An assessment of rufinamide as an anti-epileptic in comparison with other drugs in clinical development

Pharmacological diversity amongst approved and emerging antiseizure medications for the treatment of developmental and epileptic encephalopathies

Developmental and epileptic encephalopathies (DEEs) are rare neurodevelopmental disorders characterised by early-onset and often intractable seizures and developmental delay/regression, and include Dravet syndrome and Lennox-Gastaut syndrome (LGS). Rufinamide, fenfluramine, stiripentol, cannabidiol and ganaxolone are antiseizure medications (ASMs) with diverse mechanisms of action that have been approved for treating specific DEEs. Rufinamide is thought to suppress neuronal hyperexcitability by preventing the functional recycling of voltage-gated sodium channels from the inactivated to resting state. It is licensed for adjunctive treatment of seizures associated with LGS. Fenfluramine increases extracellular serotonin levels and may reduce seizures via activation of specific serotonin receptors and positive modulation of the sigma-1 receptor. Fenfluramine is licensed for adjunctive treatment of seizures associated with Dravet syndrome and LGS. Stiripentol is a positive allosteric modulator of type-A gamma-aminobutyric acid (GABAA) receptors. As a broad-spectrum inhibitor of cytochrome P450 enzymes, its antiseizure effects may additionally arise through pharmacokinetic interactions with co-administered ASMs. Stiripentol is licensed for treating seizures associated with Dravet syndrome in patients taking clobazam and/or valproate. The mechanism(s) of action of cannabidiol remains largely unclear although multiple targets have been proposed, including transient receptor potential vanilloid 1, G protein-coupled receptor 55 and equilibrative nucleoside transporter 1. Cannabidiol is licensed as adjunctive treatment in conjunction with clobazam for seizures associated with Dravet syndrome and LGS, and as adjunctive treatment of seizures associated with tuberous sclerosis complex. Like stiripentol, ganaxolone is a positive allosteric modulator at GABAA receptors. It has recently been licensed in the USA for the treatment of seizures associated with cyclin-dependent kinase-like 5 deficiency disorder. Greater understanding of the causes of DEEs has driven research into the potential use of other novel and repurposed agents. Putative ASMs currently in clinical development for use in DEEs include soticlestat, carisbamate, verapamil, radiprodil, clemizole and lorcaserin.

Real-world data on rufinamide treatment in patients with Lennox-Gastaut syndrome: Results from a European noninterventional registry study

INTRODUCTION

Rufinamide is approved for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome (LGS) in patients aged ≥4years. The objective of this study was to provide real-world, long-term data on patients with LGS initiating rufinamide as add-on therapy and patients with LGS receiving other antiepileptic drugs (AEDs).

METHODS

A Phase IV, noninterventional, multicenter registry study was conducted in patients with LGS aged ≥4years requiring modification to any AED treatment, including initiation of add-on rufinamide therapy. Safety/tolerability was assessed by evaluating treatment-emergent adverse events (TEAEs), and efficacy was assessed using a generic seizure frequency scale.

RESULTS

A total of 111 patients from 64 sites in 8 European countries were included, of whom 64 initiated rufinamide ("rufinamide" group) and 21 did not receive rufinamide at any time during the study ("no-rufinamide" group). Mean ages were 16.1years (rufinamide) and 15.0years (no rufinamide). The median duration of follow-up was >2years (range: 1.3-46.4months). Antiepileptic drug-related TEAEs were reported for 40.6% (rufinamide) and 33.3% (no rufinamide) of patients and led to discontinuation of 7.8% and 4.8%, respectively. The most frequently reported rufinamide-related TEAEs (≥5% patients) were somnolence (7.8%) and decreased appetite (6.3%). There were no unexpected safety/tolerability findings. At month 12, the proportion of patients with improvement in all seizures ("much improved" or "very much improved") was 28.6% (12/42) for the rufinamide group and 14.3% (2/14) for the no-rufinamide group.

CONCLUSION

The study provided valuable information on LGS and its management, and evidence that rufinamide has a consistent and generally favorable safety/tolerability profile when used in routine clinical practice. CLINICALTRIALS.

GOV IDENTIFIER

NCT01991041.

