Safety, efficacy, and mechanisms of action of cannabinoids in neurological disorders.

In the past two decades, there has been an increasing interest in the therapeutic potential of cannabinoids for neurological disorders such as epilepsy, multiple sclerosis, pain, and neurodegenerative diseases. Cannabis-based treatments for pain and spasticity in patients with multiple sclerosis have been approved in some countries. Randomised controlled trials of plant-derived cannabidiol for treatment of Lennox-Gastaut syndrome and Dravet syndrome, two severe childhood-onset epilepsies, provide evidence of anti-seizure effects. However, small clinical trials of cannabinoids in other neurological disorders such as Huntington's disease, attention deficit hyperactivity disorder, and dementia, have not found any effect. Despite positive results in these two severe epilepsy syndromes, further studies are needed to determine if the anti-seizure effects of cannabidiol extend to other forms of epilepsy, to overcome pharmacokinetic challenges with oral cannabinoids, and to uncover the exact mechanisms by which cannabidiol or other exogenous and endogenous cannabinoids exert their therapeutic effects.

Disease modification in epilepsy: from animal models to clinical applications.

Several relevant animal models of epileptogenesis and biomarkers have emerged for evaluating the antiepileptogenic potential of an investigational drug. Although several promising candidate compounds and approaches have been identified in these preclinical models, no treatment has yet successfully navigated the path from preclinical efficacy to clinical validation. Until such an agent can move from preclinical proof of concept to clinical success, the need remains to continually develop and optimize preclinical models and clinical trial design in an effort to guide potential clinical investigations. This review describes several available models of disease modification and/or epileptogenesis, preclinical studies in these models and potential biomarkers useful for evaluating the efficacy of a potential therapeutic agent in the preclinical setting. The results that emerge from such efforts may then guide the clinical evaluation of a candidate compound. This review discusses some of the known limitations and hurdles to moving compounds found effective in these models to clinical practice, in the hope that knowledge of this information will facilitate the design and conduct of clinical studies and effectively facilitate the identification of a first-in-class disease-modifying or antiepileptogenic agent.

The challenge and promise of anti-epileptic therapy development in animal models.

Translation of successful target and compound validation studies into clinically effective therapies is a major challenge, with potential for costly clinical trial failures. This situation holds true for the epilepsies-complex diseases with different causes and symptoms. Although the availability of predictive animal models has led to the development of effective antiseizure therapies that are routinely used in clinical practice, showing that translation can be successful, several important unmet therapeutic needs still exist. Available treatments do not fully control seizures in a third of patients with epilepsy, and produce substantial side-effects. No treatment can prevent the development of epilepsy in at-risk patients or cure patients with epilepsy. And no specific treatment for epilepsy-associated comorbidities exists. To meet these demands, a redesign of translational approaches is urgently needed.

Cannabidiol: pharmacology and potential therapeutic role in epilepsy and other neuropsychiatric disorders.

To present a summary of current scientific evidence about the cannabinoid, cannabidiol (CBD) with regard to its relevance to epilepsy and other selected neuropsychiatric disorders. We summarize the presentations from a conference in which invited participants reviewed relevant aspects of the physiology, mechanisms of action, pharmacology, and data from studies with animal models and human subjects. Cannabis has been used to treat disease since ancient times. Δ(9) -Tetrahydrocannabinol (Δ(9) -THC) is the major psychoactive ingredient and CBD is the major nonpsychoactive ingredient in cannabis. Cannabis and Δ(9) -THC are anticonvulsant in most animal models but can be proconvulsant in some healthy animals. The psychotropic effects of Δ(9) -THC limit tolerability. CBD is anticonvulsant in many acute animal models, but there are limited data in chronic models. The antiepileptic mechanisms of CBD are not known, but may include effects on the equilibrative nucleoside transporter; the orphan G-protein-coupled receptor GPR55; the transient receptor potential of vanilloid type-1 channel; the 5-HT1a receptor; and the α3 and α1 glycine receptors. CBD has neuroprotective and antiinflammatory effects, and it appears to be well tolerated in humans, but small and methodologically limited studies of CBD in human epilepsy have been inconclusive. More recent anecdotal reports of high-ratio CBD:Δ(9) -THC medical marijuana have claimed efficacy, but studies were not controlled. CBD bears investigation in epilepsy and other neuropsychiatric disorders, including anxiety, schizophrenia, addiction, and neonatal hypoxic-ischemic encephalopathy. However, we lack data from well-powered double-blind randomized, controlled studies on the efficacy of pure CBD for any disorder. Initial dose-tolerability and double-blind randomized, controlled studies focusing on target intractable epilepsy populations such as patients with Dravet and Lennox-Gastaut syndromes are being planned. Trials in other treatment-resistant epilepsies may also be warranted. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.

