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Summary Objective Brivaracetam (BRV) and levetiracetam (LEV) are antiepileptic drugs that bind synaptic vesicle glycoprotein 2A (SV2A). In vitro and in vivo animal studies suggest faster brain penetration and SV2A occupancy (SO) after dosing with BRV than LEV. We evaluated human brain penetration and SO time course of BRV and LEV at therapeutically relevant doses using the SV2A positron emission tomography (PET) tracer 11C‐UCB‐J (EP0074; NCT02602860). Methods Healthy volunteers were recruited into three cohorts. Cohort 1 (n = 4) was examined with PET at baseline and during displacement after intravenous BRV (100 mg) or LEV (1500 mg). Cohort 2 (n = 5) was studied during displacement and 4 hours postdose (BRV 50‐200 mg or LEV 1500 mg). Cohort 3 (n = 4) was examined at baseline and steady state after 4 days of twice‐daily oral dosing of BRV (50‐100 mg) and 4 hours postdose of LEV (250‐600 mg). Half‐time of 11C‐UCB‐J signal change was computed from displacement measurements. Half‐saturation concentrations (IC 50) were determined from calculated SO. Results Observed tracer displacement half‐times were 18 ± 6 minutes for BRV (100 mg, n = 4), 9.7 and 10.1 minutes for BRV (200 mg, n = 2), and 28 ± 6 minutes for LEV (1500 mg, n = 6). Estimated corrected half‐times were 8 minutes shorter. The SO was 66%‐70% for 100 mg intravenous BRV, 84%‐85% for 200 mg intravenous BRV, and 78%‐84% for intravenous 1500 mg LEV. The IC 50 of BRV (0.46 μg/mL) was 8.7‐fold lower than of LEV (4.02 μg/mL). BRV data fitted a single SO versus plasma concentration relationship. Steady state SO for 100 mg BRV was 86%‐87% (peak) and 76%‐82% (trough). Significance BRV achieves high SO more rapidly than LEV when intravenously administered at therapeutic doses. Thus, BRV may have utility in treating acute seizures; further clinical studies are needed for confirmation.

Brivaracetam (BRV) is a selective, high-affinity ligand for synaptic vesicle protein 2A (SV2A), recently approved as adjunctive treatment for drug-refractory partial-onset seizures in adults. BRV binds SV2A with higher affinity than levetiracetam (LEV), and was shown to have a differential interaction with SV2A. Because LEV was reported to interact with multiple excitatory and inhibitory ligand-gated ion channels and that may impact its pharmacological profile, we were interested in determining whether BRV directly modulates inhibitory and excitatory ionotropic receptors in central neurons. Voltage-clamp experiments were performed in primary cultures of mouse hippocampal neurons. At a supratherapeutic concentration of 100 mu m, BRV was devoid of any direct effect on currents gated by -aminobutyric acidergic type A, glycine, kainate, N-methyl-D-aspartate, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid. Similarly to LEV, BRV reveals a potent ability to oppose the action of negative modulators on the inhibitory receptors. In conclusion, these results show that BRV contrasts with LEV by not displaying any direct action on inhibitory or excitatory postsynaptic ligand-gated receptors at therapeutic concentrations and thereby support BRV's role as a selective SV2A ligand. These findings add further evidence to the validity of SV2A as a relevant antiepileptic drug target and emphasize the potential for exploring further presynaptic mechanisms as a novel approach to antiepileptic drug discovery. G.M. and J.-M.R. have served as paid consultants for UCB. All other authors are employed by UCB.

SummaryObjective To evaluate acute and long-term effects of intravenous brivaracetam (BRV) and BRV + diazepam (DZP) combination treatment in a rat model of self-sustaining status epilepticus (SSSE). Methods Rats were treated with BRV (10 mg/kg) 10 min after initiation of perforant path stimulation (PPS) as early treatment; or BRV (10–300 mg/kg), DZP (1 mg/kg), or BRV (0.3–10 mg/kg) + DZP (1 mg/kg) 10 min after the end of PPS (established SSSE). Seizure activity was recorded electrographically for 24 h posttreatment (acute effects), and for 1 week at 6–8 weeks or 12 months' posttreatment (long-term effects). All treatments were compared with control rats using one-way analysis of variance (ANOVA) and Bonferroni's test, or Kruskal-–Wallis and Dunn's multiple comparison tests, when appropriate. Results Treatment of established SSSE with BRV (10–300 mg/kg) resulted in dose-dependent reduction in SSSE duration and cumulative seizure time, achieving statistical significance at doses ≥100 mg/kg. Lower doses of BRV (0.3–10 mg/kg) + low-dose DZP (1 mg/kg) significantly reduced SSSE duration and number of seizures. All control rats developed spontaneous recurrent seizures (SRS) 6–8 weeks after SSSE, whereas seizure freedom was noted in 2/10, 5/10, and 6/10 rats treated with BRV 200 mg/kg, 300 mg/kg, and BRV 10 mg/kg + DZP, respectively. BRV (10–300 mg/kg) showed a dose-dependent trend toward reduction of SRS frequency, cumulative seizure time, and spike frequency, achieving statistical significance at 300 mg/kg. Combination of BRV (10 mg/kg) + DZP significantly reduced SRS frequency, cumulative seizure time, and spike frequency. In the 12-month follow-up study, BRV (0.3–10 mg/kg) + low-dose DZP markedly reduced SRS frequency, cumulative seizure time, and spike frequency, achieving statistical significance at some doses. Early treatment of SSSE with BRV 10 mg/kg significantly reduced long-term SRS frequency. Significance These findings support clinical evaluation of BRV for treatment of status epilepticus or acute repetitive seizures.

