sec-Butyl-propylacetamide (SPD) and two of its stereoisomers rapidly terminate paraoxon-induced status epilepticus in rats

Pesticides at brain borders: Impact on the blood-brain barrier, neuroinflammation, and neurological risk trajectories

Pesticides are omnipresent, and they pose significant environmental and health risks. Translational studies indicate that acute exposure to high pesticide levels is detrimental, and prolonged contact with low concentrations of pesticides, as single and cocktail, could represent a risk factor for multi-organ pathophysiology, including the brain. Within this research template, we focus on pesticides' impact on the blood-brain barrier (BBB) and neuroinflammation, physical and immunological borders for the homeostatic control of the central nervous system (CNS) neuronal networks. We examine the evidence supporting a link between pre- and postnatal pesticide exposure, neuroinflammatory responses, and time-depend vulnerability footprints in the brain. Because of the pathological influence of BBB damage and inflammation on neuronal transmission from early development, varying exposures to pesticides could represent a danger, perhaps accelerating adverse neurological trajectories during aging. Refining our understanding of how pesticides influence brain barriers and borders could enable the implementation of pesticide-specific regulatory measures directly relevant to environmental neuroethics, the exposome, and one-health frameworks.

Current and future pharmacotherapy options for drug-resistant epilepsy

INTRODUCTION

Epilepsy is one of the most common and serious neurological conditions, affecting over 70 million individuals worldwide and despite advances in treatment, the proportion of drug-resistant patients has remained largely unchanged.

AREAS COVERED

The present paper reviews current and future (under preclinical and clinical development) pharmacotherapy options for the treatment of drug-resistant focal and generalized epilepsies.

EXPERT OPINION

Current pharmacotherapy options for drug-resistant epilepsy include perampanel, brivaracetam and the newly approved cenobamate for focal epilepsies; cannabidiol (Epidiolex) for Lennox-Gastaut Syndrome (LGS), Dravet and Tuberous Sclerosis Complex (TSC); fenfluramine for Dravet syndrome and ganaxolone for seizures in Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder. Many compounds are under clinical development and may hold promise for future pharmacotherapies. For adult focal epilepsies, padsevonil and carisbamate are at a more advanced Phase III stage of clinical development followed by compounds at Phase II like selurampanel, XEN1101 and JNJ-40411813. For specific epilepsy syndromes, XEN 496 is under Phase III development for potassium voltage-gated channel subfamily Q member 2 developmental and epileptic encephalopathy (KCNQ2-DEE), carisbamate is under Phase III development for LGS and Ganaxolone under Phase III development for TSC. Finally, in preclinical models several molecular targets including inhibition of glycolysis, neuroinflammation and sodium channel inhibition have been identified in animal models although further data in animal and later human studies are needed.

Refractory and Super-Refractory Status Epilepticus in Nerve Agent-Poisoned Rats Following Application of Standard Clinical Treatment Guidelines

Nerve agents (NAs) induce a severe cholinergic crisis that can lead to status epilepticus (SE). Current guidelines for treatment of NA-induced SE only include prehospital benzodiazepines, which may not fully resolve this life-threatening condition. This study examined the efficacy of general clinical protocols for treatment of SE in the specific context of NA poisoning in adult male rats. Treatment with both intramuscular and intravenous benzodiazepines was entirely insufficient to control SE. Second line intervention with valproate (VPA) initially terminated SE in 35% of rats, but seizures always returned. Phenobarbital (PHB) was more effective, with SE terminating in 56% of rats and 19% of rats remaining seizure-free for at least 24 h. The majority of rats demonstrated refractory SE (RSE) and required treatment with a continuous third-line anesthetic. Both ketamine (KET) and propofol (PRO) led to high levels of mortality, and nearly all rats on these therapies had breakthrough seizure activity, demonstrating super-refractory SE (SRSE). For the small subset of rats in which SE was fully resolved, significant improvements over controls were observed in recovery metrics, behavioral assays, and brain pathology. Together these data suggest that NA-induced SE is particularly severe, but aggressive treatment in the intensive care setting can lead to positive functional outcomes for casualties.

