Quantitative assessment of sustained-release 4-aminopyridine for symptomatic treatment of multiple sclerosis

Selective NMR detection of individual reaction components hyperpolarised by reversible exchange with para-hydrogen

NMR spectroscopy can sometimes be hampered by two inherent weaknesses: low sensitivity and overlap of signals in complex mixtures. Hyperpolarisation techniques using para-hydrogen (including the method known as SABRE) can...

Phase IIB Randomized Trial on the Use of 4-Aminopyridine in Guillain-Barré Syndrome

OBJECTIVE

To determine the safety and efficacy of orally delivered 4-aminopyridine (4-AP) in persons with Guillain-Barré Syndrome (GBS) >6 months from initial diagnosis.

DESIGN

A randomized, double-blind, placebo-controlled, crossover study.

SETTING

Tertiary care clinical outpatient program.

PARTICIPANTS

Nineteen participants enrolled (14 male, 5 female; N=19), neurologic impairment secondary to GBS and functional loss on the FIM motor score (stable for ≥12mo) and >3.0 but <5.0 on the American Spinal Injury motor scale. Twelve participants (mean age, 59y; range, 23-77y) completed the study.

INTERVENTIONS

A 4-AP dose-escalation study with 8 weeks in each period with a 3-week washout period, followed by 3 months open-label follow-up.

MAIN OUTCOME MEASURES

FIM motor score was the primary outcome measure; also evaluated were the American Spinal Injury motor strength score (all limbs), handheld dynamometer, 6-minute walk test, Medical Outcomes Study 12-Item Short Form, Center for Epidemiological Studies Depression scale, Positive and Negative Affect Schedule, pain, GBS disability scale, Jepsen-Taylor Hand Function Test, Minnesota Manual Dexterity Test and Minnesota Rate of Manipulation Test, Get Up and Go Test, McGill Pain Inventory, Craig Handicap Assessment and Reporting Technique, and participant self-evaluation.

RESULTS

Seven participants discontinued the study prematurely: 3 because of adverse events, 3 because of travel difficulties or relocation, and 1 because of pretreatment laboratory abnormalities. After removing 3 participants with maximum FIM scores, 4-AP arm trended superior to placebo (P=.065). Patients subjectively could always tell when they were on the active agent usually by tingling sensations or a sense of wellness. No statistically significant differences were found for other outcome measures although there were strong trends.

CONCLUSIONS

This study demonstrates the safety of 4-AP in the patient population with GBS as the predominate goal of the study. A trend toward improved function after treatment was noted with most patients electing to stay on the medication after the trial.

Neuroprotective Properties of 4-Aminopyridine

As an antagonist of voltage-gated potassium (Kv) channels, 4-aminopyridine (4-AP) is used as symptomatic therapy in several neurologic disorders. The improvement of visual function and motor skills and relieve of fatigue in patients with MS have been attributed to 4-AP. Its prolonged release formulation (fampridine) has been approved for the symptomatic treatment of walking disability in MS. The beneficial effects were explained by the blockade of axonal Kv channels, thereby enhancing conduction along demyelinated axons. However, an increasing body of evidence suggests that 4-AP may have additional properties beyond the symptomatic mode of action. In this review, we summarize preclinical and clinical data on possible neuroprotective features of 4-AP.

Aminopiridines in the treatment of multiple sclerosis and other neurological disorders

Symptomatic treatment has a great relevance for the management of patients with neurologic diseases, since it reduces disease burden and improves quality of life. Aminopyridines (APs) are a group of potassium (K+) channel blocking agents that exert their activity both at central nervous system level and on neuromuscular junction. This review describes the use of APs for the symptomatic treatment of neurological conditions. We will describe trials leading to the approval of the extended-release 4-aminopyridine for MS and evidence in support of the use in other neurological diseases.

Crystal structure and Hirshfeld surface analysis of 4-amino-pyridinium thio-cyanate-4-amino-pyridine (1/1)

In the crystals of the title compound, C5H7N2 +·CNS-·C5H6N2, the components are linked by three N-H⋯N and two N-H⋯S hydrogen bonds, resulting in two inter-penetrating three-dimensional networks. Hirshfeld surface analysis shows that the most important contributions to the crystal packing are from H⋯H (36.6%), C⋯H/H⋯C (20.4%), S⋯H/H⋯S (19.7%) and N⋯H/H⋯N (13.4%) inter-actions.

