Stereoselective anticonvulsant and pharmacokinetic analysis of valnoctamide, a CNS-active derivative of valproic acid with low teratogenic potential

Gene Environment Interactions in the Etiology of Neural Tube Defects

Human structural congenital malformations are the leading cause of infant mortality in the United States. Estimates from the United States Center for Disease Control and Prevention (CDC) determine that close to 3% of all United States newborns present with birth defects; the worldwide estimate approaches 6% of infants presenting with congenital anomalies. The scientific community has recognized for decades that the majority of birth defects have undetermined etiologies, although we propose that environmental agents interacting with inherited susceptibility genes are the major contributing factors. Neural tube defects (NTDs) are among the most prevalent human birth defects and as such, these malformations will be the primary focus of this review. NTDs result from failures in embryonic central nervous system development and are classified by their anatomical locations. Defects in the posterior portion of the neural tube are referred to as meningomyeloceles (spina bifida), while the more anterior defects are differentiated as anencephaly, encephalocele, or iniencephaly. Craniorachischisis involves a failure of the neural folds to elevate and thus disrupt the entire length of the neural tube. Worldwide NTDs have a prevalence of approximately 18.6 per 10,000 live births. It is widely believed that genetic factors are responsible for some 70% of NTDs, while the intrauterine environment tips the balance toward neurulation failure in at risk individuals. Despite aggressive educational campaigns to inform the public about folic acid supplementation and the benefits of providing mandatory folic acid food fortification in the United States, NTDs still affect up to 2,300 United States births annually and some 166,000 spina bifida patients currently live in the United States, more than half of whom are now adults. Within the context of this review, we will consider the role of maternal nutritional status (deficiency states involving B vitamins and one carbon analytes) and the potential modifiers of NTD risk beyond folic acid. There are several well-established human teratogens that contribute to the population burden of NTDs, including: industrial waste and pollutants [e.g., arsenic, pesticides, and polycyclic aromatic hydrocarbons (PAHs)], pharmaceuticals (e.g., anti-epileptic medications), and maternal hyperthermia during the first trimester. Animal models for these teratogens are described with attention focused on valproic acid (VPA; Depakote). Genetic interrogation of model systems involving VPA will be used as a model approach to discerning susceptibility factors that define the gene-environment interactions contributing to the etiology of NTDs.

Synthesis and Enantioselective Pharmacokinetic/Pharmacodynamic Analysis of New CNS-Active Sulfamoylphenyl Carbamate Derivatives

We recently reported a new class of carbamate derivatives as anticonvulsants. Among these, 3-methylpentyl(4-sulfamoylphenyl)carbamate (MSPC) stood out as the most potent compound with ED₅₀ values of 13 mg/kg (i.p.) and 28 mg/kg (p.o.) in the rat maximal electroshock test (MES). 3-Methylpropyl(4-sulfamoylphenyl)carbamate (MBPC), reported and characterized here, is an MSPC analogous compound with two less aliphatic carbon atoms in its structure. As both MSPC and MBPC are chiral compounds, here, we studied the carbonic anhydrase inhibitory and anticonvulsant action of both MBPC enantiomers in comparison to those of MSPC as well as their pharmacokinetic properties. Racemic-MBPC and its enantiomers showed anticonvulsant activity in the rat maximal electroshock (MES) test with ED₅₀ values in the range of 19–39 mg/kg. (R)-MBPC had a 65% higher clearance than its enantiomer and, consequently, a lower plasma exposure (AUC) than (S)-MSBC and racemic-MSBC. Nevertheless, (S)-MBPC had a slightly better brain permeability than (R)-MBPC with a brain-to-plasma (AUC) ratio of 1.32 (S-enantiomer), 1.49 (racemate), and 1.27 (R-enantiomer). This may contribute to its better anticonvulsant-ED₅₀ value. The clearance of MBPC enantiomers was more enantioselective than the brain permeability and MES-ED₅₀ values, suggesting that their anticonvulsant activity might be due to multiple mechanisms of action.

Stereoselective pharmacokinetic and pharmacodynamic analysis of a CNS-active sulphamoylphenyl carbamate derivative

