Doses Evaluated in Clinical Pharmacology Studies Investigating the Effect of Intrinsic and Extrinsic Factors on PK and Safety: Case Examples from Approved Drug Development Programs

Dose selection for investigations of intrinsic and extrinsic factors of pharmacokinetic variability as well as safety is a challenging question in the early clinical stage of drug development. The dose of an investigational product is chosen considering the compound information available to date, feasibility of the assessments, regulatory requirements, and the intent to maximize information for later regulatory submission. This review selected 37 programs as case examples of recently approved drugs to explore the doses selected with focus on studies of drug interaction, renal and hepatic impairment, food effect and concentration-QTc assessment.The review found that regulatory agencies may consider alternative approaches if justified and safe as illustrated in these examples. It is thus recommendable to use the first in human trial as an opportunity to assess QT-prolongation and drug interactions using probes or endogenous markers while maximizing the DDI potential, increasing sensitivity and ensuring safety. Early understanding of dose proportionality assists dose finding and simple and fast to conduct DDI study designs are advantageous. Single dose impairment studies despite non-proportional/time-dependent PK are often acceptability.Overall, the early understanding of the drug's safety profile is essential to ensure the safety of doses selected while preventing clinical trials with unnecessary exposure when using high doses or multiple doses. The information collected in this retrospective survey is a good reminder to tailor the early clinical program to the profile and needs of the molecule and consider regulatory opportunities to streamline the development path.

Brivaracetam exposure-response predictions in pediatric patients from age 1 month: Extrapolation of levetiracetam adult-pediatric scaling to brivaracetam

BACKGROUND

An adult population pharmacokinetic/pharmacodynamic (PK/PD) model for the antiseizure medication (ASM) brivaracetam (BRV) was previously extended to children aged 4-16 years by using a pediatric BRV population PK model. Effects were scaled using information from a combined adult-pediatric PK/PD model of a related ASM, levetiracetam (LEV).

OBJECTIVE

To scale an existing adult population PK/PD model for BRV to children aged 1 month to < 4 years using information from a combined adult-pediatric PK/PD model for LEV, and to predict the effective dose of BRV in children aged 1 month to < 4 years using the adult BRV PK/PD model modified for the basal seizure rate in children.

MATERIAL AND METHODS

An existing adult population PK/PD model for BRV was scaled to children aged from 1 month to < 4 years using information from a combined adult-pediatric PK/PD model for LEV, an ASM binding to the same target protein as BRV. An existing adult-pediatric PK/PD model for LEV was extended using data from UCB study N01009 (NCT00175890) to include children as young as 1 month of age. The BRV population PK model was updated with data up to 180 days after first administration from BRV pediatric studies N01263 (NCT00422422) and N01266 (NCT01364597). PK and PD simulations for BRV were performed for a range of mg/kg doses to predict BRV effect in pediatric participants, and to provide dosing recommendations.

RESULTS

The extended adult-pediatric LEV PK/PD model was able to describe the adult and pediatric data using the same PD model parameters in adults and children and supported the extension of the adult BRV PK/PD model to pediatric patients aged 1 month to < 4 years. Simulations predicted exposures similar to adults receiving BRV 100 mg twice daily (b.i.d.), when using 3 mg/kg b.i.d. for weight < 10 kg, 2.5 mg/kg b.i.d. for weight ≥ 10 kg and < 20 kg, and 2 mg/kg b.i.d. for weight ≥ 20 kg in children aged 1 month to < 4 years. PK/PD simulations show that maximum BRV response is expected to occur with 2-3 mg/kg b.i.d. dosing of BRV in children aged 1 month to < 4 years, with an effective dose of 1 mg/kg b.i.d. for some participants.

CONCLUSION

Development of an adult-pediatric BRV PK/PD model allowed characterization of the exposure-response relationship of BRV in children aged 1 to < 4 years, providing a maximal dose allowance based on weight.

Pharmacokinetics, Safety, and Tolerability of Brivaracetam in Healthy Elderly Participants

The pharmacokinetics, metabolism, safety, and tolerability of the antiseizure medication brivaracetam (BRV) were characterized in 16 healthy elderly participants (8 men/8 women) aged 65-78 years who received a single 200-mg oral dose of BRV on day 1, followed by 200 mg twice daily from day 3 until day 12. BRV and three metabolites were determined in plasma and urine. Adverse events, vital signs, electrocardiograms, laboratory tests, general and neurological examinations, and psychometric rating scales were recorded at regular intervals. No clinically relevant changes or abnormalities were detected. The adverse events were similar to those observed in pivotal trials. Rating scales indicated transiently increased sedation and decreased alertness. BRV pharmacokinetics and metabolism were unchanged relative to younger populations. Based on our observations in this healthy elderly population receiving oral BRV 200 mg twice daily (twice the maximum recommended dose), dose reductions are not warranted relative to other, younger populations. Further investigations may be necessary in frail elderly populations aged >80 years.