Efficacy and safety of fampridine for walking disability in multiple sclerosis

Fampridine is the only drug approved for the treatment of walking impairment in multiple sclerosis. Around a third of the patients on treatment obtained an improvement in walking speed during the development phase. The effects are clinically significant, appear soon after the start of the treatment and are long-lasting, but disappear soon after the drug is withdrawn. In the real-world setting, the number of patients with a significant response to the treatment seems to be higher (around 70%). The tolerance is good, with mild to moderate, and transient adverse events. The most commonly reported are insomnia, headache, fatigue, back pain, dizziness, nausea and balance disorders. The main contraindications are a history of seizures, renal impairment and concomitant treatment with OCT2 inhibitors.

Concomitant polymorphic forms of 3-cyclopropyl-5-(2-hydrazinylpyridin-3-yl)-1,2,4-oxadiazole

The dipharmacophore compound 3-cyclopropyl-5-(2-hydrazinylpyridin-3-yl)-1,2,4-oxadiazole, C10H11N5O, was studied on the assumption of its potential biological activity. Two concomitant polymorphs were obtained on crystallization from isopropanol solution and these were thoroughly studied. Identical conformations of the molecules are found in both structures despite the low difference in energy between the four possible conformers. The two polymorphs differ crucially with respect to their crystal structures. A centrosymmetric dimer formed due to both stacking interactions of the `head-to-tail' type and N—H...N(π) hydrogen bonds is the building unit in the triclinic structure. The dimeric building units form an isotropic packing. In the orthorhombic polymorphic structure, the molecules form stacking interactions of the `head-to-head' type, which results in their organization in a column as the primary basic structural motif. The formation of N—H...N(lone pair) hydrogen bonds between two neighbouring columns allows the formation of a double column as the main structural motif. The correct packing motifs in the two polymorphs could not be identified without calculations of the pairwise interaction energies. The triclinic structure has a higher density and a lower (by 0.60 kcal mol−1) lattice energy according to periodic calculations compared to the orthorhombic structure. This allows us to presume that the triclinic form of 3-cyclopropyl-5-(2-hydrazinylpyridin-3-yl)-1,2,4-oxadiazole is the more stable.

Effects of modified-release fampridine on upper limb impairment in patients with Multiple Sclerosis

BACKGROUND

Modified-release 4-aminopyridine (fampridine-MR) is used in the symptomatic treatment of walking disability in patients with multiple sclerosis (MS).  Its potential for use in other MS symptoms remains unproven and its mode of action in this context is uncertain. Interest is growing in the use of upper limb outcome measures in clinical trials in patients with Multiple Sclerosis, particularly in advanced or progressive disease.  This study tests the following hypotheses: (1) Fampridine-MR improves upper limb function in patients with MS and upper limb impairment.  (2) Treatment with fampridine-MR is associated with measurable alterations in objective electrophysiological parameters (evoked potentials and transcranial magnetic stimulation (TMS)) which may predict response to drug treatment.

METHODS

Study population: patients with MS of any disease subtype, duration and severity who have symptomatic impairment of one or both upper limbs.  A healthy control group was included for validation of clinical and electrophysiological measures.  Study design: randomised double blind placebo-controlled trial.  Treatment details: participants allocated to either fampridine-MR 10 mg bd or placebo of identical appearance for 8 weeks.  Primary outcome: performance on 9-hole peg test (9HPT) after 4 weeks.  Secondary outcomes: persistence of effect on 9HPT; grip strength; visual acuity and contrast sensitivity; modified fatigue impact scale score; sensory discrimination capacity; visual, somatosensory and motor evoked potentials; resting motor threshold; paired-pulse TMS; peripheral nerve conduction studies.

RESULTS

40 patients with MS (60% female, median age 52, median disease duration 13.5 years, median EDSS 6.0) were enrolled.  Treatment with fampridine-MR was not associated with any change in upper limb function as measured by the clinical primary or secondary outcomes.  Treatment with fampridine-MR was also not associated with any difference in electrophysiological measures of upper limb function.  This held true after adjustment for hand dominance, disease duration and severity.  Four patients withdrew from the trial because of lack of efficacy or side-effects; all were in the placebo arm.  Three patients were admitted to hospital during the study period; one with MS exacerbation (placebo group), one with syncope (drug group) and one with UTI (drug group); otherwise there were no serious adverse events.