3-Methylpentyl(4-sulphamoylphenyl)carbamate (MSPC) came as the most potent compound out of a new series of carbamates composed of phenyl-ethanol or branched aliphatic alcohols, and 4-benzenesulphonamide-carbamic acid. In this study, the anticonvulsant activity and pharmacokinetics (PKs) of MSPC-two individual enantiomers were comparatively analysed in rats as well as their carbonic anhydrase (CA) inhibition. The anticonvulsant activity of MSPC enantiomers was evaluated at the rat-maximal electroshock (MES) test, and their CA inhibition evaluated. (R)-MSPC had a 29% higher clearance and consequently, a lower plasma exposure area under the curve (AUC) than (S)-MSPC and racemic-MSPC. Nevertheless, (R)-MSPC had a better brain permeability than its (S)-enantiomer with brain-to-plasma-(AUC)-ratio (BPR) of 2.07 ((R)-enantiomer), 1.85 (racemate), and 0.79 ((S)-enantiomer). As a whole body (in vivo) pharmacodynamic (PD) measure, MSPC-anticonvulsant maximal electroshock seizure (MES) activity was less enantioselective than MSPC-CA inhibition. The lack of significant differences between racemic-MSPC and its individual enantiomers suggest that their anticonvulsant activity might be due to multiple mechanisms of action.

Amidic derivatives of valproic acid, valpromide and valnoctamide, inhibit HSV-1 infection in oligodendrocytes

Herpes simplex virus type 1 (HSV-1) is a ubiquitous infectious agent that can establish latency in neurons, and in some cases, viral retrograde transport results in infection of the central nervous system (CNS). Several antivirals have been identified with the ability to inhibit HSV-1 replication in human cells to a greater or lesser degree, most of which are nucleoside analogues that unfortunately exhibit teratogenic potential, embryotoxicity, carcinogenic or antiproliferative activities and resistances in immunocompromised patients, specially. In the present study, we assessed two amidic derivatives of valproic acid (VPA) - valpromide (VPD) and valnoctamide (VCD) - which are already used in clinic treatments, as feasible HSV-1 antivirals in glial cells. Both VPD and VCD have exhibited increased efficacy in bipolar disorders and as anticonvulsant drugs compared to VPA, while being less teratogenic and hepatotoxic. Cytotoxicity assays carried out in our laboratory showed that VPD and VCD were not toxic in a human oligodendroglioma cell line (HOG), at least at the concentrations established for human treatments. Infectivity assays showed a significant inhibition of HSV-1 infection in HOG cells after VPD and VCD treatment, being more pronounced in VPD-treated cells, comparable to the effects obtained with acyclovir. Furthermore, the same antiherpetic effects of VPD were observed in other oligodendrocytic cell lines and rat primary oligodendrocytes (OPCs), confirming the results obtained in HOG cells. Altogether, our results allow us to propose VPD as a potential antiherpetic drug that is able to act directly on oligodendrocytes of the CNS.

Moving beyond sodium valproate: choosing the right anti-epileptic drug in children

Introduction: Sodium valproate is a widely used anti-epileptic drug with a broad spectrum of activity and mechanism of action. It has consequently been the first-line drug for most seizure types in children for the past fifty years. A wide range of side effects come along with these exceptional properties, including teratogenicity and neuro-cognitive impairments in offspring. Therefore, epilepsy treatment in children and adolescents should be reassessed in light of newer antiepileptic drugs as well as a more targeted-approach with older drugs. Areas covered: The authors review the main concerns of valproate use in terms of adverse effects on different systems and drug interactions. The current alternatives to valproate in absence, myoclonic, tonic-clonic and focal onset seizures in children/adolescents are also reviewed. Expert opinion: There are several issues that research should address in antiepileptic therapy and in clinical studies with children, given the peculiarity of this population. Future perspectives in epilepsy therapy should now lead towards an individualized treatment.

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.

Teratogenicity of valproic acid and its constitutional isomer, amide derivative valnoctamide in mice

OBJECTIVES

The anticonvulsant valproic acid (VPA) has a known teratogenic effect capable of inducing major congenital malformations and developmental disorders. A comparative teratogenicity study of VPA and its analog valnoctamide (VCD), which is a new generation candidate antiepileptic drug, was carried out using Swiss Vancouver (SWV) mice.

METHODS

Pregnant SWV dams were treated with either a single intraperitoneal injection of VPA (1.8 and 2.7 mmol/kg), VCD (1.8 and 2.7 mmol/kg), or vehicle on E8:12 (gestational day:hour). The numbers of implantation and resorption, viable and dead fetuses, and the presence of gross fetal visceral and skeletal abnormalities were determined (E18). Real-time Polymerase chain reaction (RT-PCR) arrays were used to analyze the expression of 84 genes related to the processes of neurogenesis and neural stem cell differentiation.

RESULTS

Significant decreases in pregnancy weight gain and the number of live fetuses were observed when VPA was administered at the high dose, whereas the percentage of exencephalic fetuses was significantly increased in VPA treated compared with an equivalent VCD dosage group. There was a dose-related increase in visceral defects in the VPA-exposed fetuses. Missing skull bones and fused vertebrae in fetuses occurred at the high dose of VPA. Three genes (Mtap2, Bmp8b, and Stat3) were significantly upregulated and one (Heyl) was downregulated in samples from VPA-treated dams.

