What is the promise of new antiepileptic drugs in status epilepticus? Focus on brivaracetam, carisbamate, lacosamide, NS-1209, and topiramate

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.

Lacosamide in status epilepticus: Systematic review of current evidence

OBJECTIVE

The intravenous formulation of lacosamide (LCM) and its good overall tolerability and safety favor the use in status epilepticus (SE). The aim of this systematic review was to identify and evaluate studies reporting on the use of LCM in SE.

METHODS

We performed a systematic literature search of electronic databases using a combined search strategy from 2008 until October 2016. Using a standardized assessment form, information on the study design, methodologic framework, data sources, efficacy, and adverse events attributed to LCM were extracted from each publication and systematically reported.

RESULTS

In total, 522 SE episodes (51.7% female) in 486 adults and 36 children and adolescents were evaluated with an overall LCM efficacy of 57%. Efficacy was comparable between use in nonconvulsive (57%; 82/145) and generalized-convulsive (61%; 30/49; p = 0.68) SE, whereas overall success rate was better in focal motor SE (92%; 34/39, p = 0.013; p < 0.001). The efficacy with later positioning of LCM decreased from 100% to 20%. The main adverse events during treatment of SE are dizziness, abnormal vision, diplopia, and ataxia. Overall, lacosamide is well tolerated and has no clinically relevant drug-drug interactions.

SIGNIFICANCE

The available data regarding the use of LCM in SE are promising, with a success rate of 57%. The strength of LCM is the lack of interaction potential and the option for intravenous use in emergency situations requiring rapid uptitration.

NS1209/SPD 502, A Novel Selective AMPA Antagonist for Stroke, Neuropathic Pain or Epilepsy? Drug Development Lessons Learned

Preclinical Research The selective AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor antagonist, NS1209 (also known as SPD 502) has been explored in several research and development campaigns since its selection as a lead drug candidate in the early 1990s by the Danish biotechnology company, NeuroSearch. The compound was successively tested in animal models of stroke, neuropathic pain and epilepsy. The preclinical data to support development for the treatment of stroke were incomplete, as the compound was administered after the stroke episode, and did not protect subcortical areas of the brain. Preclinical data for neuropathic pain and epilepsy appeared more promising, but the design of the Phase IIa studies in both indications was suboptimal, and an exploratory study in neuropathic pain, like one in refractory epilepsy gave inconclusive results. Preclinical data in pain models were much less convincing than reported by the authors in abstract and discussion sections. Due to a long preclinical sequential testing phase and insufficiently powered clinical trials, NS 1209 disappeared from the CNS development pipeline, while its patent protection exclusivity was markedly reduced due to the unfortunate slow speed in development-a phenomenon far from unusual in CNS drug discovery. NeuroSearch ceased operations as an R&D entity in 2012 and its R & D portfolio was transferred to Teva Pharmaceuticals and to a spin off, Saniona A/S. Based on an in-depth case analysis of the development of NS 1209, a number of recommendations are given to reduce chances of failure during clinical development of neuropathic pain compounds and, more generally, of CNS compounds. Drug Dev Res 78 : 75-80, 2017. © 2017 Wiley Periodicals, Inc.

Brivaracetam in the treatment of focal and idiopathic generalized epilepsies and of status epilepticus

Brivaracetam is the latest approved antiepileptic drug in focal epilepsy and exhibits high affinity as SV2A-ligand. More than two thousand patients have received brivaracetam within randomized placebo-controlled trials. Significant median seizure reduction rates of 30.5% to 53.1% for 50 mg/d, 32.5% to 37.2% for 100 mg/d and 35.6% for 200 mg/d were reported. Likewise, 50% responder rates were 32.7% to 55.8% for 50 mg/d, 36% to 38.9% for 100 mg/d and 37.8% for 200 mg/d. Overall, brivaracetam is well tolerated. The main adverse events are fatigue, dizziness, and somnolence. Immediate switch from levetiracetam to brivaracetam at a conversion ratio between 10:1 to 15:1 is feasible, and might alleviate the behavioral side effects associated with levetiracetam. Brivaracetam has the potential to perform as an important, possibly broad-spectrum AED, initially in patients with drug-refractory epilepsies. Its intravenous formulation may be a new and desirable alternative for status epilepticus, but there is so far no experience in these patients.

Single versus combinatorial therapies in status epilepticus: Novel data from preclinical models

Drug-refractory status epilepticus (RSE) is a major medical emergency with a mortality of up to 40% and the risk of severe long-term consequences. The mechanisms involved in RSE are incompletely understood. Animal models are important in developing treatment strategies for more effective termination of SE and prevention of its long-term outcomes. The pilocarpine and lithium-pilocarpine rat models are widely used in this respect. In these models, resistance to diazepam and other antiseizure drugs (ASDs) develops during SE so that an SE that is longer than 30 min is difficult to suppress. Furthermore, because all ASDs used in SE treatment are much more rapidly eliminated by rodents than by humans, SE recurs several hours after ASD treatment. Long-term consequences include hippocampal damage, behavioral alterations, and epilepsy with spontaneous recurrent seizures. In this review, different rational polytherapies for SE, which are more effective than monotherapies, are discussed, including a novel polytherapy recently developed by our group. Based on data from diverse seizure models, we hypothesized that cholinergic mechanisms are involved in the mechanisms underlying ASD resistance of SE. We, therefore, developed an intravenous drug cocktail, consisting of diazepam, phenobarbital, and the anticholinergic scopolamine. This drug combination irreversibly terminated SE when administered 60, 90, or 120 min after SE onset. The efficacy of this cocktail in terminating SE was comparable with the previously reported efficacy of polytherapies with the glutamate receptor antagonist ketamine. Furthermore, when injected 60 min after SE onset, the scopolamine-containing cocktail prevented development of epilepsy and hippocampal neurodegeneration, which was not observed with high doses of diazepam or a combination of phenobarbital and diazepam. Our data add to the existing preclinical evidence that rational polytherapy can be more effective than monotherapy in the treatment of SE and that combinatorial therapy may offer a clinically useful option for the treatment of RSE. This article is part of a Special Issue entitled "Status Epilepticus".