CONCLUSION

Treatment with fampridine-MR was well-tolerated but did not produce clinical benefit in terms of upper limb function, vision or fatigue, nor was there any measurable effect on objective electrophysiological parameters.

Cognitive Fatigability Interventions in Neurological Conditions: A Systematic Review

INTRODUCTION

Although fatigue is a well-studied concept in neurological disease, cognitive fatigability (CF) is less understood. While most studies measure fatigue using subjective self-report, fewer have measured CF objectively. Given the negative impact of CF on quality-of-life, there is a need for targeted interventions. The objective of this review was to determine which procedural, behavioural and pharmacological treatments for objectively measured CF are available to people living with neurological conditions.

METHODS

In accordance with the PRISMA guidelines, systematic searches for randomized control trials (RCTs), case-controlled studies and case reports/series were conducted across the Ovid Medline, PsycInfo, EMBASE and Cochrane Library databases. English-language articles published between 1980 and February 2019 were considered for eligibility. Included were those that objectively measured CF in individuals with neurological disease/disorder/dysfunction between the ages of 18 and 65 years. Studies were reviewed using a modified Cochrane Data Extraction Template. Risk of bias was assessed using the Cochrane Risk of Bias tool. The review process was facilitated using Covidence software (www.covidence.org). Two authors reviewed articles independently, with a third resolving conflicts regarding article inclusion.

RESULTS

The search identified 450 records. After duplicates were removed and remaining titles/abstracts were screened for eligibility, 28 full-text articles were assessed, and two studies were included in the qualitative synthesis. Studies were a priori divided into those with pharmacological, procedural or behavioural interventions. Two studies met eligibility criteria; both of these included participants with multiple sclerosis. One study utilized a procedural intervention (i.e. transcranial direct current stimulation), while the other utilized a pharmacological intervention (i.e. fampridine-SR). Studies were evaluated for risk of bias, and evidence from both eligible studies was discussed.

CONCLUSION

Despite the positive results of the procedural intervention, the paucity of eligible studies and the nascent nature of the field suggests that more studies are required before firm conclusions can be drawn regarding the amenability of CF to treatment.

TRIAL REGISTRATION

The review was registered with PROSPERO (CRD42019118706).

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.

2-Amino-6-chloropyridinium 3-carboxy-4-hydroxybenzenesulfonate

In the 3-carboxy-4-hydroxybenzenesulfonate anion of the title salt, C5H6ClN2 +·C7H5O6S−, an intramolecular O—H...O hydrogen bond with an S(6) ring motif is observed. In the crystal, the anions are linked into a chain structure running along [1\overline{1}0] via an O—H...O hydrogen bond formed between the carboxy and sulfonate groups. The 2-amino-6-chloropyridinium cations bridge the anion chains via N—H...O and C—H...O hydrogen bonds, forming a sheet parallel to the ab plane. In the sheet, a C—H...Cl interaction between the cations is also observed.

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.

Randomized, Placebo-controlled Crossover Study of Dalfampridine Extended-release in Transverse Myelitis

Background

Dalfampridine has the potential to be effective in patients with transverse myelitis (TM) as this rare disorder shares some clinical and pathogenic similarities with multiple sclerosis.

Methods

This is a randomized, double-blind, placebo-controlled crossover study of dalfampridine extended-release (D-ER, Ampyra®). Sixteen adult study participants with monophasic TM confirmed by MRI were enrolled if their baseline timed 25-foot walking speed was between 5 and 60 seconds. Participants were randomized to receive 10 mg twice-daily doses of either D-ER or placebo control for eight weeks, then crossed over to the second arm of placebo or dalfampridine for eight weeks. The primary outcome measure was the timed 25-foot walk.

Results

Of 16 enrolled participants, three withdrew and 13 completed the trial. Among the 13 completers, nine individuals showed an average timed walk that was faster in the D-ER arm compared to the placebo arm, but only four participants met the stricter statistical threshold to be classified as a responder. Analyses of secondary clinical outcome measures including strength, balance assessments, spasticity, and Expanded Disability Status Scale (EDSS) score showed trends toward improvement with D-ER.