CONCLUSIONS

The study demonstrates that the teratogenicity of VPA was significantly greater than that of an equimolar dose of VCD. Four genes (Mtap2, Bmp8b, Stat3, and Heyl) represent candidate target genes for the underlying teratogenic mechanism responsible for VPA-induced malformations.

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.

Valnoctamide, which reduces rat brain arachidonic acid turnover, is a potential non-teratogenic valproate substitute to treat bipolar disorder

BACKGROUND

Valproic acid (VPA), used for treating bipolar disorder (BD), is teratogenic by inhibiting histone deacetylase. In unanaesthetized rats, chronic VPA, like other mood stabilizers, reduces arachidonic acid (AA) turnover in brain phospholipids, and inhibits AA activation to AA-CoA by recombinant acyl-CoA synthetase-4 (Acsl-4) in vitro. Valnoctamide (VCD), a non-teratogenic constitutional isomer of VPA amide, reported effective in BD, also inhibits recombinant Acsl-4 in vitro.

HYPOTHESIS

VCD like VPA will reduce brain AA turnover in unanaesthetized rats.

METHODS

A therapeutically relevant (50mg/kg i.p.) dose of VCD or vehicle was administered daily for 30 days to male rats. AA turnover and related parameters were determined using our kinetic model, following intravenous [1-¹⁴C]AA in unanaesthetized rats for 10min, and measuring labeled and unlabeled lipids in plasma and high-energy microwaved brain.

RESULTS

VCD, compared with vehicle, increased λ, the ratio of brain AA-CoA to unesterified plasma AA specific activities; and decreased turnover of AA in individual and total brain phospholipids.

CONCLUSIONS

VCD's ability like VPA to reduce rat brain AA turnover and inhibit recombinant Acsl-4, and its efficacy in BD, suggest that VCD be further considered as a non-teratogenic VPA substitute for treating BD.

Valnoctamide Inhibits Cytomegalovirus Infection in Developing Brain and Attenuates Neurobehavioral Dysfunctions and Brain Abnormalities

Cytomegalovirus (CMV) is the most common infectious cause of brain defects and neurological dysfunction in developing human babies. Due to the teratogenicity and toxicity of available CMV antiviral agents, treatment options during early development are markedly limited. Valnoctamide (VCD), a neuroactive mood stabilizer with no known teratogenic activity, was recently demonstrated to have anti-CMV potential. However, it is not known whether this can be translated into an efficacious therapeutic effect to improve CMV-induced adverse neurological outcomes. Using multiple models of CMV infection in the developing mouse brain, we show that subcutaneous low-dose VCD suppresses CMV by reducing the level of virus available for entry into the brain and by acting directly within the brain to block virus replication and dispersal. VCD during the first 3 weeks of life restored timely acquisition of neurological milestones in neonatal male and female mice and rescued long-term motor and behavioral outcomes in juvenile male mice. CMV-mediated brain defects, including decreased brain size, cerebellar hypoplasia, and neuronal loss, were substantially attenuated by VCD. No adverse side effects on neurodevelopment of uninfected control mice receiving VCD were detected. Treatment of CMV-infected human fetal astrocytes with VCD reduced both viral infectivity and replication by blocking viral particle attachment to the cell, a mechanism that differs from available anti-CMV drugs. These data suggest that VCD during critical periods of neurodevelopment can effectively suppress CMV replication in the brain and safely improve both immediate and long-term neurological outcomes.SIGNIFICANCE STATEMENT Cytomegalovirus (CMV) can irreversibly damage the developing brain. No anti-CMV drugs are available for use during fetal development, and treatment during the neonatal period has substantial limitations. We studied the anti-CMV actions of valnoctamide (VCD), a psychiatric sedative that appears to lack teratogenicity and toxicity, in the newborn mouse brain, a developmental period that parallels that of an early second-trimester human fetus. In infected mice, subcutaneous VCD reaches the brain and suppresses viral replication within the CNS, rescuing the animals from CMV-induced brain defects and neurological problems. Treatment of uninfected control animals exerts no detectable adverse effects. VCD also blocks CMV replication in human fetal brain cells.

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.

Mood stabilizers inhibit cytomegalovirus infection

Cytomegalovirus (CMV) infection can generate debilitating disease in immunocompromised individuals and neonates. It is also the most common infectious cause of congenital birth defects in infected fetuses. Available anti-CMV drugs are partially effective but are limited by some toxicity, potential viral resistance, and are not recommended for fetal exposure. Valproate, valpromide, and valnoctamide have been used for many years to treat epilepsy and mood disorders. We report for the first time that, in contrast to the virus-enhancing actions of valproate, structurally related valpromide and valnoctamide evoke a substantial and specific inhibition of mouse and human CMV in vitro. In vivo, both drugs safely attenuate mouse CMV, improving survival, body weight, and developmental maturation of infected newborns. The compounds appear to act by a novel mechanism that interferes with CMV attachment to the cell. Our work provides a novel potential direction for CMV therapeutics through repositioning of agents already approved for use in psychiatric disorders.

