Sustained-release oral fampridine in multiple sclerosis: a randomised, double-blind, controlled trial

Effect of food on the single-dose pharmacokinetics and tolerability of dalfampridine extended-release tablets in healthy volunteers

PURPOSE

The pharmacokinetics, bioavailability, and tolerability of dalfampridine extended-release tablets in healthy adults under fed and fasted conditions were evaluated.

METHODS

The study participants (n = 30) were randomly assigned to receive one 10-mg dalfampridine tablet in a fasted condition (no food for 10-12 hours) or a fed condition (after a high-fat meal); after a seven-day washout period, participants received the same dalfampridine dosage under the converse condition. The endpoints were the maximum plasma drug concentration (C(max)) and areas under the plasma-concentration curve (AUC) for 24-hour exposure (AUC(0-24)) and total exposure (AUC(0-∞)). A 90% two-sided confidence interval (CI) within predefined limits for the fed:fasted ratio of the geometric mean values was used as the standard for determining the absence of a significant food effect.

RESULTS

Among the participants who received both treatments (n = 28), food intake was associated with a 23% increase in the log-transformed geometric mean C(max) of dalfampridine (p ≤ 0.10) but no significant change in mean AUC values. Eight (26.7%) of the study participants reported a total of 13 adverse events (AEs), of which only dizziness and upper abdominal pain occurred in more than one participant; all AEs were of mild-to-moderate severity.

CONCLUSION

When a single 10-mg dose of dalfampridine was given to healthy volunteers after a high-fat meal, a significant increase in C(max) was observed. However, overall differences in dalfampridine pharmacokinetics when the drug was administered to participants under fasting and fed conditions did not exceed predefined limits, indicating that the extended-release formulation may be taken without regard to meals.

Spinal cord clinical trials and the role for bioengineering

There is considerable need for bringing effective therapies for spinal cord injury (SCI) to the clinic. Excellent medical and surgical management has mitigated poor prognoses after SCI; however, few advances have been made to return lost function. Bioengineering approaches have shown great promise in preclinical rodent models, yet there remains a large translational gap to carry these forward in human trials. Herein, we provide a framework of human clinical trials, an overview of past trials for SCI, as well as bioengineered approaches that include: directly applied pharmacologics, cellular transplantation, biomaterials and functional neurorehabilitation. Success of novel therapies will require the correct application of comprehensive preclinical studies with well-designed and expertly conducted human clinical trials. While biologics and bioengineered strategies are widely considered to represent the high potential benefits for those who have sustained a spinal injury, few such therapies have been thoroughly tested with appreciable efficacy for use in human SCI. With these considerations, we propose that bioengineered strategies are poised to enter clinical trials.

Management options in multiple sclerosis-associated fatigue

INTRODUCTION

Multiple sclerosis (MS) is a chronic, inflammatory, autoimmune disease of the CNS. Its characteristic early clinical course includes exacerbations and remissions of neurologic disability. Fatigue is one of the most common symptoms of MS and is associated with a reduced quality of life; it is described as the worst symptom of the disease by 50 - 60% of patients. Yet, due to limitations of available evidence, current therapeutic approaches for treating fatigue are based mainly on preliminary studies and expert consensus.

AREAS COVERED

This review summarizes current knowledge on the physiopathology, diagnosis and therapeutic options for MS-associated fatigue, including both pharmacological and non-pharmacological strategies.

EXPERT OPINION

Large, rigorously designed trials can provide more reliable results on the efficacy of interventions for fatigue, their functional impact on everyday activities and patient quality of life. Future research should also address a better understanding of the physiopathologic mechanisms of fatigue and the development and validation of objective assessment tools to be used together with patient self-ratings.

Spinal cord injury clinical trials translational process, review of past and proposed acute trials with reference to recommended trial guidelines

Within the past few years there has been increasing interest in the translation of experimental therapeutic interventions to improve functional outcomes after spinal cord injury (SCI). The number of reported successes using preclinical animal models has been substantial and this has encouraged the development of several clinical trial programs. We will briefly discuss a desired process for the translation of preclinical therapeutic discoveries, as well as the design and conduct of valid human SCI studies. Past SCI trials are examined and current ongoing human studies are outlined. We identify some of the confounding factors that can influence the accurate interpretation of study outcomes. The discussion here will be restricted to treatment strategies that involve drug administration and cell transplants, not that these are currently the most beneficial treatments, but cell transplants are already being offered to patients without completing a valid clinical trial program.

Minimally important clinical difference of the Timed 25-Foot Walk Test: results from a randomized controlled trial in patients with multiple sclerosis

BACKGROUND

Limited data define what constitutes a clinically significant change on the Timed 25-Foot Walk (T25FW) in multiple sclerosis (MS); however, most studies suggest a value of ≥20%. Analyses were undertaken to estimate the minimally important clinical difference (MICD) in walking speed as measured by the T25FW in patients with MS.

METHODS

Data from MS-F203, a randomized trial of dalfampridine extended release tablets, 10 mg twice daily (prolonged-release/sustained-release fampridine outside the US) in patients with MS, were used to calculate the MICD, as an absolute and percentage value, for the T25FW test. Both anchor- (using the Clinician Global Impression [CGI]) and distribution-based (2.77 × standard error of measurement or 0.50 standard deviation units) approaches were used. Using the anchor-based estimations, the proportion of patients in the dalfampridine and placebo groups achieving at least a MICD in MS-F203 was determined.

RESULTS

A correlation between change in T25FW speed during and CGI at the end of double-blind period was found (Spearman r = -0.39, p < 0.0001). Irrespective of treatment group, participants categorized 'minimally improved' by the CGI had a mean improvement in T25FW speed of 0.36 feet/second or a 17.2% relative change from an average baseline walking speed of 2.1 feet/second (effect size = 0.49); values representing MICDs. MICD estimates of 0.35 and 0.37 feet/second were generated using distribution-based approaches. In MS-F203, a greater proportion of patients receiving dalfampridine achieved ≥0.36 feet/second (12/72 vs. 78/224, p = 0.007) and a 17.2% (11/72 vs. 87/224, p = 0.0005) improvement in T25FW speed compared to placebo.

