Sustained-release fampridine for symptomatic treatment of multiple sclerosis

Ultra-High Performance Liquid Chromatography Method for Bioanalysis of Fampridine Using Dried Blood Spot (DBS) Methodology: Application to Pharmacokinetic Study in Albino Rats

Fampridine (dalfampridine) is used to improve walking in people who have multiple sclerosis (a disease in which the nerves do not function properly and may cause weakness, numbness, loss of muscle coordination and problems with vision, speech and bladder control). Measurement of fampridine plasma concentrations is not practical at sites lacking the facilities to prepare and process blood samples. A dried blood spot (DBS) sampling method, in which a few drops of blood, drawn by lancet from the finger, are applied onto specially manufactured absorbent filter paper, can be used as an alternative to plasma monitoring and would allow for simplified sample storage and transport. Using blood samples from pharmacokinetic studies, an ultra-high performance liquid chromatography assay method for quantification of fampridine in DBS is developed and validated for specificity, selectivity, accuracy, precision, reproducibility and stability. Method was specific and selective relative to endogenous compounds, with required process efficiency, and no matrix effect. Inaccuracy and precision for intra-day and inter-day analyses were tested at all concentrations. Quantification of fampridine in DBS assay was not affected by blood deposit volume and punch position within spot, and hematocrit level had a limited but acceptable effect on measurement accuracy. Fampridine was stable for at least 2 months at room temperature. The correlation between DBS and plasma concentrations with an average blood-to-plasma ratio is determined. DBS sampling is a simple and practical method for monitoring fampridine concentrations. The method is completely validated as per ICH guidelines and extended to the in vivo determination of fampridine in male albino rats.

Structural Basis for Voltage Gating and Dalfampridine Binding in the Shaker Potassium Channel

The generation and propagation of action potentials in neurons depend on the coordinated activation of voltage-dependent sodium and potassium channels. Potassium channels of the Shaker family regulate neuronal excitability through voltage-dependent opening and closing of their ion conduction pore. This family of channels is an important therapeutic target, particularly in multiple sclerosis where the inhibitor dalfampridine (4-aminopyridine) is used to improve nerve conduction. The molecular details of how the voltage sensor domain drives opening of the pore domain has been limited by the lack of closed-state structures, also impairing the search for novel drugs. Using AlphaFold2-based conformational sampling methods we identify a structural model for the closed Shaker potassium channel where movement of the voltage sensor drives the opening trough interactions between the S4-S5 linker and S6 helix. We show experimentally that breakage of a backbone hydrogen bond is a critical part of the activation pathway. Through docking we identify a hydrophobic cavity formed by the pore domain helices that binds dalfampridine in the closed state. Our results demonstrate how voltage sensor movement drives pore opening and provide a structural framework for developing new therapeutic agents targeting the closed state. We anticipate this work will enable structure-based drug design efforts focused on state-dependent modulation of voltage-gated ion channels for the treatment of neurological disorders.

Comparison of K+ Channel Families

K⁺ channels enable potassium to flow across the membrane with great selectivity. There are four K⁺ channel families: voltage-gated K (K_v), calcium-activated (K_Ca), inwardly rectifying K (K_ir), and two-pore domain potassium (K_2P) channels. All four K⁺ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the K_v, K_Ca, and K_ir channels) or tetramer-like (2x2P = 4P for the K_2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K⁺ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (K_v), intracellular calcium oscillations (K_Ca), cellular mediators (K_ir), or temperature (K_2P).

The recent advancement of low-dimensional nanostructured materials for drug delivery and drug sensing application: A brief review

