Temporal relationship between levetiracetam nonadherence and breakthrough seizures in a preclinical model of temporal lobe epilepsy.

OBJECTIVE: Poor medication adherence remains a concern for individuals managing their epilepsy with antiseizure medicines (ASMs); however, ethical concerns around withholding medication make it impossible to study the causal relationship between missed doses and seizures in patients. Previous preclinical studies from our group suggest that mechanistically distinct ASMs have varying degrees of forgiveness when a dose is missed. However, with only a few ASMs studied in the context of nonadherence, we sought to expand on previous work to understand the relationship between levetiracetam (LEV) nonadherence and breakthrough seizures. METHODS: Chronic oral dosing was initiated in rats with established epilepsy via our automated medication-in-food delivery system coupled to 24/7 video-electroencephalographic recording. Baseline seizure burden was established for 4 weeks before enrolling subjects into a 4-week treatment period with LEV in a 100% fully adherent (75 mg/kg four times daily) or 50% variably adherent paradigm. The temporal relationship between missed doses and breakthrough seizures was correlated with LEV plasma and brain concentrations in separate cohorts of animals. RESULTS: Full adherence to LEV significantly improved seizure control by 50% in half of the animals. Poor adherence worsened seizure frequency by 85%, with most rats having more severe seizures that formed in clusters following missed doses. LEV concentrations remained below therapeutic levels (<10 µg/mL) in nonadherent animals, with brain and plasma levels directly correlating with the degree of adherence in a 24-h period. Missed doses of LEV immediately increased the risk of breakthrough seizures; however, this risk was significantly reduced with improved adherence in a 24-h period. SIGNIFICANCE: These findings enhance our understanding of ASM nonadherence in preclinical models, highlighting that the timing of missed doses and their impact on seizures may vary between different ASMs. Notably, LEV demonstrates a robust pharmacokinetic reliance on missed doses leading to breakthrough seizures.

Diet composition and sterilization modifies intestinal microbiome diversity and burden of Theiler's virus infection-induced acute seizures.

OBJECTIVE: Brain infection with Theiler's murine encephalomyelitis virus (TMEV) in C57BL/6J mice can induce acquired epileptogenesis. Diet alters acute seizure incidence in TMEV-infected mice; yet it is unclear whether intestinal dysbiosis may also impact acute or chronic behavioral comorbidities. This study thus assessed the impact of diet formulation and sterilization on acute seizure presentation, gut microbiome composition, and epilepsy-related chronic behavioral comorbidities. METHODS: Baseline fecal samples were collected from male C57BL/6J mice (4- to 5-weeks-old; Jackson Labs) upon facility arrival. Mice were randomized to either autoclaved (AC) or irradiated diet (IR) (Prolab RMH 3000) or IR (Picolab 5053). Three days later, mice underwent intracerebral TMEV or phosphate-buffered saline (PBS) injection. Fecal samples were collected from a subset of mice at infection (Day 0) and Day 7 post-infection. Epilepsy-related working memory deficits and seizure threshold were assessed 6 weeks post-infection. Gut microbiome diversity was determined by 16S rRNA amplicon sequencing of fecal samples. RESULTS: TMEV-infected mice displayed acute handling-induced seizures, regardless of diet: 28 of 57 IR Picolab 5053 (49.1%), 30 of 41 IR Prolab RMH 3000 (73.2%), and 47 of 77 AC Prolab RMH 3000 (61%) mice displayed seizures. The number of observed seizures differed significantly by diet: IR Picolab 5053 diet-fed mice had 2.2 ± 2.8 seizures (mean ± standard deviation), IR Prolab RMH 3000 diet-fed mice had 3.5 ± 2.9 seizures, and AC Prolab RMH 3000 diet-fed mice had 4.4 ± 3.8 seizures during the 7-day monitoring period. Gut microbiome composition differed significantly in TMEV-infected mice fed the AC Prolab RMH 3000 diet, with measured differences in gram-positive bacteria. These mice also displayed worsened long-term working memory deficits. SIGNIFICANCE: Diet-induced differences in intestinal dysbiosis in the TMEV model are associated with marked changes in acute seizure presentation, symptomatic recovery, and onset of chronic behavioral comorbidities of epilepsy. Our study reveals a novel disease-modifying impact of dietary manipulation on intestinal bacterial species after TMEV-induced acute seizures.

