Potent Anticonvulsant Urea Derivatives of Constitutional Isomers of Valproic Acid

In silico inspired design of urea noscapine congeners as anticancer agents: Chemical synthesis and experimental evaluation using breast cancer cells and a xenograft mouse model

A series of semisynthetic noscapine-urea congeners (7a-7h) as potential tubulin-binding agents are being developed by integrating a urea pharmacophore at the C-9 position of the noscapine scaffold. Their binding affinity to tubulin was predicted through molecular docking, molecular dynamics (MD) simulations, and the MM-PBSA approach. These molecules were subsequently chemically synthesized and assessed using breast cancer cell lines (MCF-7 and MDA-MB-231) and normal human embryonic kidney cells (HEK). Both the docking score and the predicted binding free energy (ΔGbind,pred) revealed that urea congeners had a stronger affinity towards tubulin than noscapine and effectively inhibited the proliferation of all cancer cell types without affecting normal healthy cells. The results indicated that compound 7g exhibited the most promise and was chosen for further studies. Moreover, MDA-MB-231 cells treated with 7g at its IC50 concentration showed morphological changes such as membrane blebbing, fragmented nuclei, and the presence of apoptotic bodies. Apoptosis induction was further confirmed by flow cytometry. Moreover, the tubulin binding assay revealed a greater binding affinity with an equilibrium dissociation constant (KD) of 42 ± 2.4 μM for compound 7g. The number of MCF-7 cells engrafted as breast tumors in nude mice was found to be reduced significantly without any adverse effects. Noscapine is already in clinical trials, but the urea noscapine congener offers an advantage because of its increased potency without impacting the nontoxic profile of noscapine.

Design, synthesis, structure elucidation, antimicrobial, molecular docking, and SAR studies of novel urea derivatives bearing tricyclic aromatic hydrocarbon rings

The targeted compounds were prepared using both (9H-fluoren-9-ylidene)hydrazine (1) and 10H-phenothiazine (2) as starting materials. The treatment of 1 or 2 with different isocyanates afforded the title compounds 7a-d, 8a, and 8b in excellent yield. All compounds were characterized and ascertained by infrared, nuclear magnetic resonance, and elemental analyses as well as single-crystal X-ray diffraction. The antimicrobial efficiency of all was tested in vitro, and a noticeable inhibition activity against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Candida albicans was obtained by compounds 7a, 7b, 8a, and 8b. Moreover, the biofilm mechanism activity was strongly inhibited by compounds 7b and 8b for all bacterial pathogens, with a percentage ratio of more than 55%. The findings from the molecular docking simulation revealed that compounds 7a, 7b, 8a, and 8b exhibited favorable binding energies and interacted effectively with the active sites of sterol 14-demethylase, dihydropteroate synthase, gyrase B, LasR (major transcriptional activator of P. aeruginosa), and carbapenemase for C. albicans, S. aureus, B. subtills, K. pneumoniae, and P. aeruginosa, respectively. These results suggest that the compounds have the potential to inhibit the activity of these enzymes and demonstrate promising antimicrobial properties. Moreover, the in silico evaluation of drug likeness and absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles for compounds 7a, 7b, 8a, and 8b demonstrated their compatibility with Lipinski's, Ghose's, Veber's, Muegge's, and Egan's rules. These findings suggest that these compounds possess favorable physicochemical properties, making them promising candidates for continued drug development efforts.