Conclusions

D-ER may be beneficial in TM to improve walking speed and other neurological functions.

Fampridine Prolonged Release: A Review in Multiple Sclerosis Patients with Walking Disability

Oral fampridine prolonged release (PR) [Fampyra^®] is a lipid-soluble selective potassium channel blocker that is approved in the EU for the improvement of walking in adult multiple sclerosis (MS) patients with walking disability (expanded disability status scale score of 4-7). In clinical trials (MS-F203 and MS-F204) using an objective measure of walking improvement [the timed 25-foot walk (T25FW)], more than one-third of patients receiving fampridine PR achieved a consistent on-treatment improvement in walking speed (i.e. became TW responders) over 9-14 weeks of treatment. Fampridine PR recipients who fulfilled the definition of TW responder had mean improvements of ≈25% from baseline in T25FW walking speed. In a clinical trial (ENHANCE) that used a patient-rated measure of walking improvement [12-item MS walking scale (MSWS-12)], a significantly greater proportion of fampridine PR recipients than placebo recipients achieved a ≥8-point improvement on the MSWS-12 with 24 weeks of treatment. Where reported, adverse events were mostly mild or moderate in severity, and generally consistent with the underlying disease or mechanism of action of fampridine PR. Fampridine PR is a useful treatment option to consider in adult MS patients with walking disability.

The effect of Fampridine-SR on cognitive fatigue in a randomized double-blind crossover trial in patients with MS

BACKGROUND

Cognitive fatigue (CF) is a common complaint in persons with MS (PwMS). Fampridine-SR improves ambulation, fatigue and endurance, due to enhancing action potential formation by blocking potassium channels in demyelinated axons. Thus, through this same mechanism, it is hypothesized that Fampridine-SR could improve CF.

OBJECTIVE

To determine if Fampridine-SR objectively improves CF in PwMS.

METHODS

Sixty PwMS of any type with CF, defined as 3 or less correct responses when comparing the last third to the first third on the Paced Auditory Serial Addition Test (PASAT), were recruited from a tertiary care MS clinic in London (ON) Canada. Subjects also had to be between 18 and 64 years of age, inclusive, not had a relapse in the last 60 days or corticosteroids in the last 30 days, EDSS 0.0-7.0, and no other diagnosis that could cause cognitive impairment. A randomized double blind crossover design was used: subjects were randomized to either placebo or Fampridine-SR for 4 weeks, then after at least a one week washout, received the opposite treatment. Subjects were assessed before and after each treatment block. The primary outcome was the PASAT CF score after treatment with Fampridine-SR compared to placebo. T-tests and chi-square were used to compare demographics between the two groups (placebo-Fampridine-SR vs. Fampridine SR-placebo). Treatment effects were assessed using factorial ANOVA, with treatment (Fampridine-SR vs. placebo) and time (before and after treatment) as within-subject variables.

RESULTS

Of the 60 subjects randomized, 48 completed the study; three were removed due to an adverse event while in the treatment arm (one due to relapse while on placebo, one due to urinary retention and one due to dizziness and headache while on Fampridine-SR). The subjects had a mean age of 46.5±10.0 years, education of 13.6±1.9 years, and were diagnosed with MS 10.6±9.6 years ago. The majority were female (46, 76.7%), had relapsing remitting MS (41, 68.3%) with median EDSS of 3.5 (range 1.0-7.0). There were no significant demographic differences between the two groups. The treatment x time interaction within the factorial ANOVA on PASAT CF scores was statistically significant, F(1, 45)=8.28, p=0.006, suggesting there is a difference between the treatments (placebo vs. Fampridine-SR), over the course of the study. An evaluation of the mean scores suggests, however, that subjects saw a greater improvement when they were given the placebo, than when they were given the active medication. Similarly, individuals showed a greater increase in their information processing speed (as measured by the PASAT) over the course of treatment when they were given the placebo, as compared with the active medication F(1,45)=4.17, p=0.047.

CONCLUSION

Although this small pilot study does not suggest that Fampridine-SR results in a statistically significant improvement of CF in MS patients, as compared to placebo, individuals demonstrated an improvement in both information processing speed and CF, suggesting further studies are warranted.

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.

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.