Aims Synaptic vesicle proteins 2 (SV2) are neuronal vesicles membrane glycoproteins that appear as important targets in the treatment of partial and generalized epilepsies. Therefore, we analysed the expression of SV2 isoforms in the hippocampus of patients with temporal lobe epilepsy (TLE). Methods SV2A, SV2B and SV2C immunostaining and QuantiGene branched DNA assay were performed on biopsies from 31 consecutive TLE patients with mesial temporal sclerosis (MTS) and compared with 10 autopsy controls. SV2 expression was further compared with Timm's staining, and synaptophysin, Zinc transporter 3 (ZnT3), dynorphin, vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter (VGAT) expression. Results In TLE patients, SV2A and SV2B expression was decreased in areas of synaptic loss. SV2C, which is weakly expressed or absent in the hippocampus of controls, was overexpressed in 10/11 cases with classical MTS1A and mossy fibre sprouting but not in cases with other types of MTS. SV2C staining was located in the inner molecular layer of the dentate gyrus and colocalized with dynorphin, ZnT3 and VGLUT1, suggesting selective expression in presynaptic glutamatergic Zn2+-rich terminals of abnormal sprouting fibres. SV2 expression patterns correlated with histological subtypes of MTS, but not with clinical features or therapeutic regimens in this patient cohort. Conclusion In classical MTS1A, the expression of SV2 isoforms is altered with a marked decrease of SV2A and SV2B paralleling synaptic loss and a selective increase of SV2C in sprouting mossy fibres. These findings suggest a different physiology of sprouting synapses and the possibility to target them with SV2C-specific strategies.

There is a pressing need to address the current major gaps in epilepsy treatment, in particular drug-resistant epilepsy, antiepileptogenic therapies, and comorbidities. A major concern in the development of new therapies is that current preclinical testing is not sufficiently predictive for clinical efficacy. Methodologic limitations of current preclinical paradigms may partly account for this discrepancy. Here we propose and discuss a strategy for implementing a "phase II" multicenter preclinical drug trial model based on clinical phase II/III studies designed to generate more rigorous preclinical data for efficacy. The goal is to improve the evidence resulting from preclinical studies for investigational new drugs that have shown strong promise in initial preclinical "phase I" studies. This should reduce the risk for expensive clinical studies in epilepsy and therefore increase the appeal for funders (industry and government) to invest in their clinical development.

The antiepileptic drugs (AEDs) introduced during the past two decades have provided several benefits: they offered new treatment options for symptomatic treatment of seizures, improved ease of use and tolerability, and lowered risk for hypersensitivity reactions and detrimental drug-drug interactions. These drugs, however, neither attenuated the problem of drug-refractory epilepsy nor proved capable of preventing or curing the disease. Therefore, new preclinical screening strategies are needed to identify AEDs that target these unmet medical needs. New therapies may derive from novel targets identified on the basis of existing hypotheses for drug-refractory epilepsy and the biology of epileptogenesis; from research on genetics, transcriptomics, and epigenetics; and from mechanisms relevant for other therapy areas. Novel targets should be explored using new preclinical screening strategies, and new technologies should be used to develop medium- to high-throughput screening models. In vivo testing of novel drugs should be performed in models mimicking relevant aspects of drug refractory epilepsy and/or epileptogenesis. To minimize the high attrition rate associated with drug development, which arises mainly from a failure to demonstrate sufficient clinical efficacy of new treatments, it is important to define integrated strategies for preclinical screening and experimental trial design. An important tool will be the discovery and implementation of relevant biomarkers that will facilitate a continuum of proof-of-concept approaches during early clinical testing to rapidly confirm or reject preclinical findings, and thereby lower the risk of the overall development effort. In this review, we overview some of the issues related to these topics and provide examples of new approaches that we hope will be more successful than those used in the past.

