in advancing a greater understanding of DRE at a mechanistic level and for hypothesis testing as new experimental evidence becomes available. This review provides a critical discussion of the pharmacology of models of adult focal epilepsy that allow for the selection of ASM responders and nonresponders and those models that display a pharmacoresistance per se to two or more ASMs. In addition, the pharmacology of animal models of major genetic epilepsies is discussed. Importantly, in addition to testing chemical compounds, several of the models discussed here can be used to evaluate other potential therapies for epilepsy such as neurostimulation, dietary treatments, gene therapy, or cell transplantation. This review also discusses the challenges associated with identifying novel therapies in the absence of a greater understanding of the mechanisms that contribute to DRE. Finally, this review discusses the lessons learned from the profile of the recently approved highly efficacious and broad-spectrum ASM cenobamate.

Structural Analogs of the GABAkine KRM-II-81 Are Orally Bioavailable Anticonvulsants without Sedation

To provide back-up compounds to support the development of the GABAA receptor (GABAAR) potentiator KRM-II-81, three novel analogs were designed: replacing the pyridinyl with 2'-Cl-phenyl (FR-II-60), changing the positions of the N and O atoms in the oxazole ring with addition of an ethyl group (KPP-III-34 and KPP-III-51), or substituting a Br atom for the ethynyl of KRM-II-81 (KPP-III-34). The compounds bound to brain GABAARs. Intraperitoneal administration of FR-II-60 and KPP-III-34 produced anticonvulsant activity in mice [maximal electroshock (MES)-induced seizures or 6 Hz-induced seizures], whereas KPP-III-51 did not. Although all compounds were orally bioavailable, structural changes reduced the plasma and brain (FR-II-60 and KPP-III-51) exposures relative to KRM-II-81. Oral administration of each compound produced dose-dependent increases in the latency for both clonic and tonic seizures and the lethality induced by pentylenetetrazol (PTZ) in mice. Since KPP-III-34 produced the highest brain area under the curve (AUC) exposures, it was selected for further profiling. Oral administration of KPP-III-34 suppressed seizures in corneal-kindled mice, hippocampal paroxysmal discharges in mesial temporal lobe epileptic mice, and PTZ-induced convulsions in rats. Only transient sensorimotor impairment was observed in mice, and doses of KPP-III-34 up to 500 mg/kg did not produce impairment in rats. Molecular docking studies demonstrated that all compounds displayed a reduced propensity for binding to α1His102 compared with the sedating compound alprazolam; the bromine-substituted KPP-III-34 achieved the least interaction. Overall, these findings document the oral bioavailability and anticonvulsant efficacy of three novel analogs of KRM-II-81 with reduced sedative effects. SIGNIFICANCE STATEMENT: A new non-sedating compound, KRM-II-81, with reduced propensity for tolerance is moving into clinical development. Three new analogs were orally bioavailable, produced anticonvulsant effects in rodents, and displayed low sensorimotor impairment. KPP-III-34 demonstrated efficacy in models of pharmacoresistant epilepsy. Docking studies demonstrated a low propensity for compound binding to the α1His102 residue implicated in sedation. Thus, three additional structures have been added to the list of non-sedating imidazodiazepine anticonvulsants that could serve as backups in the clinical development of KRM-II-81.

Comparative anticonvulsant activity of the GABAkine KRM-II-81 and a deuterated analog

A series of imidazodiazepines has been developed that possess reduced sedative liabilities but retain efficacy in anticonvulsant screening models. The latest of these compounds, (5-(8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazole[1,5-α][1,4]diazepin-3-yl) oxazole known as KRM-II-81) is currently awaiting advancement into the clinic. A deuterated structural analog (D5-KRM-II-81) was made as a potential backup compound and studied here in comparison to KRM-II-81. In the present study, both compounds significantly prevented seizures in mice induced by 6 Hz (44 mA) electrical stimulation without significantly altering motoric function on a rotarod after intraperitoneal administration. Both compounds also significantly prevented clonic seizures, tonic seizures, and lethality induced by pentylenetetrazol in mice when given orally. D5-KRM-II-81 had a slightly longer duration of action against clonic and tonic seizures than KRM-II-81. Oral administration of 100 mg/kg of either KRM-II-81 or D5-KRM-II-81 was significantly less disruptive of sensorimotor function in mice than diazepam (5 mg/kg, p.o.). The present report documents that D5-KRM-II-81 represents another in this series of imidazodiazepines with anticonvulsant activity at doses that do not impair sensorimotor function.

Akkermansia muciniphila plays critical roles in host health

Akkermansia muciniphila, an intestinal microorganism, belongs to Verrucomicrobia, one of the most abundant microorganisms in the mammalian gut. It is a mucin-degrading bacterium that can colonise intestines of mammals such as humans and mice by utilising mucin as the only nitrogen and carbon source. When A. muciniphila colonises the intestine, its metabolites interact with the intestinal barrier, affecting host health by consolidating the intestinal barrier, regulating metabolic functions of the intestinal and circulatory systems, and regulating immune functions. This review summarised the mechanisms of A. muciniphila-host interactions that are relevant to host health. We focussed on characteristics of A. muciniphila in relation to its metabolites to provide a comprehensive understanding of A. muciniphila and its effects on host health and disease processes.