Overview of Chemistry and Therapeutic Potential of Non-Nitrogen Heterocyclics as Anticonvulsant Agents

Epilepsy is a chronic neurological disorder, characterized by the predisposition of unprovoked seizures affecting the neurobiological, psychological, cognitive, economic, and social wellbeing of the patient. As per the 2019 report by World Health Organization, it affects nearly 80% of the population, which comes from middle to low-income countries. It has been suggested that 70% of such cases can be treated effectively if properly diagnosed. It is one of the most common neurological diseases affecting 50 million people globally. Most of the antiepileptic drugs used in clinical practice are only 60-80% effective in controlling the disease. These drugs suffer from serious drawbacks of non-selectivity and toxicity that limit their clinical usefulness. Hence, there is a need to search for safe, potent, and effective anti-epileptic drugs. One of the emerging strategies to discover and develop selective and non-toxic anticonvulsant molecules focuses on the design of non-nitrogen heterocyclic compounds (NNHC). Drugs such as valproic acid, gabapentin, viagabatrin, fluorofelbamate, tiagabine, progabide, pregabalin, gamma amino butyric acid (GABA), etc. do not contain a nitrogen heterocyclic ring but are as effective anticonvulsants as conventional heterocyclic nitrogen compounds. This review covers the various classes of NNHC which have been developed in the recent past as anticonvulsants along with their chemistry, percentage yield, structure-activity relationship and biological activity. The most potent compound in each series has been identified for comparative studies, for further structural modification and to improve the pharmacokinetic profile. Various optimized synthetic pathways and diverse functionalities other than nitrogen-containing rings discussed in the article may help medicinal chemists to design safe and effective anticonvulsant drugs in near future.

Insights into Structural Modifications of Valproic Acid and Their Pharmacological Profile

Valproic acid (VPA) is a well-established anticonvulsant drug discovered serendipitously and marketed for the treatment of epilepsy, migraine, bipolar disorder and neuropathic pain. Apart from this, VPA has potential therapeutic applications in other central nervous system (CNS) disorders and in various cancer types. Since the discovery of its anticonvulsant activity, substantial efforts have been made to develop structural analogues and derivatives in an attempt to increase potency and decrease adverse side effects, the most significant being teratogenicity and hepatotoxicity. Most of these compounds have shown reduced toxicity with improved potency. The simple structure of VPA offers a great advantage to its modification. This review briefly discusses the pharmacology and molecular targets of VPA. The article then elaborates on the structural modifications in VPA including amide-derivatives, acid and cyclic analogues, urea derivatives and pro-drugs, and compares their pharmacological profile with that of the parent molecule. The current challenges for the clinical use of these derivatives are also discussed. The review is expected to provide necessary knowledgebase for the further development of VPA-derived compounds.

Reactive metabolites of the anticonvulsant drugs and approaches to minimize the adverse drug reaction

Several generations of antiepileptic drugs (AEDs) are available in the market for the treatment of seizures, but these are amalgamated with acute to chronic side effects. The most common side effects of AEDs are dose-related, but some are idiosyncratic adverse drug reactions (ADRs) that transpire due to the formation of reactive metabolite (RM) after the bioactivation process. Because of the adverse reactions patients usually discontinue the medication in between the treatment. The AEDs such as valproic acid, lamotrigine, phenytoin etc., can be categorized under such types because they form the RM which may prevail with life-threatening adverse effects or immune-mediated reactions. Hepatotoxicity, teratogenicity, cutaneous hypersensitivity, dizziness, addiction, serum sickness reaction, renal calculi, metabolic acidosis are associated with the metabolites of drugs such as arene oxide, N-desmethyldiazepam, 2-(1-hydroxyethyl)-2-methylsuccinimide, 2-(sulphamoy1acetyl)-phenol, E-2-en-VPA and 4-en-VPA and carbamazepine-10,11-epoxide, etc. The major toxicities are associated with the moieties that are either capable of forming RM or the functional groups may itself be too reactive prior to the metabolism. These functional groups or fragment structures are typically known as structural alerts or toxicophores. Therefore, minimizing the bioactivation potential of lead structures in the early phases of drug discovery by a modification to low-risk drug molecules is a priority for the pharmaceutical companies. Additionally, excellent potency and pharmacokinetic (PK) behaviour help in ensuring that appropriate (low dose) candidate drugs progress into the development phase. The current review discusses about RMs in the anticonvulsant drugs along with their mechanism vis-a-vis research efforts that have been taken to minimize the toxic effects of AEDs therapy.

