Design of innovative therapeutics for pharmacoresistant epilepsy: challenges and needs

S(+)-(2E)-N-(2-Hydroxypropyl)-3-Phenylprop-2-Enamide (KM-568): A Novel Cinnamamide Derivative with Anticonvulsant Activity in Animal Models of Seizures and Epilepsy

Epilepsy is one of the most frequent neurological disorders affecting about 1% of the world’s human population. Despite availability of multiple treatment options including antiseizure drugs, it is estimated that about 30% of seizures still remain resistant to pharmacotherapy. Searching for new antiseizure and antiepileptic agents constitutes an important issue within modern medicinal chemistry. Cinnamamide derivatives were identified in preclinical as well as clinical studies as important drug candidates for the treatment of epilepsy. The cinnamamide derivative presented here: S(+)-(2E)-N-(2-hydroxypropyl)-3-phenylprop-2-enamide (S(+)-N-(2-hydroxypropyl)cinnamamide, compound KM-568) showed anticonvulsant activity in several models of epilepsy and seizures in mice and rats. It was active in a genetic animal model of epilepsy (Frings audiogenic seizure-susceptible mouse model, ED₅₀ = 13.21 mg/kg, i.p.), acute seizures induced electrically (maximal electroshock test ED₅₀ = 44.46 mg/kg mice i.p., ED₅₀ = 86.6 mg/kg mice p.o., ED₅₀ = 27.58 mg/kg rats i.p., ED₅₀ = 30.81 mg/kg rats p.o., 6-Hz psychomotor seizure model 32 mA ED₅₀ = 71.55 mg/kg mice i.p., 44 mA ED₅₀ = 114.4 mg/kg mice i.p.), chronic seizures induced electrically (corneal kindled mouse model ED₅₀ = 79.17 mg/kg i.p., hippocampal kindled rat model ED₅₀ = 24.21 mg/kg i.p., lamotrigine-resistant amygdala kindled seizure model in rats ED₅₀ = 58.59 mg/kg i.p.), acute seizures induced chemically (subcutaneous metrazol seizure threshold test ED₅₀ = 104.29 mg/kg mice i.p., ED₅₀ = 107.27 mg/kg mice p.o., ED₅₀ = 41.72 mg/kg rats i.p., seizures induced by picrotoxin in mice ED₅₀ = 94.11 mg/kg i.p.) and the pilocarpine-induced status epilepticus model in rats (ED₅₀ = 279.45 mg/kg i.p., ED₉₇ = 498.2 mg/kg i.p.). The chemical structure of the compound including configuration of the chiral center was confirmed by NMR spectroscopy, LC/MS spectroscopy, elemental analysis, and crystallography. Compound KM-568 was identified as a moderately stable derivative in an in vitro mouse liver microsome system. According to the Ames microplate format mutagenicity assay performed, KM-568 was not a base substitution or frameshift mutagen. Cytotoxicity evaluation in two cell lines (HepG2 and H9c2) proved the safety of the compound in concentrations up to 100 µM. Based on the results of anticonvulsant activity and safety profile, S(+)-(2E)-N-(2-hydroxypropyl)-3-phenylprop-2-enamide could be proposed as a new lead compound for further preclinical studies on novel treatment options for epilepsy.

The beneficial effect of probiotics as a supplementary treatment in drug-resistant epilepsy: a pilot study

Epilepsy is a neurological disease with high global prevalence. Despite the range of drug-based treatments currently available to control the condition, one in 3 patients experiences epileptic seizures. Therapeutic alternatives for these patients include the ketogenic diet, surgery or the cerebral implantation of neurostimulators; however these are benefits with limits. The target of this study is to find a new complementary treatment for these patients, studying the effectiveness of probiotics for controlling epileptic seizures in patients with drug-resistant epilepsy. A prospective study was designed in which a group of patients with drug-resistant epilepsy was administered a probiotic mixture for 4 months. Patients were assessed before and after taking the probiotics; among other variables, number of seizures and patients' quality of life (QOLIE-10) were monitored. Levels of cD-14, interleukin 6, and γ-aminobutyric acid were also analysed throughout the study. 45 patients were included in the study. In an intention-to-treat analysis, 28.9% of all patients displayed a greater than 50% reduction in the number of seizures (the parameter required in clinical trials). A significant improvement was also observed in patients' quality of life. We found that probiotics may be an option for supplementary therapy. Since the use of probiotics is safe, they may contribute to improving seizure control, and therefore quality of life, in patients with drug-resistant epilepsy. The study has been registered in https://clinicaltrials.gov with number NCT03403907.