Perampanel's forgiveness factor in a variable medication adherence paradigm in a rat model of chronic epilepsy.

BACKGROUND: Poor medication adherence contributes to increased morbidity and mortality in patients with epilepsy and may be under-addressed in clinical practice. Ethical concerns make it impossible to study the impact of medication nonadherence in clinical trials, but our previous work emphasizes the importance of using preclinical approaches to address these questions. With over 30 clinically available antiseizure medicines (ASM's), it remains an important question to understand the relationship between poor adherence and seizure incidence across mechanistically distinct ASM's, including the broad-spectrum ASM, perampanel (PER). METHODS: We formulated PER into chow pellets to deliver to rats in a 100% fully adherent or 50% variable nonadherent paradigm via our novel automated medication-in-food delivery system. Chronic oral dosing was initiated in male rats with chronic epilepsy while monitoring 24/7 for videoEEG evidence of seizures during a 4-week placebo baseline and 4-week treatment phase. PER concentrations were monitored in plasma at 1-week intervals and correlated with degree of seizure control. The relationship between missed doses and extended patterns of nonadherence were correlated with breakthrough seizures. RESULTS: Fully adherent rats demonstrated a median reduction in seizure frequency of 50%, whereas nonadherent rats had a median increase of 54%. Plasma concentrations of PER were stable over the 4-week treatment period in both fully adherent and nonadherent groups, with levels being twice as high in fully adherent animals. There was no correlation between a single missed dose or series of missed doses and the incidence of breakthrough seizures. However, those animals in the nonadherent group that received PER for every meal during a 24-h period had a reduced likelihood of seizure incidence. CONCLUSIONS: If our preclinical data is supported in the clinic, PER's favorable pharmacokinetic profile in humans, combined with a lowered risk of breakthrough seizures suggests that it may provide a certain forgiveness factor if a dose is missed within a 24-h window.

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.

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.

Progress report on new antiepileptic drugs: A summary of the Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI): II. Drugs in more advanced clinical development.

The Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI) was held in Madrid, Spain on May 22-25, 2022 and was attended by 157 delegates from 26 countries representing basic and clinical science, regulatory agencies, and pharmaceutical industries. One day of the conference was dedicated to sessions presenting and discussing investigational compounds under development for the treatment of seizures and epilepsy. The current progress report summarizes recent findings and current knowledge for seven of these compounds in more advanced clinical development for which either novel preclinical or patient data are available. These compounds include bumetanide and its derivatives, darigabat, ganaxolone, lorcaserin, soticlestat, STK-001, and XEN1101. Of these, ganaxolone was approved by the US Food and Drug Administration in March 2022 for the treatment of seizures associated with cyclin-dependent kinase-like 5 deficiency disorder in patients 2 years of age and older.

Progress report on new antiepileptic drugs: A summary of the Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI): I. Drugs in preclinical and early clinical development.

The Eilat Conferences have provided a forum for discussion of novel treatments of epilepsy among basic and clinical scientists, clinicians, and representatives from regulatory agencies as well as from the pharmaceutical industry for 3 decades. Initially with a focus on pharmacological treatments, the Eilat Conferences now also include sessions dedicated to devices for treatment and monitoring. The Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI) was held in Madrid, Spain, on May 22-25, 2022 and was attended by 157 delegates from 26 countries. As in previous Eilat Conferences, the core of EILAT XVI consisted of a sequence of sessions where compounds under development were presented and discussed. This progress report summarizes preclinical and, when available, phase 1 clinical data on five different investigational compounds in preclinical or early clinical development, namely GAO-3-02, GRT-X, NBI-921352 (formerly XEN901), OV329, and XEN496 (a pediatric granular formulation of retigabine/ezogabine). Overall, the data presented in this report illustrate novel strategies for developing antiseizure medications, including an interest in novel molecular targets, and a trend to pursue potential new treatments for rare and previously neglected severe epilepsy syndromes.

