Characterization of [(3)H]ucb 30889 binding to synaptic vesicle protein 2A in the rat spinal cord

Assessment of the toxic effects of levetiracetam on biochemical, functional, and redox parameters of salivary glands in male Wistar rats

Levetiracetam (LEV) is an anticonvulsant for epilepsy. The toxic effects of this medication in tissues have been associated with redox state imbalance, which can lead to salivary gland dysfunction. Therefore, the current work investigated the effects of LEV on the biochemical, functional, and redox parameters of the parotid and submandibular glands in rats. For this, male Wistar rats (Rattus norvegicus albinus) were randomly divided into 3 groups (n = 10/group): Control (0.9% saline solution), LEV100 (100 mg/kg), and LEV300 (300 mg/kg). After 21 consecutive days of intragastric gavage treatments, pilocarpine stimulated saliva secretion was collected for salivary biochemical analysis. The extracted salivary glands were utilized for histomorphometry and redox state analyses. Our results showed that LEV300 increased plasma hepatotoxicity markers and reduced salivary amylase activity and the acinar surface area of the parotid gland. Total oxidant capacity and oxidative damage to lipids and proteins were higher in the parotid gland, while total antioxidant capacity and uric acid levels were reduced in the submandibular gland of the LEV100 group compared to Control. On the other hand, total oxidant capacity, oxidative damage to lipids and proteins, total antioxidant capacity, and uric acid levels were lower in both salivary glands of the LEV300 group compared to Control. Superoxide dismutase and glutathione peroxidase activities were lower in the salivary glands of treated animals compared to Control. In conclusion our data suggest that treatment with LEV represents a potentially toxic agent, that contributes to drug-induced salivary gland dysfunction.

SV2A PET Imaging Is a Noninvasive Marker for the Detection of Spinal Damage in Experimental Models of Spinal Cord Injury

Traumatic spinal cord injury (SCI) is a neurologic condition characterized by long-term motor and sensory neurologic deficits as a consequence of an external physical impact damaging the spinal cord. Anatomic MRI is considered the gold-standard diagnostic tool to obtain structural information for the prognosis of acute SCI; however, it lacks functional objective information to assess SCI progression and recovery. In this study, we explored the use of synaptic vesicle glycoprotein 2A (SV2A) PET imaging to detect spinal cord lesions noninvasively after SCI. Methods: Mice (n = 7) and rats (n = 8) subjected to unilateral moderate cervical (C5) contusion were euthanized 1 wk after SCI for histologic and autoradiographic (³H-labeled (4R)-1-[(3-methylpyridin-4-yl)methyl]-4-(3,4,5-trifluorophenyl)pyrrolidin-2-one [UCB-J]) investigation of SV2A levels. Longitudinal ¹¹C-UCB-J PET/CT imaging was performed in sham (n = 7) and SCI rats (n = 8) 1 wk and 6 wk after SCI. Animals also underwent an ¹⁸F-FDG PET scan during the latter time point. Postmortem tissue SV2A analysis to corroborate in vivo PET findings was performed 6 wk after SCI. Results: A significant SV2A loss (ranging from -70.3% to -87.3%; P < 0.0001) was measured at the epicenter of the impact in vitro in both mouse and rat contusion SCI models. Longitudinal ¹¹C-UCB-J PET imaging detected SV2A loss in SCI rats (-49.0% ± 8.1% at 1 wk and -52.0% ± 12.9% at 6 wk after SCI), with no change observed in sham rats. In contrast, ¹⁸F-FDG PET imaging measured only subtle hypometabolism (-17.6% ± 14.7%). Finally, postmortem ³H-UCB-J autoradiography correlated with the in vivo SV2A PET findings (r = 0.92, P < 0.0001). Conclusion:¹¹C-UCB-J PET/CT imaging is a noninvasive marker for SV2A loss after SCI. Collectively, these findings indicate that SV2A PET may provide an objective measure of SCI and thus represent a valuable tool to evaluate novel therapeutics. Clinical assessment of SCI with SV2A PET imaging is highly recommended.