Dynamic walking features and improved walking performance in multiple sclerosis patients treated with fampridine (4-aminopyridine)

BACKGROUND

Impaired walking capacity is a frequent confinement in Multiple Sclerosis (MS). Patients are affected by limitations in coordination, walking speed and the distance they may cover. Also abnormal dynamic walking patterns have been reported, involving continuous deceleration over time. Fampridine (4-aminopyridine), a potassium channel blocker, may improve walking in MS. The objective of the current study was to comprehensively examine dynamic walking characteristics and improved walking capacity in MS patients treated with fampridine.

METHODS

A sample of N = 35 MS patients (EDSS median: 4) underwent an electronic walking examination prior to (Time 1), and during treatment with fampridine (Time 2). Patients walked back and forth a distance of 25 ft for a maximum period of 6 min (6-minute 25-foot-walk). Besides the total distance covered, average speed on the 25-foot distance and on turns was determined separately for each test minute, at Time 1 and Time 2.

RESULTS

Prior to fampridine administration, 27/35 patients (77 %) were able to complete the entire 6 min of walking, while following the administration, 34/35 patients (97 %) managed to walk for 6 min. In this context, walking distance considerably increased and treatment was associated with faster walking and turning across all six test minutes (range of effect sizes: partial eta squared = .34-.72). Importantly, previously reported deceleration across test minutes was consistently observable at Time 1 and Time 2.

DISCUSSION

Fampridine administration is associated with improved walking speed and endurance. Regardless of a treatment effect of fampridine, the previously identified, abnormal dynamic walking feature, i.e. the linear decline in walking speed, may represent a robust feature.

CONCLUSIONS

The dynamic walking feature might hence be considered as a candidate for a new outcome measure in clinical studies involving interventions other than symptomatic treatment, such as immune-modulating medication.

TRIAL REGISTRATION

DRKS00009228 (German Clinical Trials Register). Date obtained: 25.08.2015.

Crystal structure of 2-amino-pyridinium 6-chloro-nicotinate

In the title salt, C5H7N(+)·C6H3ClNO(-), the 2-amino-pyri-din-ium cation inter-acts with the carboxyl-ate group of the 6-chloro-nicotinate anion through a pair of independent N-H⋯O hydrogen bonds, forming an R 2 (2)(8) ring motif. In the crystal, these dimeric units are connected further via N-H⋯O hydrogen bonds, forming chains along [001]. In addition, weak C-H⋯N and C-H⋯O hydrogen bonds, together with weak π-π inter-actions, with centroid-centroid distances of 3.6560 (5) and 3.6295 (5) Å, connect the chains, forming a two-dimensional network parallel to (100).

"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.

A pooled analysis of two phase 3 clinical trials of dalfampridine in patients with multiple sclerosis

BACKGROUND

Two phase 3 clinical trials demonstrated that dalfampridine extended-release 10-mg tablets (D-ER), twice daily, significantly improved walking relative to placebo in patients with multiple sclerosis (MS). The objective of this study was to evaluate the efficacy and safety of D-ER in patients with MS using pooled data from the two phase 3 trials.

METHODS

Data were pooled from the two trials, and D-ER was compared with placebo for timed-walk responder rate, changes in walking speed, and the 12-item Multiple Sclerosis Walking Scale (MSWS-12). Response rates were evaluated with respect to demographic and clinical characteristics.

RESULTS

D-ER had a significantly higher proportion of timed-walk responders relative to placebo (37.6% vs. 8.9%; P < .0001). The responder rate was independent of age, gender, race, body-mass index, type of MS, duration of MS, baseline Expanded Disability Status Scale score, baseline walking speed, and concomitant use of immunomodulatory therapies. Significant improvements were observed in walking speed and in MSWS-12 score for the pooled D-ER group compared with placebo. The safety profile was consistent with the individual studies; no new safety or tolerability concerns were identified.

CONCLUSIONS

D-ER demonstrated efficacy for the improvement of walking in patients with MS; response was independent of demographic and clinical characteristics.

Crystal structure of 2-amino-4-methyl-pyridin-1-ium (2R,3R)-3-carb-oxy-2,3-di-hydroxy-propano-ate monohydrate

The title mol-ecular salt, C6H9N2 (+)·C4H5O6 (-)·H2O, crystallized with two 2-amino-4-methyl-pyridin-1-ium cations, two l-(+)-tartaric acid monoanions [systematic name: (2R,3R)-3-carb-oxy-2,3-di-hydroxy-propano-ate] and two water mol-ecules in the asymmetric unit. In the crystal, the cations, anions and water mol-ecules are linked via a number of O-H⋯O and N-H⋯O hydrogen bonds, and a C-H⋯O hydrogen bond, forming a three-dimensional structure.