The ups and downs of alkyl-carbamates in epilepsy therapy: How does cenobamate differ?

Since 1955, several alkyl-carbamates have been developed for the treatment of anxiety and epilepsy, including meprobamate, flupirtine, felbamate, retigabine, carisbamate, and cenobamate. They have each enjoyed varying levels of success as antiseizure drugs; however, they have all been plagued by the emergence of serious and sometimes life-threatening adverse events. In this review, we compare and contrast their predominant molecular mechanisms of action, their antiseizure profile, and where possible, their clinical efficacy. The preclinical, clinical, and mechanistic profile of the prototypical γ-aminobutyric acidergic (GABAergic) modulator phenobarbital is included for comparison. Like phenobarbital, all of the clinically approved alkyl-carbamates share an ability to enhance inhibitory neurotransmission through modulation of the GABAA receptor, although the specific mechanism of interaction differs among the different drugs discussed. In addition, several alkyl-carbamates have been shown to interact with voltage-gated ion channels. Flupirtine and retigabine share an ability to activate K+ currents mediated by KCNQ (Kv7) K+ channels, and felbamate, carisbamate, and cenobamate have been shown to block Na+ channels. In contrast to other alkyl-carbamates, cenobamate seems to be unique in its ability to preferentially attenuate the persistent rather than transient Na+ current. Results from recent randomized controlled clinical trials with cenobamate suggest that this newest antiseizure alkyl-carbamate possesses a degree of efficacy not witnessed since felbamate was approved in 1993. Given that ceno-bamate's mechanistic profile is unique among the alkyl-carbamates, it is not clear whether this impressive efficacy reflects an as yet undescribed mechanism of action or whether it possesses a unique synergy between its actions at the GABAA receptor and on persistent Na+ currents. The high efficacy of cenobamate is, however, tempered by the risk of serious rash and low tolerability at higher doses, meaning that further safety studies and clinical experience are needed to determine the true clinical value of cenobamate.

Continuous seizure emergency evoked in mice with pharmacological, electrographic, and pathological features distinct from status epilepticus.

OBJECTIVES: Benzodiazepines are the standard of care for the management of sustained seizure emergencies, including status epilepticus (SE) and seizure clusters. Seizure clusters are a variably defined seizure emergency wherein a patient has multiple seizures above a baseline rate, with intervening periods of recovery, distinguishing clusters from SE. Although these seizure emergencies are phenotypically distinct, the precise pathophysiological and mechanistic differences between SE and seizure clusters are understudied. Emergency-specific preclinical models may differentiate the behavioral and pathological mechanisms that are acutely associated with seizure emergencies and seizure termination to better manage these events. METHODS: Herein we characterize a novel model of sustained seizure emergency induced in CF-1 mice through the combined administration of high-dose phenytoin (PHT; 50 mg/kg, i.p.) and pentylenetetrazol (PTZ; 100 mg/kg, s.c.). RESULTS: We presently describe a mouse model of sustained seizure emergency that is pathologically, pharmacologically, and behaviorally distinct from SE. Acute administration of PHT 1 h prior to PTZ led to significantly more mice with unremitting continuous seizure activity (CSA; 73.4%) vs vehicle-pretreated mice (13.8%; p < .0001). CSA was sensitive to lorazepam and valproic acid when administered at seizure onset and 30 minutes later. Carbamazepine worsened seizure control and post-CSA survival. Mice in CSA exhibited electroencephalography (EEG) patterns distinct from kainic acid-induced SE and PTZ alone, clearly differentiating CSA from SE and PTZ-induced myoclonic seizures. Neuropathological assessment by Fluoro-Jade C staining of brains collected 24 h post-CSA revealed no neurodegeneration in any mouse that underwent CSA, whereas there was widespread neuronal death in brains from KA-SE mice. Finally, immunohistochemistry revealed acute seizure-induced astrogliosis (glial fibrillary acid protein; GFAP) in hippocampal structures, whereas hippocampal neuronal nuclei (NeuN) protein expression was only reduced in KA-SE mice. SIGNIFICANCE: We present a novel mouse model on which to further elucidate the mechanistic differences between sustained seizure emergencies (ie, SE and seizure clusters) to improve clinical interventions and define mechanisms of seizure termination.