Physiologically based pharmacokinetic modeling of brivaracetam and its interactions with rifampin based on CYP2C19 phenotypes

Brivaracetam (BRV), a third-generation antiepileptic drug (AED), is primarily metabolized through amidase hydrolysis and CYP2C19-mediated hydroxylation in vivo. This study utilized physiologically based pharmacokinetic (PBPK) modeling to explore the pharmacokinetics of BRV and drug interactions between BRV and rifampin (RIF), a CYP2C19 inducer, based on CYP2C19 genetic polymorphisms. A PBPK model of BRV was developed in the general population and in individuals with different CYP2C19 phenotypes by adjusting catalytic rate constants (k_cat), and the model was validated with observed clinical data. The model was then extrapolated to predict BRV steady-state plasma concentration in individuals with different CYP2C19 phenotypes, with or without coadministration of RIF. The developed model adequately described BRV exposure in the abovementioned populations. The predicted steady-state area under the curve (AUC_τ-ss) increases by 20% in heterozygous extensive metabolizers (hEMs) and 55% in poor metabolizers (PMs), compared to homozygous extensive metabolizer (EMs). When coadministered with RIF, the model predicted the most significant magnitude of drug-drug interaction (DDI) in EMs, while the exposure change of BRV was minimal in PMs. Referencing the recommended concentration for therapeutic drug monitoring (TDM), we concluded that the current clinical maintenance dose of BRV is acceptable regardless of CYP2C19 polymorphisms and coadministration with RIF.

Individualizing doses of antiepileptic drugs

INTRODUCTION

This review aims to identify the optimal therapeutic dosage of anti-epileptic drugs in terms of efficacy and safety in patients with multiple comorbidities.

AREAS COVERED

We have analyzed changes in terms of pharmacokinetics and pharmacodynamics of Brivaracetam, Carbamazepine, Lacosamide, Lamotrigine, Levetiracetam, Topiramate, Valproate, and Zonisamide in liver disease, chronic kidney disease, and in patients admitted to intensive care unit. Our literature search covers the past 5 years. We used PubMed, Google Scholar, and EMBASE database's to support our article.

EXPERT OPINION

To ensure that the patient with seizure receives the best treatment in relation to their comorbidities, careful clinical-laboratory monitoring is necessary to maximize effectiveness while maintaining safety, especially in the case of polytherapy.

Reactive metabolites of the anticonvulsant drugs and approaches to minimize the adverse drug reaction

Several generations of antiepileptic drugs (AEDs) are available in the market for the treatment of seizures, but these are amalgamated with acute to chronic side effects. The most common side effects of AEDs are dose-related, but some are idiosyncratic adverse drug reactions (ADRs) that transpire due to the formation of reactive metabolite (RM) after the bioactivation process. Because of the adverse reactions patients usually discontinue the medication in between the treatment. The AEDs such as valproic acid, lamotrigine, phenytoin etc., can be categorized under such types because they form the RM which may prevail with life-threatening adverse effects or immune-mediated reactions. Hepatotoxicity, teratogenicity, cutaneous hypersensitivity, dizziness, addiction, serum sickness reaction, renal calculi, metabolic acidosis are associated with the metabolites of drugs such as arene oxide, N-desmethyldiazepam, 2-(1-hydroxyethyl)-2-methylsuccinimide, 2-(sulphamoy1acetyl)-phenol, E-2-en-VPA and 4-en-VPA and carbamazepine-10,11-epoxide, etc. The major toxicities are associated with the moieties that are either capable of forming RM or the functional groups may itself be too reactive prior to the metabolism. These functional groups or fragment structures are typically known as structural alerts or toxicophores. Therefore, minimizing the bioactivation potential of lead structures in the early phases of drug discovery by a modification to low-risk drug molecules is a priority for the pharmaceutical companies. Additionally, excellent potency and pharmacokinetic (PK) behaviour help in ensuring that appropriate (low dose) candidate drugs progress into the development phase. The current review discusses about RMs in the anticonvulsant drugs along with their mechanism vis-a-vis research efforts that have been taken to minimize the toxic effects of AEDs therapy.

MetaClass, a Comprehensive Classification System for Predicting the Occurrence of Metabolic Reactions Based on the MetaQSAR Database

(1) Background: Machine learning algorithms are finding fruitful applications in predicting the ADME profile of new molecules, with a particular focus on metabolism predictions. However, the development of comprehensive metabolism predictors is hampered by the lack of highly accurate metabolic resources. Hence, we recently proposed a manually curated metabolic database (MetaQSAR), the level of accuracy of which is well suited to the development of predictive models. (2) Methods: MetaQSAR was used to extract datasets to predict the metabolic reactions subdivided into major classes, classes and subclasses. The collected datasets comprised a total of 3788 first-generation metabolic reactions. Predictive models were developed by using standard random forest algorithms and sets of physicochemical, stereo-electronic and constitutional descriptors. (3) Results: The developed models showed satisfactory performance, especially for hydrolyses and conjugations, while redox reactions were predicted with greater difficulty, which was reasonable as they depend on many complex features that are not properly encoded by the included descriptors. (4) Conclusions: The generated models allowed a precise comparison of the propensity of each metabolic reaction to be predicted and the factors affecting their predictability were discussed in detail. Overall, the study led to the development of a freely downloadable global predictor, MetaClass, which correctly predicts 80% of the reported reactions, as assessed by an explorative validation analysis on an external dataset, with an overall MCC = 0.44.