Paroxysmal slow cortical activity in Alzheimer's disease and epilepsy is associated with blood-brain barrier dysfunction

A growing body of evidence shows that epileptic activity is frequent but often undiagnosed in patients with Alzheimer's disease (AD) and has major therapeutic implications. Here, we analyzed electroencephalogram (EEG) data from patients with AD and found an EEG signature of transient slowing of the cortical network that we termed paroxysmal slow wave events (PSWEs). The occurrence per minute of the PSWEs was correlated with level of cognitive impairment. Interictal (between seizures) PSWEs were also found in patients with epilepsy, localized to cortical regions displaying blood-brain barrier (BBB) dysfunction, and in three rodent models with BBB pathology: aged mice, young 5x familial AD model, and status epilepticus-induced epilepsy in young rats. To investigate the potential causative role of BBB dysfunction in network modifications underlying PSWEs, we infused the serum protein albumin directly into the cerebral ventricles of naïve young rats. Infusion of albumin, but not artificial cerebrospinal fluid control, resulted in high incidence of PSWEs. Our results identify PSWEs as an EEG manifestation of nonconvulsive seizures in patients with AD and suggest BBB pathology as an underlying mechanism and as a promising therapeutic target.

Midazolam and isoflurane combination reduces late brain damage in the paraoxon-induced status epilepticus rat model

Organophosphates (OPs) are widely used as pesticides and have been employed as warfare agents. OPs inhibit acetylcholinesterase, leading to over-stimulation of cholinergic synapses and can cause status epilepticus (SE). OPs poisoning can result in irreversible brain damage and death. Despite termination of SE, recurrent seizures and abnormal brain activity remain common sequelae often associated with long-term neural damage and cognitive dysfunction. Therefore, early treatment for prevention of seizures is of high interest. Using a rat model of paraoxon poisoning, we tested the efficacy of different neuroprotective and anti-epileptic drugs (AEDs) in suppressing early seizures and preventing brain damage. Electrocorticographic recordings were performed prior, during and after injection of 4.5 LD₅₀ paraoxon, followed by injections of atropine and toxogonin (obidoxime) to prevent death. Thirty minutes later, rats were injected with midazolam alone or in combination with different AEDs (lorazepam, valproic acid, phenytoin) or neuroprotective drugs (losartan, isoflurane). Outcome measures included SE duration, early seizures frequency and epileptiform activity duration in the first 24 -hs after poisoning. To assess delayed brain damage, we performed T2-weighted magnetic resonance imaging one month after poisoning. SE duration and the number of recurrent seizures were not affected by the addition of any of the drugs tested. Delayed brain injury was most prominent in the septum, striatum, amygdala and piriform network. Only isoflurane anesthesia significantly reduced brain damage. We show that acute treatment with isoflurane, but not AEDs, reduces brain damage following SE. This may offer a new therapeutic approach for exposed individuals.

Novel treatment approaches and pediatric research networks in status epilepticus

This paper contains five contributions which were presented as part of the novel therapies section of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures. These illustrate recent advances being made in the management and therapy of status epilepticus. The five contributions concern: genetic variations in Na + channel genes and their importance in status epilepticus; the European Reference Network for rare and complex epilepsies EpiCARE; the North American Pediatric Status Epilepticus Research Group (pSERG); Fenfluramine as a potential therapy for status epilepticus' and the valproate derivatives, valnoctamide and sec-butylpropylacetamide (SPD), as potential therapies for status epilepticus. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures".

Comparative efficacy of valnoctamide and sec-butylpropylacetamide (SPD) in terminating nerve agent-induced seizures in pediatric rats

OBJECTIVES

Children and adults are likely to be among the casualties in a civilian nerve agent exposure. This study evaluated the efficacy of valnoctamide (racemic-VCD), sec-butylpropylacetamide (racemic-SPD), and phenobarbital for stopping nerve agent seizures in both immature and adult rats.