Synthesis and characterization of a series of N,N'-substituted urea derivatives by using electrospray ionization tandem mass spectrometry: Differentiation of positional isomers

RATIONALE

Characterization of N,N'-substituted ureas was found to be challenging by nuclear magnetic resonance (NMR) spectroscopy, particularly N-di- and tri-alkylated ureas because of the absence of adjacent protons. In the present study, electrospray ionization tandem mass spectrometry has been used to differentiate positional isomeric pairs and to characterize a series of N,N'-substituted ureas, as these compounds have significant importance for drug discovery. Additionally, urea is an essential functionality in several bioactive compounds as well as a variety of clinically approved therapies.

METHODS

High-resolution electrospray ionization tandem mass spectrometry (ESI-HR-MS/MS) has been used to characterize a series of N,N'-substituted urea derivatives and differentiate two pairs of positional isomers. The data was acquired by Xcaliber application in positive ionization mode.

RESULTS

ESI-HR-MS/MS spectra of [M + H]⁺ ions of the positional isomeric urea derivatives 8a and 8b show distinct fragmentation patterns. For example, the MS/MS spectrum of the [M + H]⁺ ion of isomer 8a displays the abundant fragment ion at m/z 285.1595, which was totally absent in isomer 8b. This would be plausibly formed by the cleavage of the C-N bond of the urea group with the elimination of the isocyanate moiety. In contrast, the MS/MS spectrum of the [M + H]⁺ ion of isomer 8b shows an intense ion at m/z 311.1389 which is completely absent in isomer 8a which would be formed by the cleavage of the C-N bond attached to the ring nitrogen. Similarly, another pair of positional isomers, 8c and 8d, have been clearly distinguished by their fragmentation behaviour. In addition, a series of N,N'-substituted urea derivatives were studied to investigate the impact of different substitution on the fragmentation behaviour.

CONCLUSIONS

The present study demonstrates that ESI-HR-MS/MS can be used to differentiate pairs of N,N'-substituted urea positional isomers and characterize a series of derivatives. It was observed that a characteristic fragment ion was formed by the C-N bond cleavage with the elimination of an isocyanate moiety. The proposed mechanism of fragmentation was supported by the change in the fragmentation pathway upon alkylation of the NH. In order to generalize this fragmentation pattern, a series of N-alkylated ureas was synthesized and studied by MS/MS.

Recent advances in urea- and thiourea-containing compounds: focus on innovative approaches in medicinal chemistry and organic synthesis

Urea and thiourea represent privileged structures in medicinal chemistry. Indeed, these moieties constitute a common framework of a variety of drugs and bioactive compounds endowed with a broad range of therapeutic and pharmacological properties. Herein, we provide an overview of the state-of-the-art of urea and thiourea-containing pharmaceuticals. We also review the diverse approaches pursued for (thio)urea bioisosteric replacements in medicinal chemistry applications. Finally, representative examples of recent advances in the synthesis of urea- and thiourea-based compounds by enabling chemical tools are discussed.

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, antimicrobial, anti-cancer and in silico studies of new urea derivatives