Development of an antiepileptogenesis drug screening platform: Effects of everolimus and phenobarbital.

OBJECTIVE: The kainic acid (KA)-induced status epilepticus (SE) model in rats is a well-defined model of epileptogenesis. This model closely recapitulates many of the clinical and pathological characteristics of human temporal lobe epilepsy (TLE) that arise following SE or another neurological insult. Spontaneous recurrent seizures (SRS) in TLE can present after a latent period following a neurological insult (traumatic brain injury, SE event, viral infection, etc.). Moreover, this model is suitable for preclinical studies to evaluate the long-term process of epileptogenesis and screen putative disease-modifying/antiepileptogenic agents. The burden of human TLE is highly variable, similar to the post-KA SE rat model. In this regard, this model may have broad translational relevance. This report thus details the pharmacological characterization and methodological refinement of a moderate-throughput drug screening program using the post-KA-induced SE model of epileptogenesis in male Sprague Dawley rats to identify potential agents that may prevent or modify the burden of SRS. Specifically, we sought to demonstrate whether our protocol could prevent the development of SRS or lead to a reduced frequency/severity of SRS. METHODS: Rats were administered either everolimus (2-3 mg/kg po) beginning 1, 2, or 24 h after SE onset, or phenobarbital (60 mg/kg ip) beginning 1 h after SE onset. All treatments were administered once/day for 5-7 days. Rats in all studies (n = 12/treatment dose/study) were then monitored intermittently by video-electroencephalography (2 weeks on, 2 weeks off, 2 weeks on epochs) to determine latency to onset of SRS and disease burden. RESULTS: Although no adverse side effects were observed in our studies, no treatment significantly modified disease or prevented the presentation of SRS by 6 weeks after SE onset. SIGNIFICANCE: Neither phenobarbital nor everolimus administered at several time points after SE onset prevented the development of SRS. Nonetheless, we demonstrate a practical and moderate-throughput screen for potential antiepileptogenic agents in a rat model of TLE.

Community pharmacists' role in caring for people living with epilepsy: A scoping review.

OBJECTIVE: To identify and describe studies about pharmacist-provided services for people with epilepsy and their caregivers. METHODS: PubMed/MEDLINE and EMBASE were searched for articles that were: (1) written in English, (2) published in 1985 or later, (3) a peer-reviewed empirical study or practice report, and (4) describing an intervention provided by a pharmacist for people with epilepsy and/or their caregivers in an outpatient pharmacy setting. The abstracts and full text, when necessary, were reviewed by two investigators to assess eligibility. Data were extracted from each article by two investigators using a standardized abstraction form based on the Pharmacist Patient Care Services Intervention Reporting (PaCIR) checklist. Data elements of interest included components of service, mode of service delivery, frequency, number and duration of sessions for the service, roles and responsibilities of the community pharmacist, type of community pharmacy, outcomes and measures evaluated along with data sources, and findings and results. Risk of bias was not assessed due to the descriptive nature of the review. RESULTS: Twelve articles were included, seven of which reported services conducted in the United States. The most common service reported was medication management (n = 7) followed by education and counseling (n = 4). One article described a care coordination documentation tool that could be used by pharmacists and physicians in epilepsy care. Most interventions were evaluated using observational designs (n = 5) or did not have an evaluation component (n = 4). SIGNIFICANCE: This review provides examples of community pharmacists providing care to people living with epilepsy that extend beyond dispensing medications. Findings demonstrate that there is little published evidence on community pharmacists' contributions to epilepsy care and suggest opportunities for further exploration and innovation. This review serves as the first step in a project that seeks to develop a stakeholder-driven community pharmacist integrated population health intervention for people living with epilepsy.