In this review article, we have presented a detailed analysis of the recent advancement of quantum mechanical calculations in the applications of the low-dimensional nanomaterials (LDNs) into biomedical fields like biosensors and drug delivery systems development. Biosensors play an essential role for many communities, e.g. law enforcing agencies to sense illicit drugs, medical communities to remove overdosed medications from the human and animal body etc. Besides, drug delivery systems are theoretically being proposed for many years and experimentally found to deliver the drug to the targeted sites by reducing the harmful side effects significantly. In current COVID-19 pandemic, biosensors can play significant roles, e.g. to remove experimental drugs during the human trials if they show any unwanted adverse effect etc. where the drug delivery systems can be potentially applied to reduce the side effects. But before proceeding to these noble and expensive translational research works, advanced theoretical calculations can provide the possible outcomes with considerable accuracy. Hence in this review article, we have analyzed how theoretical calculations can be used to investigate LDNs as potential biosensor devices or drug delivery systems. We have also made a very brief discussion on the properties of biosensors or drug delivery systems which should be investigated for the biomedical applications and how to calculate them theoretically. Finally, we have made a detailed analysis of a large number of recently published research works where theoretical calculations were used to propose different LDNs for bio-sensing and drug delivery applications.

Restoring Axonal Function with 4-Aminopyridine: Clinical Efficacy in Multiple Sclerosis and Beyond

The oral potassium channel blocker 4-aminopyridine has been used in various neurological conditions for decades. Numerous case reports and studies have supported its clinical efficacy in ameliorating the clinical presentation of certain neurological disorders. However, its short half-life, erratic drug levels, and safety-related dose restrictions limited its use as a self-compounded drug in clinical practice. This changed with the introduction of a prolonged-release formulation, which was successfully tested in patients with multiple sclerosis. It was fully approved by the US FDA in January 2010 but initially received only conditional approval from the European Medicines Agency (EMA) in July 2011. After additional clinical studies, this conditional approval was changed to unrestricted approval in August 2017. This article reviews and discusses these recent studies and places aminopyridines and their clinical utility into the context of a broader spectrum of neurological disorders, where clinical efficacy has been suggested. In 2010, prolonged-release 4-aminopyridine became the first drug specifically licensed to improve walking in patients with multiple sclerosis. About one-third of patients across disease courses benefit from this treatment. In addition, various reports indicate clinical efficacy beyond multiple sclerosis, which may broaden its use in clinical practice.

Potent block of potassium channels by MEK inhibitor U0126 in primary cultures and brain slices

U0126 (1,4-diamino-2,3-dicyano-1,4-bis (2-aminophenylthio) butadiene), a widely used mitogen-activated protein kinase kinase (MEK) inhibitor, was found to accelerate voltage-gated K⁺ channel (K_V) inactivation in heterologous cells expressing several types of K_V. The goal of this study was to examine whether U0126 at a concentration thought to specifically inhibit MEK signaling also inhibits K_V in native neurons of primary cultures or brain slices. U0126 caused a dose-dependent inhibition of both the transient (I_A) and sustained (I_DR) components of K⁺ currents in hippocampal neurons. U0126 also exhibited much higher potency on the I_A and I_DR than the classical K_V blockers 4-aminopyridine (4-AP) and tetraethylammonium (TEA). Consistent with its inhibitory effect on K_V, U0126 broadened action potential duration, profoundly affected the repolarizing phase, and dramatically reduced firing frequency in response to current pulse injections. Despite the potent and reversible action of U0126 on K_v channels, PD98059, a structurally-unrelated MEK inhibitor, did not induce such an effect, suggesting U0126 may act independently of MEK inhibition. Together, these results raise cautions for using U0126 as a specific inhibitor for studying MEK signaling in neurons; on the other hand, further studies on the blocking mechanisms of U0126 as a potent inhibitor of K_V may provide useful insights into the structure-function relationship of K_V in general.

Experience with fampridine in clinical practice: analysis of a possible marker of clinical response

PURPOSE OF THE STUDY

Approximately 85% of patients with multiple sclerosis experience reduced mobility, which negatively affects quality of life. Fampridine is the first symptomatic treatment aimed at improving gait. We analyzed effectiveness and tolerance in clinical practice. We also sought a prevalent gait pattern in responders as a potential clinical response marker.

MATERIAL AND METHODS

Six-month prospective study of fampridine in patients with multiple sclerosis. Response was evaluated using the Timed 25-Foot Walk Test (T25FW) and the 12-Item Multiple Sclerosis Walking Scale (MSWS-12). Response was defined as increased gait speed (≥20%) and decreased MSWS-12 score (≥4 points).