Feasibility of imaging synaptic density in the human spinal cord using [11C]UCB-J PET

PURPOSE

Neuronal damage and synapse loss in the spinal cord (SC) have been implicated in spinal cord injury (SCI) and neurodegenerative disorders such as Amyotrophic Lateral Sclerosis (ALS). Current standards of diagnosis for SCI include CT or MRI imaging to evaluate injury severity. The current study explores the use of PET imaging with [11C]UCB-J, which targets the synaptic vesicle protein 2A (SV2A), in the human spinal cord, as a way to visualize synaptic density and integrity in vivo.

RESULTS

First, simulations of baseline and blocking [11C]UCB-J HRRT scans were performed, based on SC dimensions and SV2A distribution to predict VT, VND, and VS values. Next, human baseline and blocking [11C]UCB-J HRRT images were used to estimate these values in the cervical SC (cSC). Simulation results had excellent agreement with observed values of VT, VND, and VS from the real human data, with baseline VT, VND, and VS of 3.07, 2.15, and 0.92 mL/cm3, respectively, with a BPND of 0.43. Lastly, we explored full SC imaging with whole-body images. Using automated SC regions of interest (ROIs) for the full SC, cSC, and thoracic SC (tSC), the distribution volume ratio (DVR) was estimated using the brain gray matter as a reference region to evaluate SC SV2A density relative to the brain. In full body imaging, DVR values of full SC, cSC, and tSC were 0.115, 0.145, and 0.112, respectively. Therefore, measured [11C]UCB-J uptake, and thus SV2A density, is much lower in the SC than in the brain.

CONCLUSIONS

The results presented here provide evidence for the feasibility of SV2A PET imaging in the human SC, however, specific binding of [11C]UCB-J is low. Ongoing and future work include further classification of SV2A distribution in the SC as well as exploring higher-affinity PET radioligands for SC imaging.

Imaging Synaptic Density: The Next Holy Grail of Neuroscience?

The brain is the central and most complex organ in the nervous system, comprising billions of neurons that constantly communicate through trillions of connections called synapses. Despite being formed mainly during prenatal and early postnatal development, synapses are continually refined and eliminated throughout life via complicated and hitherto incompletely understood mechanisms. Failure to correctly regulate the numbers and distribution of synapses has been associated with many neurological and psychiatric disorders, including autism, epilepsy, Alzheimer’s disease, and schizophrenia. Therefore, measurements of brain synaptic density, as well as early detection of synaptic dysfunction, are essential for understanding normal and abnormal brain development. To date, multiple synaptic density markers have been proposed and investigated in experimental models of brain disorders. The majority of the gold standard methodologies (e.g., electron microscopy or immunohistochemistry) visualize synapses or measure changes in pre- and postsynaptic proteins ex vivo. However, the invasive nature of these classic methodologies precludes their use in living organisms. The recent development of positron emission tomography (PET) tracers [such as (¹⁸F)UCB-H or (¹¹C)UCB-J] that bind to a putative synaptic density marker, the synaptic vesicle 2A (SV2A) protein, is heralding a likely paradigm shift in detecting synaptic alterations in patients. Despite their limited specificity, novel, non-invasive magnetic resonance (MR)-based methods also show promise in inferring synaptic information by linking to glutamate neurotransmission. Although promising, all these methods entail various advantages and limitations that must be addressed before becoming part of routine clinical practice. In this review, we summarize and discuss current ex vivo and in vivo methods of quantifying synaptic density, including an evaluation of their reliability and experimental utility. We conclude with a critical assessment of challenges that need to be overcome before successfully employing synaptic density biomarkers as diagnostic and/or prognostic tools in the study of neurological and neuropsychiatric disorders.

A metabolically stable PET tracer for imaging synaptic vesicle protein 2A: synthesis and preclinical characterization of [18F]SDM-16

PURPOSE

To quantify the synaptic vesicle glycoprotein 2A (SV2A) changes in the whole central nervous system (CNS) under pathophysiological conditions, a high affinity SV2A PET radiotracer with improved in vivo stability is desirable to minimize the potential confounding effect of radiometabolites. The aim of this study was to develop such a PET tracer based on the molecular scaffold of UCB-A, and evaluate its pharmacokinetics, in vivo stability, specific binding, and nonspecific binding signals in nonhuman primate brains, in comparison with [11C]UCB-A, [11C]UCB-J, and [18F]SynVesT-1.