Pharmacokinetic Drug-Drug Interactions among Antiepileptic Drugs, Including CBD, Drugs Used to Treat COVID-19 and Nutrients

Anti-epileptic drugs (AEDs) are an important group of drugs of several generations, ranging from the oldest phenobarbital (1912) to the most recent cenobamate (2019). Cannabidiol (CBD) is increasingly used to treat epilepsy. The outbreak of the SARS-CoV-2 pandemic in 2019 created new challenges in the effective treatment of epilepsy in COVID-19 patients. The purpose of this review is to present data from the last few years on drug–drug interactions among of AEDs, as well as AEDs with other drugs, nutrients and food. Literature data was collected mainly in PubMed, as well as google base. The most important pharmacokinetic parameters of the chosen 29 AEDs, mechanism of action and clinical application, as well as their biotransformation, are presented. We pay a special attention to the new potential interactions of the applied first-generation AEDs (carbamazepine, oxcarbazepine, phenytoin, phenobarbital and primidone), on decreased concentration of some medications (atazanavir and remdesivir), or their compositions (darunavir/cobicistat and lopinavir/ritonavir) used in the treatment of COVID-19 patients. CBD interactions with AEDs are clearly defined. In addition, nutrients, as well as diet, cause changes in pharmacokinetics of some AEDs. The understanding of the pharmacokinetic interactions of the AEDs seems to be important in effective management of epilepsy.

An update on brivaracetam for the treatment of pediatric partial epilepsy

Introduction: Brivaracetam (BRV) is an antiseizure medication (ASM), which has been approved as an adjunctive treatment in adults and pediatric patients aged four years and older with focal onset seizures. It is a second-generation levetiracetam (LEV) derivative, sharing the same mechanism of action, binding synaptic vesicles 2A (SV2A). BRV shows higher binding affinity and selectivity and higher brain permeability than LEV.Areas covered: This article reviews randomized controlled trials, retrospective and prospective studies published up to December 2020, searched in electronic databases MEDLINE, EMBASE and the Clinical Trial Database and provide an overview of efficacy, safety and tolerability of BRV in pediatric patients with partial epilepsy. Furthermore, the authors provide their expert opinion on the drug and give their future perspectives.Expert opinion: The analysis of the literature data has demonstrated the safety and efficacy of BRV in pediatric patients, with more evidence in children aged 4 to 16 years with an onset of focal seizures. However, a positive response was also achieved in patients affected by some encephalopathic epilepsies. Comparative efficacy studies between BRV and other ASMs, in addition to well-designed RCTs that include larger pediatric populations are needed to better define the role and potentiality of this ASM.

Potential role of brivaracetam in pediatric epilepsy

Brivaracetam (BRV) is a new antiseizure medication (ASM) that is currently approved for adjunctive treatment in patients with focal onset seizures. Similarly to levetiracetam (LEV), BRV works by binding SV2A vesicles with a high affinity and a linear pharmacokinetic profile. Retrospective studies and randomized clinical trials have already proven the efficacy of BRV, even in patients who failed treatment with LEV. Most studies about the efficacy and tolerability conducted so far were performed in adult cohorts, whereas few studies have been performed in children; however, BRV was proven to be a useful ASM for pediatric focal epilepsies, with fewer studies and conflicting results among patients with generalized epilepsies and epileptic syndromes. Retention rates were high in the cohorts analyzed, and no serious treatment-emergent adverse events were reported in the majority of patients, with somnolence, drowsiness, irritability, aggression, and decreased appetite being the most frequently reported side effects. Although there are few original papers published on the subject so far, the analysis of the literature data demonstrated the efficacy and safety of BRV in pediatric patients, with more evidence for children aged 4-16 years with an onset of focal seizures. However, a positive response was also achieved in patients affected by encephalopathic epilepsies (eg, Jeavons' epilepsy, Dravet syndrome, Lennox-Gastaut syndrome, and juvenile myoclonic epilepsy), and ongoing studies are now testing BRV in order to widen its application to other forms of epilepsy and to test its effectiveness when used in monotherapy. This review aims to provide a comprehensive analysis of the literature surrounding the efficacy and tolerability of BRV for pediatric patients.

Brivaracetam for the treatment of focal-onset seizures: pharmacokinetic and pharmacodynamic evaluations

INTRODUCTION

The goal of pharmacologic therapy with antiseizure medications (ASMs) is to achieve a seizure-free state with minimal side effects. About one third of patients treated with available ASMs continue to experience uncontrolled seizures. There is still need for new ASMs with enhanced effectiveness and tolerability.

AREAS COVERED

The present manuscript is based on an extensive Internet and PubMed search from 1999 to 2020. It is focused on the clinical and pharmacological properties of brivaracetam (BRV) in the treatment of epilepsy.