RESULTS

Fifty-five patients (67.3% women; mean age, 51.7 [11.1] years) with a baseline Expanded Disability Status Scale (EDSS) score of 5.8. Gait pattern was paraparetic (40%), hemiparetic (21.8%) and ataxic (38.2%). Of all patients, 70.9% demonstrated clinical benefit based on response criteria established, at the 14-d follow-up, 61.8% at 3 months and 45.5% at 6 months. A similar response pattern was observed in the MSWS-12. A significant decrease in the mean (SD) EDSS score was observed in responders at 6 months (6.1 [0.9] vs. 5.64 [0.1], p < 0.05). Adverse effects were recorded in 50.9%, although most were mild-moderate and resolved completely. We did not identify a prevalent gait pattern among responders. After a washout period, some patients received fampridine a second time obtaining response recovery.

CONCLUSIONS

In our patients' cohort, fampridine proved clinical benefit, being safe and well tolerated in most cases. We did not identify a gait pattern that was predictive of clinical response.

Clinical response and tolerability of fampridine in clinical practice

Background: Gait disorder is very prevalent in multiple sclerosis. After 15 years of disease progression, 50% of patients need assistive devices for walking. Materials & methods: We performed a multicenter observational study, including multiple sclerosis patients with an Expanded Disability Status Scale score between 4.0 and 7.0, normal kidney function and no previous history of seizures. Results: The study sample comprised 138 patients with average age of 50.3 years median Expanded Disability Status Scale of 6.0. After treatment, a significant reduction was observed in both the Timed 25-Foot Walk test (baseline, 20.3 s; 14 days, 13.2 s; p < 0.001; 3 months, 12.1 s; p < 0.001) and the 12-Item Multiple Sclerosis Walking Scale score (baseline, 82.3; 14 days, 59.4; p < 0.001; 3 months, 57.2; p < 0.001). Adverse events were recorded in 39.9% of patients.

Amantadine and rimantadine for influenza A in children and the elderly

BACKGROUND

Influenza is an acute respiratory illness caused by influenza A and B viruses. Complications may occur, especially among children and the elderly.

OBJECTIVES

To assess the effectiveness and safety of amantadine and rimantadine in preventing, treating and shortening the duration of influenza A in children and the elderly.

SEARCH METHODS

We searched CENTRAL (2014, Issue 9), MEDLINE (1966 to September week 4, 2014) and EMBASE (1980 to October 2014).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing amantadine and/or rimantadine with no intervention, placebo, other antivirals or different doses or schedules of amantadine or rimantadine in children and the elderly with influenza A.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results. We extracted and analysed data using the standard Cochrane methodology.

MAIN RESULTS

We identified 12 studies (2494 participants: 1586 children and 908 elderly) comparing amantadine and rimantadine with placebo, paracetamol (one trial: 69 children) or zanamivir (two trials: 545 elderly) to treat influenza A.Amantadine was effective in preventing influenza A in children (773 participants, risk ratio (RR) 0.11; 95% confidence interval (CI) 0.04 to 0.30). The assumed risk of influenza A in the control group was 10 per 100. The corresponding risk in the rimantadine group was one per 100 (95% CI 0 to 3). Nevertheless, the quality of the evidence was low and the safety of the drug was not well established.For treatment, rimantadine was beneficial in abating fever on day three of treatment in children: one selected study with low risk of bias, moderate evidence quality and 69 participants (RR 0.36; 95% CI 0.14 to 0.91). The assumed risk was 38 per 100. The corresponding risk in the rimantadine group was 14 per 100 (95% CI 5 to 34).Rimantadine did not show any prophylactic effect in the elderly. The quality of evidence was very low: 103 participants (RR 0.45; 95% CI 0.14 to 1.41). The assumed risk was 17 per 100. The corresponding risk in the rimantadine group was 7 per 100 (95% CI 2 to 23).There was no evidence of adverse effects caused by treatment with amantadine or rimantadine.We found no studies assessing amantadine in the elderly.