METHODS

The racemic SDM-16 (4-(3,5-difluorophenyl)-1-((2-methyl-1H-imidazol-1-yl)methyl)pyrrolidin-2-one) and its two enantiomers were synthesized and assayed for in vitro binding affinities to human SV2A. We synthesized the enantiopure [18F]SDM-16 using the corresponding enantiopure arylstannane precursor. Nonhuman primate brain PET scans were performed on FOCUS 220 scanners. Arterial blood was drawn for the measurement of plasma free fraction (fP), radiometabolite analysis, and construction of the plasma input function. Regional time-activity curves (TACs) were fitted with the one-tissue compartment (1TC) model to obtain the volume of distribution (VT). Nondisplaceable binding potential (BPND) was calculated using either the nondisplaceable volume of distribution (VND) or the centrum semiovale (CS) as the reference region.

RESULTS

SDM-16 was synthesized in 3 steps with 44% overall yield and has the highest affinity (Ki = 0.9 nM) to human SV2A among all reported SV2A ligands. [18F]SDM-16 was prepared in about 20% decay-corrected radiochemical yield within 90 min, with greater than 99% radiochemical and enantiomeric purity. This radiotracer displayed high specific binding in monkey brains and was metabolically more stable than the other SV2A PET tracers. The fP of [18F]SDM-16 was 69%, which was higher than those of [11C]UCB-J (46%), [18F]SynVesT-1 (43%), [18F]SynVesT-2 (41%), and [18F]UCB-H (43%). The TACs were well described with the 1TC. The averaged test-retest variability (TRV) was 7 ± 3%, and averaged absolute TRV (aTRV) was 14 ± 7% for the analyzed brain regions.

CONCLUSION

We have successfully synthesized a novel SV2A PET tracer [18F]SDM-16, which has the highest SV2A binding affinity and metabolical stability among published SV2A PET tracers. The [18F]SDM-16 brain PET images showed superb contrast between gray matter and white matter. Moreover, [18F]SDM-16 showed high specific and reversible binding in the NHP brains, allowing for the reliable and sensitive quantification of SV2A, and has potential applications in the visualization and quantification of SV2A beyond the brain.

Synaptic vesicle glycoprotein 2A is affected in the CNS of Huntington's Disease mice and post-mortem human HD brain

Synaptic dysfunction is a primary mechanism underlying Huntington's Disease (HD) progression. This study investigated changes in synaptic vesicle glycoprotein 2A (SV2A) density by means of ¹¹C-UCB-J microPET imaging in the central nervous system (CNS) of HD mice. METHODS: Dynamic ¹¹C-UCB-J microPET imaging was performed at clinically relevant disease stages (at 3, 7, 10, and 16 months, M) in the heterozygous knock-in Q175DN mouse model of HD and WT littermates (n = 16-18/genotype and time point). Cerebral ¹¹C-UCB-J analyses were performed to assess genotypic differences during pre-symptomatic (3M) and symptomatic (7-16M) disease stages. ¹¹C-UCB-J binding in the spinal cord was quantified at 16M. 3H-UCB-J autoradiography and SV2A immunofluorescence were performed post-mortem in mouse and human brain tissue. RESULTS: ¹¹C-UCB-J binding was declined in symptomatic heterozygous mice compared to WT littermates in parallel with disease progression (7M: p<0.01, 16M: p<0.0001). Specific ¹¹C-UCB-J binding was detectable in the spinal cord, with symptomatic heterozygous mice displaying a significant reduction (p<0.0001). 3H-UCB-J autoradiography and SV2A immunofluorescence corroborated the in vivo measurements demonstrating lowered SV2A in heterozygous mice (p<0.05). Finally, preliminary analysis of SV2A in post-mortem human brain suggested lower SV2A in HD gene carrier compared to nondemented control. CONCLUSION: ¹¹C-UCB-J PET detects SV2A deficits during symptomatic disease in heterozygous mice in both brain and spinal cord, offering a novel marker of synaptic integrity widely distributed in CNS. Upon clinical application, ¹¹C-UCB-J PET imaging yields promise for SV2A measurement in patients with HD during disease progression and following disease-modifying therapeutic strategies.

