Dalfampridine in multiple sclerosis: from symptomatic treatment to immunomodulation

Clinical assessment, management, and rehabilitation of walking impairment in MS: an expert review

INTRODUCTION

One of the most common and life-altering consequences of Multiple Sclerosis (MS) is walking impairment. The distance, speed, and Gait pattern functions are components of the International Classification of Functioning, Disability, and Health (ICF) and are also predictors of dependency in terms of daily living activities in patients with MS (pwMS).

AREAS COVERED

This article provides an overview of walking impairment in pwMS, with focus on the assessment of gait and the rehabilitation approaches.

EXPERT OPINION

The authors recommend that pwMS undergo gait assessment integrating the ICF perspective using validated clinical outcome measures that cover spatiotemporal gait parameters. Moreover, assessment of walking speed with short walking capacity tests such as the timed 25-foot walk (T25FW) or the 10-m walk test (10 MWT) and tests for walking distance with middle distance tests such as the 2-min walk test (2MWT) and the 6-min walk test (6MWT). This review further highlights strategies that may restore walking function including pharmacological symptomatic treatment and non-pharmacological rehabilitation approaches such as exercise and task-specific training providing an appraisal of mobility targeted therapies to be considered when planning multidisciplinary comprehensive-care of pwMS. Finally, new and novel strategies such as motor imagery and rhythmic auditory stimulation have been developed to improve walking speed and distance in pwMS.

Human equivalent dose of oral 4-aminopyridine differentiates nerve crush injury from transection injury and improves post-injury function in mice

4-Aminopyridine (4-AP), an FDA-approved drug for the symptomatic treatment of multiple sclerosis, is used to improve neuromuscular function in patients with diverse demyelinating disorders. We recently demonstrated that local, transdermal or injectable forms of 4-AP improve myelination, nerve conduction velocity, muscle atrophy, and motor function after traumatic peripheral nerve injury in mice. While oral 4-AP is most commonly used in the clinic, it is unknown whether human equivalent oral doses of 4-AP have effects on traumatic peripheral nerve injury differentiation, myelination, muscle atrophy, functional recovery, and post-injury inflammatory processes in animals. Mice with sciatic nerve crush or denervation injury received oral or intraperitoneal 4-AP (10 μg) or vehicle alone and were examined for pharmacokinetics, motor function, muscle mass, intrinsic muscle force, nerve morphological and gene expression profiles. 4-AP showed linear pharmacokinetics and the maximum plasma 4-AP concentrations were proportional to 4-AP dose. Acute single dose of oral 4-AP administration induced a rapid transient improvement in motor function that was different in traumatic peripheral nerve injury with or without nerve continuity, chronic daily oral 4-AP treatment significantly enhanced post crush injury motor function recovery and this effect was associated with improved myelination, muscle mass, and ex vivo muscle force. Polymerase chain reaction array analysis with crushed nerve revealed significant alterations in gene involved in axonal inflammation and regeneration. These findings provide convincing evidence that regardless of the route of administration, 4-AP can acutely differentiate traumatic peripheral nerve injury with or without nerve continuity and can enhance in vivo functional recovery with better preservation of myelin sheaths, muscle mass, and muscle force. The animal experiments were approved by the University Committee on Animal Research (UCAR) at the University of Rochester (UCAR-2009-019) on March 31, 2017.

Effects of Fampridine in People with Multiple Sclerosis: A Systematic Review and Meta-analysis

BACKGROUND

Prolonged-release (PR) fampridine is a potassium channel blocker used as a symptomatic treatment for walking disability in patients with multiple sclerosis (MS). Its clinical effects in such patients have not been systematically reviewed, and may be more wide-ranging than expected.

OBJECTIVES

To summarize the evidence on the effects of PR fampridine in patients with MS.

METHODS

A systematic search of Pubmed, Scopus (including EMBASE), and PsycINFO (completed in 01/2019) was carried out to identify randomized controlled trials (RCT) that compared PR fampridine to placebo. When appropriate, data were pooled using a random-effects model, and standardized mean differences (SMD) were computed. Study quality was assessed using the Downs and Black checklist. PRISMA guidelines were followed. All retrieved functional outcomes were categorized according to the International Classification of Functioning, Disability and Health (ICF).