Treatment of Adults with Lennox-Gastaut Syndrome: Further Analysis of Efficacy and Safety/Tolerability of Rufinamide

INTRODUCTION

Management of Lennox-Gastaut syndrome (LGS) in adulthood can be particularly challenging. Published reports describing the use of rufinamide specifically in adult patients with LGS are scarce. A post hoc subgroup analysis of data from a phase III trial was conducted to investigate the efficacy and safety/tolerability of rufinamide in adults with LGS.

METHODS

A randomized, double-blind, placebo-controlled trial was conducted in patients with LGS, aged 4 years and above. During an 84-day, double-blind treatment period, patients received either adjunctive rufinamide therapy or placebo. Efficacy and safety/tolerability were assessed in a post hoc subgroup analysis of adult patients (≥18 years). Efficacy was assessed as change from baseline in 28-day seizure frequency, 50% responder rate, and seizure freedom rate; each calculated for total seizures and drop attacks. Safety/tolerability assessments included the evaluation of adverse events (AEs).

RESULTS

Thirty-one adults aged 18-37 years with LGS received treatment with either rufinamide (n = 21) or placebo (n = 10). Three patients in the rufinamide group did not complete the trial. The median change from baseline in seizure frequency was -31.5% for rufinamide versus +22.1% for placebo (P = 0.008) for all seizures and -54.9% versus +21.7% (P = 0.002) for drop attacks. Responder rates were 33.3% for rufinamide versus 0% for placebo (P = 0.066) for all seizures and 57.1% versus 10.0% (P = 0.020) for drop attacks. No patient achieved freedom from all seizures but two rufinamide-treated patients (9.5%) became free of drop attacks. Overall, 71.4% of patients treated with rufinamide and 60.0% of patients treated with placebo experienced AEs; most commonly, somnolence (33.3% vs. 20.0%) and vomiting (19.0% vs. 0%). Most AEs were of mild or moderate intensity.

CONCLUSION

Rufinamide demonstrated favorable efficacy and was generally well tolerated when used as adjunctive treatment for adults with LGS.

FUNDING

Eisai.

The discovery of medicines for rare diseases

There is a pressing need for new medicines (new molecular entities; NMEs) for rare diseases as few of the 6800 rare diseases (according to the NIH) have approved treatments. Drug discovery strategies for the 102 orphan NMEs approved by the US FDA between 1999 and 2012 were analyzed to learn from past success: 46 NMEs were first in class; 51 were followers; and five were imaging agents. First-in-class medicines were discovered with phenotypic assays (15), target-based approaches (12) and biologic strategies (18). Identification of genetic causes in areas with more basic and translational research such as cancer and in-born errors in metabolism contributed to success regardless of discovery strategy. In conclusion, greater knowledge increases the chance of success and empirical solutions can be effective when knowledge is incomplete.

The contribution of mechanistic understanding to phenotypic screening for first-in-class medicines

The level of mechanistic understanding required for drug discovery is a central feature of most strategies. However, an understanding of mechanism is not required for regulatory approval. This paradox is particularly relevant to the role of phenotypic assays in drug discovery. A recent analysis revealed that phenotypic drug discovery strategies were more successful for first-in-class medicines, whereas target-based molecular strategies were more successful for followers (Nat. Rev. Drug Discov. 2011, 10, 507-519). The rationale for the success of phenotypic screening was the unbiased identification of the molecular mechanism of action. In this follow-up analysis, the format and mechanistic information used to establish the phenotypic assays that led to the first-in-class small-molecule new molecular entities approved by the U.S. Food and Drug Administration between 1999 and 2008 were analyzed and compared with those approved in 2012. Not surprisingly, some level of mechanistic understanding was used to select the assay formats and chemicals screened. It is concluded that mechanism takes on different connotations depending on context and perspective and that a target need not always be the exclusive definition of mechanism.