Clinical benefits of single vs repeated courses of mesenchymal stem cell therapy in epilepsy patients

PURPOSE

Epilepsy is defined as "drug-resistant" when existing anti-epileptic drugs (AED) are found to have minimal to no effect on patient's condition. Therefore the search and testing of new treatment strategies is warranted. This study focuses on the effects of autologous mesenchymal stem cells (MSC) in drug-resistant epilepsy patients within a Phase I/II open-label registered clinical trial NCT02497443.

MATERIALS/METHODS

A total of 67 patients was included (29 males, 38 females, mean age 33 ± 1.3 yo). The patients received either standard treatment with AEDs, or AEDs supplemented with one or two courses of therapy with autologous bone marrow-derived MSCs expanded in vitro. MSC therapy courses were 6 months apart, and each course consisted of two cell injections: an intravenous infusion of MSCs, followed within 1 week by an intrathecal injection. Primary outcome of the study was safety, secondary outcome was efficacy in terms of seizure frequency reduction and response to treatment.

RESULTS

MSC injections proved safe and did not cause any severe side effects. In MSC group (n = 34), 61.7% patients responded to therapy at 6 months timepoint (p < 0.01 vs control, n = 33), and the number rose to 76.5% by 12 months timepoint. Decrease in anxiety and depression scores and paroxysmal epileptiform activity was observed in MSC group based on HADS and EEG, respectively, and MMSE score has also improved. Another observation was that concomitant administration of levetiracetam, but not other AEDs, correlated significantly with the success of MSC therapy. Second course of MSC therapy facilitated further reduction in seizure count and epileptiform EEG activity (p < 0.05 vs single course).

CONCLUSIONS

Application of autologous mesenchymal stem cell-based therapy in patients with pharmacoresistant epilepsy demonstrated significant anticonvulsant potential. This effect lasted for at least 1 year, with repeated administration of MSCs conveying additional clinical benefit.

Levetiracetam treatment leads to functional recovery after thoracic or cervical injuries of the spinal cord

Spinal cord injury (SCI) leads to dramatic impairments of motor, sensory, and autonomic functions of affected individuals. Following the primary injury, there is an increased release of glutamate that leads to excitotoxicity and further neuronal death. Therefore, modulating glutamate excitotoxicity seems to be a promising target to promote neuroprotection during the acute phase of the injury. In this study, we evaluated the therapeutic effect of a FDA approved antiepileptic drug (levetiracetam-LEV), known for binding to the synaptic vesicle protein SV2A in the brain and spinal cord. LEV therapy was tested in two models of SCI-one affecting the cervical and other the thoracic level of the spinal cord. The treatment was effective on both SCI models. Treated animals presented significant improvements on gross and fine motor functions. The histological assessment revealed a significant decrease of cavity size, as well as higher neuronal and oligodendrocyte survival on treated animals. Molecular analysis revealed that LEV acts by stabilizing the astrocytes allowing an effective uptake of the excess glutamate from the extracellular space. Overall, our results demonstrate that Levetiracetam may be a promising drug for acute management of SCI.

Brivaracetam attenuates pain behaviors in a murine model of neuropathic pain

Background

The antiseizure racetams may provide novel molecular insights into neuropathic pain due to their unique mechanism involving synaptic vesicle glycoprotein 2A. Anti-allodynic effects of levetiracetam have been shown in animal models of neuropathic pain. Here, we studied the effect of brivaracetam, which binds to synaptic vesicle glycoprotein 2A with 20-fold greater affinity, and has fewer off-target effects.

Methods

Mice underwent unilateral sciatic nerve cuffing and were evaluated for mechanical sensitivity using von Frey filaments. Pain behaviors were assessed with prophylactic treatment using levetiracetam (100 or 10 mg/kg) or brivaracetam (10 or 1 mg/kg) beginning after surgery and continuing for 21 days, or with therapeutic treatment using brivaracetam (10 or 1 mg/kg) beginning on day 14, after allodynia was established, and continuing for 28 or 63 days. Spinal cord tissues from the prophylaxis experiment with10 mg/kg brivaracetam were examined for neuroinflammation (Iba1 and tumor necrosis factor), T-lymphocyte (CD3) infiltration, and synaptic vesicle glycoprotein 2A expression.

