New antiepileptic drugs currently in clinical trials: is there a strategy in their development?

Single-Target Versus Multi-Target Drugs Versus Combinations of Drugs With Multiple Targets: Preclinical and Clinical Evidence for the Treatment or Prevention of Epilepsy

Rationally designed multi-target drugs (also termed multimodal drugs, network therapeutics, or designed multiple ligands) have emerged as an attractive drug discovery paradigm in the last 10-20 years, as potential therapeutic solutions for diseases of complex etiology and diseases with significant drug-resistance problems. Such agents that modulate multiple targets simultaneously are developed with the aim of enhancing efficacy or improving safety relative to drugs that address only a single target or to combinations of single-target drugs. Although this strategy has been proposed for epilepsy therapy >25 years ago, to my knowledge, only one antiseizure medication (ASM), padsevonil, has been intentionally developed as a single molecular entity that could target two different mechanisms. This novel drug exhibited promising effects in numerous preclinical models of difficult-to-treat seizures. However, in a recent randomized placebo-controlled phase IIb add-on trial in treatment-resistant focal epilepsy patients, padsevonil did not separate from placebo in its primary endpoints. At about the same time, a novel ASM, cenobamate, exhibited efficacy in several randomized controlled trials in such patients that far surpassed the efficacy of any other of the newer ASMs. Yet, cenobamate was discovered purely by phenotype-based screening and its presumed dual mechanism of action was only described recently. In this review, I will survey the efficacy of single-target vs. multi-target drugs vs. combinations of drugs with multiple targets in the treatment and prevention of epilepsy. Most clinically approved ASMs already act at multiple targets, but it will be important to identify and validate new target combinations that are more effective in drug-resistant epilepsy and eventually may prevent the development or progression of epilepsy.

Synthesis of 3,4-dihydroquinolin-2(1H)-one derivatives with anticonvulsant activity and their binding to the GABAA receptor

In this study, a series of 3,4-dihydroquinolin-2(1H)-one derivatives were designed and synthesized using two experimental models, namely maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ), to test the anticonvulsant activity of the target compound in vivo (i.p. in Kunming mice). The neurotoxicity (NT) of the target compound was measured by the rotating rod method (i.p. in Kunming mice). Six compounds with potential activity were selected from the two experimental models to test the 50% effective dose (ED₅₀). In vitro binding experiments with the GABA_A receptor were also performed. The results of the pharmacological experiments showed that compound 7-((5-(pentylthio)-1,3,4-oxadiazol-2-yl)methoxy)-3,4-dihydroquinolin-2(1H)-one (5b) showed the best anticonvulsant activity (MES, ED₅₀ = 10.1 mg/kg; scPTZ, ED₅₀ = 9.3 mg/kg), which was superior to activities shown by carbamazepine and ethosuximide, and it also exhibited the most potent binding affinity to GABA_A receptors (IC₅₀ = 0.12 μM). The GABA content in Wistar rat brains (i.p.) was also investigated, and the results showed that compound 5b may have a certain effect on the GABA system, as it increased the GABA concentration in the brain of rats. Molecular docking was used to study the binding mode of compound 5b and the GABA_A receptor. Compound 5b showed significant interactions with residues at the benzodiazepines binding site on the GABA_A receptor. The physicochemical and pharmacokinetic properties of the target compounds were predicted using Discovery Studio 2019 and ChemBioDraw Ultra 14.0.

Synthesis of 1,3,4-oxadiazole derivatives with anticonvulsant activity and their binding to the GABAA receptor

In this study, a series of 1,3,4-oxadiazole derivatives (5a-s, 10a-s, and 16a-d) were designed and synthesized using maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) models, to test the anticonvulsant activity of the target compounds in vivo. The neurotoxicity (NT) of the target compounds was measured using the rotating rod (ROT) method. Seven compounds with potential activity were selected to test the 50% effective dose (ED₅₀) and 50% toxic dose (TD₅₀). Pharmacological experiments revealed that 6-((5-(pentylthio)-1,3,4-oxadiazol-2-yl)methoxy)-3,4-dihydroquinolin-2(1H)-one (5b) showed the best anticonvulsant activity (MES, ED₅₀ = 8.9 mg/kg; scPTZ, ED₅₀ = 10.2 mg/kg), which was greater than the activities of carbamazepine and ethosuximide. Compound 5b exhibited the most potent binding affinity toward the GABA_A receptor (IC₅₀ = 0.11 μM) in the in vitro binding experiments. Compound 5b displayed significant anxiolytic activity at a low dose (1 mg/kg) in the elevated plus maze (EPM) test. The GABA content in rat brains was also investigated, and the results showed that compound 5b might have affected the GABA system. In our molecular docking experiment, compound 5b showed significant interactions with residues present at the benzodiazepine binding site on the GABA_A receptor. The structure and physicochemical and pharmacokinetic properties of the target compound were predicted using Discovery Studio 2019 and ChemBioDraw Ultra 14.0. Finally we demonstrated that compound 5b mainly acted on GABA_A receptor. Thus the present study has provided potential candidates for further investigation in epilepsy.