Background and purpose: Screening of 12 000 compounds for binding affinity to the synaptic vesicle protein 2A (SV2A), identified a high-affinity pyrrolidone derivative, brivaracetam (ucb 34714). This study examined its pharmacological profile in various in vitro and in vivo models of seizures and epilepsy, to evaluate its potential as a new antiepileptic drug.

The in vivo anticonvulsant effects and in vitro metabotropic glutamate receptor selectivity of (S)-4-carboxy-3-hydroxy-phenylglycine [(S)-4C3HPG] were examined. Intracerebroventricular injection of (S)-4C3HPG dose-dependently antagonized audiogenic-induced clonic and tonic convulsions in DBA/2 mice with ED50 values of 76 and 110-nmol per mouse, respectively. (S)-4C3HPG dose-dependently inhibited the spontaneously evoked epileptic spikes in a cingulate cortex-corpus callosum slice preparation. (S)-4C3HPG displaced the binding of [3H]glutamate in membranes prepared from baby hamster kidney (BHK) cells expressing the metabotropic glutamate receptor mGluR1a with an EC50 of 5 +/- 1 microM. (S)-4C3HPG dose-dependently antagonized glutamate-stimulated phosphoinositide hydrolysis in BHK cells expressing mGluR1a with an IC50 of 15 +/- 3 microM. (S)-4C3HPG was, however, an agonist at mGluR2 with an EC50 of 21 +/- 4 microM for inhibition of forskolin-stimulated cyclic AMP formation in BHK cells expressing the mGluR2. (S)-4C3HPG had no effects at mGluR4a. These data suggest that the anticonvulsant action of (S)-4C3HPG is mediated by combined antagonism of mGluR1a and agonism of mGluR2. These results suggest the importance of mGluR1a and/or mGluR2 in the control of epileptic activity.

Gene expression profiling by microarrays is a powerful tool for identification of genes that may encode key proteins involved in molecular mechanisms underlying epileptogenesis. Using the Affymetrix oligonucleotide microarray, we have surveyed the expression levels of more than 26,000 genes and expressed sequence tags (ESTs) in the amygdala-kindling model of temporal lobe epilepsy. Furthermore, the effect of the antiepileptic drug levetiracetam (LEV) on kindling-induced alterations of gene expression was studied. Treatment of rats with LEV during kindling acquisition significantly suppressed kindling development. For gene expression profiling, six groups of rats were included in the present study: (i) and (ii) sham-operated rats treated with saline or LEV; (iii) and (iv) electrode-implanted but non-kindled rats treated with saline or LEV; (v) and (vi) kindled rats treated with saline or LEV. Treatment was terminated after 11 or 12 daily amygdala stimulations, when all vehicle-treated rats had reached kindling criterion, i.e. a stage 5 seizure. Twenty-four hours later, the ipsilateral temporal lobe was dissected for mRNA preparation. Six temporal lobe preparations from each group were analysed for differential gene expression. In control (non-kindled) rats, LEV treatment was devoid of any significant effect on gene expression. In saline-treated kindled rats, a large number of genes were observed to display mRNA expression alterations compared with non-kindled rats. LEV treatment induced marked effects on gene expression from kindled rats. Previously described epilepsy-related genes, such as neuropeptide Y (NPY), thyrotropin-releasing hormone (TRH) and glial fibrillary acidic protein (GFAP) were confirmed to be up-regulated by kindling and partially normalized by LEV treatment. Real-time quantitative polymerase chain reaction confirmed NPY, TRH and GFAP expression data from chip experiments. Furthermore, a number of novel genes were identified from the gene chip experiments. A subgroup of these genes demonstrated correlation between expression changes and kindled phenotype measurements. In summary, this study identified many genes with potentially important roles in epileptogenesis and highlighted several important issues in using the gene chip technology for the study of animal models of CNS disorders.

Long-term dopamine replacement therapy of Parkinson's disease leads to the occurrence of dyskinesias. Altered firing patterns of neurons of the internal globus pallidus, involving a pathological synchronization/desynchronization process, may contribute significantly to the genesis of dyskinesia. Levetiracetam, an antiepileptic drug that counteracts neuronal (hyper)synchronization in animal models of epilepsy, was assessed in the MPTP-lesioned marmoset model of Parkinson's disease, after coadministration with (1) levodopa (L-dopa) or (2) ropinirole/L-dopa combination. Oral administration of levetiracetam (13-60 mg/kg) in combination with either L-dopa (12 mg/kg) alone or L-dopa (8 mg/kg)/ropinirole (1.25 mg/kg) treatments was associated with significantly less dyskinesia, in comparison to L-dopa monotherapy during the first hour after administration. Thus, new nondopaminergic treatment strategies targeting normalization of abnormal firing patterns in basal ganglia structures may prove useful as an adjunct to reduce dyskinesia induced by dopamine replacement therapy without affecting its antiparkinsonian action.