Results

When used prophylactically, levetiracetam, 100 mg/kg, and brivaracetam, 10 mg/kg, prevented the development of allodynia, with lower doses of each being less effective. When used therapeutically, brivaracetam extinguished allodynia, requiring 10 days with 10 mg/kg, and six weeks with 1 mg/kg. Brivaracetam was associated with reduced neuroinflammation and reduced T-lymphocyte infiltration in the dorsal horn. After sciatic nerve cuffing, synaptic vesicle glycoprotein 2A expression was identified in neurons, activated astrocytes, microglia/macrophages, and T lymphocytes in the dorsal horn.

Conclusion

Synaptic vesicle glycoprotein 2A may represent a novel target for neuropathic pain. Brivaracetam may warrant study in humans with neuropathic pain due to peripheral nerve injury.

Do antiepileptic drugs increase the risk of infectious diseases? A meta-analysis of placebo-controlled studies

AIMS

Experimental studies show that some antiepileptic drugs (AEDs) may modify natural immune defences, thus influencing the risk of developing infectious diseases. The aim of this meta-analysis was to explore whether AEDs as a class of drugs or singularly may increase risk of infectious diseases.

METHODS

A meta-analysis of all randomized, double-blind, placebo-controlled trials (RCTs) investigating any AED in any condition was performed. All terms that could be coded in the System Organ Classes (SOCs) of infections and infestations using the Medical Dictionary for Regulatory Activities were recorded. Additional subanalyses were performed also pooling together AEDs sharing similar mechanisms of action.

RESULTS

Two hundreds and sixty-nine double-blind, placebo-controlled studies were identified and, among them, 127 RCTs with 16 AEDs (brivaracetam, gabapentin, lacosamide, levetiracetam, lamotrigine, oxcarbazepine, perampanel, pregabalin, phenytoin, remacemide, retigabine, rufinamide, tiagabine, topiramate, valproate, zonisamide) reported at least one of 19 symptoms or diseases that could be included in the Medical Dictionary for Regulatory Activities SOC term infections and infestations. These terms were singularly recorded and then pooled together in the SOC term infection and infestation. Topiramate was significantly associated with an increased risk of infection (risk difference = 0.04; 95% confidence interval = 0.01/0.06), while oxcarbazepine was significantly associated with a lower risk (-0.005; -0.09/-0.01). Risk difference of all studies with all AEDs showed a slight, but significantly increased risk of infection (0.01; 0.00/0.002). Levetiracetam and brivaracetam RCTs, when pooled together, were associated with a significantly increased risk of infection (0.03; 0.01/0.05).

CONCLUSIONS

Some AEDs are associated with a mild increased risk of infection.

Synthesis and Preclinical Evaluation of 11C-UCB-J as a PET Tracer for Imaging the Synaptic Vesicle Glycoprotein 2A in the Brain

The synaptic vesicle glycoprotein 2A (SV2A) is found in secretory vesicles in neurons and endocrine cells. PET with a selective SV2A radiotracer will allow characterization of drugs that modulate SV2A (e.g., antiepileptic drugs) and potentially could be a biomarker of synaptic density (e.g., in neurodegenerative disorders). Here we describe the synthesis and characterization of the SV2A PET radiotracer (11)C-UCB-J ((R)-1-((3-((11)C-methyl-(11)C)pyridin-4-yl)methyl)-4-(3,4,5-trifluorophenyl)pyrrolidin-2-one) in nonhuman primates, including whole-body biodistribution.

METHODS

(11)C-UCB-J was prepared by C-(11)C-methylation of the 3-pyridyl trifluoroborate precursor with (11)C-methyl iodide via the Suzuki-Miyaura cross-coupling method. Rhesus macaques underwent multiple scans including coinjection with unlabeled UCB-J (17, 50, and 150 μg/kg) or preblocking with the antiepileptic drug levetiracetam at 10 and 30 mg/kg. Scans were acquired for 2 h with arterial sampling and metabolite analysis to measure the input function. Regional volume of distribution (VT) was estimated using the 1-tissue-compartment model. Target occupancy was assessed using the occupancy plot; the dissociation constant (Kd) was determined by fitting self-blocking occupancies to a 1-site model, and the maximum number of receptor binding sites (Bmax) values were derived from baseline VT and from the estimated Kd and the nondisplaceable distribution volume (VND).

