Cenobamate: real-world data from a retrospective multicenter study.

OBJECTIVE: To report the effects of adjunctive cenobamate and concomitant antiseizure medications (ASMs) on weight from two double-blind, placebo-controlled, phase 2 studies (YKP3089C013 [C013] and YKP3089C017 [C017]) and their open-label extensions (OLEs) and from a long-term, open-label phase 3 safety study, YKP3089C021 (C021). BACKGROUND: Cenobamate is an ASM approved in the US and EU for treatment of focal seizures in adults. Some ASMs are associated with weight gain (e.g., valproate, gabapentin, pregabalin), which can negatively affect patient health. DESIGN/METHODS: Patients with uncontrolled focal seizures taking stable doses of 1-3 ASMs were enrolled in each study. In C013, cenobamate was titrated to a target dose of 200 mg/day (max OLE dose 400 mg/day). In C017, patients were randomized to cenobamate 100, 200, or 400 mg/day (max OLE dose 400 mg/day). In C021, cenobamate was titrated to a target dose of 200 mg/day (max dose 400 mg/day). Median weight changes at 1 and 2 years from baseline were analyzed post hoc. RESULTS: Analyses included 39, 206, and 1054 patients from C013, C017 (dose groups combined), and C021, respectively. Median weight changes from baseline ranged from -0.2 to -0.9 kg at 1 year and from -1.0 to +1.0 kg at 2 years. Some numerical reductions in weight were noted in patients who discontinued valproate by 1 (-13.0 kg, C013, n=1) or 2 years (-24.5 kg, C017, n=2) and in patients who discontinued gabapentin by 1 (-7.1 kg, C017, n=2) or 2 years (-7.0 kg, C017, n=2). Otherwise, median weight changes from baseline for patients receiving concomitant valproate, gabapentin, or pregabalin ranged from -3.1 to +2.6 kg at 1 year and from -1.6 to +2.7 kg at 2 years. CONCLUSIONS: Adjunctive cenobamate was not associated with clinically significant changes in weight from baseline in patients treated for 1 and 2 years, including those receiving concomitant valproate, gabapentin, or pregabalin.

Drosophila melanogaster as a versatile model organism to study genetic epilepsies: An overview.

Epilepsy is one of the most prevalent neurological disorders, affecting more than 45 million people worldwide. Recent advances in genetic techniques, such as next-generation sequencing, have driven genetic discovery and increased our understanding of the molecular and cellular mechanisms behind many epilepsy syndromes. These insights prompt the development of personalized therapies tailored to the genetic characteristics of an individual patient. However, the surging number of novel genetic variants renders the interpretation of pathogenetic consequences and of potential therapeutic implications ever more challenging. Model organisms can help explore these aspects in vivo. In the last decades, rodent models have significantly contributed to our understanding of genetic epilepsies but their establishment is laborious, expensive, and time-consuming. Additional model organisms to investigate disease variants on a large scale would be desirable. The fruit fly Drosophila melanogaster has been used as a model organism in epilepsy research since the discovery of "bang-sensitive" mutants more than half a century ago. These flies respond to mechanical stimulation, such as a brief vortex, with stereotypic seizures and paralysis. Furthermore, the identification of seizure-suppressor mutations allows to pinpoint novel therapeutic targets. Gene editing techniques, such as CRISPR/Cas9, are a convenient way to generate flies carrying disease-associated variants. These flies can be screened for phenotypic and behavioral abnormalities, shifting of seizure thresholds, and response to anti-seizure medications and other substances. Moreover, modification of neuronal activity and seizure induction can be achieved using optogenetic tools. In combination with calcium and fluorescent imaging, functional alterations caused by mutations in epilepsy genes can be traced. Here, we review Drosophila as a versatile model organism to study genetic epilepsies, especially as 81% of human epilepsy genes have an orthologous gene in Drosophila. Furthermore, we discuss newly established analysis techniques that might be used to further unravel the pathophysiological aspects of genetic epilepsies.