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.

Comparative teratogenicity analysis of valnoctamide, risperidone, and olanzapine in mice

OBJECTIVES

Based on the recent findings from animal studies, it has been proposed that the therapeutic use of valnoctamide, an anxiolytic drug developed in the early 1960s, be extended to treat other neurological disorders such as epilepsy and bipolar disease. Given the scarcity of adequate data on its prenatal toxicity, a comparative teratogenicity study of valnoctamide and two of the most commonly used drugs to treat bipolar disorder, risperidone and olanzapine, was carried out in a mouse model system.

METHODS

Pregnant dams were treated with the aforementioned three drugs at the dose levels calculated as an equal proportion of the respective LD50 values of these drugs. The main reproductive indices examined included the numbers of implantations and resorptions, viable and dead fetuses, and fetal gross, visceral and skeletal abnormalities.

RESULTS

The outcomes of the present study indicated that olanzapine was the most teratogenic of the three drugs, inducing maternal-, embryo-, and fetotoxicity. Risperidone also exerted a significant prenatal toxicity, but its adverse effect was less pronounced than that induced by olanzapine. Valnoctamide did not show any teratogenic effect, even when used in relatively higher dosages than olanzapine and risperidone. The observed increased skeletal abnormalities in one of the valnoctamide treatment groups were nonspecific and, as such, signaled a modest developmental delay rather than an indication that the compound could induce structural malformations.

CONCLUSIONS

Under our experimental conditions, valnoctamide demonstrated the lowest prenatal toxicity of the three tested drugs.

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".

Pharmacodynamic and pharmacokinetic analysis of CNS-active constitutional isomers of valnoctamide and sec-butylpropylacetamide--Amide derivatives of valproic acid

Valnoctamide (VCD) and sec-butylpropylacetamide (SPD) are CNS-active closely related amide derivatives of valproic acid with unique anticonvulsant activity. This study evaluated how small chemical changes affect the pharmacodynamics (PD; anticonvulsant activity and teratogenicity) and pharmacokinetics (PK) of three constitutional isomers of SPD [sec-butylisopropylacetamide (SID) and tert-butylisopropylacetamide (TID)] and of VCD [tert-butylethylacetamide (TED)]. The anticonvulsant activity of SID, TID, and TED was comparatively evaluated in several rodent anticonvulsant models. The PK-PD relationship of SID, TID, and TED was evaluated in rats, and their teratogenicity was evaluated in a mouse strain highly susceptible to teratogen-induced neural tube defects (NTDs). sec-Butylisopropylacetamide and TID have a similar PK profile to SPD which may contribute to their similar anticonvulsant activity. tert-Butylethylacetamide had a better PK profile than VCD (and SPD); however, this did not lead to a superior anticonvulsant activity. sec-Butylisopropylacetamide and TED did not cause NTDs at doses 4-7 times higher than their anticonvulsant ED50 values. In rats, SID, TID (ip), and TED exhibited a broad spectrum of anticonvulsant activity. However, combined anticonvulsant analysis in mice and rats shows SID as the most potent compound with similar activity to that of SPD, demonstrating that substitution of the isobutyl moiety in the SPD or VCD molecule by tert-butyl as well as a propyl-to-isopropyl replacement in the SPD molecule did not majorly affect the anticonvulsant activity.

Valnoctamide enhances phasic inhibition: a potential target mechanism for the treatment of benzodiazepine-refractory status epilepticus

Valnoctamide (VCD), a derivative of valproate, suppresses electrographic seizures in animal models of status epilepticus (SE), even when the seizures are resistant to benzodiazepines (BZDs). We therefore tested the effect of VCD on miniature inhibitory postsynaptic currents (mIPSCs) in CA1 pyramidal cells to determine if VCD acts directly on γ-aminobutyric acid (GABA)A receptors. Bath-applied VCD induced a specific, rapid, dose-dependent, and reversible slowing of the decay of mIPSCs (i.e., increased time constant) with no effect on their frequency or amplitude. This is similar to the effect of BZDs on mIPSCs, but the effect of VCD persisted in the presence of the BZD-binding site antagonist flumazenil, and was additive to the effect of the BZD, diazepam. These data suggest that VCD acts through a different binding site than that of BZDs, which likely accounts for its effect on BZD-refractory SE. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.