The reaction of an alkyl or aryl isocyanates with some primary amines in acetonitrile at room temperature afforded the corresponding alkyl- and aryl-urea derivatives. All the prepared urea compounds have been elucidated by FTIR, NMR, and elemental analysis. The compounds 1 and 3 were confirmed by single-crystal X-ray diffraction. The 4-tolylsulfonyl isocyanate reacted with the aryl amines 1, 2, 3, and 2,4-dichloroaniline to afford the corresponding sulfonylurea derivatives 5-8. Likewise, the reaction of the isocyanates with 2,4-dichloroaniline, 5-methyl isoxazole-3-amine, and 2-aminothiazole derivatives gave the corresponding urea derivatives 9-17. All the prepared compounds 5-17 were tested in vitro as anti-microbial and anti-HepG2 agents. Moreover, analyzing gene expression of TP53-exon4 and TP53-exon7, DNA damage values, and DNA fragmentation percentages have been discussed. The compounds 5 and 8 recorded the highest activity against the tested microbial strains with maximum activity against C. albicans (50 mm) and B. mycoides (40 mm), respectively. The compounds 5 inhibited the growth of E. coli, S. aureus, and C. Albicans at the MIC level of 0.0489 µM, while the compound 8 was able to inhibit the visible growth of E. coli and C. albicans at MIC value of 3.13 µM and S. aureus at 0.3912 µM. In the same line, compound 5 showed the best cytotoxic activity against the HepG2 cell line (IC₅₀ = 4.25 µM) compared to 5 fluorouracil with IC₅₀ = 316.25 µM. Expression analysis of liver cancer related to a gene including TP53-exon4 and TP53-exon7 was used in HepG2 Liver cancer cell lines using RT-qPCR. The expression values of TP53-exon4 and TP53-exon7 genes were decreased. The DNA damage values and DNA fragmentation percentages were increased significantly (P < 0.01) in the treated HepG2 (5) sample compared with the negative control. Docking studies were performed for the synthetic compounds against 2 bacterial proteins (DNA gyrase subunit B, and penicillin binding protein 1a) that are known targets for some antibiotics, and one cell division protein kinase 2 (CDK2) as target for anticancer drugs.

Molecular arrangements in crystals of racemic and enantiopure forms of N-carbamoyl-2-phenylbutyramide and 2-phenylbutyramide: differences and similarities

As solid drugs may be regarded as “pharmaceutical materials”, molecular pharmaceutics of such drugs is expected to benefit from application of materials science concepts. In this paper, we used a structural chemistry approach to explain the dramatic difference in solubility between two structurally related antiepileptic drugs, N-carbamoyl-2-phenylbutyramide (NC2PBA) and 2-phenylbutyramide (2PBA). Since both of these compounds are chiral, we chromatographically separated the enantiomers and examined them along with the racemic forms. A combination of experimental (single-crystal X-ray diffraction, IR spectroscopy) and computational (crystal lattice energy calculations, Hirshfeld surface analysis) techniques was employed to determine the structural differences between these two compounds in the crystalline state. We found that while NC2PBA and 2PBA have similar molecular packing arrangements, the former compound is distinguished by a more extensive network of hydrogen bonds. Thus, the higher density, higher melting point, and lower solubility of crystalline NC2PBA compared to crystalline 2PBA may be largely explained by the differences in hydrogen bonding. We also found that for each of these compounds there are no major differences in molecular packing (and, correspondingly, in crystal lattice energies) between racemic and enantiopure forms.

Copper(II)-Catalyzed Reactions of α-Keto Thioesters with Azides via C-C and C-S Bond Cleavages: Synthesis of N-Acylureas and Amides

Cu(II)-catalyzed reaction of α-keto thioesters with trimethylsilyl azide (TMSN₃) proceeds with the transformation of the thioester group into urea through C-C and C-S bond cleavages, constituting a practical and straightforward synthesis of N-acylureas. When diphenyl phosphoryl azide (DPPA) is used instead as the azide source in an aqueous environment, primary amides are formed via substitution of the thioester group. The reactions are proposed to proceed through Curtius rearrangement of the initially formed α-keto acyl azide to generate an acyl isocyanate intermediate, which reacts further with an additional amount of azide or water and rearranges to afford the corresponding products. To demonstrate the potentiality of the method, one-step syntheses of pivaloylurea and isovaleroylurea, displaying anticonvulsant activities, have been carried out.

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.