AUTHORS' CONCLUSIONS

The quality of the evidence combined with a lack of knowledge about the safety of amantadine and the limited benefits of rimantadine, do not indicate that amantadine and rimantadine compared to control (placebo or paracetamol) could be useful in preventing, treating and shortening the duration of influenza A in children and the elderly.

Inhibition of neuronal degenerin/epithelial Na+ channels by the multiple sclerosis drug 4-aminopyridine

The voltage-gated K(+) (Kv) channel blocker 4-aminopyridine (4-AP) is used to target symptoms of the neuroinflammatory disease multiple sclerosis (MS). By blocking Kv channels, 4-AP facilitates action potential conduction and neurotransmitter release in presynaptic neurons, lessening the effects of demyelination. Because they conduct inward Na(+) and Ca(2+) currents that contribute to axonal degeneration in response to inflammatory conditions, acid-sensing ion channels (ASICs) contribute to the pathology of MS. Consequently, ASICs are emerging as disease-modifying targets in MS. Surprisingly, as first demonstrated here, 4-AP inhibits neuronal degenerin/epithelial Na(+) (Deg/ENaC) channels, including ASIC and BLINaC. This effect is specific for 4-AP compared with its heterocyclic base, pyridine, and the related derivative, 4-methylpyridine; and akin to the actions of 4-AP on the structurally unrelated Kv channels, dose- and voltage-dependent. 4-AP has differential actions on distinct ASICs, strongly inhibiting ASIC1a channels expressed in central neurons but being without effect on ASIC3, which is enriched in peripheral sensory neurons. The voltage dependence of the 4-AP block and the single binding site for this inhibitor are consistent with 4-AP binding in the pore of Deg/ENaC channels as it does Kv channels, suggesting a similar mechanism of inhibition in these two classes of channels. These findings argue that effects on both Kv and Deg/ENaC channels should be considered when evaluating the actions of 4-AP. Importantly, the current results are consistent with 4-AP influencing the symptoms of MS as well as the course of the disease because of inhibitory actions on Kv and ASIC channels, respectively.

Enhancing neural transmission in multiple sclerosis (4-aminopyridine therapy)

Enhancing neural transmission by improving axonal conduction and synaptic neurotransmitter release is a novel strategy to improve symptoms in multiple sclerosis. Dalfampridine (4-aminopyridine extended-release) is a first-in-class medication that targets the damaged nervous system through blockage of voltage-gated potassium channels. Through a series of clinical trials, dalfampridine (dosed at 10 mg twice daily) has been found to improve walking speed by approximately 25 % on average in one third of individuals with multiple sclerosis regardless of disease stage. Furthermore, it significantly improves patients' perception of their ambulatory disability and may improve lower extremity strength. Given the mechanism of action, the most serious adverse effect is its pro-convulsant property, which occurs more frequently at high serum concentrations. The most common adverse events include increased falls, urinary tract infections, dizziness, insomnia, and headaches. Despite these potential side-effects, the vast majority of individuals who derive benefit continue on the treatment. The exact mechanism of action is uncertain, as is the reason for response variability. The medication serves as proof-of-concept that targeting axonal transmission can improve disability in multiple sclerosis.

4-aminopyridine toxicity: a case report and review of the literature

INTRODUCTION

4-Aminopyridine (4-AP) selectively blocks voltage-gated potassium channels, prolongs the action potential, increases calcium influx, and subsequently, enhances interneuronal and neuromuscular synaptic transmission. This medication has been studied and used in many disease processes hallmarked by poor neuronal transmission in both the central and peripheral nervous systems including: multiple sclerosis (MS), spinal cord injuries (SCI), botulism, Lambert-Eaton syndrome, and myasthenia gravis. It has also been postulated as a potential treatment of verapamil toxicity and reversal agent for anesthesia-induced neuromuscular blockade. To date, there have been limited reports of either intentional or accidental 4-AP toxicity in humans. Both a case of a patient with 4-AP toxicity and review of the literature are discussed, highlighting commonalities observed in overdose.

CASE REPORT

A 37-year-old man with progressive MS presented with diaphoresis, delirium, agitation, and choreathetoid movements after a presumed 4-AP overdose. 4-AP concentration at 6 h was 140 ng/mL. With aggressive benzodiazepine administration and intubation, he recovered uneventfully.