Cenobamate (XCOPRI): Can preclinical and clinical evidence provide insight into its mechanism of action?

Approximately one-third of people living with epilepsy are unable to obtain seizure control with the currently marketed antiseizure medications (ASMs), creating a need for novel therapeutics with new mechanisms of action. Cenobamate (CBM) is a tetrazole alkyl carbamate derivative that received US Food and Drug Administration approval in 2019 for the treatment of adult partial onset (focal) seizures. Although CBM displayed impressive seizure reduction in clinical trials across all seizure types, including focal aware motor, focal impaired awareness, and focal to bilateral tonic-clonic seizures, the precise mechanism(s) through which CBM exerts its broad-spectrum antiseizure effects is not known. Experimental evidence suggests that CBM differentiates itself from other ASMs in that it appears to possess dual modes of action (MOAs); that is, it predominately blocks persistent sodium currents and increases both phasic and tonic γ-aminobutyric acid (GABA) inhibition. In this review, we analyze the preclinical efficacy of CBM alongside ASMs with similar MOAs to better understand the mechanism(s) through which CBM achieves such broad-spectrum seizure protection. CBM's preclinical performance in tests, including the mouse 6-Hz model of treatment-resistant seizures, the chemoconvulsant seizure models of generalized epilepsy, and the rat hippocampal kindling model of focal epilepsy, was distinct from other voltage-gated sodium channel blockers and GABAA modulators. This distinction, in light of its proposed mechanism(s) of action, provides insight into the impressive clinical efficacy of CBM in the adult patient with focal onset epilepsy. The results of this comparative reverse translational analysis suggest that CBM is a mechanistically distinct ASM that offers an important advancement in drug development for treatment of therapy-resistant epilepsy.

Antiseizure drug efficacy and tolerability in established and novel drug discovery seizure models in outbred vs inbred mice.

OBJECTIVE: Initial identification of new investigational drugs for the treatment of epilepsy is commonly conducted in well-established mouse acute and chronic seizure models: for example, maximal electroshock (MES), 6 Hz, and corneal kindling. Comparison of the median effective dose (ED50) of approved antiseizure drugs (ASDs) vs investigational agents in these models provides evidence of their potential for clinical efficacy. Inbred and outbred mouse strains exhibit differential seizure susceptibility. However, few comparisons exist of the ED50 or median behaviorally impairing dose (TD50) of prototype ASDs in these models in inbred C57Bl/6 vs outbred CF-1 mice, both of which are often used for ASD discovery. METHODS: We defined the strain-related ED50s and TD50s of several mechanistically distinct ASDs across established acute seizure models (MES, 6 Hz, and corneal-kindled mouse). We further quantified the strain-related effect of the MES ED50 of each ASD on gross behavior in a locomotor activity assay. Finally, we describe a novel pharmacoresistant corneal-kindling protocol that is suitable for moderate-throughput ASD screening and demonstrates highly differentiated ASD sensitivity. RESULTS: We report significant strain-related differences in the MES ED50 of valproic acid (CF-1 ED50: 90 mg/kg [95% confidence interval (CI) 165-214] vs C57Bl/6: 276 mg/kg [226-366]), as well as significant differences in the ED50 of levetiracetam in the pharmacoresistant 6 Hz test (CF-1: 22.5 mg/kg [14.7-30.2] vs C57Bl/6: >500 mg/kg [CI not defined]). There were no differences in the calculated TD50 of these ASDs between strains. Furthermore, the MES ED50 of phenobarbital significantly enhanced locomotor activity of outbred CF-1, but not C57Bl/6, mice. SIGNIFICANCE: Altogether, this study provides strain-related information to differentiate investigational agents from ASD standards-of-care in commonly employed preclinical discovery models and describes a novel kindled seizure model to further explore the mechanisms of drug-resistant epilepsy.