Valproic acid enhances Oct4 promoter activity through PI3K/Akt/mTOR pathway activated nuclear receptors

Valproic acid (VPA) has been shown to increase the reprogramming efficiency of induced pluripotent stem cells (iPSC) from somatic cells, but the mechanism by which VPA enhances iPSC induction has not been defined. Here we demonstrated that VPA directly activated Oct4 promoter activity through activation of the PI3K/Akt/mTOR signaling pathway that targeted the proximal hormone response element (HRE, -41∼-22) in this promoter. The activating effect of VPA is highly specific as similar compounds or constitutional isomers failed to instigate Oct4 promoter activity. We further demonstrated that the upstream 2 half-sites in this HRE were essential to the activating effect of VPA and they were targeted by a subset of nuclear receptors, such as COUP-TFII and TR2. These findings show the first time that NRs are implicated in the VPA stimulated expression of stem cell-specific factors and should invite more investigation on the cooperation between VPA and NRs on iPSC induction.

Propylisopropylacetic acid (PIA), a constitutional isomer of valproic acid, uncompetitively inhibits arachidonic acid acylation by rat acyl-CoA synthetase 4: a potential drug for bipolar disorder

BACKGROUND

Mood stabilizers used for treating bipolar disorder (BD) selectively downregulate arachidonic acid (AA) turnover (deacylation-reacylation) in brain phospholipids, when given chronically to rats. In vitro studies suggest that one of these, valproic acid (VPA), which is teratogenic, reduces AA turnover by inhibiting the brain long-chain acyl-CoA synthetase (Acsl)4 mediated acylation of AA to AA-CoA. We tested whether non-teratogenic VPA analogues might also inhibit Acsl4 catalyzed acylation, and thus have a potential anti-BD action.

METHODS

Rat Acsl4-flag protein was expressed in Escherichia coli, and the ability of three VPA analogues, propylisopropylacetic acid (PIA), propylisopropylacetamide (PID) and N-methyl-2,2,3,3-tetramethylcyclopropanecarboxamide (MTMCD), and of sodium butyrate, to inhibit conversion of AA to AA-CoA by Acsl4 was quantified using Michaelis-Menten kinetics.

RESULTS

Acsl4-mediated conversion of AA to AA-CoA in vitro was inhibited uncompetitively by PIA, with a Ki of 11.4mM compared to a published Ki of 25mM for VPA, while PID, MTMCD and sodium butyrate had no inhibitory effect.

CONCLUSIONS

PIA's ability to inhibit conversion of AA to AA-CoA by Acsl4 in vitro suggests that, like VPA, PIA may reduce AA turnover in brain phospholipids in unanesthetized rats, and if so, may be effective as a non-teratogenic mood stabilizer in BD patients.

Structure-function studies for the panacea, valproic acid

The anticonvulsant properties of VPA (valproic acid), a branched short-chain fatty acid, were serendipitously discovered in 1963. Since then, therapeutic roles of VPA have increased to include bipolar disorder and migraine prophylaxis, and have more recently been proposed in cancer, Alzheimer's disease and HIV treatment. These numerous therapeutic roles elevate VPA to near 'panacea' level. Surprisingly, the mechanisms of action of VPA in the treatment of many of these disorders remain unclear, although it has been shown to alter a wide variety of signalling pathways and a small number of direct targets. To analyse the mechanism of action of VPA, a number of studies have defined the structural characteristics of VPA-related compounds giving rise to distinct therapeutic and cellular effects, including adverse effects such as teratogenicity and hepatotoxicity. These studies raise the possibility of identifying target-specific novel compounds, providing better therapeutic action or reduced side effects. This short review will describe potential therapeutic pathways targeted by VPA, and highlight studies showing structural constraints necessary for these effects.