Pharmacodynamic synergism contributes to the antiseizure action of cannabidiol and clobazam

The management of refractory epilepsy involves treatment with more than one antiseizure medication (ASM). Combination of ASMs with distinct mechanisms of action are hypothesized to improve overall treatment effectiveness. In clinical trials, concomitant use of cannabidiol (CBD) and clobazam (CLB) was associated with increased seizure reduction and bidirectional elevation in levels of their active metabolites, 7-hydroxy-cannabidiol (7-OH-CBD) and nor-clobazam (n-CLB). Using isobolographic analysis, we investigated whether CBD and CLB interacted pharmacodynamically. In the mouse maximal electroshock seizure (MES) test, brain tissue levels of CBD and CLB corresponding to seizure prevention in 50% of animals (brain Effective Exposure, bEE₅₀) were 7.9 μM and 1.6 μM, respectively. In the 6 Hz psychomotor seizure model, 7-OH-CBD displayed a 5-fold greater potency than CBD (b-EE₅₀, 8.7 μM vs 47.3 μM). Isobolographic analysis performed on combination of CBD/CLB at 1:1, 3:1, and 1:3 ratios based on equi-effective bEE₅₀ values revealed synergism at all doses with combination indices (CI) of 0.43, 0.62 and 0.75 respectively. These outcomes were independent of pharmacokinetic interaction between CBD and CLB. These findings identify pharmacodynamic synergism as an important factor underlying enhanced antiseizure effect during concomitant CBD and CLB use.

Isobolographic analysis of adjunct antiseizure activity of the FDA-approved cannabidiol with neurosteroids and benzodiazepines in adult refractory focal onset epilepsy

Epilepsy is a serious neurological disorder associated with recurrent and unpredictable seizures and extensive neuropsychiatric comorbidities. There is no cure for epilepsy, and over one third of epileptic patients have been diagnosed with drug-refractory epilepsy, indicating the critical need for novel antiseizure medications (ASMs). Cannabidiol (CBD) has been shown to decrease seizures in pediatric epilepsies, such as Dravet and Lennox-Gastaut syndromes; however, it has not been rigorously tested for adult seizures or in models of refractory focal epilepsy. Although the exact mechanism is unknown, it is likely to act in a way that is unique to certain GABA-A receptor-modulating drugs, such as neurosteroids and benzodiazepines. In this study, we sought to determine the adjunct antiseizure activity of a clinical CBD product in an adult 6-Hz model of focal refractory epilepsy. CBD was evaluated alone in both a dose-response and time-course manner and in an adjunct combination with two ASMs ganaxolone (neurosteroid) and midazolam (benzodiazepine) against 6-Hz-induced refractory focal onset, generalized seizures. In pharmacological studies, CBD produced dose-dependent protection against seizures (ED50, 53 mg/kg, i.p.) without any side effects. CBD significantly reduced both electrographic activity and behavioral ictal responses with no apparent sex differences. CBD was evaluated in an isobologram design in conjunction with ganaxolone or midazolam at three standard ratios (1:1, 1:3, 3:1). Isobolographic analysis shows the combination regimens of CBD + ganaxolone and CBD + midazolam exerted combination index of 0.313 and 0.164, indicating strong synergism for seizure protection, with little to no toxicity. Together, these results demonstrate the therapeutic potential of CBD monotherapy and as an adjunct therapy for adult focal refractory epilepsy in combination with GABAergic ASMs.

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.

Translational Considerations in the Development of Intranasal Treatments for Epilepsy

Epilepsy is a common and serious neurological disorder, to which a high proportion of patients continue to be considered "drug-resistant", despite the availability of a host of anti-seizure drugs. Investigation into new treatment strategies is therefore of great importance. One such strategy is the use of the nose to deliver drugs directly to the brain with the help of pharmaceutical formulation to overcome the physical challenges presented by this route. The following review explores intranasal delivery of anti-seizure drugs, covering the link between the nose and seizures, pathways from the nose to the brain, current formulations in clinical use, animal seizure models and their proposed application in studying intranasal treatments, and a critical discussion of relevant pre-clinical studies in the literature.

MEPIRAPIM-derived synthetic cannabinoids inhibit T-type calcium channels with divergent effects on seizures in rodent models of epilepsy

