Time course of 75%-100% efficacy response of adjunctive brivaracetam.

BACKGROUND: Time to sustained seizure frequency reduction can provide clinically meaningful epilepsy outcomes. AIMS OF THE STUDY: To examine the time course of brivaracetam (BRV) efficacy in adults with focal seizures and focal to bilateral tonic-clonic seizures (FBTCS). METHODS: Post hoc analysis of data pooled from three randomized controlled trials of oral adjunctive BRV in adults with epilepsy. Patients with focal epilepsy and a subpopulation with FBTCS receiving BRV 50, 100, or 200 mg/d (initiated without up-titration) or placebo for 12 weeks were analyzed for time to sustained ≥75%, ≥90%, and 100% seizure reduction without interruption from first day until trial ends. RESULTS: Evaluation included 1160 patients with focal seizures, including 352 patients with FBTCS. Sustained ≥75%, ≥90%, and 100% response in focal seizures was higher from day 1 for BRV 100 and 200 mg/d vs placebo (P < .01). Sustained ≥75% and 100% FBTCS reduction from day 1 was higher for BRV 100 and 200-mg/d groups vs placebo (P < .01). CONCLUSIONS: The majority of patients achieving 75%-100% sustained seizure frequency reduction (all focal seizure types and the subpopulation with FBTCS) with oral BRV (100 or 200 mg/d) achieved this response on the first-treatment day.

Time course of drug-related treatment-emergent adverse side effects of brivaracetam.

OBJECTIVE: Treatment-emergent adverse events (TEAEs) in clinical trials are typically reported for the full duration of the treatment period including titration and maintenance. Drug-related central nervous system (CNS) TEAEs are common with antiseizure medications (ASMs) and can affect drug tolerability. In this report, we test the hypothesis that drug-related CNS TEAEs have early onset and decrease with time. Unlike prior ASM clinical trials, a novel design was used for brivaracetam (BRV) without initial drug titration allowing assessment of habituation to TEAEs separate from dose titration. METHODS: Data were pooled from three studies (N01252 [NCT00490035], N01253 [NCT00464269], N01358 [NCT01261325]) in adult patients (≥16 years of age) with focal seizures receiving BRV adjunctive therapy. This post hoc analysis reports data on the prevalence and incidence of all drug-related CNS TEAEs and all TEAEs over time in patients who received BRV doses of 50-200 mg/day (without titration) vs. placebo during a 12-week treatment period. RESULTS: A total of 1262 patients received the following: placebo (n = 459), BRV 50 mg/day (n = 200), BRV 100 mg/day (n = 353), and BRV 200 mg/day (n = 250). Both the incidence (p < .0001) and prevalence (p < .0001) of drug-related CNS TEAEs (all with frequency ≥ 5%) changed across time with peak TEAEs in week 1 then significantly reducing over the first 6 weeks for prevalence and the first 3 weeks for incidence. CONCLUSIONS: Drug-related CNS TEAEs occurred early and substantially habituated over several weeks. TEAEs of ASMs might be better represented by division into early and late phases to guide clinician monitoring and patient expectations.

Altered function of the SCN1A voltage-gated sodium channel leads to gamma-aminobutyric acid-ergic (GABAergic) interneuron abnormalities.

Voltage-gated sodium channels are required for the initiation and propagation of action potentials. Mutations in the neuronal voltage-gated sodium channel SCN1A are associated with a growing number of disorders including generalized epilepsy with febrile seizures plus (GEFS+),(7) severe myoclonic epilepsy of infancy, and familial hemiplegic migraine. To gain insight into the effect of SCN1A mutations on neuronal excitability, we introduced the human GEFS+ mutation SCN1A-R1648H into the orthologous mouse gene. Scn1a(RH/RH) mice homozygous for the R1648H mutation exhibit spontaneous generalized seizures and premature death between P16 and P26, whereas Scn1a(RH/+) heterozygous mice exhibit infrequent spontaneous generalized seizures, reduced threshold and accelerated propagation of febrile seizures, and decreased threshold to flurothyl-induced seizures. Inhibitory cortical interneurons from P5-P15 Scn1a(RH/+) and Scn1a(RH/RH) mice demonstrated slower recovery from inactivation, greater use-dependent inactivation, and reduced action potential firing compared with wild-type cells. Excitatory cortical pyramidal neurons were mostly unaffected. These results suggest that this SCN1A mutation predominantly impairs sodium channel activity in interneurons, leading to decreased inhibition. Decreased inhibition may be a common mechanism underlying clinically distinct SCN1A-derived disorders.

Neuronal voltage-gated ion channels are genetic modifiers of generalized epilepsy with febrile seizures plus.