Advancing the management of childhood epilepsies

Childhood epilepsies comprise a heterogeneous group of disorders and syndromes that vary in terms of severity, prognosis and treatment requirements. Effective management requires early, accurate recognition and diagnosis, and a holistic approach that addresses each individual's medical and psychosocial needs within the context of their overall health status and quality of life. With increasing understanding of underlying aetiologies, new approaches to management and treatment are emerging. For example, genetic testing is beginning to provide a tool to aid differential diagnosis and a means of predicting predisposition to particular types of epilepsy. Despite the availability of an increasing number of antiepileptic drugs (AEDs)--due not only to the development of new AEDs, but also to changes in regulatory requirements that have facilitated clinical development--seizure control and tolerability continue to be suboptimal in many patients, and there is therefore a continuing need for new treatment strategies. Surgery and other non-pharmacological treatments (e.g. vagus nerve stimulation, ketogenic diet) are already relatively well established in paediatric epilepsy. New pharmacological treatments include generational advances on existing AEDs and AEDs with novel modes of action, and non-AED pharmacological interventions, such as immunomodulation. Emerging technologies include novel approaches allowing the delivery of medicinal agents to specific areas of the brain, and 'closed-loop' experimental devices employing algorithms that allow treatment (e.g., electrical stimulation) to be targeted both spatially and temporally. Although in early stages of development, cell-based approaches (e.g., focal targeting of adenosine augmentation) and gene therapy may also provide new treatment choices in the future.

Chemical properties of antiepileptic drugs (AEDs)

Between 1990 and 2011 the following fifteen new antiepileptic drugs (AEDs) were approved: eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, retigabine, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin, and zonisamide. These AEDs (except felbamate) offer appreciable advantages in terms of their favorable pharmacokinetics, improved tolerability and lower potential for drug interactions. All AEDs introduced after 1990 that are not second generation drugs (with the exception of vigabatrin and tiagabine) were developed empirically (sometimes serendipitously) utilizing mechanism-unbiased anticonvulsant animal models. The empirical nature of the discovery of new AEDs in the last three decades coupled with their multiple mechanisms of action explains their diverse chemical structures. The availability of old and new AEDs with various activity spectra and different tolerability profiles enables clinicians to better tailor drug choice to the characteristics of individual patients. With fifteen new AEDs having entered the market in the past 20years the antiepileptic market is crowded. Consequently, epilepsy alone is not attractive in 2011 to the pharmaceutical industry even though the clinical need of refractory epilepsy remains unmet. Due to this situation, future design of new AEDs must also have a potential in non-epileptic CNS disorders such as neuropathic pain, migraine prophylaxis and bipolar disorder or fibromyalgia as demonstrated by the sales revenues of pregabalin, topiramate and valproic acid. This review analyzes the effect that the emerging knowledge on the chemical properties of the old AEDs starting from phenobarbital (1912) has had on the design of subsequent AEDs and new therapeutics as well as the current approach to AED discovery.

How were new medicines discovered?

Preclinical strategies that are used to identify potential drug candidates include target-based screening, phenotypic screening, modification of natural substances and biologic-based approaches. To investigate whether some strategies have been more successful than others in the discovery of new drugs, we analysed the discovery strategies and the molecular mechanism of action (MMOA) for new molecular entities and new biologics that were approved by the US Food and Drug Administration between 1999 and 2008. Out of the 259 agents that were approved, 75 were first-in-class drugs with new MMOAs, and out of these, 50 (67%) were small molecules and 25 (33%) were biologics. The results also show that the contribution of phenotypic screening to the discovery of first-in-class small-molecule drugs exceeded that of target-based approaches - with 28 and 17 of these drugs coming from the two approaches, respectively - in an era in which the major focus was on target-based approaches. We postulate that a target-centric approach for first-in-class drugs, without consideration of an optimal MMOA, may contribute to the current high attrition rates and low productivity in pharmaceutical research and development.

Activation of suicidal ideation with adjunctive rufinamide in bipolar disorder

Antiepileptic drugs are effective psychotropics, especially for bipolar disorder, which leads to their use off-label in treatment-refractory cases. A recent publication suggests that rufinamide may be beneficial adjunctively for bipolar disorder with comorbid psychopathology. This report addresses two negative cases with significant psychiatric adverse effects: increased depression, agitation, and activation of suicidal ideation. These findings suggest that adjunctive rufinamide may lead to increased suicidal ideation in patients with treatment-refractory bipolar disorder. Secondary to the course of severe bipolar disorder, rufinamide cannot be specifically implicated; however, clinicians should be aware of this potential significant adverse effect and monitor high-risk patients. Further studies are required to address rufinamide treatment efficacy and severity of adverse effects in patients with bipolar disorder.