Background: T-type Ca²⁺ channels (Ca_v3) represent emerging therapeutic targets for a range of neurological disorders, including epilepsy and pain. To aid the development and optimisation of new therapeutics, there is a need to identify novel chemical entities which act at these ion channels. A number of synthetic cannabinoid receptor agonists (SCRAs) have been found to exhibit activity at T-type channels, suggesting that cannabinoids may provide convenient chemical scaffolds on which to design novel Ca_v3 inhibitors. However, activity at cannabinoid type 1 (CB₁) receptors can be problematic because of central and peripheral toxicities associated with potent SCRAs. The putative SCRA MEPIRAPIM and its analogues were recently identified as Ca_v3 inhibitors with only minimal activity at CB₁ receptors, opening the possibility that this scaffold may be exploited to develop novel, selective Ca_v3 inhibitors. Here we present the pharmacological characterisation of SB2193 and SB2193F, two novel Ca_v3 inhibitors derived from MEPIRAPIM. Methods: The potency of SB2193 and SB2193F was evaluated in vitro using a fluorometric Ca²⁺ flux assay and confirmed using whole-cell patch-clamp electrophysiology. In silico docking to the cryo-EM structure of Ca_v3.1 was also performed to elucidate structural insights into T-type channel inhibition. Next, in vivo pharmacokinetic parameters in mouse brain and plasma were determined using liquid chromatography-mass spectroscopy. Finally, anticonvulsant activity was assayed in established genetic and electrically-induced rodent seizure models. Results: Both MEPIRAPIM derivatives produced potent inhibition of Ca_v3 channels and were brain penetrant, with SB2193 exhibiting a brain/plasma ratio of 2.7. SB2193 was further examined in mouse seizure models where it acutely protected against 6 Hz-induced seizures. However, SB2193 did not reduce spontaneous seizures in the Scn1a ^+/- mouse model of Dravet syndrome, nor absence seizures in the Genetic Absence Epilepsy Rat from Strasbourg (GAERS). Surprisingly, SB2193 appeared to increase the incidence and duration of spike-and-wave discharges in GAERS animals over a 4 h recording period. Conclusion: These results show that MEPIRAPIM analogues provide novel chemical scaffolds to advance Ca_v3 inhibitors against certain seizure types.

KM-408, a novel phenoxyalkyl derivative as a potential anticonvulsant and analgesic compound for the treatment of neuropathic pain

BACKGROUND

Epilepsy frequently coexists with neuropathic pain. Our approach is based on the search for active compounds with multitarget profiles beneficial in terms of potential side effects and on the implementation of screening for potential multidirectional central activity.

METHODS

Compounds were synthesized by means of chemical synthesis. After antiseizure and neurotoxicity screening in vivo, KM-408 and its enantiomers were chosen for analgesic activity evaluations. Further safety studies included acute toxicity in mice, the effect on normal electrocardiogram and on blood pressure in rats, whole body plethysmography in rats, and in vitro and biochemical assays. Pharmacokinetics has been studied in rats after iv and po administration. Metabolism has been studied in vivo in rat serum and urine. Radioligand binding studies were performed as part of the mechanism of action investigation.

RESULTS

Selected results for KM-408: K_i sigma = 7.2*10^-8; K_i 5-HT_1A = 8.0*10^-7; ED₅₀ MES (mice, ip) = 13.3 mg/kg; formalin test (I phase, mice, ip)-active at 30 mg/kg; SNL (rats, ip)-active at 6 mg/kg; STZ-induced pain (mice, ip)-active at 1 mg/kg (von Frey) and 10 mg/kg (hot plate); hot plate test (mice, ip)-active at 30 mg/kg; ED₅₀ capsaicin test (mice, ip) = 18.99 mg/kg; tail immersion test (mice)-active at 0.5%; corneal anesthesia (guinea pigs)-active at 0.125%; infiltration anesthesia (guinea pigs)-active at 0.125%.

CONCLUSIONS

Within the presented study a novel compound, R,S-2-((2-(2-chloro-6-methylphenoxy)ethyl)amino)butan-1-ol hydrochloride (KM-408) with dual antiseizure and analgesic activity has been developed for potential use in neuropathic pain treatment.

Advances and Challenges of Cannabidiol as an Anti-Seizure Strategy: Preclinical Evidence

The use of Cannabis for medicinal purposes has been documented since ancient times, where one of its principal cannabinoids extracted from Cannabis sativa, cannabidiol (CBD), has emerged over the last few years as a promising molecule with anti-seizure potential. Here, we present an overview of recent literature pointing out CBD's pharmacological profile (solubility, metabolism, drug-drug interactions, etc.,), CBD's interactions with multiple molecular targets as well as advances in preclinical research concerning its anti-seizure effect on both acute seizure models and chronic models of epilepsy. We also highlight the recent attention that has been given to other natural cannabinoids and to synthetic derivatives of CBD as possible compounds with therapeutic anti-seizure potential. All the scientific research reviewed here encourages to continue to investigate the probable therapeutic efficacy of CBD and its related compounds not only in epilepsy but also and specially in drug-resistant epilepsy, since there is a dire need for new and effective drugs to treat this disease.