RESULTS

(11)C-UCB-J was synthesized with greater than 98% purity. (11)C-UCB-J exhibited high free fraction (0.46 ± 0.02) and metabolized at a moderate rate (39% ± 5% and 24% ± 3% parent remaining at 30 and 90 min) in plasma. In the monkey brain, (11)C-UCB-J displayed high uptake and fast kinetics. VT was high (∼25-55 mL/cm(3)) in all gray matter regions, consistent with the ubiquitous expression of SV2A. Preblocking with 10 and 30 mg/kg of levetiracetam resulted in approximately 60% and 90% occupancy, respectively. Analysis of the self-blocking scans yielded a Kd estimate of 3.4 nM and Bmax of 125-350 nM, in good agreement with the in vitro inhibition constant (Ki) of 6.3 nM and regional Bmax in humans. Whole-body biodistribution revealed that the liver and the brain are the dose-limiting organs for males and females, respectively.

CONCLUSION

(11)C-UCB-J exhibited excellent characteristics as an SV2A PET radiotracer in nonhuman primates. The radiotracer is currently undergoing first-in-human evaluation.

Identification of the antiepileptic racetam binding site in the synaptic vesicle protein 2A by molecular dynamics and docking simulations

Synaptic vesicle protein 2A (SV2A) is an integral membrane protein necessary for the proper function of the central nervous system and is associated to the physiopathology of epilepsy. SV2A is the molecular target of the anti-epileptic drug levetiracetam and its racetam analogs. The racetam binding site in SV2A and the non-covalent interactions between racetams and SV2A are currently unknown; therefore, an in silico study was performed to explore these issues. Since SV2A has not been structurally characterized with X-ray crystallography or nuclear magnetic resonance, a three-dimensional (3D) model was built. The model was refined by performing a molecular dynamics simulation (MDS) and the interactions of SV2A with the racetams were determined by docking studies. A reliable 3D model of SV2A was obtained; it reached structural equilibrium during the last 15 ns of the MDS (50 ns) with remaining structural motions in the N-terminus and long cytoplasmic loop. The docking studies revealed that hydrophobic interactions and hydrogen bonds participate importantly in ligand recognition within the binding site. Residues T456, S665, W666, D670 and L689 were important for racetam binding within the trans-membrane hydrophilic core of SV2A. Identifying the racetam binding site within SV2A should facilitate the synthesis of suitable radio-ligands to study treatment response and possibly epilepsy progression.

Levetiracetam in brain ischemia: clinical implications in neuroprotection and prevention of post-stroke epilepsy

Several new antiepileptic drugs (AEDs) have been introduced for clinical use recently. These new AEDs, like the classic AEDs, target multiple cellular sites both pre- and postsynaptically. The use of AEDs as a possible neuroprotective strategy in brain ischemia is receiving increasing attention and the antiepileptic drug levetiracetam, a 2S-(2-oxo-1-pyrrolidiny1) butanamide, belonging to the pyrrolidone family, could have a crucial role in regulation of epileptogenesis and neuroprotection. Recent observations suggest that levetiracetam is both safe and effective against post-stroke seizures. In this review, the potential neuroprotective role in brain ischemia and the therapeutic implications of levetiracetam in post-stroke epilepsy are discussed.

Antinociceptive efficacy of levetiracetam in a mice model for painful diabetic neuropathy

BACKGROUND AND OBJECTIVE

Despite important advances in available knowledge, management of neuropathic pain remains incomplete, and results from experimental and clinical studies indicate that some anticonvulsants show promise for treating neuropathic pain. The aim of this study was to assess the antinociceptive efficacy of levetiracetam (LEV, ucb L059) in a mice model for painful diabetic neuropathy using the in vivo nociceptive behavioral 'hot-plate test.'

METHODS

The hot-plate test consisted of placing individual mice (adult male Balb/C) on the hot plate at 50+/-0.1 degrees C and timing the delay for the first hind paw lift (nociceptive threshold). After obtaining control values, diabetes was induced by injection of streptozotocin [200 mg/kg intraperitoneally (i.p.)] and 2 weeks after induction of diabetes (serum glucose > or =400 mg/dL) LEV was administered i.p. and hot-plate tests were repeated. Pain threshold values were determined and analyzed by Kruskal-Wallis one-way analysis of variance (ANOVA) followed by a pairwise comparison using a Dunnett's t-test on the ranked data.