EXPERT OPINION

BRV is approved as add-on or monotherapy (in US) for the treatment of focal-onset seizures with or without secondary generalization. BRV is a high affinity synaptic vesicle glycoprotein 2A ligand, with 15-30-fold higher affinity than levetiracetam. The selectivity of BRV may be associated with fewer clinical adverse effects. BRV shares many of the pharmacokinetic characteristics of an ideal ASMs. Additionally, BRV has a low potential for clinically relevant drug-drug interactions. Its pharmacokinetic profile makes BRV a promising agent for the treatment of status epilepticus (SE). Although BRV is not approved for the treatment of SE, it has demonstrated promising preliminary results. Further studies are needed to explore the efficacy and tolerability of BRV in SE.

Development and Validation of an UHPLC-MS/MS Assay for the Therapeutic Monitoring of Brivaracetam Plasma Concentrations in Patients with Epilepsy

BACKGROUND

Brivaracetam is an antiepileptic drug used as an add-on therapy for partial-onset seizures in subjects aged 4 years and older. Owing to potential drug interactions and intersubject variability in plasma concentrations, therapeutic monitoring for brivaracetam may be useful. The aim of this study was to develop a simplified method for measuring brivaracetam plasma concentrations applicable to therapeutic drug monitoring in epilepsy.

METHODS

An ultra high-pressure liquid chromatography-tandem mass spectrometry method was developed and validated according to current guidelines for bioanalytical methods. Sample preparation (100 µL) involved only a simple precipitation step by acetonitrile. Brivaracetam-d7 was used as internal standard. The chromatographic analysis was performed by a Synergi Fusion column using 0.1% formic acid in water/acetonitrile as a binary gradient mobile phase, at a flow rate of 0.3 mL/min. Both brivaracetam and the internal standard eluted at 1.01 minutes. This method was applied to measure trough and 1-hour postmorning dose brivaracetam plasma concentrations of 11 patients with epilepsy.

RESULTS

The method was validated over a concentration range of 0.10-10 mcg/mL. The mean recovery was 95%. Both intra- and inter-assay imprecision and inaccuracy were <15% for all quality control samples. The lower limit of quantitation and detection was 0.10 and 0.05 mcg/mL, respectively. No interferences or carry-over was observed. Median (25%-75% quartiles) trough and 1-hour postdosing brivaracetam plasma concentrations were 0.61 mcg/mL (0.47-0.83 mcg/mL) and 1.55 mcg/mL (1.24-2.12 mcg/mL), respectively, at a median dose of 80 mg/d (50-150 mg/d). Large, up to 8-fold, intrasubject fluctuations of brivaracetam concentrations between trough and 1-hour postdosing were observed.

CONCLUSIONS

The present assay is faster and simpler than previously published analytical reports for brivaracetam in human plasma and is suitable for therapeutic drug monitoring.

Levetiracetam and brivaracetam: a review of evidence from clinical trials and clinical experience

Until the early 1990s, a limited number of antiepileptic drugs (AEDs) were available. Since then, a large variety of new AEDs have been developed and introduced, several of them offering new modes of action. One of these new AED families is described and reviewed in this article. Levetiracetam (LEV) and brivaracetam (BRV) are pyrrolidone derivate compounds binding at the presynaptic SV2A receptor site and are thus representative of AEDs with a unique mode of action. LEV was extensively investigated in randomized controlled trials and has a very promising efficacy both in focal and generalized epilepsies. Its pharmacokinetic profile is favorable and LEV does not undergo clinically relevant interactions. Adverse reactions comprise mainly asthenia, somnolence, and behavioral symptoms. It has now been established as a first-line antiepileptic drug. BRV has been recently introduced as an adjunct antiepileptic drug in focal epilepsy with a similarly promising pharmacokinetic profile and possibly increased tolerability concerning psychiatric adverse events. This review summarizes the essential preclinical and clinical data of LEV and BRV that is currently available and includes the experiences at a large tertiary referral epilepsy center.

Brivaracetam: a newly approved medication for epilepsy

Brivaracetam (BRV) in both the USA and EU was developed as a novel molecule for the adjunctive treatment of partial-onset (focal) seizures in patients ≥16 years of age and as of September 2017 was approved for use as monotherapy in the USA uniquely as an antiseizure medication that may be prescribed without a dose finding uptitration. This article reviews BRV's pharmacology, efficacy, safety and adverse event profiles, along with the relevant and noted regulatory hurdles in the USA and the EU. Available postmarketing data will also be summarized. Approximately 3000 patients were studied over about 9 years in the clinical trial program illustrating that BRV has efficacy at 50–200 mg/day with an acceptable adverse event profile.