A companion to the preclinical common data elements for phenotyping seizures and epilepsy in rodent models. A report of the TASK3-WG1C: Phenotyping working group of the ILAE/AES joint translational task force

Epilepsy is a heterogeneous disorder characterized by spontaneous seizures and behavioral comorbidities. The underlying mechanisms of seizures and epilepsy across various syndromes lead to diverse clinical presentation and features. Similarly, animal models of epilepsy arise from numerous dissimilar inciting events. Preclinical seizure and epilepsy models can be evoked through many different protocols, leaving the phenotypic reporting subject to diverse interpretations. Serendipity can also play an outsized role in uncovering novel drivers of seizures or epilepsy, with some investigators even stumbling into epilepsy research because of a new genetic cross or unintentional drug effect. The heightened emphasis on rigor and reproducibility in preclinical research, including that which is conducted for epilepsy, underscores the need for standardized phenotyping strategies. To address this goal as part of the TASK3-WG1C Working Group of the International League Against Epilepsy (ILAE)/American Epilepsy Society (AES) Joint Translational Task Force, we developed a case report form (CRF) to describe the common data elements (CDEs) necessary for the phenotyping of seizure-like behaviors in rodents. This companion manuscript describes the use of the proposed CDEs and CRF for the visual, behavioral phenotyping of seizure-like behaviors. These phenotyping CDEs and accompanying CRF can be used in parallel with video-electroencephalography (EEG) studies or as a first visual screen to determine whether a model manifests seizure-like behaviors before utilizing more specialized diagnostic tests, like video-EEG. Systematic logging of seizure-like behaviors may help identify models that could benefit from more specialized diagnostic tests to determine whether these are epileptic seizures, such as video-EEG.

Stereospecific antiseizure activity in mouse and rat epilepsy models by a pyridinium inhibitor of TNFα/NFκB signaling

Epilepsy affects over 50 million people worldwide and increases the risk of death. An intrinsic state of central inflammation, mainly driven by TNFα/NFκB signaling, may contribute to the refractory nature of some epilepsies. We have therefore hypothesized that inhibitors of this signaling pathway might be therapeutic. To test this hypothesis, we have measured the antiseizure properties of the enantiomeric compounds MRS-2481 and MRS-2485 in rodent seizure model systems. In the 6 Hz (44 mA) induced seizure test in mice, the (S) species, MRS-2485, was found to have higher protective potency and lower toxicity than the (R) species MRS-2481. However, neither of these enantiomers were protective in the MES-induced seizure test. MRS-2485 was also found to be protective in the corneal kindled mouse test. Finally, MRS-2485 reduced the post-kainate rat hippocampal slice electrical burst rate and duration. We conclude that MRS-2485, the (S)-enantiomer, is a potent inhibitor of seizure activity in mouse and rat models of epilepsy.

Glyceryl triacetate feeding in mice increases plasma acetate levels but has no anticonvulsant effects in acute electrical seizure models

INTRODUCTION

Acetate has been shown to have neuroprotective and anti-inflammatory effects. It is oxidized by astrocytes and can thus provide auxiliary energy to the brain in addition to glucose. Therefore, we hypothesized that it may protect against seizures, which is investigated here by feeding glyceryl triacetate (GTA), to provide high amounts of acetate without raising sodium or acid levels.

METHOD

CD1 male mice were fed controlled diets with or without GTA for up to three weeks. Body weights, blood glucose levels, plasma short-chain fatty acid levels, and other hematological parameters were monitored. Seizure thresholds were determined in 6 Hz and maximal electroshock seizure threshold (MEST) tests. Antioxidant capacities were evaluated in the cerebral cortex and plasma using a ferric reducing antioxidant power (FRAP) assay and Trolox equivalent antioxidant capacity assay.

RESULTS

Body weight gain was similar with both diets with and without GTA in two experiments. Glyceryl triacetate-fed groups showed 2-3- and 1.6-fold increased acetate and propionate levels in plasma, respectively. Glucose levels were unaltered in blood collected from the tail tip but increased in trunk blood. No differences were found in the activity of cerebral cortex acetyl-CoA synthetase. In the 6 Hz threshold test, seizure thresholds were lower by 3 mA and 2.4 mA after 8 and 14 days, respectively, in the GTA compared to the control diet-fed group, but showed no difference on day 16, showing that GTA has small, but inconsistent proconvulsant effects in this model. In MEST tests, a slightly increased seizure threshold (1 mA) was found on day 19 in the GTA-fed group, but not in another experiment on day 21. There were no differences in antioxidant capacity in plasma or cortex between the two groups.

CONCLUSION

Glyceryl triacetate feeding showed no antioxidant effects nor beneficial changes in acute electrical seizure threshold mouse models, despite its ability to increase plasma acetate levels.

Synergistic effects of the galanin analog 810-2 with the antiseizure medication levetiracetam in rodent seizure models

OBJECTIVE

The use of many antiseizure medications (ASMs) is limited due to pharmacoresistance and dose-limiting side effects, suggesting an unmet need for novel therapeutic approaches. The neuropeptide galanin reduces seizures in several preclinical seizure and epilepsy models, but its clinical utility is limited due to rapid metabolism and poor blood-brain barrier penetration. The lead galanin analog 810-2 is systemically bioavailable and reduces seizures when administered alone. Further development of this analog, with the potential for use as an add-on therapy in patients with epilepsy, requires a better understanding of the use of this analog in combination with approved ASMs. We sought to evaluate 810-2 in combination with commonly used ASMs in rodent models of seizures.

METHODS

The mouse 6-Hz seizure assay was used to test efficacy of 810-2 in combination with levetiracetam (LEV), valproic acid (VPA), or lacosamide (LCM) using a 1:1 dose ratio in isobolographic studies. Further characterization was performed for the combination of 810-2 and LEV in the mouse corneal kindling and rat 6-Hz assays.