Development of new treatment approaches for epilepsy: unmet needs and opportunities.

A working group was created to address clinical "gaps to care" as well as opportunities for development of new treatment approaches for epilepsy. The working group primarily comprised clinicians, trialists, and pharmacologists. The group identified a need for better animal models for both efficacy and tolerability, and noted that animal models for potential disease-modifying or antiepileptogenic effect should mirror conditions in human trials. For antiseizure drugs (ASDs), current animal models have not been validated with respect to their relationship to efficacy in common epilepsy syndromes. The group performed an "expert opinion" survey of perceived efficacy of the available ASDs, and identified a specific unmet need for ASDs to treat tonic-atonic and myoclonic seizures. No correlation has as yet been demonstrated between animal models of tolerability and adverse effects (AEs), versus tolerability in humans. There is a clear opportunity for improved therapies in relation to dose-related AEs. The group identified common and rare epilepsy syndromes that could represent opportunities for clinical trials. They identified opportunities for antiepileptogenic (AEG) therapies in both adults and children, acknowledging that the presence of a biomarker would substantially improve the chances of a successful trial. However, the group acknowledged that disease-modifying therapies (given after the first seizure or after the development of epilepsy) would be easier to study than AEG therapies.

Long-term behavioral, electrophysiological, and neurochemical monitoring of the safety of an experimental antiepileptic implant, the muscimol-delivering Subdural Pharmacotherapy Device in monkeys.

OBJECT: The authors evaluated the extent to which the Subdural Pharmacotherapy Device (SPD), chronically implanted over the frontal cortex to perform periodic, localized muscimol-delivery/CSF removal cycles, affects overall behavior, motor performance, electroencephalography (EEG) activity, and blood and CSF neurochemistry in macaque monkeys. METHODS: Two monkeys were used to adjust methodology and 4 monkeys were subjected to comprehensive testing. Prior to surgery, the animals' behavior in a large test chamber was monitored, and the motor skills required to remove food pellets from food ports located on the walls of the chamber were determined. The monkeys underwent implantation of the subdural and extracranial SPD units. The subdural unit, a silicone strip integrating EEG electrodes and fluid-exchange ports, was positioned over the right frontal cortex. The control unit included a battery-powered, microprocessor-regulated dual minipump and radiofrequency module secured to the cranium. After implantation, the SPD automatically performed periodic saline or muscimol (1.0 mM) deliveries at 12-hour intervals, alternating with local CSF removals at 6-hour intervals. The antiepileptic efficacy of this muscimol concentration was verified by demonstrating its ability to prevent focal acetylcholine-induced seizures. During SPD treatment, the monkeys' behavior and motor performance were again monitored, and the power spectrum of their radiofrequency-transmitted EEG recordings was analyzed. Serum and CSF muscimol levels were measured with high-performance liquid chromatography electrochemical detection, and CSF protein levels were measured with turbidimetry. RESULTS: The SPD was well tolerated in all monkeys for up to 11 months. The behavioral study revealed that during both saline and muscimol SPD treatment, the monkeys could achieve the maximum motor performance of 40 food-pellet removals per session, as before surgery. The EEG study showed that local EEG power spectra were not affected by muscimol treatment with SPD. The neurochemical study demonstrated that the administration of 1.0 mM muscimol into the neocortical subarachnoid space led to no detectable levels of this compound in the blood and cisternal CSF, as measured 1-125 minutes after delivery. Total protein levels were within the normal range in the cisternal CSF, but protein levels in the cortical-site CSF were significantly higher than normal: 361 ± 81.6 mg/dl. Abrupt discontinuation of 3-month, periodic, subdural muscimol treatments induced withdrawal seizures, which could be completely prevented by gradually tapering off the subdural muscimol concentration from 1.0 mM to 0.12-0.03 mM over a period of 2 weeks. The monkeys' general health and weight were maintained. Infection occurred only in one monkey 9 months after surgery. CONCLUSIONS: Long-term, periodic, transmeningeal muscimol delivery with the SPD is essentially a safe procedure. If further improved and successfully adapted for use in humans, the SPD can be used for the treatment of intractable focal neocortical epilepsy affecting approximately 150,000 patients in the US.

Electrical stimulation of the anterior nucleus of thalamus for treatment of refractory epilepsy.