Brivaracetam efficacy and safety in focal epilepsy

Introduction: Brivaracetam (BRV) is an analog of levetiracetam (LEV) with 15-30 times greater affinity to SV2A and greater brain permeability than LEV. These properties have stimulated interest in its clinical trial data and post-marketing experience. Areas covered: The authors provide a background on epilepsy and its treatment, discuss the racetam family of antiepileptic drugs to which BRV belongs, and then discuss BRV properties and its efficacy and tolerability in the treatment of epilepsy. Expert opinion: While preclinical data suggest a broad spectrum of efficacy, BRV is only approved for focal epilepsy. The recommended starting dose is 100 mg per day, but in the absence of urgency, it may be prudent to start at 50 mg per day, considered the lowest effective dose. There was no added benefit when BRV was used adjunctively with LEV in clinical trials. However, post-marketing data suggest that some patients may experience improved seizure control when switching from LEV. Behavioral adverse effects seemed less common than with LEV, and most patients switched to BRV after experiencing behavioral adverse effects on LEV reported improvement. Prior or anticipated intolerability to LEV is the strongest indication for BRV in clinical practice.

Brivaracetam in the treatment of epilepsy: a review of clinical trial data

Brivaracetam (BRV), an analog of levetiracetam (LEV), was discovered during a target-based rational drug discovery program that aimed to identify potent synaptic vesicle protein 2A (SV2A) ligands. Among the 12,000 compounds screened in vitro, BRV was found to have 15-30 times greater affinity for SV2A and faster brain permeability than LEV. Although preclinical and post-marketing studies suggest broad spectrum of efficacy, BRV is currently only approved as monotherapy and adjunctive therapy of focal-onset seizures in patients age 4 years and older. This review examines the use of BRV as add-on (5-200 mg/day) therapy for epilepsy with a particular emphasis on the six regulatory randomized clinical trialsinvolving 2399 participants. Participants receiving BRV add-on at doses of 50-200 mg/day were more likely to experience a 50% or greater reduction in seizure frequency (pooled risk ratio [RR]) 1.79 with 95% CI of 1.51-2.12) than those receiving placebo. Participants receiving BRV were also more likely to attain seizure freedom (57 [3.3%] vs 4 [0.5%]; RR 4.74, 95% CI 2.00-11.25) than those receiving placebo. In addition, BRV demonstrated a favorable safety profile similar to placebo across all BRV doses. Treatment emergent adverse events significantly associated with BRV were irritability, fatigue, somnolence, and dizziness. Post-hoc analysis of regulatory trials, post-marketing studies, and indirect comparison meta-analyses demonstrated equivalent efficacy and better tolerability of BRV when compared to other antiseizure drugs. Further, these studies appear to suggest that behavioral adverse events are likely to be less frequent and less severe with BRV than LEV. Therefore, switching to BRV may be considered for patients who have seizure control with LEV, but who cannot tolerate its behavioral adverse effects. In this setting, immediate switch from LEV to BRV at a 10:1-15:1 ratio without titration is feasible. Further research is needed to examine the long-term tolerability and efficacy of BRV as well as its role in the treatment of other types of epilepsies, particularly dementia-related epilepsy and brain tumor-related epilepsy.

Pharmacokinetics and Drug Interaction of Antiepileptic Drugs in Children and Adolescents

Selecting the most appropriate antiepileptic drug (AED) or combination of drugs for each patient and identifying the most suitable therapeutic regimen for their needs is increasingly challenging, especially among pediatric populations. In fact, the pharmacokinetics of several drugs vary widely in children with epilepsy because of age-related factors, which can influence the absorption, distribution, metabolism, and elimination of the pharmacological agent. In addition, individual factors, such as seizure type, associated comorbidities, individual pharmacokinetics, and potential drug interactions, may contribute to large fluctuations in serum drug concentrations and, therefore, clinical response. Therapeutic drug concentration monitoring (TDM) is an essential tool to deal with this complexity, enabling the definition of individual therapeutic concentrations and adaptive control of dosing to minimize drug interactions and prevent loss of efficacy or toxicity. Moreover, pharmacokinetic/pharmacodynamic modelling integrated with dashboard systems have recently been tested in antiepileptic therapy, although more clinical trials are required to support their use in clinical practice. We review the mechanism of action, pharmacokinetics, drug-drug interactions, and safety/tolerability profiles of the main AEDs currently used in children and adolescents, paying particular regard to issues of relevance when treating this patient population. Indications for TDM are provided for each AED as useful support to the clinical management of pediatric patients with epilepsy by optimizing pharmacological therapy.

Off-line solid phase extraction and liquid chromatography-tandem mass spectrometry method for the quantitation of brivaracetam acid metabolites: Method validation and application to in vitro metabolism assays