Adjunctive rufinamide in Lennox-Gastaut syndrome: a long-term, open-label extension study

OBJECTIVE

This open-label extension evaluated the long-term efficacy and tolerability of rufinamide in patients with Lennox-Gastaut syndrome (LGS) who had previously completed a 12-week double-blind study.

MATERIALS AND METHODS

In total, 124 patients (aged 4-37 years), receiving 1-3 concomitant antiepileptic drugs, were treated with rufinamide approximately 25-60 mg/kg/day. Efficacy was assessed by seizure frequency; tolerability by adverse events (AEs) and laboratory tests.

RESULTS

Overall, patients were treated with rufinamide for a median (range) of 432 (10-1149) days. Reductions in seizure frequency were observed throughout the study; during the last 12 months of treatment, 41.0% and 47.9% of patients had > or = 50% reduction in total and tonic-atonic seizure frequency, respectively. The most common AEs were vomiting (30.6%) and pyrexia (25.8%).

CONCLUSIONS

In this open-label extension, rufinamide appeared to be an effective long-term adjunctive therapy for the treatment of LGS-associated seizures in children and young adults.

A 24-week multicenter, randomized, double-blind, parallel-group, dose-ranging study of rufinamide in adults and adolescents with inadequately controlled partial seizures

OBJECTIVE

To assess the efficacy, safety, tolerability, and pharmacokinetics of adjunctive rufinamide in adults and adolescents with inadequately controlled partial seizures receiving treatment with one to three concomitant antiepileptic drugs (AEDs).

METHODS

A 24-week multicenter Phase II clinical study was conducted (n=647), comprising a 12-week prospective baseline phase and a 12-week randomized double-blind, parallel-group, five-arm (placebo and rufinamide 200, 400, 800, and 1600mg/day) treatment phase.

RESULTS

The linear trend of dose response for seizure frequency per 28 days in the double-blind treatment phase - the primary efficacy outcome measure - was statistically significant in favor of rufinamide (estimated slope=-0.049, P=0.003; minimally efficacious dose, 400mg/day). Response rates, defined as a >or=50% reduction in seizure frequency per 28 days, also revealed a significant linear trend of dose response (P=0.0019, logistic regression analysis). Adverse events were comparable between placebo and all rufinamide groups except the 1600mg/day group; no safety signals were observed.

CONCLUSIONS

These results suggest that in the dose range of 400-1600mg/day, add-on rufinamide therapy may benefit patients with inadequately controlled partial seizures and is generally well tolerated. These data also suggest that higher doses may confer additional efficacy without adversely affecting safety and tolerability.

Effectiveness and tolerability of rufinamide in children and adults with refractory epilepsy: first European experience

OBJECTIVE

The aim of the study was to explore the effectiveness and tolerability of rufinamide in a heterogeneous group of patients with refractory epilepsies in Europe, immediately after the drug became available as an orphan drug for the adjunctive treatment of Lennox-Gastaut syndrome (LGS).

METHODS

This observational study was conducted as a collection of retrospective data from multiple centers in Germany and Austria. Clinical course in patients treated with rufinamide was documented. Initial dosage and titration schedule of rufinamide were at the discretion of the treating physician according to medical need. The observation period was 12 weeks. Effectiveness was evaluated by comparing the frequency of seizures with limitations to the countability between baseline and the last 4-week period of observation.

RESULTS

The study population consisted of 45 children and 15 adults (mean age: 14.5+/-11.6 years, range: 1-50) with various severe and inadequately controlled epilepsy syndromes, that is, LGS (n=31), idiopathic generalized epilepsy syndromes (n=5), cryptogenic unclassified generalized epilepsy (n=7), and partial epilepsy (n=17). The response rate (50% reduction in countable seizures) was 46.7% (28 of 60 patients) in total; 25.0% experienced a 75% reduction in seizure frequency and 21.7% experienced a 50-75% reduction. Complete seizure control was achieved by 8.3%. The highest response rate was observed in patients with LGS (17/31, 54.8%), and the lowest in patients with partial epilepsy (4/17, 23.5%). Response rate in patients with unclassified generalized epilepsy was 42.8% (3/7 patients). A total of 67 adverse events were reported by 35 of 60 patients. The most frequently occurring adverse events were fatigue (18.3%), vomiting (13.3%), and loss of appetite (10.0%). No serious adverse events were observed.

