Effects of 3-4 diaminopyridine (DAP) in motor neuron diseases

Non-motor symptoms in patients with amyotrophic lateral sclerosis: current state and future directions

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive degeneration of both upper and lower motor neurons. A defining histopathological feature in approximately 97% of all ALS cases is the accumulation of phosphorylated trans-activation response (TAR) DNA-binding protein 43 protein (pTDP-43) aggregates in the cytoplasm of neurons and glial cells within the central nervous system. Traditionally, it was believed that the accumulation of TDP-43 aggregates and subsequent neurodegeneration primarily occurs in motor neurons. However, contemporary evidence suggests that as the disease progresses, other systems and brain regions are also affected. Despite this, there has been a limited number of clinical studies assessing the non-motor symptoms in ALS patients. These studies often employ various outcome measures, resulting in a wide range of reported frequencies of non-motor symptoms in ALS patients. The importance of assessing the non-motor symptoms reflects in a fact that they have a significant impact on patients' quality of life, yet they frequently go underdiagnosed and unreported during clinical evaluations. This review aims to provide an up-to-date overview of the current knowledge concerning non-motor symptoms in ALS. Furthermore, we address their diagnosis and treatment in everyday clinical practice.

Reduced Fatigue Symptoms in the Post-COVID Syndrome With Amifampridine: A Collective Casuistry With Double-Blind Discontinuation Trials

After a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, approximately 10-20% of patients are affected by the post-COVID syndrome (PCS). This condition leads to a variety of functional complaints, including symptoms of fatigue. To date, there is still no adequate treatment option. Five patients are presented, including the self-observation of one of the authors, in whom the administration of amifampridine as an "off-label use" led to a normalization of the unphysiologically increased need for sleep with a simultaneous increase in the Bell score. This effect was confirmed in a double-blind discontinuation trial (the medication was discontinued on a trial basis) in two of the patients. The five patients, who were previously unable to lead a normal life due to their fatigue symptoms, were able to return to everyday life after treatment with amifampridine. This offers hope to millions of affected patients.

Treatment of fatigue in amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is terminal, progressive neurological condition for which there are no curative treatments. Among people with ALS/MND, fatigue is a common and debilitating symptom, which is characterised by reversible motor weakness and whole-body tiredness that is only partially relieved by rest. The effectiveness of pharmacological or non-pharmacological treatments for fatigue in ALS/MND is not yet established.

OBJECTIVES

To assess the effects of pharmacological and non-pharmacological interventions for fatigue in ALS/MND.

SEARCH METHODS

We searched the following databases on 5 September 2017: Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL Plus, and ERIC. We also searched two clinical trials registries.

SELECTION CRITERIA

We selected randomised and quasi-randomised controlled trials of any intervention which sought to reduce fatigue for people with ALS/MND. We included studies if reduction in fatigue was a primary or secondary outcome of the trial.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included one pharmacological (modafinil) study and three non-pharmacological studies (resistance exercise, respiratory exercise, and repetitive transcranial magnetic stimulation (rTMS)), involving a total of 86 participants with ALS/MND. None of the included studies were free from risk of bias. Since there was only one trial for each intervention, no meta-analysis was possible. All studies assessed fatigue using the Fatigue Severity Scale (FSS; scale from 9 to 63, higher scores indicate more fatigue). Information for assessing bias was often lacking in study reports, making the risk of bias unclear across several domains in all trials. Blinding of participants was not possible in exercise trials, but the outcome assessment was blinded.We found very low-quality evidence suggesting possible improvements in fatigue for modafinil treatment versus placebo (MD -11.00, 95% CI -23.08 to 1.08), respiratory exercise versus a sham intervention (MD -9.65, 95% CI -22.04 to 2.73), and rTMS versus sham rTMS (data not provided), which warrant further investigation to clarify the efficacy of these treatments for fatigue in ALS/MND. We found no clear improvements in fatigue for resistance exercise versus usual care (MD 0.20, 95% CI -10.98 to 11.38; very low-quality evidence).Three participants in the modafinil group dropped out of the modafinil study, two citing issues with headache and one with chest tightness; other adverse effects were anxiety, nausea, dizziness, and sialorrhoea (probably ALS-related). The trials reported no adverse effects of exercise or rTMS.We cannot be certain about the effects of any of the interventions studied because of imprecision (small numbers of participants, wide CI), and possible study limitations.

AUTHORS' CONCLUSIONS

It is impossible to draw firm conclusions about the effectiveness of interventions to improve fatigue for people with ALS/MND as there are few randomised studies, and the quality of available evidence is very low.

Complete reversal of Lambert-Eaton myasthenic syndrome synaptic impairment by the combined use of a K+ channel blocker and a Ca2+ channel agonist

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder in which a significant fraction of the presynaptic P/Q-type Ca(2+) channels critical to the triggering of neurotransmitter release at the neuromuscular junction (NMJ) are thought to be removed. There is no cure for LEMS, and the current most commonly used symptomatic treatment option is a potassium channel blocker [3,4-diaminopyridine (3,4-DAP)] that does not completely reverse symptoms and can have dose-limiting side-effects. We previously reported the development of a novel Ca(2+) channel agonist, GV-58, as a possible alternative treatment strategy for LEMS. In this study, we tested the hypothesis that the combination of GV-58 and 3,4-DAP will elicit a supra-additive increase in neurotransmitter release at LEMS model NMJs. First, we tested GV-58 in a cell survival assay to assess potential effects on cyclin-dependent kinases (Cdks) and showed that GV-58 did not affect cell survival at the relevant concentrations for Ca(2+) channel effects. Then, we examined the voltage dependence of GV-58 effects on Ca(2+) channels using patch clamp techniques; this showed the effects of GV-58 to be dependent upon Ca(2+) channel opening. Based on this mechanism, we predicted an interaction between 3,4-DAP and GV-58. We tested this hypothesis using a mouse passive transfer model of LEMS. Using intracellular electrophysiological ex vivo recordings, we demonstrated that a combined application of 3,4-DAP plus GV-58 had a supra-additive effect that completely reversed the deficit in neurotransmitter release magnitude at LEMS model NMJs. This reversal contrasts with the less significant improvement observed with either compound alone. Our data indicate that a combination of 3,4-DAP and GV-58 represents a promising treatment option for LEMS and potentially for other disorders of the NMJ.

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.