Brivaracetam (BRV) is a new high affinity synaptic vesicle protein 2A ligand recently approved for adults with partial-onset seizures. As a support to in vitro metabolism assays, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method coupled to off-line solid phase extraction (SPE) was developed to quantify BRV acid metabolites, that is, BRV-AC (carboxylic derivative derived from BRV hydrolysis) and BRV-OHAC (corresponding to hydroxylated BRV-AC). The method was validated for various incubates (liver and kidney tissue homogenates and blood, all from humans) and applied to in vitro metabolism assays. The analytes were isolated from buffered samples using ISOLUTE C8 96-well SPE plates. Chromatographic separation was achieved on a Waters Atlantis T3 C18 analytical column (2.1 mm × 50 mm, 5 μm) with detection accomplished using a Waters Premier tandem mass spectrometer in positive ion electrospray and multiple reaction monitoring (MRM) mode. The standard curves, which ranged from 1.00 to 200 ng/mL for BRV-AC, BRV-OHAC, were fitted to a 1/x² weighted linear regression model. The intra-assay precision and inter-assay precision (expressed as coefficient of variation -%CV) were <8.5%, and the assay accuracy (deviation - %Dev) was within ±7.1% for the different matrices. This accurate, precise, and selective SPE/LC-MS/MS method has been successfully applied to in vitro assays aimed at characterizing the kinetics of BRV hydrolysis. BRV was found to be a better substrate for hydrolysis than its hydroxylated metabolite BRV-OH. BRV hydrolysis was detected in blood, liver and kidneys, demonstrating the broad distribution of the enzyme catalyzing the reaction.

A review of the pharmacology and clinical efficacy of brivaracetam

Brivaracetam (BRV; Briviact) is a new antiepileptic drug (AED) approved for adjunctive treatment of focal (partial-onset) seizures in adults. BRV is a selective, high-affinity ligand for synaptic vesicle 2A (SV2A) with 15- to 30-fold higher affinity than levetiracetam, the first AED acting on SV2A. It has high lipid solubility and rapid brain penetration, with engagement of the target molecule, SV2A, within minutes of administration. BRV has potent broad-spectrum antiepileptic activity in animal models. Phase I studies indicated BRV was well tolerated and showed a favorable pharmacokinetic profile over a wide dose range following single (10–1,000 mg) and multiple (200–800 mg/day) oral dosing. Three pivotal Phase III studies have demonstrated promising efficacy and a good safety and tolerability profile across doses of 50–200 mg/day in the adjunctive treatment of refractory focal seizures. Long-term data indicate that the response to BRV is sustained, with good tolerability and retention rate. BRV is highly effective in patients experiencing secondarily generalized tonic–clonic seizures. Safety data to date suggest a favorable psychiatric adverse effect profile in controlled studies, although limited postmarketing data are available. BRV is easy to use, with no titration and little drug–drug interaction. It can be initiated at target dose with no titration. Efficacy is seen on day 1 of oral use in a significant percentage of patients. Intravenous administration in a 2-minute bolus and 15-minute infusion is well tolerated. Here, we review the pharmacology, pharmacokinetics, and clinical data of BRV.

Brivaracetam: a novel antiepileptic drug for focal-onset seizures

Brivaracetam (BRV), the n-propyl analogue of levetiracetam (LEV), is the latest antiepileptic drug (AED) to be licensed in Europe and the USA for the adjunctive treatment of focal-onset seizures with or without secondary generalization in patients aged 16 years or older. Like LEV, BRV binds to synaptic vesicle protein 2A (SV2A), but BRV has more selective binding and a 15- to 30-fold higher binding affinity than LEV. BRV is more effective than LEV in slowing synaptic vesicle mobilization and the two AEDs may act at different binding sites or interact with different conformational states of the SV2A protein. In animal models, BRV provides protection against focal and secondary generalized seizures and has significant anticonvulsant effects in genetic models of epilepsy. The drug undergoes first-order pharmacokinetics with an elimination half-life of 7-8 h. Although BRV is metabolized extensively, the main circulating compound is unchanged BRV. Around 95% of metabolites undergo renal elimination. No dose reduction is required in renal impairment, but it is recommended that the daily dose is reduced by one-third in hepatic dysfunction that may prolong half-life. BRV has a low potential for drug interactions. The efficacy and tolerability of adjunctive BRV in adults with focal-onset seizures have been explored in six randomized, placebo-controlled studies. These showed significant efficacy outcomes for doses of 50-200 mg/day. The most common adverse events reported were headache, somnolence, dizziness, fatigue and nausea. Patients who develop psychiatric symptoms with LEV appear to be at risk of similar side effects with BRV, although preliminary data suggest that these issues are likely to be less frequent and perhaps less severe. As with all AEDs, a low starting dose and slow titration schedule help to minimize side effects and optimize seizure control and thereby quality of life.

The Pharmacology and Toxicology of Third-Generation Anticonvulsant Drugs

Epilepsy is a neurologic disorder affecting approximately 50 million people worldwide, or about 0.7% of the population [1]. Thus, the use of anticonvulsant drugs in the treatment of epilepsy is common and widespread. There are three generations of anticonvulsant drugs, categorized by the year in which they were developed and released. The aim of this review is to discuss the pharmacokinetics, drug-drug interactions, and adverse events of the third generation of anticonvulsant drugs. Where available, overdose data will be included. The pharmacokinetic properties of third-generation anticonvulsant drugs include relatively fewer drug-drug interactions, as well as several unique and life-threatening adverse events. Overdose data are limited, so thorough review of adverse events and knowledge of drug mechanism will guide expectant management of future overdose cases. Reporting of these cases as they occur will be necessary to further clarify toxicity of these drugs.