Mutations in the neuronal voltage-gated sodium channel genes SCN1A and SCN2A are associated with inherited epilepsies, including genetic epilepsy with febrile seizures plus (GEFS+) and Dravet syndrome (severe myoclonic epilepsy of infancy). The clinical presentation and severity of these epilepsies vary widely, even in people with the same mutation, suggesting the action of environmental or genetic modifiers. To gain support for the hypothesis that genetic modifiers can influence clinical presentation in patients with SCN1A-derived GEFS+, we used mouse models to study the effect of combining the human GEFS+ mutation SCN1A-R1648H with SCN2A, KCNQ2, and SCN8A mutations. Knock-in mice heterozygous for the R1648H mutation (Scn1a(RH/+)) have decreased thresholds to induced seizures and infrequent spontaneous seizures, whereas homozygotes display spontaneous seizures and premature lethality. Scn2a(Q54) transgenic mice have a mutation in Scn2a that results in spontaneous, adult-onset partial motor seizures, and mice carrying the Kcnq2-V182M mutation exhibit increased susceptibility to induced seizures, and rare spontaneous seizures as adults. Combining the Scn1a-R1648H allele with either Scn2a(Q54) or Kcnq2(V182M/+) results in early-onset, generalized tonic-clonic seizures and juvenile lethality in double heterozygous mice. In contrast, Scn8a mutants exhibit increased resistance to induced seizures. Combining the Scn1a-R1648H and Scn8a-med-jo alleles restores normal thresholds to flurothyl-induced seizures in Scn1a(RH/+) heterozygotes and improved survival of Scn1a(RH/RH) homozygotes. Our results demonstrate that variants in Scn2a, Kcnq2, and Scn8a can dramatically influence the phenotype of mice carrying the Scn1a-R1648H mutation and suggest that ion channel variants may contribute to the clinical variation seen in patients with monogenic epilepsy.

Determination of the formal reduction potential of Lumbricus terrestris hemoglobin using thin layer spectroelectrochemistry.

The formal reduction potential (Eo') of Lumbricus terrestris hemoglobin was determined using thin layer spectroelectrochemistry as 0.073 (+/-0.005) V vs Ag/AgCl (0.281 V vs SHE, standard hydrogen electrode). Nernst plots of Lumbricus terrestris hemoglobin with tris-bipyridinecobalt(II) as a mediator titrant have similar linear slopes as Nernst plots of horse heart myoglobin with hexaamineruthenium(II) as a mediator titrant.

Characterization of 5' untranslated regions of the voltage-gated sodium channels SCN1A, SCN2A, and SCN3A and identification of cis-conserved noncoding sequences.

The human voltage-gated sodium channel gene cluster on chromosome 2q24 contains three paralogs, SCN1A, SCN2A, and SCN3A, which are expressed in the central nervous system. Mutations in SCN1A and SCN2A cause several subtypes of idiopathic epilepsy. Furthermore, many SCN1A mutations are predicted to reduce protein levels, emphasizing the importance of precise sodium channel gene regulation. To investigate the genetic factors that regulate the expression of SCN1A, SCN2A, and SCN3A, we characterized the 5' untranslated region of each gene. We identified multiple noncoding exons and observed brain region differences in the expression levels of noncoding exons. Comparative sequence analysis revealed 33 conserved noncoding sequences (CNSs) between the orthologous mammalian genes and 6 CNSs between the three human paralogs. Seven CNSs corresponded to noncoding exons. Twelve CNSs were evaluated for their ability to alter the transcription of a luciferase reporter gene, and 3 resulted in a modest, but statistically significant change.

The voltage-gated sodium channel Scn8a is a genetic modifier of severe myoclonic epilepsy of infancy.

The mammalian genome contains four voltage-gated sodium channel genes that are primarily expressed in the central nervous system: SCN1A, SCN2A, SCN3A and SCN8A. Mutations in SCN1A and SCN2A are responsible for several dominant idiopathic epilepsy disorders, including generalized epilepsy with febrile seizures plus (GEFS+) and severe myoclonic epilepsy of infancy (SMEI). Mutations in SCN8A are associated with cognitive deficits and neuropsychiatric illness in humans and movement disorders in mice; however, a role for SCN8A (Na(v)1.6) in epilepsy has not been investigated. To determine the relationship between Na(v)1.6 dysfunction and seizure susceptibility, we examined the thresholds of two Scn8a mouse mutants, Scn8a(med) and Scn8a(med-jo), to flurothyl- and kainic acid (KA)-induced seizures. Both mutants were more seizure resistant than wild-type littermates, suggesting that altered Na(v)1.6 function reduces neuronal excitability. To determine whether impaired Na(v)1.6 function could ameliorate seizure severity in a mouse model of SMEI, we generated Scn1a(+/-); Scn8a(med-jo/+) double heterozygous mice. Unlike Scn1a(+/-) mice that are more susceptible to flurothyl-induced seizures, Scn1a(+/-); Scn8a(med-jo/+) mice displayed thresholds that were comparable to wild-type littermates. The Scn8a(med-jo) allele was also able to rescue the premature lethality of Scn1a(+/-) mice and extend the lifespan of Scn1a(-/-) mutants. These results demonstrate that genetic interactions can alter seizure severity and support the hypothesis that genetic modifiers contribute to the clinical variability observed in SMEI and GEFS+.