RESULTS

LEV (60, 300 and 900 mg/kg) had no significant effect on the nociceptive threshold in normal mice (n=8 for each dose, P>0.05). There were significant decreases in pain threshold latency in diabetic mice compared with the normal healthy group and these were significantly and dose-dependently restored by much lower doses of LEV (20, 100 and 200 mg/kg) in a reversible manner.

CONCLUSION

Results obtained from the in vivo behavioral test lend support to the validation of the promising therapeutic potential of the novel antiepileptic agent LEV in the treatment of neuropathic pain.

Brivaracetam: a new drug in development for epilepsy and neuropathic pain

BACKGROUND

Epilepsy is a neurological disorder with a worldwide prevalence estimated to be 0.5-1.0% of the population. Many potent antiepileptic drugs (AED) have been used for treatment but still about 30% of patients are resistant to current AEDs. Some AEDs are also used for the treatment of neuropathic pain.

OBJECTIVE

The aim of this report is to present preclinical and clinical studies of brivaracetam (UCB-34714), a new drug developed by UCB Pharma.

METHODS

Published results of preclinical studies in several animal models of epilepsy, neuropathic pain, essential tremor and results of Phase I and II evaluations of brivaracetam have been analysed.

RESULTS/CONCLUSION

Brivaracetam represents a new mechanism of action being a ligand of synaptic vesicle protein 2A. It is undergoing Phase III evaluation after a successful Phase II programme in which was effective as an adjunctive treatment in partial-onset epilepsy (50 mg/day). It is well tolerated, without serious adverse side effects.

Levetiracetam Reduces Anesthetic-Induced Hyperalgesia in Rats

BACKGROUND

As part of an increase in excitability, small doses of pentobarbital, propofol, and midazolam induce an increased sensitivity to pain. Specific therapy to prevent or reduce this excitability may offer advantages over current clinical management with analgesics and sedatives. The pharmacological profile of the novel antiepileptic drug, levetiracetam, suggests that it may reduce the intensity of the excitatory stages of anesthesia.

METHODS

We examined the influence of levetiracetam on the reduction of the nociceptive reflex threshold in rats by sedative doses of pentobarbital, propofol, and midazolam. Measurements of nociceptive reflex threshold to pressure and heat were made and then repeated after intraperitoneal injection of saline or one of three doses of levetiracetam (100, 200, 500 mg/kg). Pentobarbital (30 mg/kg), propofol (30 mg/kg), or midazolam (1.9 mg/kg) were then administered. The reflex threshold was measured every 10 min, starting at 5 min after the sedative injection, until 65 min had elapsed.

RESULTS

Levetiracetam did not alter nociceptive reflex threshold in nonsedated animals (P = 0.11) or influence the degree or duration of sedation. The three anesthetic/sedative drugs reduced the nociceptive reflex threshold by 20%-30% of control values. Levetiracetam reduced the hyperreflexia associated with pentobarbital and midazolam (P < 0.05), but not propofol.

CONCLUSIONS

These findings support further investigation into the role of levetiracetam in the prevention of anesthetic-induced excitability.

Levetiracetam: past, present and future

Levetiracetam is an antiepileptic drug approved for use as an adjunctive agent in partial-onset seizures in adults. This approval was recently extended to children over 4 years of age. Among the currently approved antiepileptic drugs, levetiracetam is unique in its mechanism of action. Its CNS binding site, the synaptic vesicle protein SV2A, was discovered recently. Binding at this site may be important for the antiseizure activity of levetiracetam and the role of this binding site and its modulation by levetiracetam is an area of active research in epilepsy. Levetiracetam is generally safe, has near to ideal pharmacokinetics and does not interact with other medications. The most serious adverse events are behavioral in nature. Recent studies suggest that levetiracetam may be effective in generalized epilepsies, status epilepticus, pain and selected movement disorders. Intriguing studies using the kindling model of epilepsy suggest that levetiracetam may protect against the development of kindling and chronic epilepsy. A parenteral formulation of levetiracetam may soon become available and may lead to larger studies of levetiracetam in status epilepticus.