Synthesis, Antibacterial Activity and Molecular Docking Studies of New Pyrazole Derivatives

Background:

The pyrazole structure is an important heterocyclic structure and plays critical roles in agriculture, industrial and medicine. Furthermore, compounds containing pyrazole are known to exhibit various biological properties such as antibacterial, antifungal, anticancer, antiinflammatory, antidepressant, antipyretic, antiviral, anti-tubercular and anti-HIV activities. Because of these properties, pyrazole molecules have become a very popular topic for organic chemists.

Methods:

A series newly substituted pyrazole molecules were synthesized and characterized. Their antimicrobial activities were investigated by disk diffusion method against some gram positive bacteria and gram negative bacteria.

Results:

The present results indicated that the some test compounds were active in a broad spectrum against important human pathogenic microorganisms. The substituted pyrazoles including carbazone (7a, b) and thiazolidine (8a, b) showed a wide variety of biological activities. The results showed that synthesized pyrazole, compounds 7b and 8b are highly active and more potent in both biological and molecular docking simulation studies.

Conclusion:

The synthesized pyrazole molecules showed moderate antibacterial activities against the tested microorganism compared to antibiotic drug. Some test compounds (7b and 8b) might be used as new antibacterial agents.

Studies on the anticonvulsant activity of 4-alkyl-1,2,4-triazole-3-thiones and their effect on GABAergic system

A series of 4-alkyl-5-(3-chlorobenzyl/2,3-dichlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones (1a-14a) were designed, synthesized and screened for their anticonvulsant properties. Moreover, the acute adverse-effect profile of the active compounds (1a-7a, 12a) with respect to impairment of motor performance was evaluated in the chimney test. Among 4-alkyl-5-(3-chlorobenzyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones, ethyl, butyl, pentyl, hexyl, and heptyl derivatives administered intraperitoneally in a dose of 300 mg/kg protected 100% of the tested animals at four pretreatment times (i.e., 15, 30, 60, 120 min). Taking into account the median effective and toxic doses as well as the time-course profile of anticonvulsant activity, 5-(3-chlorobenzyl)-4-hexyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (4a) was proposed as the best tolerated and the most promising potential drug candidate. Finally, a radioligand binding assay was used to check whether the anticonvulsant activity of 4-alkyl-1,2,4-triazole-3-thiones was a result of their interactions (direct or allosteric) with GABAA receptor complex and/or their affinity to benzodiazepine (BDZ) binding sites.

Conantokins derived from the Asprella clade impart conRl-B, an N-methyl d-aspartate receptor antagonist with a unique selectivity profile for NR2B subunits

Using molecular phylogeny has accelerated the discovery of peptidic ligands targeted to ion channels and receptors. One clade of venomous cone snails, Asprella, appears to be significantly enriched in conantokins, antagonists of N-methyl d-aspartate receptors (NMDARs). Here, we describe the characterization of two novel conantokins from Conus rolani, including conantokin conRl-B that has shown an unprecedented selectivity for blocking NMDARs that contain NR2B subunits. ConRl-B shares only some sequence similarity with the most studied NR2B selective conantokin, conG. The divergence between conRl-B and conG in the second inter-Gla loop was used to design analogues for structure-activity studies; the presence of Pro10 was found to be key to the high potency of conRl-B for NR2B, whereas the ε-amino group of Lys8 contributed to discrimination in blocking NR2B- and NR2A-containing NMDARs. In contrast to previous findings for Tyr5 substitutions in other conantokins, conRl-B[L5Y] showed potencies on the four NR2 NMDA receptor subtypes that were similar to those of the native conRl-B. When delivered into the brain, conRl-B was active in suppressing seizures in the model of epilepsy in mice, consistent with NR2B-containing NMDA receptors being potential targets for antiepileptic drugs. Circular dichroism experiments confirmed that the helical conformation of conRl-B is stabilized by divalent metal ions. Given the clinical applications of NMDA antagonists, conRl-B provides a potentially important pharmacological tool for understanding the differential roles of NMDA receptor subtypes in the nervous system. This work shows the effectiveness of coupling molecular phylogeny, chemical synthesis, and pharmacology for discovering new bioactive natural products.

Preliminary efficacy and safety of lacosamide in children with refractory epilepsy

BACKGROUND

Despite the introduction of multiple new antiepileptic drugs (AEDs) in the past 20 years, about 30% of patients with epilepsy continue to experience uncontrolled seizures or significant side effects.