RESULTS

Whereas the combination of 810-2 with VPA and LCM yielded additive interactions, the combination of 810-2 with LEV demonstrated a synergistic interaction in the mouse 6-Hz assay. Supra-additive effects were also observed in the mouse corneal kindling and rat 6-Hz assays for this combination.

SIGNIFICANCE

The combination of 810-2 with LEV suggests the potential for this galanin analog to be further developed as an add-on therapy for patients with epilepsy, particularly when coadministered with LEV.

Evaluating the efficacy of prototype antiseizure drugs using a preclinical pharmacokinetic approach

OBJECTIVE

Pharmacokinetics (PK) of a drug drive its exposure, efficacy, and tolerability. A thorough preclinical PK assessment of antiseizure medications (ASMs) is therefore essential to evaluate the clinical potential. We tested protection against evoked seizures of prototype ASMs in conjunction with analysis of plasma and brain PK as a proof-of-principle study to enhance our understanding of drug efficacy and duration of action using rodent seizure models.

METHODS

In vivo seizure protection assays were performed in adult male CF-1 mice and Sprague Dawley rats. Clobazam (CLB), N-desmethyl CLB (NCLB), carbamazepine (CBZ), CBZ-10,11-epoxide (CBZE), sodium valproate (VPA), and levetiracetam (LEV) concentrations were quantified in plasma and brain using liquid chromatography-tandem mass spectrometry. Mean concentrations of each analyte were calculated and used to determine PK parameters via noncompartmental analysis in Phoenix WinNonLin.

RESULTS

NCLB concentrations were approximately 10-fold greater than CLB in mice. The antiseizure profile of CLB was partially sustained by NCLB in mice. CLB concentrations were lower in rats than in mice. CBZE plasma exposures were approximately 70% of CBZ in both mice and rats, likely contributing to the antiseizure effect of CBZ. VPA showed a relatively short half-life in both mice and rats, which correlated with a sharp decline in efficacy. LEV had a prolonged brain and plasma half-life, associated with a prolonged duration of action in mice.

SIGNIFICANCE

The study demonstrates the utility of PK analyses for understanding the seizure protection time course in mice and rats. The data indicate that distinct PK profiles of ASMs between mice and rats likely drive differences in drug efficacy between rodent models.

Higher susceptibility to 6 Hz corneal kindling and lower responsiveness to antiseizure drugs in mouse models of Alzheimer's disease

OBJECTIVE

Epileptic spikes and seizures seem present early in the disease process of Alzheimer's disease (AD). However, it is unclear how soluble and insoluble amyloid beta (Aβ) and tau proteins affect seizure development in vivo. We aim to contribute to this field by assessing the vulnerability to 6 Hz corneal kindling of young female mice from two well-characterized transgenic AD models and by testing their responsiveness to selected antiseizure drugs (ASDs).

METHODS

We used 7-week-old triple transgenic (3xTg) mice that have both amyloid and tau mutations, and amyloid precursor protein Swedish/presenillin 1 dE9 (APP/PS1) mice, bearing only amyloid-related mutations. We assessed the absence of plaques via immunohistochemistry and analyzed the concentrations of both soluble and insoluble forms of Aβ_1-42 and total tau (t-tau) in brain hippocampal and prefrontal cortical tissue. Seven-week-old mice of the different genotypes were subjected to the 6 Hz corneal kindling model. After kindling acquisition, we tested the anticonvulsant effects of three marketed ASDs (levetiracetam, brivaracetam, and lamotrigine) in fully kindled mice.

RESULTS

No Aβ plaques were present in either genotype. Soluble Aβ_1-42 levels were increased in both AD genotypes, whereas insoluble Aβ_1-42 concentrations were only elevated in APP/PS1 mice compared with their respective controls. Soluble and insoluble forms of t-tau were increased in 3xTg mice only. 3xTg and APP/PS1 mice displayed more severe seizures induced by 6 Hz corneal kindling from the first stimulation onward and were more rapidly kindled compared with control mice. In fully kindled AD mice, ASDs had less-pronounced anticonvulsive effects compared with controls.

SIGNIFICANCE

Mutations increasing Aβ only or both Aβ and tau in the brain enhance susceptibility for seizures and kindling in mice. The effect of ASDs on seizures measured by the Racine scale is less pronounced in both investigated AD models and suggests that seizures of young AD mice are more difficult to treat.