RESULTS

A total of 706 articles were screened for inclusion. Twenty RCTs involving 2616 patients met the eligibility criteria. Most studies were of good-to-excellent quality. PR fampridine administration resulted in significant benefits in relation to walking short distances (SMD: 1.23 (95% IC 0.65-1.81)) and perceived walking capacity (0.64 (0.27-1.02)). Its effects on muscle strength and middle-distance walking were not significant (0.53 (- 0.04 to 1.10) and 0.31 (- 0.18 to 0.80), respectively). No effect on higher-level cognitive functions (- 0.07 (- 0.58 to 0.45)) or hand and arm use (0.16 (- 0.33 to 0.64)) was observed. Individual studies reported effects on other outcomes across the ICF domains.

CONCLUSIONS

There is strong evidence that PR fampridine exerts strong effects on the ability to walk short distances and on perceived walking capacity. Other effects of PR fampridine according to the ICF are possible but still unclear.

4-aminopyridine – the new old drug for the treatment of neurodegenerative diseases

In this review are described the preclinical and clinical pharmacological data as well as new therapeutic indications for the use of 4-aminopyridine. 4-aminopyridine is a potassium (K+) channel blocker that has a long history and various application areas. It is a chemical agent developed in 1963 as a bird poison. The first approval for clinical application of 4-aminopyridine was in 70’s in Bulgaria, since anesthetists in that country have confirmed its effect as reversal agent for nondepolarizing myorelaxants. The Bulgarian pharmaceutical company Sopharma commersialized 4-aminopyridine under the trade name Pymadin. Since then 4-aminopyridine was extensively studied and in 2010 is approved in the USA for the treatment of walking disabilities in patients with multiple sclerosis. In recent years, data from clinical trials indicated that K-channel blockade may prove to be an appropriate strategy to overcome disturbances in nerve impulses conduction associated with demyelination of the central nervous system.

Evaluating dalfampridine for the treatment of relapsing-remitting multiple sclerosis: does it add to the treatment armamentarium?

Introduction: Multiple sclerosis (MS) is a demyelinating disease, causing axonal damage and disability. Dalfampridine (DAL) is an extended-release formulation of 4-aminopyridine (4AP) and broad-spectrum voltage-dependent potassium channel blocker that is reported to improve motor, visual and cognitive functions. Furthermore, it is presently the only approved drug for walking impairment in MS. Areas covered: Herein, the authors evaluate DAL as a relapsing-remitting MS treatment, reporting and commenting on all aspects of the drug including its chemistry, safety, pharmacokinetics, and cost-effectiveness. A bibliographic search was performed on PubMed using the terms 'dalfampridine OR fampridine OR 4-aminopyridine'. Expert opinion: Evidence from post-marketing studies suggests that DAL, consistent with the effects of 4AP, may not only improve walking speed, but also arm function, fatigue, mood and cognition through restored nerve conduction in central nervous system demyelinated areas. Long-term safety data confirm that the approved dose of 10 mg twice daily is generally well tolerated. However, despite the reported efficacy, the extent of the benefits is limited in real life activities, although significant improvements have been demonstrated in the clinical setting. Patients often complain of side effects (such as cramps and painful paraesthesia) or lack of efficacy. Also, its considerably higher pricing in comparison to 4AP represents an important limitation.

Suppression of Inflammatory Demyelinaton and Axon Degeneration through Inhibiting Kv3 Channels

The development of neuroprotective and repair strategies for treating progressive multiple sclerosis (MS) requires new insights into axonal injury. 4-aminopyridine (4-AP), a blocker of voltage-gated K⁺ (Kv) channels, is used in symptomatic treatment of progressive MS, but the underlying mechanism remains unclear. Here we report that deleting Kv3.1—the channel with the highest 4-AP sensitivity—reduces clinical signs in experimental autoimmune encephalomyelitis (EAE), a mouse model for MS. In Kv3.1 knockout (KO) mice, EAE lesions in sensory and motor tracts of spinal cord were markedly reduced, and radial astroglia were activated with increased expression of brain derived neurotrophic factor (BDNF). Kv3.3/Kv3.1 and activated BDNF receptors were upregulated in demyelinating axons in EAE and MS lesions. In spinal cord myelin coculture, BDNF treatment promoted myelination, and neuronal firing via altering channel expression. Therefore, suppressing Kv3.1 alters neural circuit activity, which may enhance BNDF signaling and hence protect axons from inflammatory insults.