Progress report on new antiepileptic drugs: A summary of the Fifteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XV). I. Drugs in preclinical and early clinical development.

Since 1992, the Eilat Conferences have provided a forum for all stakeholders in the epilepsy community to appraise the latest data on new antiepileptic drugs and emergency seizure treatments, including, in recent years, updates on progress with the development of novel monitoring and therapeutic devices. Because of the COVID-19 pandemic, the Fifteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XV) was held as a fully virtual conference on July 27-30, 2020 for the sessions on drugs and on August 3, 2020 for the sessions on devices, and was attended during the 5 days by >500 participants from 63 countries. This progress report summarizes key preclinical and initial (phase 1) clinical data on eight investigational treatments that are currently in early development, including 2-deoxy-D-glucose, GAO-3-02, JNJ-40411813, NBI-921352, NTX-001, sec-butylpropylacetamide, XEN1101, and XEN496. This report provides an overview of current scenarios in the area of treatment discovery and development. The information presented illustrates a variety of innovative strategies, including exploration of compounds with novel mechanisms of action, transplantation of interneurons into epileptogenic brain regions, and the targeting of rare, previously neglected syndromes.

Progress report on new antiepileptic drugs: A summary of the Fifteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XV). II. Drugs in more advanced clinical development.

The Fifteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XV) was held as a fully virtual conference from July 27 to July 30, 2020 for the sessions on drugs, and on August 3, 2020 for the sessions on devices. A total of 534 delegates from 63 countries attended lectures and interactive discussions, representing a broad range of disciplines from basic science, clinical research, and clinical care. This progress report provides summaries of recent findings on investigational compounds for which preclinical data as well as data from patient studies were presented. The report includes the following five compounds: anakinra, cenobamate, CVL-865, fenfluramine, and ganaxolone, all with novel modes of action compared to more established antiepileptic drugs. Some of these compounds demonstrated promising results in placebo-controlled phase 3 trials, and two have recently received approval from the US Food and Drug Administration (FDA). These include cenobamate, which was approved by the FDA on November 21, 2019 for the treatment of partial onset (focal) seizures in adults, and fenfluramine oral solution, which was approved by the FDA on June 25, 2020 for the treatment of seizures associated with Dravet syndrome in patients 2 years and older.

A multiorganism pipeline for antiseizure drug discovery: Identification of chlorothymol as a novel γ-aminobutyric acidergic anticonvulsant.

OBJECTIVE: Current medicines are ineffective in approximately one-third of people with epilepsy. Therefore, new antiseizure drugs are urgently needed to address this problem of pharmacoresistance. However, traditional rodent seizure and epilepsy models are poorly suited to high-throughput compound screening. Furthermore, testing in a single species increases the chance that therapeutic compounds act on molecular targets that may not be conserved in humans. To address these issues, we developed a pipeline approach using four different organisms. METHODS: We sequentially employed compound library screening in the zebrafish, Danio rerio, chemical genetics in the worm, Caenorhabditis elegans, electrophysiological analysis in mouse and human brain slices, and preclinical validation in mouse seizure models to identify novel antiseizure drugs and their molecular mechanism of action. RESULTS: Initially, a library of 1690 compounds was screened in an acute pentylenetetrazol seizure model using D rerio. From this screen, the compound chlorothymol was identified as an effective anticonvulsant not only in fish, but also in worms. A subsequent genetic screen in C elegans revealed the molecular target of chlorothymol to be LGC-37, a worm γ-aminobutyric acid type A (GABAA ) receptor subunit. This GABAergic effect was confirmed using in vitro brain slice preparations from both mice and humans, as chlorothymol was shown to enhance tonic and phasic inhibition and this action was reversed by the GABAA receptor antagonist, bicuculline. Finally, chlorothymol exhibited in vivo anticonvulsant efficacy in several mouse seizure assays, including the 6-Hz 44-mA model of pharmacoresistant seizures. SIGNIFICANCE: These findings establish a multiorganism approach that can identify compounds with evolutionarily conserved molecular targets and translational potential, and so may be useful in drug discovery for epilepsy and possibly other conditions.