AIMS

To present our experience with lacosamide therapy in children with drug-resistant epilepsy.

METHODS

We retrospectively reviewed the medical charts of all patients receiving oral lacosamide until October 2010. Efficacy was determined according to seizure frequency during the week prior to treatment initiation and the week after the maximal dosage of lacosamide was attained.

RESULTS

Seventeen patients (10 boys) aged 1.5-16 (mean - 8 ± 4.7) years were identified. Nine patients had epilepsy attributed to a structural cause, six patients had epilepsy of unknown cause, and two had Lennox-Gastaut syndrome. Mean epilepsy duration was 5.4 ± 3.3 years. The mean number of previous AEDs was 6.6 ± 2. Lacosamide was added to the baseline AEDs in13 patients. The mean duration of follow-up was 9.1 ± 4.4 months. Six (35%) patients had at least a 50%.seizure reduction (mean - 76%). Social, behavioral, and/or motor improvement were noted in seven (41%) patients. Lacosamide was discontinued in six (35%) patients because of inefficacy. Side effects were reported in 10 (59%) patients.

CONCLUSIONS

Lacosamide seems to be effective and safe according to the data in our small cohort. Further prospective studies on lacosamide efficacy and safety in a large number of children are warranted.

Review of therapeutic options for adjuvant treatment of focal seizures in epilepsy: focus on lacosamide

Epilepsy is one of the most common serious neurological conditions worldwide, with an age-adjusted incidence of approximately 50 per 100,000 persons per year in developed countries. Antiepileptic therapy can result in long-term remission in 60-70% of patients, but many patients will require combination treatment to achieve optimal seizure control, as monotherapy is ineffective at controlling seizures in 30-53% of patients. Despite the increase in available treatment options, patient outcomes have not improved significantly and there is still a need for more effective therapies. Drugs used in the treatment of focal-onset seizures are a diverse range of compounds, and in most cases their mechanism of action is unknown or poorly defined. This review discusses the efficacy and safety of the newer adjuvant antiepileptic therapies that may improve outcomes in patients unresponsive to monotherapy, including clobazam, vigabatrin, lamotrigine, gabapentin, topiramate, tiagabine, levetiracetam, oxcarbazepine, pregabalin, zonisamide and eslicarbazepine, with focus on lacosamide. Lacosamide has been shown to exert its anticonvulsant effects predominantly by enhancement of the slow inactivation of voltage-gated sodium channels. Lacosamide is indicated for use as adjuvant treatment of focal-onset seizures in patients with epilepsy, and there is some evidence that it may also be of use in patients with status epilepticus and cancer patients with epilepsy. The efficacy of lacosamide has been assessed in three randomized, double-blind, placebo-controlled clinical trials, all of which have shown lacosamide to be effective at reducing seizure frequency and increasing 50% responder rates in patients with focal-onset seizures. Long-term lacosamide treatment is generally well tolerated and is not associated with significant drug interactions; the availability of an intravenous form of the drug also makes it particularly useful for a broad range of patients.

Lacosamide for the prevention of partial onset seizures in epileptic adults

Lacosamide is a newly registered antiepileptic drug with dual mechanisms of action. It selectively enhances slow inactivation of voltage-gated sodium channels, resulting in stabilization of hyperexcitable neuronal membranes and inhibition of repetitive neuronal firing. It also binds to a collapsing-response mediator protein-2, CRMP2. Lacosamide has a favorable pharmacokinetic profile; is rapidly and completely absorbed, has a relatively long elimination half-life of 13 hours which allows twice-daily administration, linear pharmacokinetics, and has low potential for drug interactions and renal elimination. Both oral and intravenous formulations of lacosamide are being developed. In placebo-controlled clinical trials, lacosamide was effective in seizure reduction as adjunctive therapy in patients with uncontrolled partial-onset seizures. Lacosamide was generally well tolerated. The most frequently reported adverse events in placebo-controlled trials were dizziness, headache, nausea, and diplopia. Intravenous lacosamide has a comparably good safety profile.

Lacosamide as treatment for partial epilepsy: mechanisms of action, pharmacology, effects, and safety

Lacosamide (LCM) is a novel agent that has been developed as an antiepileptic drug. In vitro studies suggest that LCM modulates voltage-gated sodium channels by enhancing their slow inactivation. In addition, LCM seems to interact with collapsin-response mediator protein 2 and thus may mediate neuronal plasticity. LCM has an elimination half-life of 13 hours, no relevant protein binding, and does not induce or inhibit enzymes of the cytochrome P450 system. No clinically significant drug-drug interactions have been discovered as yet. Experimental data suggest anticonvulsant as well as analgesic effects. Large clinical studies have demonstrated its efficacy for treatment of patients with partial seizures. LCM is well tolerated, and the most common adverse events are unspecific central nervous system and gastrointestinal effects such as dizziness, vertigo, nausea, and headache. LCM is approved for treatment of partial seizures with or without secondary generalization in the United States and the European Union within a dose range of 200 to 400 mg per day, administered twice daily. In addition to the oral formulations, an intravenous infusion solution is available.