In vitro and in vivo experimental models employed in the discovery and development of antiepileptic drugs for pharmacoresistant epilepsy

Epilepsy is one of the most common chronic, recurrent and progressive neurological diseases. In spite of the large number of antiepileptic drugs currently available for the suppression of seizures, about one-third of patients develop drug-resistant epilepsy, even when they are administered the most appropriate treatment available. Thus, nonclinical models can be valuable tools for the elucidation of the mechanisms underlying the development of pharmacoresistance and also for the development of new therapeutic agents that may be promising therapeutic approaches for this unmet medical need. Up today, several epilepsy and seizure models have been developed, exhibiting similar physiopathological features of human drug-resistant epilepsy; moreover, pharmacological response to antiepileptic drugs clinically available tends to be similar in animal models and humans. Therefore, they should be more intensively used in the preclinical discovery and development of new candidates to antiepileptic drugs. Although useful, in vitro models cannot completely replicate the complexity of a living being and their potential for a systematic use in antiepileptic drug screening is limited. The whole-animal models are the most commonly employed and they can be classified as per se drug-resistant due to an inherent poor drug response or be based on the selection of subgroups of epileptic animals that respond or not to a specific antiepileptic drug. Although more expensive and time-consuming, the latter are chronic models of epilepsy that better exhibit the disease-associated alterations found in human epilepsy. Several antiepileptic drugs in development or already marketed have been already tested and shown to be effective in these models of drug-resistant epilepsy, constituting a new hope for the treatment of drug-resistant epilepsy. This review will provide epilepsy researchers with detailed information on the in vitro and in vivo nonclinical models of interest in drug-resistant epilepsy, which may enable a refined selection of most relevant models for understanding the mechanisms of the disease and developing novel antiepileptic drugs.

Cinnamamide pharmacophore for anticonvulsant activity: evidence from crystallographic studies

A number of cinnamamide derivatives possess anticonvulsant activity due to the presence of a number of important pharmacophore elements in their structures. In order to study the correlations between anticonvulsant activity and molecular structure, the crystal structures of three new cinnamamide derivatives with proven anticonvulsant activity were determined by X-ray diffraction, namely (R,S)-(2E)-N-(2-hydroxybutyl)-3-phenylprop-2-enamide-water (3/1), C₁₃H₁₇NO₂·0.33H₂O, (1), (2E)-N-(1-hydroxy-2-methylpropan-2-yl)-3-phenylprop-2-enamide, C₁₃H₁₇NO₂, (2), and (R,S)-(2E)-N-(1-hydroxy-3-methyl-butan-2-yl)-3-phenylprop-2-enamide, C₁₄H₁₉NO₂, (3). Compound (1) crystallizes in the space group P-1 with three molecules in the asymmetric unit, whereas compounds (2) and (3) crystallize in the space group P2₁/c with one and two molecules, respectively, in their asymmetric units. The carbonyl group of (2) is engaged in an intramolecular hydrogen bond with the hydroxy group. This type of interaction is observed for the first time in these kinds of derivatives. A disorder of the substituent at the N atom occurs in the crystal structures of (2) and (3). The crystal packing of all three structures is dominated by a network of O-H...O and N-H...O hydrogen bonds, and leads to the formation of chains and/or rings. Furthermore, the crystal structures are stabilized by numerous C-H...O contacts. We analyzed the molecular structures and intermolecular interactions in order to propose a pharmacophore model for cinnamamide derivatives.