Evaluation of the effects of propylisopropylacetic acid (PIA) on neuronal growth cone morphology

Propylisopropylacetic acid (PIA) is a constitutional isomer of valproic acid (VPA). It has previously been found to be a weak antiepileptic, but in common with mood stabilizers, causes inositol depletion and growth cone spreading, suggesting the basis of a new series of mood stabilizers. To assess this possibility, we have compared the effects of racemic (R,S)-PIA and its individual enantiomers to those of the mood stabilizers lithium (Li+), VPA and carbamazepine (CBZ). Unlike Li+ and VPA, but in common with CBZ and (R,S)-PIA, neither (R)-PIA nor (S)-PIA enantiomer induces T-cell factor (TCF)-mediated gene expression. However, as seen for other mood stabilizers, both enantiomers are potent inducers of growth cone spreading. To investigate the mechanism for these effects, we examined changes in the actin cytoskeleton following drug treatment with Li+, VPA, CBZ, (R,S)-PIA or its individual enantiomers. All exhibit a redistribution of F-actin to the growth cone periphery, a feature of spread growth cones. (R,S)-PIA has the strongest effect as it also elevates F-actin polymerization at the cell periphery. This change in the actin cytoskeleton is associated with a substantial increase in F-actin-rich protrusions on the surface of the growth cone and in its close vicinity. These results demonstrate an effect of (R,S)-PIA on the neuronal actin cytoskeleton shared in common with other mood stabilizers, and suggest a potential to induce structural changes within the CNS.

Synthesis and anticonvulsant activity of amino acid-derived sulfamides

Sulfamides are promising functions for the design of new antiepileptic drugs ( Bioorg. Med. Chem. 2007, 15, 1556-1567; 5604-5614 ). Following previous research in this line, a set of amino acid-derived sulfamides has been designed, synthesized, and tested as new anticonvulsant compounds. The experimental data confirmed the ability of some of the structures to suppress the convulsions originated by the electrical seizure (MES test) at low doses (100 mg/kg).

Tetramethylcyclopropyl analogue of the leading antiepileptic drug, valproic acid: evaluation of the teratogenic effects of its amide derivatives in NMRI mice

BACKGROUND

Although valproic acid (VPA) is used extensively for treating various kinds of epilepsy, it causes hepatotoxicity and teratogenicity. In an attempt to develop a more potent and safer second generation to VPA drug, the amide derivatives of the tetramethylcyclopropyl VPA analogue, 2,2,3,3-tetramethylcyclopropanecarboxamide (TMCD), N-methyl-TMCD (MTMCD), 4-(2,2,3,3-tetramethylcyclopropanecarboxamide)-benzenesulfonamide (TMCD-benzenesulfonamide), and 5-(TMCD)-1,3,4-thiadiazole-2-sulfonamide (TMCD-thiadiazolesulfonamide) were synthesized and shown to have more potent anticonvulsant activity than VPA. Teratogenic effects of these CNS-active compounds were evaluated in Naval Medical Research Institute (NMRI) mice susceptible to VPA-induced teratogenicity by comparing them to those of VPA.

METHODS

Pregnant NMRI mice were given a single sc injection of either VPA or TMC-amide derivatives on gestation day 8.5, and then the live fetuses were examined to detect any external malformations on gestation day 18. After double-staining for bone and cartilage, their skeletons were examined.

RESULTS

In contrast to VPA, which induced NTDs in a high number of fetuses at 2.4-4.8 mmol/kg, TMCD, TMCD-benzenesulfonamide, and TMCD-thiadiazolesulfonamide at 4.8 mmol/kg and MTMCD at 3.6 mmol/kg did not induce a significant number of NTDs. TMCD-thiadiazolesulfonamide exhibited a potential to induce limb defects in fetuses. Skeletal examination also revealed that fetuses exposed to all four of the tetramethylcyclopropanecarboxamide derivatives developed vertebral and rib abnormalities less frequently than those exposed to VPA. Our results established that TMCD, MTMCD, and TMCD-benzenesulfonamide are distinctly less teratogenic than VPA in NMRI mice.

CONCLUSIONS

The CNS-active amides containing a tetramethylcyclopropanecarbonyl moiety demonstrated better anticonvulsant potency compared to VPA and a lack of teratogenicity, which makes these compounds good second-generation VPA antiepileptic drug candidates.