LIMITATIONS

MICD estimates from this analysis may not apply to patients with different disease characteristics from MS-F203. A different anchor may result in a different MICD estimation.

CONCLUSION

Our MICD estimate for an improvement in T25FW is close to previous estimates of 20% change. Dalfampridine may improve walking speed in a considerable proportion of patients by a clinically relevant amount.

Responsiveness of walking-based outcome measures after multiple sclerosis relapses following steroid pulses

BACKGROUND

The aim of this study was to examine the impact of intravenous methylprednisolone therapy (IVMP) on the recovery of walking ability in patients experiencing multiple sclerosis (MS) relapses, to compare the responsiveness of walking-based measures, and to estimate the impact of different walking-based measures responsiveness on clinical trials.

MATERIAL/METHODS

The study included 49 consecutive patients with relapsing-remitting MS who received Solu-Medrol 1000 mg/day over 3 days for relapse with difficulties in walking. The following walking-based measures were administered before and a month after IVMP: the Multiple Sclerosis Walking Scale-12 (MSWS-12), the Expanded Disability Status Scale (EDSS), the 2-minute timed walk (2-minTW), the 25-foot walk test (25FWT), the Six Spot Step Test (SSST). All patients had worn the step activity monitor accelerometer (SAM) 1 week prior to IVMP was applied and wore it again the fourth week upon the corticosteroid therapy was completed. The SAM analysis utilized the average daily step count and data regarding frequency and intensity of walking over a continuous time interval. We examined: (1) the impact of IVMP on the recovery of walking ability; (2) the responsiveness of each walking-based measure; (3) the relative responsiveness of competing walking-based measures; and (4) the impact of different walking-based measures responsiveness on clinical trials.

RESULTS

All walking-based measures showed significant improvement of walking ability 1 month after the IVMP. The most responsive were MSWS-12 and EDSS. Different responsiveness implied a greater than 6-fold impact on sample size estimates.

CONCLUSIONS

All applied walking-based measures showed significant improvement of walking ability 1 month after the IVMP. Responsiveness of various walking-based measures notably differ, thus affecting sample size calculations.

The use of multiple sclerosis condition-specific measures to inform health policy decision-making: mapping from the MSWS-12 to the EQ-5D

Background: Walking impairment has a major influence on the quality of life of people with multiple sclerosis (MS). The Multiple Sclerosis Walking Scale (MSWS-12) assesses the impact of MS on walking ability from the patient’s perspective, but in its current form, is not amenable for use in many policy decision-making settings.

Objectives: Statistical ‘mapping’ methods were used to convert MSWS-12 scores to EQ-5D health state values.

Methods: The relationship between the measures was estimated using cohort data from people with MS in South West England. Regression analyses were conducted, estimation errors assessed, and predictive performance of the best models tested using longitudinal data.

Results: Model performance was in line with that of other mapping studies, with the best-performing models being an ordinary least squares (OLS) model using MSWS-12 item scores, and an OLS model using the total MSWS-12 score and its squared term.

Conclusions: A process has been described whereby data from a patient-reported outcome measure (MSWS-12) can be converted to (EQ-5D) health state values. These values may be used to consider the health-related quality of life of people with MS, to estimate quality adjusted life-years for use in effectiveness and cost-effectiveness analyses, and to inform health policy decisions.

Current therapeutic options in pediatric multiple sclerosis

OPINION STATEMENT

Therapies for relapsing-remitting pediatric multiple sclerosis (MS) are aimed at preventing relapses (disease modifying therapies), treating acute attacks, and managing disabling cognitive and physical symptoms. Initial disease modifying therapy to prevent relapses should use one of four first-line injectable therapies that are approved for adult relapsing-remitting MS: interferon beta 1a IM, interferon beta 1a SC, interferon beta 1b SC, or glatiramer acetate. If breakthrough disease occurs or the medication is poorly tolerated, the next step should be to try one of the other first-line therapies. If the first-line therapies have been exhausted, second-line therapies such as natalizumab, cyclophosphamide, or mitoxantrone may be considered. One must use caution when choosing these potent therapies, as secondary effects may include serious infection or malignancy. Phase III studies in adult MS have been published on two oral agents, fingolimod and cladribine, and fingolimod has received FDA approval for use in relapsing-remitting MS in adults. These drugs have not been evaluated in the pediatric MS population, nor have any of three other oral agents now in phase III development: laquinimod, BG-12, and teriflunomide. Acute relapses can be treated with pulse methylprednisolone at a dosage of 20 to 30 mg/kg per day (maximum 1 g per day) for 3 to 5 days. If this is ineffective, intravenous immunoglobulin (2 g/kg divided over 2-5 days) or plasmapheresis may be considered. Neuropsychological, physical therapy, and occupational therapy screening should be performed on patients with pediatric MS. Interventions focusing on visual motor integration may be particularly useful in this group Spasticity may be treated with symptomatic therapies, but one must be aware of potential adverse effects of agents such as baclofen and diazepam. Headache, fatigue, anxiety, and depression are frequently seen, and patients may need a psychiatry consultation and counseling.

Objective assessment of motor fatigue in Multiple Sclerosis using kinematic gait analysis: a pilot study

Background

Fatigue is a frequent and serious symptom in patients with Multiple Sclerosis (MS). However, to date there are only few methods for the objective assessment of fatigue. The aim of this study was to develop a method for the objective assessment of motor fatigue using kinematic gait analysis based on treadmill walking and an infrared-guided system.