Emerging drugs for focal epilepsy

INTRODUCTION

Epilepsy is one of the most common serious neurological disorders in adults, affecting approximately 50 million people worldwide at a total annual cost, in Europe, of approximately 15.5 billion Euros.

AREAS COVERED

The present paper reviews current compounds in preclinical and clinical development for the treatment of focal epilepsies, namely, ganaxolone, perampanel, BGG-492, NS-1209, belnacasan, YKP-3089, brivaracetam. New formulations in clinical development, such as intranasal midazolam, diazepam auto-injection, a new formulation of valproic acid using drug targeting technology and controlled release formulations for topiramate and pregabalin, are also discussed.

EXPERT OPINION

During the last 30 years, antiepileptic drugs (AEDs) development have been based on specific assumptions regarding the neurobiology of epilepsy but all marketed drugs have not changed the proportion of drug refractory patients. AEDs in development with new mechanisms of actions, especially anti-inflammatory agents, are of interest. AMPA blockers, especially water-soluble ones, being suitable for parenteral formulation, can be of relevance in treating refractory status epilepticus, a major life-threatening complication. Finally, new formulations, especially those adopting drug targeting technologies are promising in order to maximize the efficacy with very limited adverse effects.

What's New in the Medical Management of Pediatric Epilepsy?

Epilepsy affects approximately 45 per 100,000 children per year. While many cases respond favorably to antiepileptic therapy, approximately 20% will prove to be medically intractable. This paper reviews some of the recently identified important metabolic and autoimmune etiologies for which there are specific therapies. Additionally, newer antiepileptic medications, including rufinamide, lacosamide, retigabine, eslicarbazepine and brivaracetam and newer dietary options, including the modified Atkins diet and low-glycemic index diet are discussed.

Revisiting AMPA receptors as an antiepileptic drug target

In the 1990s there was intense interest in ionotropic glutamate receptors as therapeutic targets for diverse neurological disorders, including epilepsy. NMDA receptors were thought to play a key role in the generation of seizures, leading to clinical studies of NMDA receptor blocking drugs in epilepsy. Disappointing results dampened enthusiasm for ionotropic glutamate receptors as a therapeutic target. Eventually it became appreciated that another type of ionotropic glutamate receptor, the AMPA receptor, is actually the predominant mediator of excitatory neurotransmission in the central nervous system and moreover that AMPA receptors are critical to the generation and spread of epileptic activity. As drugs became available that selectively target AMPA receptors, it was possible to demonstrate that AMPA receptor antagonists have powerful antiseizure activity in in vitro and in vivo models. A decade later, promising clinical studies with AMPA receptor antagonists, including the potent noncompetitive antagonist perampanel, are once again focusing attention on AMPA receptors as a drug target for epilepsy therapy.

Proof of concept trials in bipolar disorder and major depressive disorder: a translational perspective in the search for improved treatments

A better understanding of the neurobiology of mood disorders, informed by preclinical research and bi-directionally translated to clinical research, is critical for the future development of new and effective treatments. Recently, diverse new targets/compounds have been specifically tested in preclinical models and in proof-of-concept studies, with potential relevance as treatments for mood disorders. Most of the evidence comes from case reports, case series, or controlled proof-of-concept studies, some with small sample sizes. These include (1) the opioid neuropeptide system, (2) the purinergic system, (3) the glutamatergic system, (4) the tachykinin neuropeptide system, (5) the cholinergic system (muscarinic system), and (6) intracellular signaling pathways. These targets may be of substantial interest in defining future directions in drug development, as well as in developing the next generation of therapeutic agents for the treatment of mood disorders. Overall, further study of these and similar drugs may lead to a better understanding of relevant and clinically useful drug targets in the treatment of these devastating illnesses.

Difficulties in Treatment and Management of Epilepsy and Challenges in New Drug Development

Epilepsy is a serious neurological disorder that affects around 50 million people worldwide. Almost 30% of epileptic patients suffer from pharmacoresistance, which is associated with social isolation, dependent behaviour, low marriage rates, unemployment, psychological issues and reduced quality of life. Currently available antiepileptic drugs have a limited efficacy, and their negative properties limit their use and cause difficulties in patient management. Antiepileptic drugs can provide only symptomatic relief as these drugs suppress seizures but do not have ability to cure epileptogenesis. The long term use of antiepileptic drugs is limited due to their adverse effects, withdrawal symptoms, deleterious interactions with other drugs and economic burden, especially in developing countries. Furthermore, some of the available antiepileptic drugs may even potentiate certain type of seizures. Several in vivo and in vitro animal models have been proposed and many new antiepileptic drugs have been marketed recently, but large numbers of patients are still pharmacoresistant. This review will highlight the difficulties in treatment and management of epilepsy and the limitations of available antiepileptic drugs and animal seizure models.