Relationship between perceived fatigue and performance fatigability in people with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Perceived fatigue (i.e., subjective perception of reduced capacity) is one of the most common and disabling symptoms for people with multiple sclerosis (MS). Perceived fatigue may also be related to performance fatigability (i.e., decline in physical performance over time), although study findings have been inconsistent.

OBJECTIVE

To locate all studies reporting the relationship between perceived fatigue and fatigability in people with MS, determine the population correlation, and examine moderating variables of the correlation size.

METHODS

In accordance with PRISMA guidelines, systematic searches were completed in Medline, PsychInfo, Google Scholar, and the Cochrane Library for peer-reviewed articles published between March 1983 and August 2016. Included articles measured perceived fatigue and performance fatigability in people with MS and provided a correlation between measures. Moderator variables expected to influence the relationship were also coded. Searches located 19 studies of 848 people with MS and a random-effects model was used to pool correlations.

RESULTS

The mean correlation between fatigue and fatigability was positive, "medium" in magnitude, and statistically significant, r=0.31 (95% CI=0.21, 0.42), p<0.001. Despite moderate between-study heterogeneity (I²=46%) no statistically significant moderators were found, perhaps due to the small number of studies per moderator category.

CONCLUSION

There is a significant relationship between perceived fatigue and fatigability in MS, such that people reporting elevated fatigue also are highly fatigable. The size of the relationship is not large enough to suggest fatigue and fatigability are the same construct, and both should continue to be assessed independently.

The safety and efficacy of vitamin K antagonist in atrial fibrillation patients with previous ulcer bleeding: Long-term results from a multicenter study

This study aimed to evaluate the safety and efficacy of vitamin K antagonist (VKA) in atrial fibrillation (AF) patients with previous ulcer bleeding.In this multicenter, retrospective analysis, clinical outcomes of 754 AF patients with a history of ulcer bleeding were evaluated. After ulcer treatment, 458 patients (61%) were treated with VKA, and the outcomes were compared to 296 patients (39%) without VKA.VKA treatment significantly increased major bleeding (7.3%/year vs 3.2%/year, P < 0.001), and reduced major adverse cardiac events (MACE) (5.4%/year vs 10.0%/year, P < 0.001). Specifically, risk of gastrointestinal bleeding was significantly higher in the VKA group than no-VKA group (5.7%/year vs 2.6%/year, P < 0.001). Consequently, there was no difference in the incidence of composite of a MACE and major bleeding, between the 2 groups. In patients with time in the therapeutic range (TTR) ≥65%, VKA significantly decreased MACE (2.8%/year vs 10.0%/year, P < 0.001) without increasing major bleeding. Net clinical benefit model showed beneficial effects of VKA in patients with TTR ≥65%, and harmful effects in those with TTR < 55%.In AF patients with previous ulcer bleeding, VKA treatment did not improve clinical outcomes unless the international normalized ratio level was constantly maintained (TTR ≥65%), as the gastrointestinal bleeding (GIB) risk significantly increased.

A guide to treating gait impairment with prolonged-release fampridine (Fampyra®) in patients with multiple sclerosis

INTRODUCTION

Gait impairment, a frequent sign in multiple sclerosis (MS), places a major burden on patients since it results in progressive loss of personal and social autonomy, along with work productivity. This guide aims to provide recommendations on how to evaluate gait impairment and use prolonged-release fampridine (PR-fampridine) as treatment for MS patients with gait impairment in Spain.

DEVELOPMENT

PR-fampridine dosed at 10mg every 12hours is currently the only drug approved to treat gait impairment in adults with MS. Additionally, PR-fampridine has been shown in clinical practice to significantly improve quality of life (QoL) in patients who respond to treatment. Treatment response can be assessed with the Timed 25-Foot Walk (T25FW) or the 12-item MS Walking Scale (MSWS-12); tests should be completed before and after starting treatment. The minimum time recommended for evaluating treatment response is 2 weeks after treatment onset. Patients are considered responders and permitted to continue the treatment when they demonstrate a decrease in their T25FW time or an increase in MSWS-12 scores. A re-evaluation is recommended at least every 6 months. The SF-36 (Short Form-36) and the MSIS-29 (MS Impact Scale-29) tests are recommended for clinicians interested in performing a detailed QoL assessment. This drug is generally well-tolerated and has a good safety profile. It should be taken on an empty stomach and renal function must be monitored regularly.