Patients and methods

Fourteen patients with clinically definite MS participated in this study. Fatigue was defined according to the Fatigue Scale for Motor and Cognition (FSMC). Patients underwent a physical exertion test involving walking at their pre-determined patient-specific preferred walking speed until they reached complete exhaustion. Gait was recorded using a video camera, a three line-scanning camera system with 11 infrared sensors. Step length, width and height, maximum circumduction with the right and left leg, maximum knee flexion angle of the right and left leg, and trunk sway were measured and compared using paired t-tests (α = 0.005). In addition, variability in these parameters during one-minute intervals was examined. The fatigue index was defined as the number of significant mean and SD changes from the beginning to the end of the exertion test relative to the total number of gait kinematic parameters.

Results

Clearly, for some patients the mean gait parameters were more affected than the variability of their movements while other patients had smaller differences in mean gait parameters with greater increases in variability. Finally, for other patients gait changes with physical exertion manifested both in changes in mean gait parameters and in altered variability. The variability and fatigue indices correlated significantly with the motoric but not with the cognitive dimension of the FSMC score (R = -0.602 and R = -0.592, respectively; P < 0.026).

Conclusions

Changes in gait patterns following a physical exertion test in patients with MS suffering from motor fatigue can be measured objectively. These changes in gait patterns can be described using the motor fatigue index and represent an objective measure to assess motor fatigue in MS patients. The results of this study have important implications for the assessments and treatment evaluations of fatigue in MS.

Symptomatic therapy and rehabilitation in primary progressive multiple sclerosis

Multiple sclerosis (MS) is an autoimmune inflammatory demyelinating disease of the central nervous system and a major cause of chronic neurological disability in young adults. Primary progressive MS (PPMS) constitutes about 10% of cases, and is characterized by a steady decline in function with no acute attacks. The rate of deterioration from disease onset is more rapid than relapsing remitting and secondary progressive MS types. Multiple system involvement at onset and rapid early progression have a worse prognosis. PPMS can cause significant disability and impact on quality of life. Recent studies are biased in favour of relapsing remitting patients as treatment is now available for them and they are more likely to be seen at MS clinics. Since prognosis for PPMS is worse than other types of MS, the focus of rehabilitation is on managing disability and enhancing participation, and application of a "neuropalliative" approach as the disease progresses. This chapter presents the symptomatic treatment and rehabilitation for persons with MS, including PPMS. A multidisciplinary approach optimizes the intermediate and long-term medical, psychological and social outcomes in this population. Restoration and maintenance of functional independence and societal reintegration, and issues relating to quality of life are addressed in rehabilitation processes.

Targeting VIP and PACAP receptor signalling: new therapeutic strategies in multiple sclerosis

MS (multiple sclerosis) is a chronic autoimmune and neurodegenerative pathology of the CNS (central nervous system) affecting approx. 2.5 million people worldwide. Current and emerging DMDs (disease-modifying drugs) predominantly target the immune system. These therapeutic agents slow progression and reduce severity at early stages of MS, but show little activity on the neurodegenerative component of the disease. As the latter determines permanent disability, there is a critical need to pursue alternative modalities. VIP (vasoactive intestinal peptide) and PACAP (pituitary adenylate cyclase-activating peptide) have potent anti-inflammatory and neuroprotective actions, and have shown significant activity in animal inflammatory disease models including the EAE (experimental autoimmune encephalomyelitis) MS model. Thus, their receptors have become candidate targets for inflammatory diseases. Here, we will discuss the immunomodulatory and neuroprotective actions of VIP and PACAP and their signalling pathways, and then extensively review the structure–activity relationship data and biophysical interaction studies of these peptides with their cognate receptors.

Persons with multiple sclerosis show altered joint kinetics during walking after participating in elliptical exercise

Patients with multiple sclerosis (MS) experience abnormal gait patterns and reduced physical activity. The purpose of this study was to determine if an elliptical exercise intervention for patients with MS would change joint kinetics during gait toward healthy control values. Gait analysis was performed on patients with MS (n = 24) before and after completion of 15 sessions of supervised exercise. Joint torques and powers were calculated, while also using walking velocity as a covariate, to determine the effects of elliptical exercise on lower extremity joint kinetics during gait. Results show that elliptical exercise significantly altered joint torques at the ankle and hip and joint powers at the ankle during stance. The change in joint power at the ankle indicates that, after training, patients with MS employed a walking strategy that is more similar to that of healthy young adults. These results support the use of elliptical exercise as a gait training tool for patients with MS.

Target populations for first-in-human embryonic stem cell research in spinal cord injury

Geron recently announced that it had begun enrolling patients in the world's first-in-human clinical trial involving cells derived from human embryonic stem cells (hESCs). This trial raises important questions regarding the future of hESC-based therapies, especially in spinal cord injury (SCI) patients. We address some safety and efficacy concerns with this research, as well as the ethics of fair subject selection. We consider other populations that might be better for this research: chronic complete SCI patients for a safety trial, subacute incomplete SCI patients for an efficacy trial, and perhaps primary progressive multiple sclerosis (MS) patients for a combined safety and efficacy trial.

Psychometric performance of a generic walking scale (Walk-12G) in multiple sclerosis and Parkinson's disease

Walking difficulties are common in neurological and other disorders, as well as among the elderly. There is a need for reliable and valid instruments for measuring walking difficulties in everyday life since existing gait tests are clinician rated and focus on situation specific capacity. The Walk-12G was adapted from the 12-item multiple sclerosis walking scale as a generic patient-reported rating scale for walking difficulties in everyday life. The aim of this study is to examine the psychometric properties of the Walk-12G in people with multiple sclerosis (MS) and Parkinson's disease (PD). The Walk-12G was translated into Swedish and evaluated qualitatively among 25 people with and without various neurological and other conditions. Postal survey (MS, n = 199; PD, n = 189) and clinical (PD, n = 36) data were used to test its psychometric properties. Respondents considered the Walk-12G relevant and easy to use. Mean completion time was 3.5 min. Data completeness was good (<5% missing item responses) and tests of scaling assumptions supported summing item scores to a total score (corrected item-total correlations >0.6). Coefficient alpha and test-retest reliabilities were >0.9, and standard errors of measurement were 2.3-2.8. Construct validity was supported by correlations in accordance with a priori expectations. Results are similar to those with previous Walk-12G versions, indicating that scale adaptation was successful. Data suggest that the Walk-12G meets rating scale criteria for clinical trials, making it a valuable complement to available gait tests. Further studies involving other samples and application of modern psychometric methods are warranted to examine the scale in more detail.