DISCUSSION

The commonalities associated with 4-AP toxicity conforms to what is known about its mechanism of action combining cholinergic features including diaphoresis, altered mental status, and seizures with dopamine-related movement abnormalities including tremor, choreoathetosis, and dystonia. Management of patients poisoned by 4-AP centers around good supportive care with definitive airway management and controlling CNS hyperexcitability aggressively with gamma-aminobutyric acid agonist agents. Adjunctive use of dopamine antagonists for extrapyramidal effects after sedation is a treatment possibility. As 4-aminopyridine recently received Federal Drug Administration approval for the treatment of ambulation in patients with MS, physicians should be keenly aware of its presentation, mechanism of action, and management in overdose.

Reversal of BoNT/A-mediated inhibition of muscle paralysis by 3,4-diaminopyridine and roscovitine in mouse phrenic nerve-hemidiaphragm preparations

Botulinum neurotoxins (BoNTs) comprise a family of neurotoxic proteins synthesized by anaerobic bacteria of the genus Clostridium. Each neurotoxin consists of two polypeptide chains: a 100kDa heavy chain, responsible for binding and internalization into the nerve terminal of cholinergic motoneurons and a 50kDa light chain that mediates cleavage of specific synaptic proteins in the host nerve terminal. Exposure to BoNT leads to cessation of voltage- and Ca(2+)-dependent acetylcholine (ACh) release, resulting in flaccid paralysis which may be protracted and potentially fatal. There are no approved therapies for BoNT intoxication once symptoms appear, and specific inhibitors of the light chain developed to date have not been able to reverse the consequences of BoNT intoxication. An alternative approach for treatment of botulism is to focus on compounds that act by enhancing ACh release. To this end, we examined the action of the K(+) channel blocker 3,4-diaminopyridine (3,4-DAP) in isolated mouse hemidiaphragm muscles intoxicated with 5pM BoNT/A. 3,4-DAP restored tension within 1-3min of application, and was effective even in totally paralyzed muscle. The Ca(2+) channel activator (R)-roscovitine (Ros) potentiated the action of 3,4-DAP, allowing for use of lower concentrations of the K(+) channel blocker. In the absence of 3,4-DAP, Ros was unable to augment tension in BoNT/A-intoxicated muscle. This is the first report demonstrating the efficacy of the combination of 3,4-DAP and Ros for the potential treatment of BoNT/A-mediated muscle paralysis.

Towards therapeutic applications of arthropod venom k(+)-channel blockers in CNS neurologic diseases involving memory acquisition and storage

Potassium channels are the most heterogeneous and widely distributed group of ion channels and play important functions in all cells, in both normal and pathological mechanisms, including learning and memory processes. Being fundamental for many diverse physiological processes, K⁺-channels are recognized as potential therapeutic targets in the treatment of several Central Nervous System (CNS) diseases, such as multiple sclerosis, Parkinson's and Alzheimer's diseases, schizophrenia, HIV-1-associated dementia, and epilepsy. Blockers of these channels are therefore potential candidates for the symptomatic treatment of these neuropathies, through their neurological effects. Venomous animals have evolved a wide set of toxins for prey capture and defense. These compounds, mainly peptides, act on various pharmacological targets, making them an innumerable source of ligands for answering experimental paradigms, as well as for therapeutic application. This paper provides an overview of CNS K⁺-channels involved in memory acquisition and storage and aims at evaluating the use of highly selective K⁺-channel blockers derived from arthropod venoms as potential therapeutic agents for CNS diseases involving learning and memory mechanisms.

Amantadine and rimantadine for influenza A in children and the elderly

BACKGROUND

The effectiveness and safety of amantadine (AMT) and rimantadine (RMT) for preventing and treating influenza A in adults has been systematically reviewed. However, little is known about these treatments in children and the elderly.