METHODS

Female and male postnatal day (PND) 21, 28, and 70 (adult) rats, previously implanted with electroencephalography (EEG) electrodes were exposed to seizure-inducing doses of the nerve agents sarin or VX and EEG was recorded continuously. Five minutes after seizure onset, animals were treated with SPD, VCD, or phenobarbital. The up-down method was used over successive animals to determine the anticonvulsant median effective dose (ED₅₀ ) of the drugs.

RESULTS

SPD-ED₅₀ values in the VX model were the following: PND21, 53 mg/kg (male) and 48 mg/kg (female); PND28, 108 mg/kg (male) and 43 mg/kg (female); and PND70, 101 mg/kg (male) and 40 mg/kg (female). SPD-ED₅₀ values in the sarin model were the following: PND21, 44 mg/kg (male) and 28 mg/kg (female); PND28, 79 mg/kg (male) and 34 mg/kg (female); and PND70, 53 mg/kg (male) and 53 mg/kg (female). VCD-ED₅₀ values in the VX model were the following: PND21, 34 mg/kg (male) and 43 mg/kg (female); PND28, 165 mg/kg (male) and 59 mg/kg (female); and PND70, 87 mg/kg (male) and 91 mg/kg (female). VCD-ED₅₀ values in the sarin model were the following: PND21, 45 mg/kg (male), 48 mg/kg (female); PND28, 152 mg/kg (male) 79 mg/kg (female); and PND70, 97 mg/kg (male) 79 mg/kg (female). Phenobarbital-ED₅₀ values in the VX model were the following: PND21, 43 mg/kg (male) and 18 mg/kg (female); PND28, 48 mg/kg (male) and 97 mg/kg (female). Phenobarbital-ED₅₀ values in the sarin model were the following: PND21, 32 mg/kg (male) and 32 mg/kg (female); PND28, 58 mg/kg (male) and 97 mg/kg (female); and PND70, 65 mg/kg (female).

SIGNIFICANCE

SPD and VCD demonstrated anticonvulsant activity in both immature and adult rats in the sarin- and VX-induced status epilepticus models. Phenobarbital was effective in immature rats, whereas in adult rats, higher doses were required that were accompanied by toxicity. Overall, significantly less drug was required to stop seizures in PND21 animals than in the older animals, and overall, males required higher amounts of drug than females.

Novel drugs and early polypharmacotherapy in status epilepticus

PURPOSE

Rescue medications for status epilepticus (SE) have a relatively high rate of failure. The purpose of this review is to summarize the evidence for the efficacy of novel drugs and early polypharmacotherapy for SE.

METHOD

Literature review.

RESULTS

New drugs and treatment strategies aim to target the pathophysiology of SE in order to improve seizure control and outcomes. Changes at the synapse level during SE include a progressive decrease in synaptic GABA_A receptors and increase in synaptic NMDA receptors. These changes tend to promote self-sustaining seizures. Current SE guidelines recommend a rapid stepwise treatment using benzodiazepines in monotherapy as the first-line treatment, targeting GABA_A synaptic receptors. Novel treatment approaches target GABA_A synaptic and extrasynaptic receptors with allopregnanolone, and NMDA receptors with ketamine. Novel rescue treatments used for SE include topiramate, brivaracetam, and perampanel, which are already marketed in epilepsy. Some available drugs not marketed for use in epilepsy have been used in the treatment of SE, and other agents are being studied for this purpose. Early polytherapy, most frequently combining a benzodiazepine with a second-line drug or an NMDA receptor antagonist, might potentially increase seizure control with relatively minor increase in side effects. Although many preclinical studies support novel drugs and early polytherapy in SE, human studies are scarce and inconclusive. Currently, evidence is lacking to recommend specific combinations of these new agents.

CONCLUSIONS

Novel drugs and strategies target the underlying pathophysiology of SE with the intent to improve seizure control and outcomes.