Which walking capacity tests to use in multiple sclerosis? A multicentre study providing the basis for a core set

BACKGROUND

Many different walking capacity test formats are being used. It is unclear whether walking speed, obtained from short tests, and walking distance, obtained from long tests, provide different clinical information.

OBJECTIVES

To determine the differential effect of various short and long walk test formats on gait velocity, and the actual relationship between walking speed and walking distance in multiple sclerosis (MS) patients with diverse ambulation status.

METHODS

A cross-sectional multicentre study design was applied. Ambulatory MS patients (Expanded Disability Status Scale (EDSS) 0-6.5; n = 189) were tested at 11 sites. Short tests consisted of the Timed 25-Foot Walk (static start, fastest speed) and 10-Metre Walk Test (dynamic start, usual and fastest speed). Long tests consisted of the 2- and 6-Minute Walk Tests (fastest speed). Subjects were divided into mild (EDSS 0-4; n = 99) or moderate (EDSS 4.5-6.5; n = 79) disability subgroups.

RESULTS

In both subgroups, the start protocol, instructed pace and length of test led to significantly different gait velocities. Fastest walking speed and 6-Minute walking distance showed the strongest correlation (R (2) = 0.78 in mild and R (2) = 0.81 in moderate MS; p < 0.01). Short tests' relative estimation errors for 6-Minute walking distance were 8-12% in mildly and 15-16% in moderately affected subjects. Based on the 2-Minute Walk Test, estimation errors significantly reduced to approximately 5% in both subgroups.

CONCLUSIONS

A single short test format at fastest speed accurately describes an MS patient's general walking capacity. For intervention studies, a long test is to be considered. We propose the Timed 25-Foot Walk and 2-Minute Walk Test as standards. Further research on responsiveness is needed.

Multiple sclerosis: new insights in pathogenesis and novel therapeutics

Concepts of multiple sclerosis (MS) have shifted from the traditional view of a T cell-mediated, demyelinating disease of the white matter to include a broad range of immunopathogenic mechanisms, axonal damage, and widespread gray matter pathology. The cause of MS remains unknown, but recent epidemiological work has focused on genetic factors; environmental factors such as vitamin D, sunlight, and Epstein-Barr virus; and the controversial theory of chronic cerebrospinal venous insufficiency. Revised criteria facilitate making the diagnosis of MS. Emerging therapies are rapidly expanding treatment options, including both parenterally administered and oral medications. Strategies to preserve tissue, promote repair, and restore function are under development, and it is anticipated that they will provide better options for patients with progressive disease.

Functional treatments in multiple sclerosis

PURPOSE OF REVIEW

This review focuses on recent advances in the understanding and management of symptoms and dysfunctions associated with multiple sclerosis (MS).

RECENT FINDINGS

A broad spectrum of dysfunctions associated with MS are under investigation. Research published in the past year and a half addresses gait dysfunction, exercise training, fatigue, bowel/bladder and sexual dysfunction, and sleep disruption. Functional electrical stimulation and strength training have been validated for improvement in gait and motor function. Exercise training has been shown to benefit mood and quality of life scores and to reduce circulating inflammatory cytokine levels. Fatigue remains a challenging problem with incremental improvements in understanding of underlying causes and effective drug therapies offered by recent work. Treatment of bowel, bladder and sexual dysfunction utilizing a variety of modalities has been investigated with some progress.

SUMMARY

In the absence of treatments to reverse neurologic injury due to MS, effective symptom management and functional improvement remain essential to mitigate disability and maintain quality of life. Basic research, as well as controlled clinical trials, in this realm offers promising insights and solutions.

Association between walking speed and age in healthy, free-living individuals using mobile accelerometry--a cross-sectional study

CONTEXT

Walking speed is a fundamental parameter of human motion and is increasingly considered as an important indicator of individuals' health status.

OBJECTIVE

To evaluate the relationship of gait parameters, and demographic and physical characteristics in healthy men and women.

DESIGN, SETTING, AND PARTICIPANTS

Recruitment of a subsample (n = 358) of male and female blood donors taking part in the Cambridge CardioResource study. Collection of demographic data, measurement of physical characteristics (height, weight and blood pressure) and assessment of 7-day, free-living activity parameters using accelerometry and a novel algorithm to measure walking speed. Participants were a median (interquartile range[IQR]) age of 49 (16) years; 45% women; and had a median (IQR) BMI of 26 (5.4).

MAIN OUTCOME MEASURE

Walking speed.

RESULTS

In this study, the hypothesis that walking speed declines with age was generated using an initial 'open' dataset. This was subsequently validated in a separate 'closed' dataset that showed a decrease of walking speed of -0.0037 m/s per year. This is equivalent to a difference of 1.2 minutes, when walking a distance of 1 km aged 20 compared to 60 years. Associations between walking speed and other participant characteristics (i.e. gender, BMI and blood pressure) were non-significant. BMI was negatively correlated with the number of walking and running steps and longest non-stop distance.

CONCLUSION

This is the first study using accelerometry which shows an association between walking speed and age in free-living, healthy individuals. Absolute values of gait speed are comparable to published normal ranges in clinical settings. This study highlights the potential use of mobile accelerometry to assess gait parameters which may be indicative of future health outcomes in healthy individuals.