Discovery of (R)-N-Benzyl-2-(2,5-dioxopyrrolidin-1-yl)propanamide [], a Novel Orally Bioavailable EAAT2 Modulator with Drug-like Properties and Potent Antiseizure Activity In Vivo

(R)-7 [(R)-AS-1] showed broad-spectrum antiseizure activity across in vivo mouse seizure models: maximal electroshock (MES), 6 Hz (32/44 mA), acute pentylenetetrazol (PTZ), and PTZ-kindling. A remarkable separation between antiseizure activity and CNS-related adverse effects was also observed. In vitro studies with primary glia cultures and COS-7 cells expressing the glutamate transporter EAAT2 showed enhancement of glutamate uptake, revealing a stereoselective positive allosteric modulator (PAM) effect, further supported by molecular docking simulations. (R)-7 [(R)-AS-1] was not active in EAAT1 and EAAT3 assays and did not show significant off-target activity, including interactions with targets reported for marketed antiseizure drugs, indicative of a novel and unprecedented mechanism of action. Both in vivo pharmacokinetic and in vitro absorption, distribution, metabolism, excretion, toxicity (ADME-Tox) profiles confirmed the favorable drug-like potential of the compound. Thus, (R)-7 [(R)-AS-1] may be considered as the first-in-class small-molecule PAM of EAAT2 with potential for further preclinical and clinical development in epilepsy and possibly other CNS disorders.

Galanin analogs prevent mortality from seizure-induced respiratory arrest in mice

Objective

Sudden Unexpected Death in Epilepsy (SUDEP) accounts for 20% of mortality in those with recurrent seizures. While risk factors, monitoring systems, and standard practices are in place, the pathophysiology of SUDEP is still not well understood. Better knowledge of SUDEP and its potential mechanisms of action is crucial to reducing risk in this patient population and developing potential treatment options. Clinical studies and animal models of SUDEP suggest that diminished post-ictal respiratory control may be the dominant mechanism contributing to mortality. Recently, it was demonstrated that the depletion of the neuropeptide galanin in the amygdala occurs in human SUDEP. The amygdala plays a key role in the central integration of respiratory signaling; the depletion of galanin may represent a critical change that predisposes individuals to SUDEP.

Materials and methods

To evaluate the impact of enhancing galaninergic signaling to potentially protect against SUDEP, we studied seizure-induced respiratory arrest (S-IRA) following central (intracerebroventricular, intra-amygdala) and systemic (intraperitoneal, subcutaneous) administration of galanin analogs. Seizure naïve and seizure experienced (fully kindled) mice were tested.

Results

Central and systemically administered galanin analogs protect against S-IRA in naïve C57Bl/6J mice. Differential efficacy between receptor subtype-selective analogs varied based on the route of administration. Sub-chronic systemic administration at doses that reduced 6 Hz seizures also protected against S-IRA. Acute treatment benefits also extended to fully kindled mice experiencing tonic extension.

Significance

These data demonstrate that galanin analogs may be protective against post-ictal respiratory collapse.

New Phenylglycinamide Derivatives with Hybrid Structure as Candidates for New Broad-Spectrum Anticonvulsants

In the present study, a focused combinatorial chemistry approach was applied to merge structural fragments of well-known TRPV1 antagonists with a potent anticonvulsant lead compound, KA-104, that was previously discovered by our group. Consequently, a series of 22 original compounds has been designed, synthesized, and characterized in the in vivo and in vitro assays. The obtained compounds showed robust in vivo antiseizure activity in the maximal electroshock (MES) test and in the 6 Hz seizure model (using both 32 and 44 mA current intensities). The most potent compounds 53 and 60 displayed the following pharmacological profile: ED₅₀ = 89.7 mg/kg (MES), ED₅₀ = 29.9 mg/kg (6 Hz, 32 mA), ED₅₀ = 68.0 mg/kg (6 Hz, 44 mA), and ED₅₀ = 73.6 mg/kg (MES), ED₅₀ = 24.6 mg/kg (6 Hz, 32 mA), and ED₅₀ = 56.3 mg/kg (6 Hz, 44 mA), respectively. Additionally, 53 and 60 were effective in the ivPTZ seizure threshold and had no influence on the grip strength and body temperature in mice. The in vitro binding and functional assays indicated a multimodal mechanism of action for 53 and 60. These molecules, beyond TRPV1 antagonism, inhibited calcium currents and fast sodium currents in patch-clamp assays. Further studies proved beneficial in vitro ADME-Tox properties for 53 and 60 (i.e., high metabolic stability, weak influence on CYPs, no neurotoxicity, etc.). Overall, 53 and 60 seem to be interesting candidates for future preclinical development in epilepsy and pain indications due to their interaction with the TRPV1 channel.

A sensitive LC-MS/MS method for quantification of phenytoin and its major metabolite with application to in vivo investigations of intravenous and intranasal phenytoin delivery

Phenytoin is a powerful antiseizure drug with complex pharmacokinetic properties, making it an interesting model drug to use in preclinical in vivo investigations, especially with regards to formulations aiming to improve drug delivery to the brain. Moreover, it has a major metabolite, 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin, which can be simultaneously studied to achieve a better assessment of its behaviour in the body. Here, we describe the development and validation of a sensitive LCMS/MS method for quantification of phenytoin and 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin in rat plasma and brain which can be used in such preclinical studies. Calibration curves produced covered a range of 7.81 to 250 ng/mL (plasma) and 23.4 to 750 ng/g (brain tissue) for both analytes. The method was validated for specificity, sensitivity, accuracy, and precision and found to be within the acceptable limits of ±15% over this range in both tissue types. The method when applied in two in vivo investigations: validation of a seizure model and to study the behaviour of a solution of intranasally administered phenytoin as a foundation for future studies into direct nose‐to‐brain delivery of phenytoin using specifically developed particulate systems, was highly sensitive for detecting phenytoin and 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin in rat plasma and brain.