PURPOSE: We report a multicenter, double-blind, randomized trial of bilateral stimulation of the anterior nuclei of the thalamus for localization-related epilepsy. METHODS: Participants were adults with medically refractory partial seizures, including secondarily generalized seizures. Half received stimulation and half no stimulation during a 3-month blinded phase; then all received unblinded stimulation. RESULTS: One hundred ten participants were randomized. Baseline monthly median seizure frequency was 19.5. In the last month of the blinded phase the stimulated group had a 29% greater reduction in seizures compared with the control group, as estimated by a generalized estimating equations (GEE) model (p = 0.002). Unadjusted median declines at the end of the blinded phase were 14.5% in the control group and 40.4% in the stimulated group. Complex partial and "most severe" seizures were significantly reduced by stimulation. By 2 years, there was a 56% median percent reduction in seizure frequency; 54% of patients had a seizure reduction of at least 50%, and 14 patients were seizure-free for at least 6 months. Five deaths occurred and none were from implantation or stimulation. No participant had symptomatic hemorrhage or brain infection. Two participants had acute, transient stimulation-associated seizures. Cognition and mood showed no group differences, but participants in the stimulated group were more likely to report depression or memory problems as adverse events. DISCUSSION: Bilateral stimulation of the anterior nuclei of the thalamus reduces seizures. Benefit persisted for 2 years of study. Complication rates were modest. Deep brain stimulation of the anterior thalamus is useful for some people with medically refractory partial and secondarily generalized seizures.

Management issues for women with epilepsy--focus on pregnancy (an evidence-based review): III. Vitamin K, folic acid, blood levels, and breast-feeding: Report of the Quality Standards Subcommittee and Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology and the American Epilepsy Society.

A committee assembled by the American Academy of Neurology (AAN) reassessed the evidence related to the care of women with epilepsy (WWE) during pregnancy, including preconceptional folic acid and prenatal vitamin K use and the clinical implications of placental and breast-milk transfer of antiepileptic drugs (AEDs). The committee evaluated the available evidence based on a structured literature review and classification of relevant articles. Preconceptional folic acid supplementation is possibly effective in preventing major congenital malformations in the newborns of WWE taking AEDs. There is inadequate evidence to determine if the newborns of WWE taking AEDs have a substantially increased risk of hemorrhagic complications. Primidone and levetiracetam probably transfer into breast milk in clinically important amounts. Valproate, phenobarbital, phenytoin, and carbamazepine probably are not transferred into breast milk in clinically important amounts. Pregnancy probably causes an increase in the clearance and a decrease in the concentrations of lamotrigine, phenytoin, and, to a lesser extent carbamazepine, and possibly decreases the level of levetiracetam and the active oxcarbazepine metabolite, the monohydroxy derivative (MHD). Supplementing WWE with at least 0.4 mg of folic acid before pregnancy may be considered. Monitoring of lamotrigine, carbamazepine, and phenytoin levels during pregnancy should be considered, and monitoring of levetiracetam and oxcarbazepine (as MHD) levels may be considered. A paucity of evidence limited the strength of many recommendations.

Development of new antiepileptic drugs: challenges, incentives, and recent advances.

Despite the introduction of many second-generation antiepileptic drugs (AEDs) in the past 15 years, a third of patients with epilepsy remain refractory to available treatments, and newer and more effective therapies are needed. Although our understanding of the mechanisms of drug resistance is fragmented, novel AED targets have been identified, and models of refractory epilepsy have been developed that can help to select candidate compounds for development. There are more than 20 compounds with potential antiepileptic activity in various stages of clinical development, and for many of these promising clinical trial results are already available. Several incentives justify further investment into the discovery of newer and more effective AEDs. Moreover, developments in clinical trial methodology enable easier completion of proof-of-concept studies, earlier definition of the therapeutic potential of candidate compounds, and more efficient completion of trials for various epilepsy indications.

VNS Therapy versus the latest antiepileptic drug.