Anticonvulsant profile and teratogenicity of 3,3-dimethylbutanoylurea: a potential for a second generation drug to valproic acid

PURPOSE

The purpose of this study was to evaluate the anticonvulsant activity and teratogenic potential of branched aliphatic acylureas represented by isovaleroylurea (IVU), pivaloylurea (PVU) and 3,3-dimethylbutanoylurea (DBU), as potential second-generation drugs to valproic acid (VPA).

METHODS

The anticonvulsant activity of IVU, PVU, and DBU was determined in mice and rats utilizing the maximal electroshock seizure (MES) and the pentylenetetrazole (scMet) tests. The ability of DBU to block electrical-, or chemical-induced seizures was further examined in three acute seizure models: the psychomotor 6 Hz model, the bicuculline and picrotoxin models and one model of chronic epilepsy (i.e., the hippocampal kindled rat model). The induction of neural tube defects (NTDs) by IVU, PVU, and DBU was evaluated after i.p. administration at day 8.5 of gestation to a mouse strain highly susceptible to VPA-induced teratogenicity. The pharmacokinetics of DBU was studied following i.v. administration to rats.

RESULTS

DBU emerged as the most potent compound having an MES-ED(50)of 186 mg/kg (mice) and 64 mg/kg (rats) and an scMet-ED(50)of 66 mg/kg (mice) and 26 mg/kg (rats). DBU underwent further evaluation in the hippocampal kindled rat (ED(50)= 35 mg/kg), the psychomotor 6 Hz mouse model (ED(50)= 80 mg/kg at 32 mA and ED(50)= 133 mg/kg at 44 mA), the bicuculline- and picrotoxin-induced seizure mouse model (ED(50)= 205 mg/kg and 167 mg/kg, respectively). In contrast to VPA, DBU, IVU, and PVU did not induce a significant increase in NTDs as compared to control. DBU was eliminated by metabolism with a half-life of 4.5 h.

CONCLUSIONS

DBU's broad spectrum and potent anticonvulsant activity, along with its high safety margin and favorable pharmacokinetic profile, make it an attractive candidate to become a new, potent, and safe AED.

Evaluation of the enantioselective antiallodynic and pharmacokinetic profile of propylisopropylacetamide, a chiral isomer of valproic acid amide

Propylisopropylacetamide (PID) is a chiral CNS-active constitutional isomer of valpromide, the amide derivative of the major antiepileptic drug valproic acid (VPA). The purpose of this work was: a) To evaluate enantiospecific activity of PID on tactile allodynia in the Chung (spinal nerve ligation, SNL) model of neuropathic pain in rats; b) To evaluate possible sedation at effective antiallodynic doses, using the rotorod ataxia test; c) To investigate enantioselectivity in the pharmacokinetics of (R)- and (S)-PID in comparison to (R,S)-PID; and d) To determine electrophysiologically whether PID has the potential to affect tactile allodynia by suppressing ectopic afferent discharge in the peripheral nervous system (PNS). (R)-, (S)- and (R,S)-PID produced dose-related reversal of tactile allodynia with ED(50) values of 46, 48, 42 mg/kg, respectively. The individual PID enantiomers were not enantioselective in their antiallodynic activity. No sedative side-effects were observed at these doses. Following i.p. administration of the individual enantiomers, (S)-PID had lower clearance (CL) and volume of distribution (V) and a shorter half-life (t(1/2)) than (R)-PID. However following administration of (R,S)-PID, both enantiomers had similar CL and V, but (R)-PID had a longer t(1/2). Systemic administration of (R,S)-PID at antiallodynic doses did not suppress spontaneous ectopic afferent discharge generated in the injured peripheral nerve, suggesting that its antiallodynic action is exerted in the CNS rather than the PNS. Both of PID's enantiomers, and the racemate, are more potent antiallodynic agents than VPA and have similar potency to gabapentin. Consequently, they have the potential to become new drugs for treating neuropathic pain.