CONCLUSIONS

These recommendations will help ensure safer and more efficient prescription practices and easier management of PR-fampridine as treatment for gait impairment in Spanish adults with MS.

"Disease modifying nutricals" for multiple sclerosis

The association between vitamin D and multiple sclerosis has (re)-opened new interest in nutrition and natural compounds in the prevention and treatment of this neuroinflammatory disease. The dietary amount and type of fat, probiotics and biologicals, salmon proteoglycans, phytoestrogens and protease inhibitor of soy, sodium chloride and trace elements, and fat soluble vitamins including D, A and E were all considered as disease-modifying nutraceuticals. Studies in experimental autoimmune encephalomyelitis mice suggest that poly-unsaturated fatty acids and their 'inflammation-resolving' metabolites and the gut microflora may reduce auto-aggressive immune cells and reduce progression or risk of relapse, and infection with whipworm eggs may positively change the gut-brain communication. Encouraged by the recent interest in multiple sclerosis-nutrition nature's pharmacy has been searched for novel compounds with anti-inflammatory, immune-modifying and antioxidative properties, the most interesting being the scorpion toxins that inhibit specific potassium channels of T cells and antioxidative compounds including the green tea flavonoid epigallocatechin-3-gallate, curcumin and the mustard oil glycoside from e.g. broccoli and sulforaphane. They mostly also inhibit pro-inflammatory signaling through NF-κB or toll-like receptors and stabilize the blood brain barrier. Disease modifying functions may also complement analgesic and anti-spastic effects of cannabis, its constituents, and of 'endocannabinoid enhancing' drugs or nutricals like inhibitors of fatty acid amide hydrolase. Nutricals will not solve multiple sclerosis therapeutic challenges but possibly support pharmacological interventions or unearth novel structures.

4-Aminopyridine for symptomatic treatment of multiple sclerosis: a systematic review

This systematic review summarizes the existing evidence on the effect of 4-aminopyridine (4-AP) as a symptomatic treatment of decreased walking capacity in patients with multiple sclerosis (MS) when administered as an immediate release compound and a slow release compound. It summarizes existing evidence on the basic mechanisms of 4-AP from experimental studies and evidence on the clinical use of the compound. A systematic literature search was conducted of the following databases: PubMed and EMBASE. Thirty-five studies were included in the review divided into 16 experimental studies, two clinical studies with paraclinical endpoints and 17 clinical studies with clinical endpoints. Animal studies show that 4-AP can improve impulse conduction through demyelinated lesions. In patients with MS this translates into improved walking speed and muscle strength of the lower extremities in a subset of patients at a level that is often of clinical relevance. Phase III trials demonstrate approximately 25% increase in walking speed in roughly 40% and improved muscle strength in the lower extremities. Furthermore, 4-AP might have an effect on other domains such as cognition, upper extremity function and bowel and bladder, but this warrants further investigation. Side effects are mainly mild to moderate, consisting primarily of paraesthesia, dizziness, nausea/vomiting, falls/balance disorders, insomnia, urinary tract infections and asthenia. Side effects are worse when administered intravenously and when administered as an immediate release compound. Serious adverse events are rarely seen in the marketed clinical dosages. In conclusion, 4-AP is easy and safe to use. Slow release 4-AP shows more robust clinical effects and a more beneficial side-effect profile than immediate release 4-AP.