Pharmacological Characterization of a Betaine/GABA Transporter 1 (BGT1) Inhibitor Displaying an Unusual Biphasic Inhibition Profile and Anti-seizure Effects.

Focal epileptic seizures can in some patients be managed by inhibiting γ-aminobutyric acid (GABA) uptake via the GABA transporter 1 (GAT1) using tiagabine (Gabitril®). Synergistic anti-seizure effects achieved by inhibition of both GAT1 and the betaine/GABA transporter (BGT1) by tiagabine and EF1502, compared to tiagabine alone, suggest BGT1 as a target in epilepsy. Yet, selective BGT1 inhibitors are needed for validation of this hypothesis. In that search, a series of BGT1 inhibitors typified by (1R,2S)-2-((4,4-bis(3-methylthiophen-2-yl)but-3-en-yl)(methyl)amino)cyclohexanecarboxylic acid (SBV2-114) was developed. A thorough pharmacological characterization of SBV2-114 using a cell-based [3H]GABA uptake assay at heterologously expressed BGT1, revealed an elusive biphasic inhibition profile with two IC50 values (4.7 and 556 µM). The biphasic profile was common for this structural class of compounds, including EF1502, and was confirmed in the MDCK II cell line endogenously expressing BGT1. The possibility of two binding sites for SBV2-114 at BGT1 was assessed by computational docking studies and examined by mutational studies. These investigations confirmed that the conserved residue Q299 in BGT1 is involved in, but not solely responsible for the biphasic inhibition profile of SBV2-114. Animal studies revealed anti-seizure effects of SBV2-114 in two mouse models, supporting a function of BGT1 in epilepsy. However, as SBV2-114 is apparent to be rather non-selective for BGT1, the translational relevance of this observation is unknown. Nevertheless, SBV2-114 constitutes a valuable tool compound to study the molecular mechanism of an emerging biphasic profile of BGT1-mediated GABA transport and the putative involvement of two binding sites for this class of compounds.

The pharmacokinetics of oral carbamazepine in rats dosed using an automated drug delivery system.

OBJECTIVE: Pharmacokinetics (PK) of antiseizure drugs differ considerably between rats and humans. Rodents require larger and more frequent doses to maintain therapeutic drug levels. This study uses the antiseizure drug (ASD) carbamazepine (CBZ) to validate the application of a previously described automated drug delivery system for delivering chronic oral medication to rats. METHODS: Treatment-naive, male Sprague-Dawley rats were treated with oral CBZ, 75 mg/kg every 6 hours for 10 days, via the automated feeder. Blood samples were collected on day 0 (acute), day 2 (steady-state), and day 9 (chronic) and used to measure plasma CBZ and carbamazepine-10,11-epoxide (CBZ-E) concentrations via high-performance liquid chromatography. The PK of CBZ and CBZ-E were modeled using Monolix v2018R1. The acute and chronic tolerability of CBZ was evaluated using the open field test. RESULTS: CBZ and CBZ-E concentrations were best described by a one-compartment parent-metabolite model with first-order absorption and elimination kinetics. Observed and predicted CBZ concentrations were maintained within the therapeutic window (4-12 µg/mL) for the duration of the study. There was no change in open-field test activity following acute or chronic oral dosing of 75 mg/kg CBZ compared to a pretreatment baseline (P > 0.4). SIGNIFICANCE: Oral administration of CBZ dosed q.i.d. in rats using an automated drug delivery system results in therapeutic concentrations of CBZ and its active metabolite. This study represents the first PK validation for this previously described preclinical drug delivery system.