1. In this study in vitro and in vivo approaches were combined in order to investigate if the anti-epileptic mechanism(s) of action of levetiracetam (LEV; Keppra) may involve modulation of inhibitory neurotransmission. 2. GABA- and glycine-gated currents were studied in vitro using whole-cell patch-clamp techniques applied on cultured cerebellar granule, hippocampal and spinal neurons. Protection against clonic convulsions was assessed in vivo in sound-susceptible mice. The effect of LEV was compared with reference anti-epileptic drugs (AEDs): carbamazepine, phenytoin, valproate, clonazepam, phenobarbital and ethosuximide. 3. LEV contrasted the reference AEDs by an absence of any direct effect on glycine-gated currents. At high concentrations, beyond therapeutic relevance, it induced a small reduction in the peak amplitude and a prolongation of the decay phase of GABA-gated currents. A similar action on GABA-elicited currents was observed with the reference AEDs, except ethosuximide. 4. These minor direct effects contrasted with a potent ability of LEV (EC(50)=1 - 10 microM) to reverse the inhibitory effects of the negative allosteric modulators zinc and beta-carbolines on both GABA(A) and glycine receptor-mediated responses. 5. Clonazepam, phenobarbital and valproate showed a similar ability to reverse the inhibition of beta-carbolines on GABA-gated currents. Blockade of zinc inhibition of GABA responses was observed with clonazepam and ethosuximide. Phenytoin was the only AED together with LEV that inhibited the antagonism of zinc on glycine-gated currents and only clonazepam and phenobarbital inhibited the action of DMCM. 6. LEV (17 mg kg(-1)) produced a potent suppression of sound-induced clonic convulsions in mice. This protective effect was significantly abolished by co-administration of the beta-carboline FG 7142, from a dose of 5 mg kg(-1). In contrast, the benzodiazepine receptor antagonist flumazenil (up to 10 mg kg(-1)) was without any effect on the protection afforded by LEV. 7. The results of the present study suggest that a novel ability to oppose the action of negative modulators on the two main inhibitory ionotropic receptors may be of relevance for the anti-epileptic mechanism(s) of action of LEV.

Levetiracetam is a new antiepileptic drug (AED) devoid of anticonvulsant activity in the two classic screening models for AEDs, the maximal electroshock and pentylenetetrazol seizure tests in both mice and rats. This contrasts a potent seizure suppression in genetic and kindled mice and rats and against chemoconvulsants inducing partial seizures in rats. The highly selective action in "epileptic" animals distinguishes levetiracetam from classic and other new AEDs that have nearly equipotent effects in normal and "epileptic" animals. Levetiracetam induces minor behavioral alterations in normal and in kindled mice and rats. This results in an unusually high safety margin in animal models reflecting both partial and primary generalized epilepsy. Furthermore, experiments in the kindling model suggest that levetiracetam may possess antiepileptogenic properties due to a potent ability to prevent the development of kindling in mice and rats at doses devoid of adverse effects. Electrophysiologic recordings from different experimental models suggest that levetiracetam exerts a selective action against abnormal patterns of neuronal activity, which probably explains its selective protection in epileptic animals and its unique tolerability. This effect appears to derive from one or more novel mechanisms of action that do not involve a conventional interaction with traditional drug targets implicated in the modulation of inhibitory and excitatory neurotransmission. Instead, ligand-binding assays have disclosed a brain-specific binding site for levetiracetam. These studies reveal a unique preclinical profile of levetiracetam, distinct from that of all known AEDs, suggesting that levetiracetam could represent the first agent in a new class of AEDs.

A new diaryl-methylene piperidine derivative, 2, displayed an atypical antipsychotic profile both in vitro and in vivo. The main pharmacological characteristics of this compound appears to reside in a more potent antagonism of the 5-HT2 serotonergic receptor than of the D2 dopaminergic receptor. This confirms that molecules displaying a D2/5-HT2 binding ratio

Levetiracetam's (Keppra) binding site and its subsequent identification as the synaptic vesicle protein 2A (SV2A) enabled the discovery of high affinity SV2A ligands with promising anticonvulsant properties. Among these, brivaracetam was selected for further development. SV2A represents an important antiepileptic drug target validated in both preclinical and clinical studies. For an expanded treatment of this topic see Jasper's basic mechanisms of the epilepsies. 4th ed. (Noebels JL, Avoli M, Rogawski MA, Olsen RW, Delgado-Escueta AV, eds) published by Oxford University Press (available on the National Library of Medicine Bookshelf [NCBI] at www.ncbi.nlm.nih.gov/ books).