Development of dalfampridine, a novel pharmacologic approach for treating walking impairment in multiple sclerosis

Walking impairment is a clinical hallmark of multiple sclerosis (MS). Dalfampridine-ER, an extended-release formulation of dalfampridine (also known by its chemical name, 4-aminopyridine, and its international nonproprietary name, fampridine), was developed to maintain drug plasma levels within a narrow therapeutic window, and assessed for its ability to improve walking in MS. The putative mechanism of action of dalfampridine-ER is restoration of axonal conduction via blockade of the potassium channels that become exposed during axonal demyelination. Two pivotal phase III clinical trials demonstrated that dalfampridine-ER 10-mg tablets administered twice daily improved walking speed and patient-reported perceptions of walking in some patients. Dalfampridine-ER was generally well tolerated, and, at the approved dose, risk of seizure was neither elevated relative to placebo nor higher than the rate in the MS population. Dalfampridine-ER (AMPYRA®) was approved in the United States for the treatment of walking in patients with MS as demonstrated by an increase in walking speed. The use of the dalfampridine-ER is contraindicated in patients with a history of seizure. It is the first pharmacologic therapy for this indication and has been incorporated into clinical management of MS.

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.

Bis(4-amino-pyridinium) hexa-aqua-nickel(II) bis-(sulfate)

In the title compound, (C₅H₇N₂)₂[Ni(H₂O)₆](SO₄)₂, the Ni^II cation is located on an inversion centre and is coordinated by six aqua ligands in a slightly distorted octa­hedral coordination environment. The [Ni(H₂O)₆]²⁺ ions are connected through an extensive network of O—H⋯O hydrogen bonds to sulfate anions, leading to the formation of layers parallel to (001). The 4-amino­pyridinium cations are located between these layers and are connected to the anionic framework by N—H⋯O hydrogen bonds. Weak π–π inter­actions between the pyridine rings, with a centroid–centroid distance of 3.754 (9) Å, provide additional stability to the crystal packing.

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.

The use of aminopyridines in neurological disorders

Aminopyridines are members of a family of monoamino and diamino derivatives of pyridine, and their principal mechanism of action is dose-dependent blockade of voltage-gated potassium channels, in particular, fast voltage-gated potassium channels. To date, only 2 main broad-spectrum potassium channel blockers, 4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP), have been used as investigational new drugs in various neurological diseases. More recently, licensed versions of these compounds including dalfampridine extended release (Fampyra, Biogen Idec) for the improvement of walking in adult patients with multiple sclerosis, and amifampridine (Firdapse, Biomarin Europe Ltd) for the treatment of Lambert-Eaton myasthenic syndrome have been released, and the costs associated with using these new products highlights the importance of evaluating the clinically meaningful treatment effects of these drugs.The current review summarizes the evidence of aminopyridine use in neurological conditions and in particular presents a systematic review of all randomized trials of 3,4-DAP in Lambert-Eaton myasthenic syndrome to determine the efficacy of this treatment using meta-analysis of clinical and electrophysiological end points.

3-Methyl-2-vinyl-pyridinium phosphate

In the title salt, C₈H₁₀N⁺·H₂PO₄⁻, the cation is essentially planar (r.m.s. deviation = 0.063 Å). In the crystal, the phosphate anions form inversion R₂²(8) dimers via pairs of O—H⋯O hydrogen bonds. These dimers are further linked by pairs of O—H⋯O hydrogen bonds, also enclosing R₂²(8) loops, forming chains running along [001]. The cations are bonded to the anions via N—H⋯O hydrogen bonds and C—H⋯O contacts.

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.

1-(2-Carb-oxy-eth-yl)-5-ethyl-2-methyl-pyridinium chloride

In the crystal structure of the title salt, C₁₁H₁₆NO₂⁺·Cl⁻, the cations and anions are linked by O—H⋯Cl hydrogen bonds. The structure is further stabilized by weak C—H⋯Cl hydrogen bonds.