Development and validation of a new method to measure walking speed in free-living environments using the actibelt® platform

Walking speed is a fundamental indicator for human well-being. In a clinical setting, walking speed is typically measured by means of walking tests using different protocols. However, walking speed obtained in this way is unlikely to be representative of the conditions in a free-living environment. Recently, mobile accelerometry has opened up the possibility to extract walking speed from long-time observations in free-living individuals, but the validity of these measurements needs to be determined. In this investigation, we have developed algorithms for walking speed prediction based on 3D accelerometry data (actibelt®) and created a framework using a standardized data set with gold standard annotations to facilitate the validation and comparison of these algorithms. For this purpose 17 healthy subjects operated a newly developed mobile gold standard while walking/running on an indoor track. Subsequently, the validity of 12 candidate algorithms for walking speed prediction ranging from well-known simple approaches like combining step length with frequency to more sophisticated algorithms such as linear and non-linear models was assessed using statistical measures. As a result, a novel algorithm employing support vector regression was found to perform best with a concordance correlation coefficient of 0.93 (95%CI 0.92–0.94) and a coverage probability CP1 of 0.46 (95%CI 0.12–0.70) for a deviation of 0.1 m/s (CP2 0.78, CP3 0.94) when compared to the mobile gold standard while walking indoors. A smaller outdoor experiment confirmed those results with even better coverage probability. We conclude that walking speed thus obtained has the potential to help establish walking speed in free-living environments as a patient-oriented outcome measure.

C5b-9-activated, K(v)1.3 channels mediate oligodendrocyte cell cycle activation and dedifferentiation

Voltage-gated potassium (K(v)) channels play an important role in the regulation of growth factor-induced cell proliferation. We have previously shown that cell cycle activation is induced in oligodendrocytes (OLGs) by complement C5b-9, but the role of K(v) channels in these cells had not been investigated. Differentiated OLGs were found to express K(v)1.4 channels, but little K(v)1.3. Exposure of OLGs to C5b-9 modulated K(v)1.3 functional channels and increased protein expression, whereas C5b6 had no effect. Pretreatment with the recombinant scorpion toxin rOsK-1, a highly selective K(v)1.3 inhibitor, blocked the expression of K(v)1.3 induced by C5b-9. rOsK-1 inhibited Akt phosphorylation and activation by C5b-9 but had no effect on ERK1 activation. These data strongly suggest a role for K(v)1.3 in controlling the Akt activation induced by C5b-9. Since Akt plays a major role in C5b-9-induced cell cycle activation, we also investigated the effect of inhibiting K(v)1.3 channels on DNA synthesis. rOsK-1 significantly inhibited the DNA synthesis induced by C5b-9 in OLG, indicating that K(v)1.3 plays an important role in the C5b-9-induced cell cycle. In addition, C5b-9-mediated myelin basic protein and proteolipid protein mRNA decay was completely abrogated by inhibition of K(v)1.3 expression. In the brains of multiple sclerosis patients, C5b-9 co-localized with NG2(+) OLG progenitor cells that expressed K(v)1.3 channels. Taken together, these data suggest that K(v)1.3 channels play an important role in controlling C5b-9-induced cell cycle activation and OLG dedifferentiation, both in vitro and in vivo.

Therapeutics for multiple sclerosis symptoms

Symptoms management in multiple sclerosis is an integral part of its care. Accurate assessment and addressing the different symptoms provides increased quality of life among patients with multiple sclerosis. Multiple sclerosis symptoms may be identified as primary, secondary, or tertiary symptoms. Primary symptoms, such as weakness, sensory loss, and ataxia, are directly related to demyelination and axonal loss. Secondary symptoms, such as urinary tract infections as a result of urinary retention, are a result of the primary symptoms. Tertiary symptoms, such as reactive depression or social isolation, are a result of the social and psychological consequences of the disease. Common multiple sclerosis symptoms include fatigue and weakness; decreased balance, spasticity and gait problems; depression and cognitive issues; bladder, bowel, and sexual deficits; visual and sensory loss; and neuropathic pain. Less-common symptoms include dysarthria and dysphagia, vertigo, and tremors. Rare symptoms in multiple sclerosis include seizures, hearing loss, and paralysis. Symptom management includes nonpharmacological methods, such as rehabilitation and psychosocial support, and pharmacological methods, ie, medications and surgical procedures. The keys to symptom management are awareness, knowledge, and coordination of care. Symptoms have to be recognized and management needs to be individualized. Multiple sclerosis therapeutics include nonpharmacological strategies that consist of lifestyle modifications, rehabilitation, social support, counseling, and pharmacological agents or surgical procedures. The goal is vigilant management to improve quality of life and promote realistic expectations and hope.

Symptomatic management in multiple sclerosis

The development of immunomodulatory therapies for multiple sclerosis (MS) has had significant impact in altering the natural history of the disease. Although these agents reduce relapse rate and MRI-associated disease activity, they are only partially effective and do not ameliorate irreversible axonal injury, which produces much of the symptomatic burden of MS. Treatment of MS-associated symptoms remains an essential cornerstone of comprehensive care of patients with MS and, arguably, more favorably enhances quality of life than do the disease-modifying medications. This article reviews strategies of symptom management in patients with MS.

Pediatric multiple sclerosis

In the past 5 years, there has been an exponential growth in the knowledge about multiple sclerosis (MS) in children and adolescents. Recent publications have shed light on its diagnosis, pathogenesis, clinical course, and treatment. However, there remain several key areas that require further exploration. This article summarizes the current state of knowledge on pediatric MS and discusses future avenues of investigation.

Treatment of walking impairment in multiple sclerosis with dalfampridine

Potassium channel blockade has long been considered a potential therapeutic strategy for treatment of multiple sclerosis (MS) based on the pathophysiology of demyelinated axons. Dalfampridine, which is also known as fampridine or 4-aminopyridine (4-AP), is the potassium channel blocker that has been studied most extensively in MS and other demyelinating neurologic disorders. An extended-release formulation of dalfampridine was recently approved by the US Food and Drug Administration to improve walking in patients with MS. In randomized, double-blind, placebo-controlled trials, with dalfampridine extended release tablets 10 mg taken twice daily, about 12 h apart, walking speed was improved in approximately one-third of treated patients; in these patients, average walking speed on therapy was about 25% above baseline. This improvement was clinically meaningful as assessed by concurrent measurement of patient-reported severity of walking-related disability. Dalfampridine extended release tablets were generally well tolerated, with a range of adverse effects that appear to be related to increases in central nervous system excitation. There is a dose-dependent increase in the occurrence of seizures at doses higher than the recommended 10 mg twice daily.