OBJECTIVES

To systematically review the effectiveness and safety of AMT and RMT in preventing and treating influenza A in children and the elderly.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 2) which contains the Cochrane Acute Respiratory Infections (ARI) Group's Specialised Register, MEDLINE (1966 to June week 3, 2011) and EMBASE (1980 to June 2011).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing AMT and/or RMT with placebo, control, other antivirals or different doses or schedules of AMT or RMT, or both, or no intervention, in children and the elderly.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion and assessed methodological quality. We resolved disagreements by consensus. In all comparisons except for one, we separately analysed the trials in children and the elderly using Review Manager software.

MAIN RESULTS

A total of 12 studies involving 2494 participants (1586 children and adolescents and 908 elderly) compared AMT and RMT with placebo, paracetamol (one trial; 69 children) or zanamivir (two trials; 545 seniors). All studies were RCTs but most were still susceptible to bias. Two trials in the elderly had a high risk of bias because of incomplete outcome data. In one of those trials there was also a lack of outcome assessment blinding. Risk of bias was unclear in 10 studies due to unclear random sequence generation and allocation concealment. Only two trials in children were considered to have a low risk of bias.AMT was effective in preventing influenza A in children. A total of 773 participants were included in this outcome (risk ratio (RR) 0.11; 95% confidence interval (CI) 0.04 to 0.30). The assumed risk of influenza in the control group was 10 per 100 and the corresponding risk in the RMT group was one per 100 (95% CI 0 to 3). The quality of the evidence was considered low. For treatment purposes, RMT was beneficial for abating fever on day three of treatment. For this purpose one study was selected with low risk of bias and included 69 children (RR 0.36; 95% CI 0.14 to 0.91). The assumed risk was 38 per 100 and the corresponding risk in the RMT group was 14 per 100, 95% CI 5 to 34. The quality of the evidence was moderate.RMT did not show a prophylactic effect against influenza in the elderly, but the quality of evidence was considered very low. There were 103 participants (RR 0.45; 95% CI 0.14 to 1.41, for an assumed risk of 17 per 100 and a corresponding risk in the RMT group of 7 per 100, 95% CI 2 to 23). We did not identify any AMT trials in the elderly that met our inclusion criteria.There was no evidence of adverse effects of AMT and RMT in children or an adverse effect of RMT in the elderly. We did not identify any AMT trials in the elderly that met our inclusion criteria.

AUTHORS' CONCLUSIONS

AMT is effective in preventing influenza A in children but the NNTB is high (NNTB: 12 (95% CI 9 to 17). RMT probably helps the abatement of fever on day three of treatment, but the quality of the evidence is poor. Due to the small number of available studies, we could not reach a definitive conclusion on the safety of AMT or the effectiveness of RMT in preventing influenza in children and the elderly.

Dalfampridine: review of its efficacy in improving gait in patients with multiple sclerosis

Multiple sclerosis (MS) is a progressive immune-mediated neurodegenerative disease of human central nervous system (CNS), which causes irreversible disability in young adults. The cause and cure for MS remain unknown. Pathophysiology of MS includes two arms: inflammatory demyelination and neurodegeneration. The inflammatory demyelination of MS which is mainly promoted by a massive activation of the immune system against putative CNS antigen(s) leads to loss of oligodendrocyte/myelin complex which slows down or halts impulse conduction in denuded axons. Practically, loss of myelin significantly reduces signal conduction along the demyelinated axons through alterations in the distribution of axonal ion channels. Dalfampridine (4-aminopyridine or 4-AP) is an oral potassium channel blocker, which was recently approved by FDA for symptomatic treatment of MS. Dalfampridine, which acts at the central and peripheral nervous systems, enhances conduction in demyelinated axons and improves walking ability of MS patients. A number of clinical trials have evaluated the safety and efficacy of fampridine in MS patients with the degree of gait improvement as the main outcome. The objective of this manuscript is to provide an overview of the pharmacology, pharmacokinetics, clinical trials, side effects and interactions of dalfampridine used in treatment of MS patients.