Evaluation of brivaracetam: a new drug to treat epilepsy

INTRODUCTION

High prevalence of therapy-resistant epilepsy demands development of anticonvulsants with new mechanisms of action. Brivaracetam is an analogue of levetiracetam which binds to the synaptic vesicle protein 2A (SV2A) and decreases release of excitatory neurotransmitters. Areas covered: Relevant published studies were searched for by predefined strategy in MEDLINE, EBSCO and SCINDEKS electronic databases. Brivaracetam is effective as adjunctive therapy for uncontrolled partial-onset seizures with or without secondary generalization in patients 16 years and older with epilepsy. It reduces baseline-adjusted focal seizure frequency per week from 7.3 to 12.8% over placebo. Adverse events rate in patients with brivaracetam is not higher than in patients with placebo. Expert opinion: Brivaracetam is an important step forward in the treatment of therapy-resistant partial-onset seizures with or without secondary generalization. Its development was systematic and targeted. Due to its efficacy and excellent safety profile, it is likely that brivaracetam will be often prescribed. In future, efficacy and safety of brivaracetam should be tested in monotherapy settings and also in the first-line therapy of partial-onset seizures.

Brivaracetam: An Adjunctive Treatment for Partial-Onset Seizures

Brivaracetam is an analogue of levetiracetam that is Food and Drug Administration-approved for adjunctive treatment of partial-onset seizures in patients 16 years and older. In placebo-controlled trials adjunct brivaracetam demonstrated efficacy in reducing the frequency of seizures. The most commonly reported adverse effects are somnolence, dizziness, and fatigue. Clinical trials have evaluated brivaracetam for safety and efficacy in adjunctive treatment of partial-onset seizures in patients 16 years and older for up to 16 weeks. Brivaracetam's mechanism is similar to that of levetiracetam but with greater receptor binding affinity on synaptic vesicle protein 2A and inhibitory effects on sodium channels. Clinically significant differences between these agents are undetermined. Brivaracetam is available as oral tablets, oral solution, and intravenous solution. The Food and Drug Administration-approved dose is 50 mg twice daily, and titration is not required. Brivaracetam does not need dose adjustment for renal impairment and has minimal drug-drug interactions. Current limitations of brivaracetam include lack of head-to-head trials, limited long-term safety and efficacy data, and cost. Overall, brivaracetam is a viable adjunct therapeutic option for refractory partial-onset seizures in those who have failed conventional therapies.

Brivaracetam population pharmacokinetics in children with epilepsy aged 1 month to 16 years

Purpose

The aims of the study were to develop a population pharmacokinetic model of orally administered brivaracetam in paediatric patients and to provide dosing suggestions.

Methods

Analysis included 600 brivaracetam plasma concentrations from a phase 2a study (NCT00422422; N01263) in 96 paediatric patients with epilepsy aged 1 month to 16 years, taking one to three concomitant antiepileptic drugs (AEDs). Pharmacokinetic analysis was performed using non-linear mixed effects modelling, and a stepwise covariate search was used to determine factors influencing brivaracetam clearance. Simulations were performed to investigate dosing regimens.

Results

The final model consisted of first-order absorption, single compartment distribution and first-order elimination components with allometric scaling of clearance and volume using lean body weight and fixed allometric exponents. Co-administration with phenobarbital or carbamazepine was associated with a 29% (95%CI 17%/39%) and 32% (22%/42%) decrease in exposure, respectively. Co-administration with valproate was associated with an 11% (1%/23%) increase in exposure. Simulations demonstrated that the majority of children were predicted to have an exposure similar to that in adults, using an age-independent dosing regimen of 2.0 mg/kg bid with a maximum of 100 mg bid for body weight >50 kg.

Conclusions

A paediatric dose adaptation of 2.0 mg/kg twice daily with a maximum of 100 mg twice daily for body weight >50 kg is predicted to ensure steady-state plasma concentrations in the same range as in adult patients receiving 100 mg twice daily (highest recommended dose). Data suggest no need to change brivaracetam dosing when used concomitantly with carbamazepine, phenobarbital or valproate.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-017-2230-6) contains supplementary material, which is available to authorized users.

Progress report on new antiepileptic drugs: A summary of the Thirteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XIII)

The Thirteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XIII) took place in Madrid, Spain, on June 26-29, 2016, and was attended by >200 delegates from 31 countries. The present Progress Report provides an update on experimental and clinical results for drugs presented at the Conference. Compounds for which summary data are presented include an AED approved in 2016 (brivaracetam), 12 drugs in phase I-III clinical development (adenosine, allopregnanolone, bumetanide, cannabidiol, cannabidivarin, 2-deoxy-d-glucose, everolimus, fenfluramine, huperzine A, minocycline, SAGE-217, and valnoctamide) and 6 compounds or classes of compounds for which only preclinical data are available (bumetanide derivatives, sec-butylpropylacetamide, FV-082, 1OP-2198, NAX 810-2, and SAGE-689). Overall, the results presented at the Conference show that considerable efforts are ongoing into discovery and development of AEDs with potentially improved therapeutic profiles compared with existing agents. Many of the drugs discussed in this report show innovative mechanisms of action and many have shown promising results in patients with pharmacoresistant epilepsies, including previously neglected rare and severe epilepsy syndromes.