Development of new antiepileptic drugs: challenges, incentives, and recent advances

Despite the introduction of many second-generation antiepileptic drugs (AEDs) in the past 15 years, a third of patients with epilepsy remain refractory to available treatments, and newer and more effective therapies are needed. Although our understanding of the mechanisms of drug resistance is fragmented, novel AED targets have been identified, and models of refractory epilepsy have been developed that can help to select candidate compounds for development. There are more than 20 compounds with potential antiepileptic activity in various stages of clinical development, and for many of these promising clinical trial results are already available. Several incentives justify further investment into the discovery of newer and more effective AEDs. Moreover, developments in clinical trial methodology enable easier completion of proof-of-concept studies, earlier definition of the therapeutic potential of candidate compounds, and more efficient completion of trials for various epilepsy indications.

Valproic Acid: second generation

The manuscript focuses on structure-activity relationship studies of CNS-active compounds derived from valproic acid (VPA) that have the potential to become second-generation VPA drugs. Valproic acid is one of the four most widely prescribed antiepileptic drugs (AEDs) and is effective (and regularly approved) in migraine prophylaxis and in the treatment of bipolar disorders. Valproic acid is also currently undergoing clinical trials in cancer patients. Valproic acid is the least potent of the established AEDs and its use is limited by two rare but potentially life-threatening side effects, teratogenicity and hepatotoxicity. Because AEDs treat the symptoms (seizure) and not the cause of epilepsy, epileptic patients need to take AEDs for a long period of time. Consequently, there is a substantial need to develop better and safer AEDs. To become a successful second-generation VPA, the new drug should possess the following characteristics: broad-spectrum antiepileptic activity, better potency than VPA, lack of teratogenicity and hepatotoxicity, and a favorable pharmacokinetic profile compared with VPA including a low potential for drug interactions.

New antiepileptic drugs that are second generation to existing antiepileptic drugs

In the last decade, 10 new antiepileptic drugs (AEDs) have been introduced that offer appreciable advantages in terms of their favourable pharmacokinetics, improved tolerability and lower potential for drug interactions. However, despite the large therapeutic range of old and new AEDs, approximately 30% of the patients with epilepsy are still not seizure free and, consequently, there is a substantial need to develop new AEDs. The new AEDs currently in development can be divided into two categories: drugs with completely new chemical structures such as lacosamide (formally harkoseride), retigabine, rufinamide and talampanel; and drugs that are derivatives or analogues of existing AEDs that can be regarded as second-generation or follow-up compounds of established AEDs. This article focuses on the second category and thus critically reviews the following second-generation compounds: eslicarbazepine acetate or BIA-2-093 and 10-hydroxy carbazepine (carbamazepine derivatives); valrocemide and NPS 1776 (isovaleramide; valproic acid derivatives); pregabalin and XP13512 (gabapentin derivatives); brivaracetam (ucb 34714) and seletracetam (ucb 44212; levetiracetam derivatives); and fluorofelbamate (a felbamate derivative). In addition, a series of valproic acid derivatives that are currently in preclinical stage has also been evaluated because some lead compounds of this series have a promising potential to become new antiepileptics and CNS drugs. For any of these follow-up compounds to become a successful second generation to an existing AED, it has to be more potent, safer and possess favourable pharmacokinetics, including low potential for pharmacokinetic and pharmacodynamic drug interactions.

Synthesis and anticonvulsant activity of a class of 2-amino 3-hydroxypropanamide and 2-aminoacetamide derivatives

Several studies have demonstrated that N-substituted amino acid derivatives exhibit weak anticonvulsant activities in vivo. In the present study, a series of amides of aminoacids structurally related to aminoacetamide have been synthesised and investigated for anticonvulsant activity. Among the molecules investigated, those containing a bicyclic (tetralinyl, indanyl) group linked to the aminoacetamide chain (40, 47 and 59) were among the most active as anticonvulsants (ED50 > 10, <100 mg/kg after oral administration) against tonic seizures in the mouse maximal electroshock, bicuculline and picrotoxin tests at doses devoid of neurotoxic activity. Altogether, these results suggest the described compounds as a class of orally available anticonvulsants. The ability of these compounds to partially block veratridine-induced aspartate efflux from rat cortical synaptosomes suggests that their anticonvulsant activity may be only partly the consequence of an interaction with neuronal voltage-dependent sodium channels. Some of the most potent compounds appear worthy of a further investigation aimed at assessing their anticonvulsant activity in other models and at elucidating the underlying mechanism of action.