Impact of extended-release dalfampridine on walking ability in patients with multiple sclerosis

Dalfampridine extended release (ER) 10 mg is an oral tablet form of the potassium (K(+)) channel-blocking compounded dalfampridine, also known as fampridine, and chemically 4-aminopyridine or 4-AP, which received regulatory approval in the United States for the treatment of walking in patients with multiple sclerosis (MS) in January 2010. Two pivotal Phase 3 clinical trials demonstrated significant improvements in walking in patients with the four primary forms of MS following administration of dalfampridine ER tablets 10 mg twice daily. The drug is thought to act by restoring conduction in focally demyelinated axons and by enhancing neurotransmission, thereby leading to improved neurological function. This review describes how dalfampridine represents a new pharmacotherapeutic approach to the clinical management of mobility impairment. It describes the mechanism of action and chemistry of dalfampridine ER, its pharmacokinetics, tolerability, and side effects, and the outcomes of multicenter trials showing its efficacy in improving walking speed. Clinician and patient global assessments, as well as patient self-assessment of the impact of MS on their gait disability, confirm clinically relevant benefit from the therapy. Patients tolerate the drug well and their improvement in terms of household and community ambulation, inferred from analysis of pooled data from several studies, is likely to translate into benefits in the performance of instrumental activities of daily living and a reduction in the neuropsychiatric burden of disease.

Potassium channel blocker, 4-aminopyridine-3-methanol, restores axonal conduction in spinal cord of an animal model of multiple sclerosis

Multiple sclerosis (MS) is a severely debilitating neurodegenerative diseases marked by progressive demyelination and axonal degeneration in the CNS. Although inflammation is the major pathology of MS, the mechanism by which it occurs is not completely clear. The primary symptoms of MS are movement difficulties caused by conduction block resulting from the demyelination of axons. The possible mechanism of functional loss is believed to be the exposure of potassium channels and increase of outward current leading to conduction failure. 4-Aminopyridine (4-AP), a well-known potassium channel blocker, has been shown to enhance conduction in injured and demyelinated axons. However, 4-AP has a narrow therapeutic range in clinical application. Recently, we developed a new fast potassium channel blocker, 4-aminopyridine-3-methanol (4-AP-3-MeOH). This novel 4-AP derivative is capable of restoring impulse conduction in ex vivo injured spinal cord without compromising the ability of axons to follow multiple stimuli. In the current study, we investigated whether 4-AP-3-MeOH can enhance impulse conduction in an animal model of MS. Our results showed that 4-AP-3-MeOH can significantly increase axonal conduction in ex vivo experimental autoimmune encephalomyelitis mouse spinal cord.

New approaches in the management of multiple sclerosis

Multiple sclerosis (MS) is a central nervous system chronic inflammatory disease that is characterized by an extensive and complex immune response. Scientific advances have occurred in immunology, pathophysiology, and diagnostic and clinical assessment tools, and recent discovery of unique therapeutic targets has spurred numerous Phase II and Phase III clinical trials. Reductions in MS relapse rates and improvements in T₂ or gadolinium-enhancing lesion burdens have been reported from Phase III trials that include fingolimod, alemtuzumab, cladribine, and rituximab. Promising Phase II trial data exist for teriflunomide, daclizumab, laquinimod, and fumarate. The optimism created by these favorable findings must be tempered with evaluation of the adverse effect profile produced by these new agents. Given the discovery of progressive multifocal leukoencephalopathy with the use of natalizumab, ongoing vigilance for rare and life-threatening reactions due to new agents should be paramount. Patients with MS often experience difficulty with ambulation, spasticity, and cognition. Recent clinical trial data from two Phase III dalfampridine-SR trials indicate certain patients receive benefits in ambulation. This article provides an overview of data from clinical trials of newer agents of potential benefit in MS.