Molecular and Clinical Repercussions of GABA Transporter 1 Variants Gone Amiss: Links to Epilepsy and Developmental Spectrum Disorders.

The human γ-aminobutyric acid (GABA) transporter 1 (hGAT-1) is the first member of the solute carrier 6 (SLC6) protein superfamily. GAT-1 (SLC6A1) is one of the main GABA transporters in the central nervous system. Its principal physiological role is retrieving GABA from the synapse into neurons and astrocytes, thus swiftly terminating neurotransmission. GABA is a key inhibitory neurotransmitter and shifts in GABAergic signaling can lead to pathological conditions, from anxiety and epileptic seizures to schizophrenia. Point mutations in the SLC6A1 gene frequently give rise to epilepsy, intellectual disability or autism spectrum disorders in the afflicted individuals. The mechanistic routes underlying these are still fairly unclear. Some loss-of-function variants impair the folding and intracellular trafficking of the protein (thus retaining the transporter in the endoplasmic reticulum compartment), whereas others, despite managing to reach their bona fide site of action at the cell surface, nonetheless abolish GABA transport activity (plausibly owing to structural/conformational defects). Whatever the molecular culprit(s), the physiological aftermath transpires into the absence of functional transporters, which in turn perturbs GABAergic actions. Dozens of mutations in the kin SLC6 family members are known to exhort protein misfolding. Such events typically elicit severe ailments in people, e.g., infantile parkinsonism-dystonia or X-linked intellectual disability, in the case of dopamine and creatine transporters, respectively. Flaws in protein folding can be rectified by small molecules known as pharmacological and/or chemical chaperones. The search for such apt remedies calls for a systematic investigation and categorization of the numerous disease-linked variants, by biochemical and pharmacological means in vitro (in cell lines and primary neuronal cultures) and in vivo (in animal models). We here give special emphasis to the utilization of the fruit fly Drosophila melanogaster as a versatile model in GAT-1-related studies. Jointly, these approaches can portray indispensable insights into the molecular factors underlying epilepsy, and ultimately pave the way for contriving efficacious therapeutic options for patients harboring pathogenic mutations in hGAT-1.

Drosophila melanogaster as a model for unraveling unique molecular features of epilepsy elicited by human GABA transporter 1 variants.

Mutations in the human γ-aminobutyric acid (GABA) transporter 1 (hGAT-1) can instigate myoclonic-atonic and other generalized epilepsies in the afflicted individuals. We systematically examined fifteen hGAT-1 disease variants, all of which dramatically reduced or completely abolished GABA uptake activity. Many of these loss-of-function variants were absent from their regular site of action at the cell surface, due to protein misfolding and/or impaired trafficking machinery (as verified by confocal microscopy and de-glycosylation experiments). A modest fraction of the mutants displayed correct targeting to the plasma membrane, but nonetheless rendered the mutated proteins devoid of GABA transport, possibly due to structural alterations in the GABA binding site/translocation pathway. We here focused on a folding-deficient A288V variant. In flies, A288V reiterated its impeded expression pattern, closely mimicking the ER-retention demonstrated in transfected HEK293 cells. Functionally, A288V presented a temperature-sensitive seizure phenotype in fruit flies. We employed diverse small molecules to restore the expression and activity of folding-deficient hGAT-1 epilepsy variants, in vitro (in HEK293 cells) and in vivo (in flies). We identified three compounds (chemical and pharmacological chaperones) conferring moderate rescue capacity for several variants. Our data grant crucial new insights into: (i) the molecular basis of epilepsy in patients harboring hGAT-1 mutations, and (ii) a proof-of-principle that protein folding deficits in disease-associated hGAT-1 variants can be corrected using the pharmacochaperoning approach. Such innovative pharmaco-therapeutic prospects inspire the rational design of novel drugs for alleviating the clinical symptoms triggered by the numerous emerging pathogenic mutations in hGAT-1.