Pro AED: The central issue in medical decision-making is risk-benefit assessment. Surgery of any type is still considered to be a major undertaking. To warrant these risks, the patient has a right to expect that they have a greater chance of a good outcome with an invasive therapy than with a non-invasive one. The main question is when, if ever, this becomes the case when comparing implantation of a VNS Therapy System versus adding an antiepileptic drug (AED)? After the first drug? The second? After all AEDs have failed? To date, no randomized trial comparing the addition of an AED against vagus nerve stimulation (VNS Therapy) has been undertaken, although several are currently being contemplated. Without this information, it is more difficult to make a case for early implementation of VNS Therapy. Unfortunately, few data are available regarding the potential for patients to become seizure-free after implantation of a VNS Therapy System. Another issue is side effects. It is important to remember that VNS Therapy also produces adverse events, albeit very different in character than those associated with AEDs, to which physicians have become accustomed. These include cough, dyspnea, pharyngitis, voice alteration and sleep apnea. A less frequently discussed, potentially negative consequence of VNS Therapy relates to the ability to obtain imaging of the patient. Patients who have undergone VNS Therapy System implantation are not candidates for imaging of the chest, breast, or abdomen. A second issue is that imaging of the brain can only be performed with MRI scanners that meet certain requirements, and as MRI technology develops, scanners meeting these requirements may become harder to find. However, to summarize, VNS Therapy is an excellent and useful treatment choice. Fortunately, the choice between AEDs and VNS Therapy is not an "either/or" decision. Each has a role in the treatment of patients with epilepsy, and the advantages and disadvantages of each should be kept in perspective. Pro VNS Therapy: VNS Therapy is no longer a new treatment for patients with refractory epilepsy. The first implant was performed in l988, and since then more than 30,000 patients have received this therapy. It is no longer considered an unusual or dangerous procedure, but it is still used almost exclusively for refractory epilepsy patients and it has not been generally accepted for use as a first line or even second line therapy. However, compared to the new AEDs, VNS Therapy has similar efficacy results in clinical trials and in many epilepsy syndromes and the long-term efficacy results are even more positive, with continued improvement in seizure reduction for up to two years. Two of the major reasons for not using VNS Therapy early are that it is a surgical procedure, and its safety during MRI procedures, especially with 3 Tesla, has not yet been elucidated. The safety profile of VNS Therapy is very favorable; the side effects being totally different from those seen with AEDs. The most important aspects are that there have been no pharmacological interactions, cognitive or sedative side effects reported, and it is safe for use in all age groups. Side effects are restricted to local irritation, hoarseness, coughing and, in a few cases, swallowing difficulties when the stimulator is on, but these tend to disappear with time. No idiosyncratic side effect has emerged during the 16 years of use. Compliance is guaranteed. The cost of the implantation of the VNS Therapy System, when spread out over 8 years (battery life), is actually less than the cost of using a new AED over an eight-year period, and real savings as regards hospital costs due to seizures can be expected.

Levetiracetam safety profiles and tolerability in epilepsy patients.

This review discusses the safety and tolerability of levetiracetam, as presented by the available literature, with attention paid to special populations. In Phase II/III trials, the adverse effects occurring more commonly in the treatment groups versus the placebo group were; somnolence (14.8 versus 8.4%), asthenia (14.7 versus 9.1%), infection (primarily common cold) (13.4 versus 7.5%), and dizziness (8.8 versus 4.1%). Adverse events usually appear within the first month after treatment initiation, are not dose-dependent, are mostly mild-to-moderate, generally resolve without medication withdrawal, and are transient when the medication is stopped. No significant changes in haematology and chemistry profiles or weight occurred. Hypersensitivity reactions were rare and no idiosyncratic event has been reported. Open-label studies have added patient data with other epileptic syndromes and from a wider patient pool, such as children and patients with prior psychiatric history. These studies have supported initial safety findings, but have reported increased behavioural adverse events in children and patients with a history of prior behavioural problems. Levetiracetam is proving to be safe and well-tolerated. So far, it appears to have a favourable safety profile in special populations, such as children, the elderly, and patients with hepatic dysfunction. Preliminary data in pregnancy are promising, but more data are needed on the impact of levetiracetam on the developing fetus and pharmacokinetic alterations caused in pregnancy. Adjustments in dosing are required for decreases in renal clearance.

Electrical stimulation of the anterior nucleus of the thalamus for the treatment of intractable epilepsy.

PURPOSE: Animal studies and sporadic case reports in human subjects have suggested that intermittent electrical stimulation of the anterior nucleus of the thalamus reduces seizure activity. We embarked on an open-label pilot study to determine initial safety and tolerability of bilateral stimulation of the anterior nucleus of the thalamus (ANT), to determine a range of appropriate stimulation parameters, and to begin to gather pilot efficacy data. METHODS: We report an open-label pilot study of intermittent electrical stimulation of the anterior nucleus of the thalamus in five patients (three men, two women; age range, 24-47 years), with follow-up between 6 and 36 months. All patients had intractable partial epilepsy. Four of the five patients also had secondarily generalized seizures. Stimulation was delivered by bilateral implantable, programmable devices by using an intermittent, relatively high-frequency protocol. Stimulation parameters were 100 cycles per second with charge-balanced alternating current; pulse width, 90 ms; and voltages ranging between 1.0 and 10.0 V. Seizure counts were monitored and compared with preimplantation baseline. RESULTS: Four of the five patients showed clinically and statistically significant improvement with respect to the severity of their seizures, specifically with respect to the frequency of secondarily generalized tonic-clonic seizures and complex partial seizures associated with falls. One patient showed a statistically significant reduction in total seizure frequency. No adverse events could clearly be attributed to stimulation. None of the patients could determine whether the stimulator was on or off at these parameters. CONCLUSIONS: Electrical stimulation of the ANT appears to be well tolerated. Preliminary evidence suggests clinical improvement in seizure control in this small group of intractable patients. Further controlled study of deep brain stimulation of the anterior nucleus is warranted.