Transcranial Alternating Current Stimulation: A Potential Risk for Genetic Generalized Epilepsy Patients (Study Case)

Transcranial alternating current stimulation (tACS) is a re-emergent neuromodulation technique that consists in the external application of oscillating electrical currents that induces changes in cortical excitability. We present the case of a 16-year-old female with pharmaco-resistant juvenile myoclonic epilepsy to 3 antiepileptic’s drugs characterized by 4 myoclonic and 20 absence seizures monthly. She received tACS at 1 mA at 3 Hz pulse train during 60 min over Fp1–Fp2 (10–20 EEG international system position) during 4 consecutive days using an Endeavor™ IOM Systems device^® (Natus Medical Incorporated, Middleton, WI, USA). At the 1-month follow-up, she reported a 75% increase in seizures frequency (only myoclonic and tonic–clonic events) and developed a 24-h myoclonic status epilepticus that resolved with oral clonazepam and intravenous valproate. At the 2-month follow-up, the patient reported a 15-day seizure-free period.

Anticonvulsant and Toxicological Evaluation of Parafluorinated/Chlorinated Derivatives of 3-Hydroxy-3-ethyl-3-phenylpropionamide

Although the anticonvulsant activity of 3-hydroxy-3-ethyl-3-phenylproionamide (HEPP) is well-known, its use is limited by the pharmacotoxicological profile. We herein tested its fluorinated and chlorinated derivatives (F-HEPP and Cl-HEPP) with two seizure models, maximal electroshock seizures (MES), and intraperitoneal pentylenetetrazole (PTZ) administration. Neurotoxicity was examined via the rotarod test. With in silico methods, binding was probed on possible protein targets-GABAA receptors and the sodium channel Nav1.2. The median effective doses (ED50) of HEPP, F-HEPP, and Cl-HEPP in the MES seizure model were 129.6, 87.1, and 62.0 mg/kg, respectively, and 66.4, 43.5, and in the PTZ seizure model 43.5 mg/kg. The HEPP-induced neurotoxic effect, which occurred at twice the ED50 against MES (p < 0.05), did not occur with F-HEPP or Cl-HEPP. Docking studies revealed that all tested ligands bound to GABAA receptors on a site near to the benzodiazepine binding site. However, on the sodium channel open pore Nav1.2, R-HEPP had interactions similar to those reported for phenytoin, while its enantiomer and the ligands F-HEPP and Cl-HEPP reached a site that could disrupt the passage of sodium. Our results show that, as anticonvulsant agents, parahalogen substituted compounds have an advantageous pharmacotoxicological profile compared to their precursor.

Direct nose-to-brain delivery of lamotrigine following intranasal administration to mice

Pharmacoresistance is considered one of the major causes underlying the failure of the anticonvulsant therapy, demanding the development of alternative and more effective therapeutic approaches. Due to the particular anatomical features of the nasal cavity, intranasal administration has been explored as a means of preferential drug delivery to the brain. The purpose of the present study was to assess the pharmacokinetics of lamotrigine administered by the intranasal route to mice, and to investigate whether a direct transport of the drug from nose to brain could be involved. The high bioavailability achieved for intranasally administered lamotrigine (116.5%) underscored the fact that a substantial fraction of the drug has been absorbed to the systemic circulation. Nonetheless, the heterogeneous biodistribution of lamotrigine in different brain regions, with higher concentration levels attained in the olfactory bulb comparatively to the frontal cortex and the remaining portion of the brain, strongly suggest that lamotrigine was directly transferred to the brain via the olfactory neuronal pathway, circumventing the blood-brain barrier. Therefore, it seems that intranasal route can be assumed as a suitable and valuable drug delivery strategy for the chronic treatment of epilepsy, also providing a promising alternative approach for a prospective management of pharmacoresistance.

Update on the use of lacosamide in the treatment of partial-onset seizures

ABSTRAT: 

Lacosamide has a novel mechanism of action, namely selective enhancement of slow inactivation of voltage-gated sodium channels. Trial data and clinical experience indicate that it is effective in the treatment of partial-onset seizures, and that it is well tolerated. Pivotal early clinical trials demonstrated median percent reductions in seizure frequency ranging from 26 to 35.3% in the 200 mg/day, from 36.4 to 39% in the 400 mg/day, and from 37.8 to 40% in the 600 mg/day treatment groups. Dose-related adverse events were similar in the early clinical trials, and were mainly CNS complaints including dizziness, nausea, vomiting, fatigue, ataxia, abnormal vision, diplopia and nystagmus. Because of the dose-dependent adverse events and lack of additional efficacy at the 600 mg/day daily dose, lacosamide has been approved as an adjunctive treatment at recommended daily doses of 200–400 mg/day.