A resurging boom in new drugs for epilepsy and brain disorders

INTRODUCTION

Epilepsy is one of the most common neurological diseases affecting approximately 50 million people worldwide. Despite many advances in epilepsy research, nearly a third of patients with epilepsy have refractory or pharmacoresistant epilepsy. Despite the approval of a dozen antiepileptic drugs (AEDs) over the past decade, there are no agents that halt the development of epilepsy. Thus, newer and better AEDs that can prevent refractory seizures and modify the disease are needed for curing epilepsy. Areas covered: In this article, we highlight the recent advances and emerging trends in new and innovative drugs for epilepsy and seizure disorders. We review in detail top new drugs that are currently in clinical trials or agents that are under development and have novel mechanisms of action. Expert commentary: Among the new agents under clinical investigation, the majority were originally developed for treating other neurological diseases (everolimus, fenfluramine, nalutozan, bumetanide, and valnoctamide); several have mechanisms of action similar to those of conventional AEDs (AP, ganaxolone, and YKP3089); and some new agents represent novel mechanisms of actions (huperzine-A, cannabidiol, tonabersat, and VX-765).

Mitochondrial Liver Toxicity of Valproic Acid and Its Acid Derivatives Is Related to Inhibition of α-Lipoamide Dehydrogenase

The liver toxicity of valproic acid (VPA) is an established side effect of this widely used antiepileptic drug, which is extremely problematic for patients with metabolic epilepsy and particularly epilepsy due to mitochondrial dysfunction. In the present report, we investigated the reason for liver mitochondrial toxicity of VPA and several acid and amide VPA analogues. While the pyruvate and 2-oxoglutarate oxidation rates of rat brain mitochondria were nearly unaffected by VPA, rat liver mitochondrial pyruvate and 2-oxoglutarate oxidation was severely impaired by VPA concentrations above 100 µM. Among the reactions involved in pyruvate oxidation, pyruvate transport and dehydrogenation steps were not affected by VPA, while α-lipoamide dehydrogenase was strongly inhibited. Strong inhibition of α-lipoamide dehydrogenase was also noted for the VPA one-carbon homolog sec -butylpropylacetic acid (SPA) and to a lesser extent for the VPA constitutional isomer valnoctic acid (VCA), while the corresponding amides of the above three acids valpromide (VPD), sec -butylpropylacetamide (SPD) and valnoctamide (VCD) showed only small effects. We conclude that the active inhibitors of pyruvate and 2-oxoglutarate oxidation are the CoA conjugates of VPA and its acid analogues affecting selectively α-lipoamide dehydrogenase in liver. Amide analogues of VPA, like VCD, show low inhibitory effects on mitochondrial oxidative phosphorylation in the liver, which might be relevant for treatment of patients with mitochondrial epilepsy.

Imaging blood-brain barrier dysfunction as a biomarker for epileptogenesis

A biomarker that will enable the identification of patients at high-risk for developing post-injury epilepsy is critically required. Microvascular pathology and related blood-brain barrier dysfunction and neuroinflammation were shown to be associated with epileptogenesis after injury. Here we used prospective, longitudinal magnetic resonance imaging to quantitatively follow blood-brain barrier pathology in rats following status epilepticus, late electrocorticography to identify epileptic animals and post-mortem immunohistochemistry to confirm blood-brain barrier dysfunction and neuroinflammation. Finally, to test the pharmacodynamic relevance of the proposed biomarker, two anti-epileptogenic interventions were used; isoflurane anaesthesia and losartan. Our results show that early blood-brain barrier pathology in the piriform network is a sensitive and specific predictor (area under the curve of 0.96, P < 0.0001) for epilepsy, while diffused pathology is associated with a lower risk. Early treatments with either isoflurane anaesthesia or losartan prevented early microvascular damage and late epilepsy. We suggest quantitative assessment of blood-brain barrier pathology as a clinically relevant predictive, diagnostic and pharmaco!dynamics biomarker for acquired epilepsy.