Symptomatic therapy in multiple sclerosis: a review for a multimodal approach in clinical practice

As more investigations into factors affecting the quality of life of patients with multiple sclerosis (MS) are undertaken, it is becoming increasingly apparent that certain comorbidities and associated symptoms commonly found in these patients differ in incidence, pathophysiology and other factors compared with the general population. Many of these MS-related symptoms are frequently ignored in assessments of disease status and are often not considered to be associated with the disease. Research into how such comorbidities and symptoms can be diagnosed and treated within the MS population is lacking. This information gap adds further complexity to disease management and represents an unmet need in MS, particularly as early recognition and treatment of these conditions can improve patient outcomes. In this manuscript, we sought to review the literature on the comorbidities and symptoms of MS and to summarize the evidence for treatments that have been or may be used to alleviate them.

Chronic progressive multiple sclerosis - pathogenesis of neurodegeneration and therapeutic strategies

Multiple sclerosis (MS) is an inflammatory, autoimmune, demyelinating disease of the central nervous system (CNS) that usually starts as a relapsing-remitting disease. In most patients the disease evolves into a chronic progressive phase characterized by continuous accumulation of neurological deficits. While treatment of relapsing-remitting MS (RRMS) has improved dramatically over the last decade, the therapeutic options for chronic progressive MS, both primary and secondary, are still limited. In order to find new pharmacological targets for the treatment of chronic progressive MS, the mechanisms of the underlying neurodegenerative process that becomes apparent as the disease progresses need to be elucidated. New animal models with prominent and widespread progressive degenerative components of MS have to be established to study both inflammatory and non-inflammatory mechanisms of neurodegeneration. Here, we discuss disease mechanisms and treatment strategies for chronic progressive MS.

Dalfampridine: a brief review of its mechanism of action and efficacy as a treatment to improve walking in patients with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) can cause progressive walking impairment that contributes to disability, loss of independence, and reduced quality of life. Dalfampridine (4-aminopyridine), a voltage-dependent potassium channel blocker, has been shown to improve walking in patients with MS, as demonstrated by an increase in walking speed.

OBJECTIVE

To summarize knowledge about the mechanism of action of dalfampridine in the context of clinical evidence of walking improvement in MS patients.

METHODS

Although this was not a systematic review, which is the primary limitation of this study, searches of PubMed were performed using relevant search terms to identify studies that examined the mechanism of action related to MS and its effects in patients with MS in clinical trials.

RESULTS

Voltage-gated potassium channels represent a family of related proteins that span cell membranes, open and close in response to changes in the transmembrane potential, and help regulate ionic potassium currents. Action potential conduction deficits in demyelinated axons result in part from the exposure after demyelination of the paranodal and internodal potassium channels that are distributed in the axonal membrane. This exposure leads to abnormal currents across the axonal membrane that can slow action potential conduction, result in conduction failure, or affect the axon's capacity for repetitive discharge. While dalfampridine is a broad-spectrum blocker of voltage-dependent potassium channels at millimolar concentrations, studies have shown improvement in action potential conduction in demyelinated axons at concentrations as low as 1 μM, and therapeutic plasma concentrations (associated with improved walking) are in the range of 0.25 µM. However, no specific potassium channel subtype has yet been characterized with significant sensitivity to dalfampridine in this range, and the effects of the drug at this low concentration appear to be quite selective. Improved conduction translates into clinical benefit as measured by objectively and subjectively assessed walking relative to placebo. Such improvements were observed in approximately one third of patients treated with an extended-release formulation of dalfampridine in clinical trials. These patients who responded to dalfampridine had an average increase in walking speed of approximately 25%, and greater improvements than nonresponders on a self-reported subjective measure of walking.

CONCLUSIONS

The extended-release formulation of dalfampridine has been shown in clinical trials to improve walking speed in approximately one third of MS patients with ambulatory impairment. The putative mechanism of action of dalfampridine is restoration of action potential conduction via blockade of an as yet uncharacterized subset of potassium channels in demyelinated axons.

Dalfampridine in multiple sclerosis: from symptomatic treatment to immunomodulation

Multiple sclerosis (MS) is a neurodegenerative disease that is deemed to affect more than 2.1 million people worldwide, and for which there is no cure. Early symptoms of MS are believed to result from axonal demyelination leading to slowing or blockade of impulse conduction. The blockade of K+ channels has been proven to improve conduction deficiencies secondary to demyelination in patients with MS. Dalfampridine is a K+ channel blocker that was recently approved by FDA for the symptomatic treatment of ambulation hardship in MS. Understanding the mechanisms by which Dalfampridine exerts its therapeutic effects is a complex issue as it blocks a wide variety of K+ channels that are distributed across multiple cell types in the nervous system but also in the immune system, and because of their molecular identities remaining unknown. This review describes Dalfampridine potential roles at the cellular and molecular levels in MS pathogenesis.

Quantitative measures detect sensory and motor impairments in multiple sclerosis

BACKGROUND

Sensory and motor dysfunction in multiple sclerosis (MS) is often assessed with rating scales which rely heavily on clinical judgment. Quantitative devices may be more precise than rating scales.

OBJECTIVE

To quantify lower extremity sensorimotor measures in individuals with MS, evaluate the extent to which they can detect functional systems impairments, and determine their relationship to global disability measures.

METHODS

We tested 145 MS subjects and 58 controls. Vibration thresholds were quantified using a Vibratron-II device. Strength was quantified by a hand-held dynamometer. We also recorded Expanded Disability Status Scale (EDSS) and Timed 25-Foot Walk (T25FW). t-tests and Wilcoxon-rank sum were used to compare group data. Spearman correlations were used to assess relationships between each measure. We also used a step-wise linear regression model to determine how much the quantitative measures explain the variance in the respective functional systems scores (FSS).