Influence of Umbelliferone on the Anticonvulsant and Neuroprotective Activity of Selected Antiepileptic Drugs: An In Vivo and In Vitro Study

Umbelliferone (7-hydroxycoumarin; UMB) is a coumarin with many biological properties, including antiepileptic activity. This study evaluated the effect of UMB on the ability of classical and novel antiepileptic drugs (e.g., lacosamide (LCM), levetiracetam (LEV), phenobarbital (PB) and valproate (VPA)) to prevent seizures evoked by the 6-Hz corneal-stimulation-induced seizure model. The study also evaluated the influence of this coumarin on the neuroprotective properties of these drugs in two in vitro models of neurodegeneration, including trophic stress and excitotoxicity. The results indicate that UMB (100 mg/kg, i.p.) significantly enhanced the anticonvulsant action of PB (p < 0.01) and VPA (p < 0.05), but not that of LCM orLEV, in the 6-Hz test. Whether alone or in combination with other anticonvulsant drugs (at their ED50 values from the 6-Hz test), UMB (100 mg/kg) did not affect motor coordination; skeletal muscular strength and long-term memory, as determined in the chimney; grip strength; or passive avoidance tests, respectively. Pharmacokinetic characterization revealed that UMB had no impact on total brain concentrations of PB or VPA in mice. The in vitro study indicated that UMB has neuroprotective properties. Administration of UMB (1 µg/mL), together with antiepileptic drugs, mitigated their negative impact on neuronal viability. Under trophic stress (serum deprivation) conditions, UMB enhanced the neurotrophic abilities of all the drugs used. Moreover, this coumarin statistically enhanced the neuroprotective effects of PB (p < 0.05) and VPA (p < 0.001) in the excitotoxicity model of neurodegeneration. The obtained results clearly indicate a positive effect of UMB on the anticonvulsant and neuroprotective properties of the selected drugs.

Anticonvulsive properties of soticlestat, a novel cholesterol 24-hydroxylase inhibitor

Objective

The formation of 24S‐hydroxycholesterol is a brain‐specific mechanism of cholesterol catabolism catalyzed by cholesterol 24‐hydroxylase (CYP46A1, also known as CH24H). CH24H has been implicated in various biological mechanisms, whereas pharmacological lowering of 24S‐hydroxycholesterol has not been fully studied. Soticlestat is a novel small‐molecule inhibitor of CH24H. Its therapeutic potential was previously identified in a mouse model with an epileptic phenotype. In the present study, the anticonvulsive property of soticlestat was characterized in rodent models of epilepsy that have long been used to identify antiseizure medications.

Methods

The anticonvulsive property of soticlestat was investigated in maximal electroshock seizures (MES), pentylenetetrazol (PTZ) acute seizures, 6‐Hz psychomotor seizures, audiogenic seizures, amygdala kindling, PTZ kindling, and corneal kindling models. Soticlestat was characterized in a PTZ kindling model under steady‐state pharmacokinetics to relate its anticonvulsive effects to pharmacodynamics.

Results

Among models of acutely evoked seizures, whereas anticonvulsive effects of soticlestat were identified in Frings mice, a genetic model of audiogenic seizures, it was found ineffective in MES, acute PTZ seizures, and 6‐Hz seizures. The protective effects of soticlestat against audiogenic seizures increased with repetitive dosing. Soticlestat was also tested in models of progressive seizure severity. Soticlestat treatment delayed kindling acquisition, whereas fully kindled animals were not protected. Importantly, soticlestat suppressed the progression of seizure severity in correlation with 24S‐hydroxycholesterol lowering in the brain, suggesting that 24S‐hydroxycholesterol can be aggressively reduced to produce more potent effects on seizure development in kindling acquisition.

Significance

The data collectively suggest that soticlestat can ameliorate seizure symptoms through a mechanism distinct from conventional antiseizure medications. With its novel mechanism of action, soticlestat could constitute a novel class of antiseizure medications for treatment of intractable epilepsy disorders such as developmental and epileptic encephalopathy.

NBI-921352, a first-in-class, NaV1.6 selective, sodium channel inhibitor that prevents seizures in Scn8a gain-of-function mice, and wild-type mice and rats