Dalfampridine extended release: in multiple sclerosis

Dalfampridine extended release (ER) is an orally administered formulation of dalfampridine (fampridine, 4-aminopyridine), a potassium channel antagonist indicated for the improvement in walking ability in patients with multiple sclerosis (MS). Oral dalfampridine ER improved walking ability in patients with MS in three randomized, double-blind trials of up to 15 weeks' duration. In a phase II trial, percentage improvements in walking speed on the Timed 25-Foot Walk (T25FW) test (primary endpoint) were not significant versus baseline or placebo during treatment with dalfampridine ER 10, 15 or 20 mg twice daily. However, according to a post hoc analysis, response rates were significantly higher with dalfampridine ER than placebo, with a consistent mean improvement in walking speed of 25-29% seen in the pooled results from dalfampridine ER responders during the double-blind treatment period. In two phase III trials, the proportion of timed walk responders (primary endpoint) was significantly greater with dalfampridine ER 10 mg twice daily than with placebo, with improvements in walking speed of approximately 25% seen during dalfampridine ER treatment amongst timed walk responders. Interim results of noncomparative extensions of the two phase III trials showed that consistent improvements in walking speed were sustained above baseline for up to 2.5 years of dalfampridine ER treatment. Oral dalfampridine ER 10 mg twice daily was generally well tolerated in patients with MS, according to the results of the three randomized, double-blind, placebo-controlled trials.

Axon-oligodendrocyte interactions during developmental myelination, demyelination and repair

In multiple sclerosis, CNS demyelination is often followed by spontaneous repair, mostly achieved by adult oligodendrocyte precursor cells. Extent of this myelin repair differs, ranging from very low, limited to the plaque border, to extensive, with remyelination throughout the 'shadow plaques.' In addition to restoring neuronal connectivity, new myelin is neuroprotective. It reduces axonal loss and thus disability progression. Reciprocal communication between neurons and oligodendrocytes is essential for both myelin biogenesis and myelin repair. Hence, deciphering neuron-oligodendrocyte communication is not only important for understanding myelination per se, but also the pathophysiology that underlies demyelinating diseases and the development of innovative therapeutic strategies.

[4-Aminopyridine (Fampridine). A new attempt for the symptomatic treatment of multiple sclerosis]

Mobility limitation is a frequent clinical symptom of multiple sclerosis (MS) that poses a therapeutic challenge. For years results of animal experiments and clinical experience have indicated that the potassium channel blocker 4-aminopyridine improves axonal excitatory circuits and thus muscular strength in demyelinating diseases. A recently conducted randomized, placebo-controlled, multicenter phase 3 clinical trial in MS patients was able to show that an oral sustained-release formulation of 4-aminopyridine (Fampridine-SR) represents a suitable agent for treatment of walking disability in MS patients.This overview presents the study data and discusses the value of 4-aminopyridine for the symptomatic treatment of MS as a neurofunctional modifier of this disabling disease.

Voltage-gated potassium channels as therapeutic targets

The human genome encodes 40 voltage-gated K(+) channels (K(V)), which are involved in diverse physiological processes ranging from repolarization of neuronal and cardiac action potentials, to regulating Ca(2+) signalling and cell volume, to driving cellular proliferation and migration. K(V) channels offer tremendous opportunities for the development of new drugs to treat cancer, autoimmune diseases and metabolic, neurological and cardiovascular disorders. This Review discusses pharmacological strategies for targeting K(V) channels with venom peptides, antibodies and small molecules, and highlights recent progress in the preclinical and clinical development of drugs targeting the K(V)1 subfamily, the K(V)7 subfamily (also known as KCNQ), K(V)10.1 (also known as EAG1 and KCNH1) and K(V)11.1 (also known as HERG and KCNH2) channels.

Seizures in patients with multiple sclerosis: epidemiology, pathophysiology and management

Seizures have been recognized to occur in multiple sclerosis (MS) since early descriptions of the disease. Various studies have attempted to determine the incidence and prevalence of seizures in MS; although they differ in the reported prevalence, seizures do appear to be more common in MS cohorts than in the general population. The pathological underpinning of seizures in MS remains indeterminate. Cortical and subcortical demyelination and inflammation may explain the increased frequency of seizures in MS, although this hypothetical correlation remains to be proven. Management of seizures in MS is similar to the management of seizures in other patients. Consideration of the underlying neurological deficits related to MS may be necessary, and dosages of antiepileptic drugs should be adjusted if increased sensitivity to the adverse effects of these agents or interaction with other centrally acting medications is suspected. The prognosis of epilepsy in patients with MS remains uncertain, with some studies suggesting a more favourable prognosis than others.