RESULTS

EDSS scores ranged from 0-7.5, mean disease duration was 10.4 ± 9.6 years, and 66% were female. In relapsing-remitting MS, but not progressive MS, poorer vibration sensation correlated with a worse EDSS score, whereas progressive groups' ankle/hip strength changed significantly with EDSS progression. Interestingly, not only did sensorimotor measures significantly correlate with global disability measures (i.e., EDSS), but they had improved sensitivity, as they detected impairments in up to 32% of MS subjects with normal sensory and pyramidal FSS.

CONCLUSIONS

Sensory and motor deficits in MS can be quantified using clinically accessible tools and distinguish differences among MS subtypes. We show that quantitative sensorimotor measures are more sensitive than FSS from the EDSS. These tools have the potential to be used as clinical outcome measures in practice and for future MS clinical trials of neurorehabilitative and neuroreparative interventions.

Treatment of walking impairment in multiple sclerosis: an unmet need for a disease-specific disability

INTRODUCTION

Walking impairment is a clinical hallmark of multiple sclerosis (MS), a chronic neurologic disease characterized by axonal demyelination and dysfunction that results in progressive disability. Until recently, there were no therapies that specifically targeted the axonal dysfunction associated with walking impairment in MS.

AREAS COVERED

The purpose of this review is to discuss the unmet need for the treatment of walking impairment in MS patients and to evaluate how a new class of pharmacologic therapies, neurofunctional modifiers, potentially addresses this unmet need. Discussion is based on clinical experience and opinions supported by publications identified in the PubMed literature using the search terms 'multiple sclerosis' and 'mobility OR walking'.

EXPERT OPINION

The development and approval of new treatments for MS show promise for improving adherence to therapy and increasing the potential for clinical effectiveness. Renewed emphasis on integrating strategies that target the underlying pathophysiology with those that address symptoms of concern to patients also has the potential to improve the lives of MS patients and their caregivers. The introduction of neurofunctional modifiers, such as dalfampridine for the improvement of walking impairment, may be of benefit by improving function, mobility and overall quality of life for MS patients.

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.

[Development of new therapies for multiple sclerosis]

BACKGROUND

Current first line treatment for multiple sclerosis is only moderately effective and is associated with frequent and disturbing side effects. We here describe opportunities and challenges related to drugs under development.

MATERIAL AND METHODS

Non-systematic search in PubMed and congress abstracts.

RESULTS AND INTERPRETATION

Monoclonal antibodies (e.g. natalizumab, alemtuzumab, rituximnab and dacklizumab) and oral agents (e.g. fingolimod and cladribine) target molecules or cells which are important in the immunopathogenesis of multiple sclerosis. These agents seem to have a considerable effect on relapsing-remitting multiple sclerosis, but may also be associated with serious side effects. Natalizumab is licensed as second line treatment for relapsing-remitting multiple sclerosis, and also as first line treatment in especially serious cases. Cladribine and fingolimod may be available in Norway in 2011.

INTERPRETATION

Treatment of exacerbations in multiple sclerosis is changing. Indication for the drugs under development is not yet clear.

Potassium channel blockers as an effective treatment to restore impulse conduction in injured axons

Most axons in the vertebral central nervous system are myelinated by oligodendrocytes. Myelin protects and insulates neuronal processes, enabling the fast, saltatory conduction unique to myelinated axons. Myelin disruption resulting from trauma and biochemical reaction is a common pathological event in spinal cord injury and chronic neurodegenerative diseases. Myelin damage-induced axonal conduction block is considered to be a significant contributor to the devastating neurological deficits resulting from trauma and illness. Potassium channels are believed to play an important role in axonal conduction failure in spinal cord injury and multiple sclerosis. Myelin damage has been shown to unmask potassium channels, creating aberrant potassium currents that inhibit conduction. Potassium channel blockade reduces this ionic leakage and improves conduction. The present review was mainly focused on the development of this technique of restoring axonal conduction and neurological function of demyelinated axons. The drug 4-aminopyridine has recently shown clinical success in treating multiple sclerosis symptoms. Further translational research has also identified several novel potassium channel blockers that may prove effective in restoring axonal conduction.

Fingolimod: a novel oral immunomodulatory treatment for multiple sclerosis

Fingolimod (FTY720), an immunomodulator that acts on sphingosine-1-phosphate receptors, is the first oral disease-modifying agent to be approved by the US FDA for the treatment of relapsing forms of multiple sclerosis (MS). Compared with other disease-modifying agents, fingolimod is unique in its mechanisms of action: it sequesters lymphocytes into lymph nodes without directly inhibiting effector functions, and it exerts pleiotropic actions on cultured oligodendrocytes and oligodendrocyte progenitors. Whether the latter contributes to the favorable response to this drug is currently being investigated. Results from Phase II and III clinical trials demonstrate that fingolimod is highly effective in relapsing–remitting MS. In this article, we review the background on MS therapy, the mechanisms and pharmacology of fingolimod and its benefit–risk profile as a novel therapy in MS.

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.

Comparison of the Timed 25-Foot and the 100-Meter Walk as Performance Measures in Multiple Sclerosis

Background. Ambulation impairment is a major component of physical disability in multiple sclerosis (MS) and a major target of rehabilitation programs. Outcome measures commonly used to evaluate walking capacities suffer from several limitations. Objectives. To define and validate a new test that would overcome the limitations of current gait evaluations in MS and ultimately better correlate with the maximum walking distance (MWD). Methods. The authors developed the Timed 100-Meter Walk Test (T100MW), which was compared with the Timed 25-Foot Walk Test (T25FW). For the T100MW, the subject is invited to walk 100 m as fast as he/she can. In MS patients and healthy control volunteers, the authors measured the test–retest and interrater intraclass correlation coefficient. Spearman rank correlations were obtained between the T25FW, the T100MW, the Expanded Disability Status Scale (EDSS), and the MWD. The coefficient of variation, Bland–Altman plots, the coefficient of determination, and the area under the receiver operator characteristic curve were measured. The mean walking speed (MWS) was compared between the 2 tests. Results. A total of 141 MS patients and 104 healthy control volunteers were assessed. Minor differences favoring the T100MW over the T25FW were observed. Interestingly, the authors demonstrated a paradoxically higher MWS on a long (T100MW) rather than on a short distance walk test (T25FW). Conclusion. The T25FW and T100MW displayed subtle differences of reproducibility, variability, and correlation with MWD favoring the T100MW. The maximum walking speed of MS patients may be poorly estimated by the T25FW since MS patients were shown to walk faster over a longer distance.