NBI-921352 (formerly XEN901) is a novel sodium channel inhibitor designed to specifically target Na_V1.6 channels. Such a molecule provides a precision-medicine approach to target SCN8A-related epilepsy syndromes (SCN8A-RES), where gain-of-function (GoF) mutations lead to excess Na_V1.6 sodium current, or other indications where Na_V1.6 mediated hyper-excitability contributes to disease (Gardella and Møller, 2019; Johannesen et al., 2019; Veeramah et al., 2012). NBI-921352 is a potent inhibitor of Na_V1.6 (IC₅₀0.051 µM), with exquisite selectivity over other sodium channel isoforms (selectivity ratios of 756 X for Na_V1.1, 134 X for Na_V1.2, 276 X for Na_V1.7, and >583 Xfor Na_V1.3, Na_V1.4, and Na_V1.5). NBI-921352is a state-dependent inhibitor, preferentially inhibiting inactivatedchannels. The state dependence leads to potent stabilization of inactivation, inhibiting Na_V1.6 currents, including resurgent and persistent Na_V1.6 currents, while sparing the closed/rested channels. The isoform-selective profile of NBI-921352 led to a robust inhibition of action-potential firing in glutamatergic excitatory pyramidal neurons, while sparing fast-spiking inhibitory interneurons, where Na_V1.1 predominates. Oral administration of NBI-921352 prevented electrically induced seizures in a Scn8a GoF mouse,as well as in wild-type mouse and ratseizure models. NBI-921352 was effective in preventing seizures at lower brain and plasma concentrations than commonly prescribed sodium channel inhibitor anti-seizure medicines (ASMs) carbamazepine, phenytoin, and lacosamide. NBI-921352 waswell tolerated at higher multiples of the effective plasma and brain concentrations than those ASMs. NBI-921352 is entering phase II proof-of-concept trials for the treatment of SCN8A-developmental epileptic encephalopathy (SCN8A-DEE) and adult focal-onset seizures.

From the North Sea to Drug Repurposing, the Antiseizure Activity of Halimide and Plinabulin

PharmaSea performed large-scale in vivo screening of marine natural product (MNP) extracts, using zebrafish embryos and larvae, to identify compounds with the potential to treat epilepsy. In this study, we report the discovery of two new antiseizure compounds, the 2,5-diketopiperazine halimide and its semi-synthetic analogue, plinabulin. Interestingly, these are both known microtubule destabilizing agents, and plinabulin could have the potential for drug repurposing, as it is already in clinical trials for the prevention of chemotherapy-induced neutropenia and treatment of non-small cell lung cancer. Both halimide and plinabulin were found to have antiseizure activity in the larval zebrafish pentylenetetrazole (PTZ) seizure model via automated locomotor analysis and non-invasive local field potential recordings. The efficacy of plinabulin was further characterized in animal models of drug-resistant seizures, i.e., the larval zebrafish ethyl ketopentenoate (EKP) seizure model and the mouse 6 Hz psychomotor seizure model. Plinabulin was observed to be highly effective against EKP-induced seizures, on the behavioral and electrophysiological level, and showed activity in the mouse model. These data suggest that plinabulin could be of interest for the treatment of drug-resistant seizures. Finally, the investigation of two functional analogues, colchicine and indibulin, which were observed to be inactive against EKP-induced seizures, suggests that microtubule depolymerization does not underpin plinabulin’s antiseizure action.

Cannabidiol Increases Seizure Resistance and Improves Behavior in an Scn8a Mouse Model

Voltage-gated sodium channel genes are an important family of human epilepsy genes. De novo missense mutations in SCN8A (encoding Na_v1.6) are associated with a spectrum of clinical presentation, including multiple seizure types, movement disorders, intellectual disability, and behavioral abnormalities such as autism. Patients with SCN8A mutations are often treated with multiple antiepileptic drugs, the most common being sodium channel blockers. Cannabidiol (CBD) has been included as a component of treatment regimens for some SCN8A patients; however, to date, there are no clinical trials that have evaluated the therapeutic potential of CBD in patients with SCN8A mutations. In the current manuscript, we demonstrated a dose-dependent increase in seizure resistance following CBD treatment in mice expressing the human SCN8A mutation R1620L (RL/+). We also found that CBD treatment improved social behavior and reduced hyperactivity in the RL/+ mutants. Our findings suggest that CBD may be beneficial in patients with SCN8A-associated disease.

Emerging therapeutic targets for epilepsy: Preclinical insights

INTRODUCTION

Around 30% of patients with epilepsy suffer from drug-resistant seizures. Drug-resistant seizures may have significant consequences such as sudden death in epilepsy, injuries, memory disturbances, and childhood learning and developmental problems. Conventional and newer available antiepileptic drugs (AEDs) work via numerous mechanisms - mainly through inhibition of voltage-operated Na⁺ and/or Ca²⁺ channels, excitation of K⁺ channels, enhancement of GABA-mediated inhibition and/or blockade of glutamate-produced excitation. However, the discovery and development of novel brain targets may improve the future pharmacological management of epilepsy and hence is of pivotal importance.

AREAS COVERED

This article examines novel drug targets such as brain multidrug efflux transporters and inflammatory pathways; it progresses to discuss possible strategies for the management of drug-resistant seizures. Reduction of the consequences of blood brain barrier dysfunction and enhancement of anti-oxidative defense are discussed.

EXPERT OPINION

Novel drug targets comprise brain multidrug efflux transporters, TGF-β, Nrf2-ARE or m-TOR signaling and inflammatory pathways. Gene therapy and antagomirs seem the most promising targets. Epileptic foci may be significantly suppressed by viral-vector-mediated gene transfer, leading to an increased in situ concentration of inhibitory factors (for instance, galanin). Also, antagomirs offer a promising possibility of seizure inhibition by silencing micro-RNAs involved in epileptogenesis and possibly in seizure generation.