CONCLUSIONS

These preliminary data suggest that rufinamide may be effective and well tolerated in the treatment of children and adults with various epilepsy syndromes and difficult-to-control seizures. The results of our study suggest that the efficacy of rufinamide in patients with generalized epilepsy might be comparable to that in patients with LGS, whereas rufinamide was less effective in patients with partial epilepsy.

New antiepileptic drugs that are second generation to existing antiepileptic drugs

In the last decade, 10 new antiepileptic drugs (AEDs) have been introduced that offer appreciable advantages in terms of their favourable pharmacokinetics, improved tolerability and lower potential for drug interactions. However, despite the large therapeutic range of old and new AEDs, approximately 30% of the patients with epilepsy are still not seizure free and, consequently, there is a substantial need to develop new AEDs. The new AEDs currently in development can be divided into two categories: drugs with completely new chemical structures such as lacosamide (formally harkoseride), retigabine, rufinamide and talampanel; and drugs that are derivatives or analogues of existing AEDs that can be regarded as second-generation or follow-up compounds of established AEDs. This article focuses on the second category and thus critically reviews the following second-generation compounds: eslicarbazepine acetate or BIA-2-093 and 10-hydroxy carbazepine (carbamazepine derivatives); valrocemide and NPS 1776 (isovaleramide; valproic acid derivatives); pregabalin and XP13512 (gabapentin derivatives); brivaracetam (ucb 34714) and seletracetam (ucb 44212; levetiracetam derivatives); and fluorofelbamate (a felbamate derivative). In addition, a series of valproic acid derivatives that are currently in preclinical stage has also been evaluated because some lead compounds of this series have a promising potential to become new antiepileptics and CNS drugs. For any of these follow-up compounds to become a successful second generation to an existing AED, it has to be more potent, safer and possess favourable pharmacokinetics, including low potential for pharmacokinetic and pharmacodynamic drug interactions.

Anti-epileptic drugs as possible neuroprotectants in cerebral ischemia

Many similarities exist between cerebral ischemia and epilepsy regarding brain-damaging and auto-protective mechanisms that are activated following the injurious insult. Therefore, drugs that are effective in minimizing seizure-induced brain damage may also be useful in minimizing ischemic injury. Use of such drugs in stroke victims may have important clinical and financial advantages. Therefore, the authors conducted a Medline search of studies involving the use of anti-epileptic drugs (AEDs) as possible neuroprotectants and summarize the data. Most AEDs have been tested in animal models of focal or global ischemia and some were already tested in humans, for a possible neuroprotective effect. The existing data is rather scant and insufficient but it appears that only drugs that have multiple mechanisms of action seem to have some potential in conferring a degree of neuroprotection that could be clinically applicable to stroke patients. In conclusion, some of the newer AEDs show promise as possible neuroprotectants in the setup of acute ischemic stroke but more studies are needed before clinical trials in humans could be undertaken.

An assessment of zonisamide as an anti-epileptic drug

A brief review of epilepsy as a disease, anti-epileptic drugs and methods of evaluation of anti-epileptic drugs are presented as a background for assessment of zonisamide, which has been approved by the FDA as add-on therapy for the treatment of partial seizures with or without secondary generalisation in adults. Chemically, zonisamide is classified as a sulphonamide and is unrelated to other anti-epileptic drugs. The mode of action of zonisamide remains unclear, but likely mechanisms are blockade of sodium and T-type calcium channels. It is also shown to have some neuroprotective effect against hypoxia and ischaemia. It has a liner pharmacokinetics with excellent oral bioavailability. Zonisamide has been approved for use in Japan for ten years prior to approval in USA and Europe. Clinical experience with zonisamide in Japan has documented its efficacy in the treatment of partial seizures (partial-onset generalised tonic-clonic, simple partial and/or complex partial seizures) and to a more variable extent, generalised tonic-clonic, generalised tonic (mainly seen in symptomatic generalised epilepsies including Lennox-Gastaut Syndrome) and compound/combination seizures. The efficacy and safety was confirmed in trials conducted in USA and Europe in adults as well as children. Zonisamide compares favourably with other newly introduced drugs and has the potential for development as a monotherapy for epilepsy.