Isoflurane prevents acquired epilepsy in rat models of temporal lobe epilepsy

OBJECTIVE

Acquired epilepsy is a devastating long-term risk of various brain insults, including trauma, stroke, infections, and status epilepticus (SE). There is no preventive treatment for patients at risk. Attributable to the complex alterations involved in epileptogenesis, it is likely that multitargeted approaches are required for epilepsy prevention. We report novel preclinical findings with isoflurane, which exerts various nonanesthetic effects that may be relevant for antiepileptogenesis.

METHODS

The effects of isoflurane were investigated in two rat models of SE-induced epilepsy: intrahippocampal kainate and systemic administration of paraoxon. Isoflurane was either administered during (kainate) or after (paraoxon) induction of SE. Magnetic resonance imaging was used to assess blood-brain barrier (BBB) dysfunction. Positron emission tomography was used to visualize neuroinflammation. Long-term electrocorticographic recordings were used to monitor spontaneous recurrent seizures. Neuronal damage was assessed histologically.

RESULTS

In the absence of isoflurane, spontaneous recurrent seizures were common in the majority of rats in both models. When isoflurane was administered during kainate injection, duration and severity of SE were not affected, but only few rats developed spontaneous recurrent seizures. A similar antiepileptogenic effect was found when paraoxon-treated rats were exposed to isoflurane after SE. Moreover, in the latter model, isoflurane prevented BBB dysfunction and neurodegeneration, whereas isoflurane reduced neuroinflammation in the kainate model.

INTERPRETATION

Given that isoflurane is a widely used volatile anesthetic, and is used for inhalational long-term sedation in critically ill patients at risk to develop epilepsy, our findings hold a promising potential to be successfully translated into the clinic. Ann Neurol 2016;80:896-908.

Status Epilepticus and Beyond: A Clinical Review of Status Epilepticus and an Update on Current Management Strategies in Super-refractory Status Epilepticus

Status epilepticus and refractory status epilepticus represent some of the most complex conditions encountered in the neurological intensive care unit. Challenges in management are common as treatment options become limited and prolonged hospital courses are accompanied by complications and worsening patient outcomes. Antiepileptic drug treatments have become increasingly complex. Rational polytherapy should consider the pharmacodynamics and kinetics of medications. When seizures cannot be controlled with medical therapy, alternative treatments, including early surgical evaluation can be considered; however, evidence is limited. This review provides a brief overview of status epilepticus, and a recent update on the management of refractory status epilepticus based on evidence from the literature, evidence-based guidelines, and experiences at our institution.

Progress report on new antiepileptic drugs: A summary of the Thirteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XIII)

The Thirteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XIII) took place in Madrid, Spain, on June 26-29, 2016, and was attended by >200 delegates from 31 countries. The present Progress Report provides an update on experimental and clinical results for drugs presented at the Conference. Compounds for which summary data are presented include an AED approved in 2016 (brivaracetam), 12 drugs in phase I-III clinical development (adenosine, allopregnanolone, bumetanide, cannabidiol, cannabidivarin, 2-deoxy-d-glucose, everolimus, fenfluramine, huperzine A, minocycline, SAGE-217, and valnoctamide) and 6 compounds or classes of compounds for which only preclinical data are available (bumetanide derivatives, sec-butylpropylacetamide, FV-082, 1OP-2198, NAX 810-2, and SAGE-689). Overall, the results presented at the Conference show that considerable efforts are ongoing into discovery and development of AEDs with potentially improved therapeutic profiles compared with existing agents. Many of the drugs discussed in this report show innovative mechanisms of action and many have shown promising results in patients with pharmacoresistant epilepsies, including previously neglected rare and severe epilepsy syndromes.