Correction of medication nonadherence results in better seizure outcomes than dose escalation in a novel preclinical epilepsy model of adherence.

OBJECTIVE: Medication nonadherence directly contributes to poor seizure control. A lack of emphasis on correcting poor adherence and failures in patient adherence can result in unwarranted alterations to a patient's drug regimen. We have modeled nonadherent patients in an animal model of epilepsy to study how alterations to pharmacotherapy, made without consideration of a patient's adherence, result in changes to seizure control. METHODS: Newly diagnosed rats with epilepsy were treated with carbamazepine (CBZ) during a 4-week baseline period to establish their baseline seizure rate in the presence of 50% adherence. Next, animals were randomized to one of three treatment interventions and monitored for 6 weeks. Groups included: (1) no change in therapy-rats continued the 50% adherent paradigm; (2) dose escalation-the dose of CBZ was doubled, and the 50% adherent paradigm continued; and (3) nonadherence corrected-rats continued the initial dose of CBZ, but the adherence rate was adjusted to 100% (ie, fully adherent). RESULTS: The rats in the no change in therapy arm displayed a 61% increase in seizure burden over the 6-week intervention phase. Similarly, rats in the dose escalation arm had a 66% worsening of their daily seizure burden. In contrast, rats in the nonadherence corrected arm displayed a 33% reduction in their daily seizure burden; a significant improvement when compared to the normalized seizure burden scores of rats in the other two treatment arms (P < 0.01). SIGNIFICANCE: We found that failure to correct medication nonadherence resulted in an increase in daily seizure burden in rats, even following dose escalation. In the presence of nonadherence, dose escalation worsened seizure control. In contrast, correcting nonadherence alone resulted in improved seizure control. These findings suggest that improving adherence should be prioritized over dose escalation in the clinical management of uncontrolled epilepsy.

Cannabidiol reduces seizures and associated behavioral comorbidities in a range of animal seizure and epilepsy models.

OBJECTIVE: Epilepsy is a progressive neurological disease characterized by recurrent seizures and behavioral comorbidities. We investigated the antiseizure effect of cannabidiol (CBD) in a battery of acute seizure models. Additionally, we defined the disease-modifying potential of chronic oral administration of CBD on associated comorbidities in the reduced intensity status epilepticus-spontaneous recurrent seizures (RISE-SRS) model of temporal lobe epilepsy (TLE). METHODS: We evaluated the acute antiseizure effect of CBD in the maximal electroshock seizure, 6-Hz psychomotor seizure, and pentylenetetrazol acute seizure tests, as well as the corneal kindling model of chronic seizures in mice following intraperitoneal administration. Median effective or behavioral toxic dose was determined in both mice and rats. Next, we tested an intravenous preparation of CBD (10 mg/kg single dose) in a rat model of pilocarpine-induced status epilepticus. We defined the effect of chronic CBD administration (200 mg/kg orally) on spontaneous seizures, motor control, gait, and memory function in the rat RISE-SRS model of TLE. RESULTS: CBD was effective in a battery of acute seizure models in both mice and rats following intraperitoneal administration. In the pilocarpine-induced status epilepticus rat model, CBD attenuated maximum seizure severity following intravenous administration, further demonstrating CBD's acute antiseizure efficacy in this rat model. We established that oral CBD attenuated the time-dependent increase in seizure burden and improved TLE-associated motor comorbidities of epileptic rats in the RISE-SRS model without affecting gait. Chronic administration of CBD after the onset of SRS ameliorated reference memory and working memory errors of epileptic animals in a spatial learning and memory task. SIGNIFICANCE: The present study illustrates that CBD is a well-tolerated and effective antiseizure agent and illustrates a potential disease-modifying effect of CBD on reducing both seizure burden and associated comorbidities well after the onset of symptomatic seizures in a model of TLE.