Patient considerations in the management of multiple sclerosis: development and clinical utility of oral agents

Multiple sclerosis (MS) is one of the most frequently occurring disabling neurological disorders among young adults in Canada. It is a chronic inflammatory disorder of the central nervous system (CNS) that is thought to be immune mediated in nature. An estimated 55,000-75,000 Canadians suffer from this debilitating disease. Starting in the mid-1990s, we witnessed the beginning of a new era in the treatment of MS. Treatments finally became available to help modify the course of the disease. Early initiation of treatment soon after diagnosis has become the expectation in many MS clinics, warranting many decisions to be made by the patient with the assistance of their health care team. Currently, there are two categories of disease-modifying therapies (DMTs) available: immunomodulatory and immunosuppressant agents. Although disease-modifying therapies are not a cure and are only moderately effective, they offer a possible slowing of any progression that may occur over time, a decrease in relapse activity, and a decrease in the amount of new lesions developing in the CNS found on magnetic resonance imaging. Not only have these agents been partly effective but up to now they have only been available parenterally, which has many limitations, including a major factor in determining the best outcome for the treatment: adherence. Four new DMTs will likely become available to Canadians over the next five years. Fingolimod, cladribine, teriflunomide, and laquinimod are likely to be marketed as the first oral DMTs in Canada. The US Food and Drug Administration approved fingolimod in September 2010 as a first-line therapy for relapsing forms of MS. Dalfampridine is also available in the US as an agent able to improve walking. Even if these agents present with higher efficacy and a promising safety and tolerability profile, thus possibly demonstrating better adherence, it will be imperative for the health care professionals to focus on monitoring and supporting the patient to ensure reliable reporting of side effects and to improve overall adherence. In the near future, more treatments will become available to the MS population, and choices will become even more complex so that ongoing support, open communication, and education are required to tame any uncertainties about decisions made regarding treatments.

Microwave assisted synthesis and solid-state characterization of lithocholyl amides of isomeric aminopyridines

Microwave (MW) assisted synthesis and solid state structural characterizations of novel lithocholyl amides of 2-, 3-, and 4-aminopyridine are reported. It is shown that the MW technique is a proper method in the preparation of N-lithocholyl amides of isomeric aminopyridines. It offers many advantages compared to conventional heating. The molecular and crystal structures as well as the polymorphic and hydrated forms of prepared conjugates with their thermodynamic stabilities have been characterized by means of high resolution liquid- and solid-state NMR spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Owing to the many biological functions of bile acids and amino substituted nitrogen heterocycles, knowledge of the crystal packing of these novel conjugates may have relevance for potential pharmaceutical applications.

A novel Caenorhabditis elegans allele, smn-1(cb131), mimicking a mild form of spinal muscular atrophy, provides a convenient drug screening platform highlighting new and pre-approved compounds

Spinal muscular atrophy (SMA), an autosomal recessive genetic disorder, is characterized by the selective degeneration of lower motor neurons, leading to muscle atrophy and, in the most severe cases, paralysis and death. Deletions and point mutations cause reduced levels of the widely expressed survival motor neuron (SMN) protein, which has been implicated in a range of cellular processes. The mechanisms underlying disease pathogenesis are unclear, and there is no effective treatment. Several animal models have been developed to study SMN function including the nematode, Caenorhabditis elegans, in which a large deletion in the gene homologous to SMN, smn-1, results in neuromuscular dysfunction and larval lethality. Although useful, this null mutant, smn-1(ok355), is not well suited to drug screening. We report the isolation and characterization of smn-1(cb131), a novel allele encoding a substitution in a highly conserved residue of exon 2, resembling a point mutation found in a patient with type IIIb SMA. The smn-1(cb131) animals display milder yet similar defects when compared with the smn-1 null mutant. Using an automated phenotyping system, mutants were shown to swim slower than wild-type animals. This phenotype was used to screen a library of 1040 chemical compounds for drugs that ameliorate the defect, highlighting six for subsequent testing. 4-aminopyridine, gaboxadol hydrochloride and N-acetylneuraminic acid all rescued at least one aspect of smn-1 phenotypic dysfunction. These findings may assist in accelerating the development of drugs for the treatment of SMA.

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.

Dalfampridine sustained-release for symptomatic improvement of walking speed in patients with multiple sclerosis

Dalfampridine sustained-release (SR) is a time-release formulation of 4-aminopyridine, recently approved by the Food and Drug Administration to improve walking in patients with multiple sclerosis (MS). In Phase II trials, walking speed and lower extremity muscle strength was increased in patients with MS, but the increase in walking speed did not reach statistical significance. A responder analysis revealed that approximately 35% of treated patients had a statistically significant and clinically meaningful increase in walking speed. When treated responders were compared with treated nonresponders, walking speed significantly increased in the responder group, but not in the nonresponder or placebo groups. This result was duplicated in two larger Phase III trials. The optimal dose to maximize the risk-benefit ratio was 10 mg twice daily. Higher doses were associated with a greater risk of seizure, but no further improvement in walking speed or in the proportion of responders. Dalfampridine SR is eliminated by renal clearance and undergoes only limited metabolism (<10%). It is contraindicated in patients with moderate or severe renal insufficiency and in those with a history of seizures or epileptiform activity on electroencephalography. The development of time-released 4-aminopyridine represents a major advance in symptomatic therapy for MS.