Pharmacokinetic-Pharmacodynamic Correlation and Brain Penetration of sec-Butylpropylacetamide, a New CNS Drug Possessing Unique Activity against Status Epilepticus

sec-Butylpropylacetamide (SPD) is the amide derivative of valproic acid (VPA). SPD possess a wide-spectrum anticonvulsant profile better than that of VPA and blocks status epilepticus (SE) induced by pilocarpine and organophosphates. The activity of SPD on SE is better than that of benzodiazepines (BZDs) in terms of the ability to block SE when given 20-60 min after the beginning of a seizure. However, intraperitoneal (i.p.) administration to rats cannot be extrapolated to humans. Consequently, in the current study a comparative pharmacokinetic (PK)-pharmacodynamic analysis of SPD was conducted following i.p., intramuscular (i.m.), and intravenous (i.v.) administrations to rats. SPD brain and plasma levels were quantified at various times after dosing following i.p. (60 mg/kg), i.v. (60 mg/kg), and i.m. administrations (120 mg/kg) to rats, and the major PK parameters of SPD were estimated. The antiseizure (SE) efficacies of SPD and its individual stereoisomers were assessed in the pilocarpine-induced BZD-resistant SE model following i.p. and i.m. administrations to rats at 30 min after seizure onset. The absolute bioavailabilities of SPD following i.p. and i.m. administrations were 76% (i.p.) and 96% (i.p.), and its clearance and half-life were 1.8-1.5 L h(-1) kg(-1) and 0.5-1.7 h, respectively. The SPD brain-to-plasma AUC ratios were 1.86 (i.v.), 2.31 (i.p.), and 0.77 (i.m.). Nevertheless, the ED50 values of SPD and its individual stereoisomers were almost identical in the rat pilocarpine-induced SE model following i.p. and i.m. administrations. In conclusion, in rats SPD is completely or almost completely absorbed after i.m. and i.p. administration and readily penetrates into the brain. Consequently, in spite of PK differences, the activities of SPD in the BZD-resistant SE model following i.m. and i.p. administrations are similar.

The potential of sec-butylpropylacetamide (SPD) and valnoctamide and their individual stereoisomers in status epilepticus

sec-Butylpropylacetamide (SPD) is a one-carbon homologue of valnoctamide (VCD), a chiral constitutional isomer of valproic acid's (VPA) corresponding amide--valpromide. Racemic-SPD and racemic-VCD possess a unique and broad-spectrum antiseizure profile superior to that of VPA. In addition, SPD blocks behavioral and electrographic status epilepticus (SE) induced by pilocarpine and the organophosphates soman and paraoxon. Valnoctamide has similar activity as SPD in the soman-induced SE model. The activity of SPD and VCD against SE is superior to that of diazepam and midazolam in terms of rapid onset, potency, and ability to block SE when given 20 to 60 min after seizure onset. sec-Butylpropylacetamide and VCD possess two stereogenic carbons in their chemical structure and, thus, exist as a racemic mixture of four individual stereoisomers. The anticonvulsant activity of the individual stereoisomers of SPD and VCD was comparatively evaluated in several anticonvulsant rodent models including the benzodiazepine-resistant SE model. sec-Butylpropylacetamide has stereoselective pharmacokinetics (PK) and pharmacodynamics (PD). The higher clearance of (2R,3S)-SPD and (2S,3R)-SPD led to a 50% lower plasma exposure and, consequently, to a lower anticonvulsant activity compared to racemic-SPD and its two other stereoisomers. Racemic-SPD, (2S,3S)-SPD, and (2R,3R)-SPD have similar anticonvulsant activities and PK profiles that are better than those of (2R,3S)-SPD and (2S,3R)-SPD. Valnoctamide has a stereoselective PK with (2S,3S)-VCD exhibiting the lowest clearance and, consequently, a twice-higher plasma exposure than all other stereoisomers. Nevertheless, there was less stereoselectivity in VCD anticonvulsant activity, and each stereoisomer had similar ED50 values in most models. sec-Butylpropylacetamide and VCD stereoisomers did not cause teratogenicity (i.e., neural tube defect) in mice at doses 3-12 times higher than their anticonvulsant-ED50 values. This article is part of a Special Issue entitled "Status Epilepticus".