Unintentional 4-Aminopyridine Overdose in a Multiple Sclerosis Patient

Objective: To discuss the clinical presentation and treatment of a 4-aminopyridine overdose resulting from a pharmacy prescription compounding error. Case Summary: A 55-year-old female with a 12-year history of multiple sclerosis is reintroduced to immediate-release 4-aminopydrine for symptom management. Four hours after the second dose, she is admitted to the emergency room with altered mental status, pulmonary edema, and seizures progressing to status epilepticus. She is intubated and managed with benzodiazepines followed by a propofol infusion. After 5 days she is discharged to home. Laboratory analysis of the capsules detected 127 mg of 4-aminopyridine, yet the prescription label indicated the contents as 12.5 mg capsules, to be taken twice a day. Discussion: There are 14 cases of previously published 4-aminopyridine toxicity in the literature. Four of those cases are due to pharmacy compounding errors. This case presents with typical and anticipated symptomatology such as acute delirium, cognitive changes, speech changes, elevated blood pressure, tachycardia, seizures, and status epilepticus. However, this case is unique in that the patient also presented with pulmonary edema, a finding not mentioned in the previous 14 cases. These adverse drug events are due to the neurotransmitter release induced through potassium channel blockade afforded by 4-aminopyridine when ingested in excessive amounts. In the context of adverse drug events, the 4-aminopyridine overdose as the causal link for the clinical findings in this case as determined by the Naranjo probability scale is ranked as definite. Conclusion: 4-Aminopyridine is a potent potassium (Kv) channel blocker and is accepted as a therapeutic agent for multiple sclerosis patients. In excess, 4-aminopyridine can produce significant adverse neurological effects most notable being status epilepticus. To date, no 4-aminopyridine overdose case reported has ended in death. Caution is advised to those pharmacists who provide compounding services.

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.

Extended-release dalfampridine in the management of multiple-sclerosis-related walking impairment

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system that causes neurological impairment in young adults. As part of the disease, ambulation remains one of the most disabling features of multiple sclerosis. Extended-release dalfampridine is a long-acting form of 4-aminopyridine that has been shown in two phase III trials to increase ambulation speed in a subset of patients with multiple sclerosis (timed walk responders). The primary endpoint of these studies was 'responder status', analyzing difference in the proportion of timed walk responders between extended-release dalfampridine and placebo groups. Extended-release dalfampridine exerts its effects by inhibiting voltage-activated K(+) channels and has been previously demonstrated to improve action potential propagation in demyelinated nerve fibers in vitro. Side effects of extended-release dalfampridine include increased urinary tract infections, insomnia, headache, asthenia, dizziness, back pain, and paresthesias. Rare seizure events are also reported on the approved dose of 10 mg every 12 h. In this review we will summarize the results of key phase II and phase III trials of extended-release dalfampridine, its safety, and potential use in patients with multiple sclerosis.

Neurological disorders and therapeutics targeted to surmount the blood-brain barrier

We are now in an aging population, so neurological disorders, particularly the neurodegenerative diseases, are becoming more prevalent in society. As per the epidemiological studies, Europe alone suffers 35% of the burden, indicating an alarming rate of disease progression. Further, treatment for these disorders is a challenging area due to the presence of the tightly regulated blood-brain barrier and its unique ability to protect the brain from xenobiotics. Conventional therapeutics, although effective, remain critically below levels of optimum therapeutic efficacy. Hence, methods to overcome the blood-brain barrier are currently a focus of research. Nanotechnological applications are gaining paramount importance in addressing this question, and yielding some promising results. This review addresses the pathophysiology of the more common neurological disorders and novel drug candidates, along with targeted nanoparticle applications for brain delivery.

K+ channel alterations in the progression of experimental autoimmune encephalomyelitis

Voltage-gated K(+) (Kv) channels play critical roles not only in regulating synaptic transmission and intrinsic excitability of neurons, but also in controlling the function and proliferation of other cells in the central nervous system (CNS). The non-specific Kv channel blocker, 4-AminoPyridine (4-AP) (Dalfampridine, Ampyra®), is currently used to treat multiple sclerosis (MS), an inflammatory demyelinating disease. However, little is known how various types of Kv channels are altered in any inflammatory demyelinating diseases. By using established animal models for MS, experimental autoimmune encephalomyelitis (EAE), we report that expression and distribution patterns of Kv channels are altered in the CNS correlating with EAE severity. The juxtaparanodal (JXP) targeting of Kv1.2/Kvβ2 along myelinated axons is disrupted within demyelinated lesions in the white matter of spinal cord in EAE. Moreover, somatodendritic Kv2.1 channels in the motor neurons of lower spinal cord significantly decrease correlating with EAE severity. Interestingly, Kv1.4 expression surrounding lesions is markedly up-regulated in the initial acute phase of both EAE models. Its expression in glial fibrillary acidic protein (GFAP)-positive astrocytes further increases in the remitting phase of remitting-relapsing EAE (rrEAE), but decreases in late chronic EAE (chEAE) and the relapse of rrEAE, suggesting that Kv1.4-positive astrocytes may be neuroprotective. Taken together, our studies reveal myelin-dependent and -independent alterations of Kv channels in the progression of EAE and lay a solid foundation for future study in search of a better treatment for MS.