4-Amino-pyridinium 5-carb-oxy-penta-noate monohydrate

In the title hydrated salt, C₅H₇N₂⁺·C₆H₉O₄⁻·H₂O, the carb­oxy H atom is disordered over two positions with equal occupancy. In the crystal, O atoms of the 5-carb­oxy­penta­noate anion link the 4-amino­pyridinium cations and water mol­ecules into a three-dimensional network via N—H⋯O hydrogen bonds. The crystal structure is further consolidated by O—H⋯O hydrogen bonds involving the anion and the solvent water mol­ecule.

Walking impairment in patients with multiple sclerosis - a new therapeutic approach and clinical potential of dalfampridine extended release tablets

Walking impairment is a clinical hallmark of multiple sclerosis (MS) that has been under-recognized as a therapeutic target for pharmacologic intervention. The development and approval of dalfampridine extended release tablets (dalfampridine-ER; known as prolonged-, modified, or sustained-release fampridine outside the USA), 10 mg taken twice daily, to improve walking in patients with MS, fills a previously unmet need. In three randomized, double-blind, placebo-controlled trials, dalfampridine-ER improved walking speed in approximately one-third (37%) of treated patients, and average walking speed on therapy among these responders improved by approximately 25% relative to baseline. Walking-speed improvement among responders was clinically significant, as determined by a statistically significant improvement in the patient-reported 12-item Multiple Sclerosis Walking Scale. Long-term extension studies indicate that responders were able to maintain benefits, compared with nonresponders over prolonged periods of treatment. Dalfampridine-ER was generally well tolerated. Dizziness, insomnia, balance disorder, headache, nausea, urinary tract infection, and asthenia were the most common adverse events. Although the incidence of seizures appeared to be dose related, among patients treated with dalfampridine-ER in the three trials, the rate of seizures was 0.25%. These efficacy and safety data suggest that dalfampridine-ER can be a useful and clinically relevant addition to the pharmacologic armamentarium for the management of MS symptoms and disabilities. Because of its narrow therapeutic index and potential for seizures, it is especially important in the clinical setting to adhere to the dosing recommended in the approved labels.

Dalfampridine: a new agent for symptomatic management of multiple sclerosis

PURPOSE The pharmacology, pharmacokinetics, clinical efficacy, safety, dosage, and place in therapy of dalfampridine are reviewed. SUMMARY Dalfampridine is a novel drug with a unique mechanism for the symptomatic management of multiple sclerosis (MS) among all classifications. Dalfampridine was approved in January 2010 to improve walking for patients with MS. Dalfampridine blocks potassium channels on demyelinated neurons and allows normal electrical conduction, thus improving locomotor difficulty. Dalfampridine is rapidly absorbed after oral administration, reaching its peak plasma concentration in 1.3 hours. Approximately 95.9% of dalfampridine and its metabolites (3-hydroxy-4-aminopyridine and 3- hydroxy-4-aminopyridine sulfate) is excreted in the urine. Dalfampridine is not an inhibitor or inducer of a major cytochrome P-450 isoenzyme; therefore, the potential for drug-drug interactions is minimal. Clinical studies have shown dalfampridine to improve walking speed. The dosage of dalfampridine varied in clinical trials, but the recommended dosage is 10 mg orally twice daily. Dalfampridine is not appropriate for patients with seizures or moderate-to-severe renal impairment. Phase III studies found that extended-release fampridine 10 mg twice daily is well tolerated. The most frequent adverse events reported in dalfampridine clinical trials were insomnia, dizziness, headache, nausea, and weakness. The Food and Drug Administration has required the manufacturer to have a risk evaluation and mitigation strategy for dalfampridine. Ongoing trials will determine the long-term benefit of dalfampridine. CONCLUSION Dalfampridine is a potassium channel blocker that has demonstrated efficacy for improving the symptoms of MS. Several studies have demonstrated increased walking speed in patients, though high doses should be avoided due to the risk of seizures.

The safety profile of dalfampridine extended release in multiple sclerosis clinical trials

BACKGROUND

Dalfampridine (fampridine outside the United States) is a broad-spectrum potassium channel blocker. Dalfampridine extended-release tablets have been approved by the US Food and Drug Administration to improve walking in patients with multiple sclerosis (MS).

OBJECTIVE

The objective of this article is to review the safety profile of dalfampridine extended-release tablets with respect to its expected use in patients with MS.