Pharmacokinetic interaction of brivaracetam on carbamazepine in adult patients with epilepsy, with and without valproate co-administration

OBJECTIVE

This Phase I, open-label, dose-escalation study investigated the effects of steady-state brivaracetam on the pharmacokinetics of carbamazepine in patients with epilepsy, with and without valproate co-administration. Valproate and brivaracetam inhibit epoxide hydrolase and increase carbamazepine epoxide levels.

METHODS

Adult patients with epilepsy being chronically treated with carbamazepine alone (n=9) or with carbamazepine and valproate (n=9) received brivaracetam during successive 1-week periods at doses of 50mg, 100mg, 200mg, and 100mg twice daily (bid). Doses of carbamazepine and valproate must have been stable for at least 3 months. Trough plasma concentrations of carbamazepine, carbamazepine epoxide, and diol metabolites were determined on Days 1, 8, 15, 22, and 29, and at the end of study visit (ESV, 2-3weeks later).

RESULTS

Eighteen patients with median (range) age of 45 (20-62) years and body weight of 74 (59-124) kg were enrolled and completed the study. In patients treated with carbamazepine alone, brivaracetam dose-dependently increased mean trough levels of carbamazepine epoxide from 1.38μg/mL on Day 1 pre-dose to 2.16μg/mL (+57%) on Day 8 (50mg bid), 2.72μg/mL (+97%) on Day 15 (100mg bid), 3.02μg/mL (+119%) on Day 22 (200mg bid), 2.67μg/mL (+94%) on Day 29 (100mg bid), and 1.22μg/mL (-12%) at ESV, respectively. In patients on carbamazepine and valproate, carbamazepine epoxide increased from 1.98μg/mL at baseline to 2.72μg/mL (+37%), 3.70μg/mL (+87%), 4.43μg/mL (+124%), 3.11μg/mL (+57%), and 1.94μg/mL (-2%), respectively. There was no trend for change in carbamazepine, carbamazepine diol or valproate levels. Brivaracetam levels increased linearly with dose. Brivaracetam was well tolerated.

CONCLUSIONS

Carbamazepine epoxide plasma concentrations were approximately doubled by brivaracetam 100 or 200mg bid. Data are consistent with a dose-dependent and reversible inhibition of epoxide hydrolase by brivaracetam. Carbamazepine epoxide was approximately 0.7μg/mL higher in presence of valproate. There is no need to limit brivaracetam dosing when used concomitantly with carbamazepine.

Brivaracetam as adjunctive therapy for the treatment of partial-onset seizures in patients with epilepsy: the current evidence base

Brivaracetam (BRV) is a novel antiepileptic drug recently licensed for the treatment of partial epilepsy in adults and adolescents over 16 years old. Like levetiracetam (LEV), it is a ligand of the synaptic vesicle protein SV2A. BRV has been shown in animal models and in studies using human brain slices to have a higher SV2A affinity and faster penetration into the brain. Its efficacy and safety have been shown in several randomized, controlled studies. The recommended initial dose is 50-100 mg, divided into two daily doses. Up-titration to a 200 mg daily dose is possible. Dizziness and somnolence are frequent side effects. There are some hints that BRV may be less frequently associated with behavioural adverse events than LEV. Long-term efficacy and safety and BRV use in special patient groups have to be assessed in the future.

Brivaracetam: A Review in Partial-Onset (Focal) Seizures in Patients with Epilepsy

Brivaracetam (Briviact(®); BRIVLERA™) is a high affinity synaptic vesicle protein 2A (SV2A) ligand available orally (as a tablet or solution) or intravenously (as a bolus or infusion) in various countries worldwide, including the USA, Canada and those of the EU. It is approved as adjunctive therapy for the treatment of partial-onset seizures (POS) in adults (aged ≥18 years) [USA, EU and Canada] and adolescents (aged 16 to <18 years) [USA and EU] with epilepsy. In multinational, phase III studies in adults and adolescents (aged ≥16 years), oral brivaracetam as adjunctive therapy to other antiepileptic drugs (AEDs) was generally associated with significant median percent reductions over placebo in seizure frequency and significant improvements in the proportion of patients achieving a ≥50 % reduction in seizure frequency compared with placebo. These benefits appeared to be sustained during up to 96 months' therapy in follow-up studies. Whether administered orally or intravenously, adjunctive brivaracetam was generally well tolerated in clinical studies, with the majority of treatment-emergent adverse events (TEAEs) being mild or moderate in intensity. In the absence of head-to-head studies, definitive conclusions on the comparative efficacy and tolerability of brivaracetam versus newer AEDs are not yet possible. In the meantime, brivaracetam extends the options currently available for the treatment of POS in patients aged ≥16 years with epilepsy.