METHODS

We reviewed published data relevant to patient safety profiles based on searches of articles in PubMed published up to December 31, 2010, using the search terms fampridine OR dalfampridine OR 4-aminopyridine AND (multiple sclerosis) in combination with toxicity, safety, clinical trial, pharmacokinetics, and seizures. These searches were supplemented with data derived from the approved package insert and relevant sections of the New Drug Application (22-250) as submitted to the US Food and Drug Administration.

RESULTS

The literature searches returned 58 unique citations, of which 26 were considered relevant for characterizing the safety profile of dalfampridine; excluded citations were as follows: reviews (19), evaluation of 3,4-diaminopyridine (4), intravenous dosing (2), inadequate information on patient doses (2), preclinical models (2), and "other" (3). Dalfampridine is nearly completely (approximately 96%) eliminated unchanged in urine, with limited transformation to 2 inactive metabolites and low risk for interaction with drugs metabolized by hepatic P450 cytochromes. However, in patients with renal impairment (creatinine clearance [CrCl], ≤80 mL/min), mean peak plasma concentrations were 68%-101% higher and apparent clearance was 43%-73% lower relative to those without impairment, precluding dalfampridine use in patients with moderate (CrCl, 30-50 mL/min) or severe renal impairment (CrCl, <30 mL/min). Dalfampridine has a narrow therapeutic range. At the therapeutic dose of 10 mg twice daily, adverse events were generally mild to moderate and, consistent with the mechanism of action of dalfampridine, were primarily related to stimulatory effects on the nervous system. A thorough QT study suggested a low risk of induction of QT prolongation and associated cardiac arrhythmias in healthy individuals at therapeutic (10 mg, twice daily) or supratherapeutic (30 mg, twice daily) doses. Although the incidence of seizures was dose related, data from the clinical trials of dalfampridine extended-release tablets suggest that the risk of seizure at the therapeutic dose, in patients with no history of seizure, is not likely to be higher than background rates in MS.

CONCLUSION

In patients with MS, dalfampridine has a narrow therapeutic range but an acceptable safety profile when used at the therapeutic dose of 10 mg twice daily.

Formulating a new basis for the treatment against botulinum neurotoxin intoxication: 3,4-Diaminopyridine prodrug design and characterization

Botulism is a disease characterized by neuromuscular paralysis and is produced from botulinum neurotoxins (BoNTs) found within the Gram positive bacterium Clostridium botulinum. This bacteria produces the most deadliest toxin known, with lethal doses as low as 1 ng/kg. Due to the relative ease of production and transport, the use of these agents as potential bioterrorist weapons has become of utmost concern. No small molecule therapies against BoNT intoxication have been approved to date. However, 3,4-diaminopyridine (3,4-DAP), a potent reversible inhibitor of voltage-gated potassium channels, is an effective cholinergic agonist used in the treatment of neuromuscular degenerative disorders that require cholinergic enhancement. 3,4-DAP has also been shown to facilitate recovery of neuromuscular action potential post botulinum intoxication by blocking K(+) channels. Unfortunately, 3,4-DAP displays toxicity largely due to blood-brain-barrier (BBB) penetration. As a dual-action prodrug approach to cholinergic enhancement we have designed carbamate and amide conjugates of 3,4-DAP. The carbamate prodrug is intended to be a slowly reversible inhibitor of acetylcholinesterase (AChE) along the lines of the stigmines thereby allowing increased persistence of released acetylcholine within the synaptic cleft. As a secondary activity, cleavage of the carbamate prodrug by AChE will afford the localized release of 3,4-DAP, which in turn, will enhance the pre-synaptic release of additional acetylcholine. Being a competitive inhibitor with respect to acetylcholine, the activity of the prodrug will be greatest at the synaptic junctions most depleted of acetylcholine. Here we report upon the synthesis and biochemical characterization of three new classes of prodrugs intended to limit previously reported stability and toxicity issues. Of the prodrugs examined, compound 32, demonstrated the most clinically relevant half-life of 2.76 h, while selectively inhibiting AChE over butyrylcholinesterase--a plasma-based high activity esterase. Future in vivo studies could provide validation of prodrug 32 as a potential treatment against BoNT intoxication as well as other neuromuscular disorders.

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.