The ClC-1 chloride channel inhibitor NMD670 improves skeletal muscle function in rat models and patients with myasthenia gravis

Charcot-Marie-Tooth disease: a review of clinical developments and its management - What's new in 2025?

INTRODUCTION

Charcot-Marie-Tooth disease (CMT) understanding and diagnostic rates are improving. Symptomatic management is still the only option, but many therapeutic approaches are under investigation, some in the clinical trial phase.

AREAS COVERED

Through a comprehensive search in PubMed, the ClinicalTrials.gov website, and the latest abstracts on the topic, the authors review the diagnostic advances and promising treatments, focusing on pharmacological and gene therapy/silencing approaches, and on clinical trial challenges. They also review current CMT management, including rehabilitation, orthotics, and associated symptoms and comorbidities.

EXPERT OPINION

The CMT field is evolving rapidly, with significant advances in genetic diagnosis and disease recognition. International networks and patient organization partnerships are vital for progress, enabling collaboration and large-scale studies. Metabolic neuropathies are relatively easier to target, and interim analysis results from the CMT-SORD trial suggest govorestat may become the first approved CMT drug. Gene therapy shows promise but currently faces safety and targeting challenges; PMP22 silencers for CMT1A are close to being tested in patients. New drugs, such as HDAC6 inhibitors, are also approaching the clinical trial phase, despite existing hurdles. Supportive care, including rehabilitation and orthotics, continues to improve quality of life. There is optimism that within the next decade, approved therapies will reduce disease burden.

Pushing the boundaries: future directions in the management of spinal muscular atrophy

Spinal muscular atrophy (SMA) is a devastating, degenerative, paediatric neuromuscular disease which until recently was untreatable. Discovery of the responsible gene 30 years ago heralded a new age of pioneering therapeutic developments. Three disease-modifying therapies (DMTs) have received regulatory approval and have transformed the disease, reducing disability and prolonging patient survival. These therapies - with distinct mechanisms, routes of administration, dosing schedules, side effect profiles, and financial costs - have dramatically altered the clinical phenotypes of this condition and have presented fresh challenges for patient care. In this review article we discuss potential strategies to maximise clinical outcomes through early diagnosis and treatment, optimised dosing, use of therapeutic combinations and state-of-the-art physiotherapy techniques, and the development of innovative therapies targeting alternative mechanisms.

Next generation of neuromuscular blockade reversal agents

PURPOSE OF THE REVIEW

The purpose of this review is to explore emerging pharmacological strategies for neuromuscular blockade (NMB) reversal, focusing on their mechanisms of action, efficacy, and potential advantages over existing agents like sugammadex and neostigmine.

RECENT FINDINGS

Several novel reversal agents are under investigation: calabadions, synthetic molecular containers that effectively reverse aminosteroidal and benzylisoquinolinium neuromuscular blocking agents (NMBAs) with rapid clearance; l-cysteine adduction, a promising method for reversing ultrashort-acting NMBAs by accelerating metabolism; adamgammadex, a modified γ-cyclodextrin with improved binding to rocuronium and reduced hypersensitivity risks, showing noninferiority to sugammadex; acyclic cucurbit[n]urils, broad-spectrum reversal agents with superior water solubility and biocompatibility; and ClC-1 channel blockers, a novel approach that enhances muscle excitability rather than directly binding to NMBAs.

SUMMARY

Emerging NMBA reversal agents offer potential improvements in safety, efficacy, and broader NMBA compatibility. These alternatives to sugammadex and neostigmine show promise in preclinical and early clinical trials. Further studies are necessary to confirm their clinical applicability and regulatory approval.

Safety, Pharmacokinetics, and Pharmacodynamics of a First-in-Class ClC-1 Inhibitor to Enhance Muscle Excitability: Phase I Randomized Controlled Trial

NMD670 is a first-in-class inhibitor of skeletal muscle-specific chloride channel ClC-1, developed to improve muscle weakness and fatigue in neuromuscular diseases. Preclinical studies show that ClC-1 inhibition enhances muscle excitability, improving muscle contractility and strength. We describe the first-in-human, randomized, double-blind, placebo-controlled study, which evaluated the safety, pharmacokinetics, and pharmacodynamics of single and multiple doses of NMD670 in healthy male and female subjects. Single-ascending doses (50-1,600 mg) were administered in a (partial) cross-over design; multiple-ascending doses (200-600 mg q.d.; 400 mg b.i.d.) were administered in a parallel design. Differences in pharmacokinetics between males/females and fed/fasted states were evaluated. Pharmacodynamic effects were evaluated using muscle velocity recovery cycles (MVRC) and analyzed using mixed-effects modeling. NMD670 was generally safe and well-tolerated in healthy subjects, with the only dose-related adverse event being myotonia occurring at the highest dose levels tested (single dose of 1,200, and 1,600 mg). Moreover, NMD670 significantly increased the following MVRC parameters after a single dose of 1,200 mg compared with placebo: early supernormality (estimated difference (ED) 2.04; 95% confidence interval (CI) 0.379, 3.70; P = 0.0242); early supernormality after 5 conditioning stimuli (ED 2.51; 95%CI 0.599, 4.41; P = 0.0177); supernormality at 20 ms (ED 2.78; 95%CI 1.377, 4.181; P = 0.0021). Importantly, the results of this study indicate pharmacological target engagement at well-tolerated dose levels in healthy subjects; firstly, because myotonia was an expected exaggerated on-target pharmacological effect, and secondly, because the effects on MVRC indicate increased muscle cell excitability. This study in healthy subjects indicates proof-of-mechanism and provides a solid base for translation to patients with neuromuscular diseases.

Neuromuscular transmission deficits in patients with CMT and ClC-1 inhibition in CMT animal models

OBJECTIVE

Charcot-Marie Tooth (CMT) is a hereditary neuropathy characterized by muscle weakness and fatigue with no approved therapies. Preclinical studies implicate neuromuscular junction (NMJ) transmission deficits in muscle dysfunction in CMT. This study aimed to evaluate NMJ function in patients with CMT types 1 and 2, and to determine whether enhancing NMJ transmission can improve muscle function in preclinical CMT models.

METHODS

First, an observational study involving single fiber electromyography (SFEMG) and clinical testing in patients with CMT 1 and 2 and healthy controls (HC) was conducted. Next, preclinical studies examined muscle function, specifically nerve-stimulated muscle force after partially inhibiting ClC-1 chloride channels with the novel small molecule NMD670.

RESULTS

Twenty-one CMT patients (46.4 ± 14.4 years) and 10 HC (43.3 ± 12.7 years) were enrolled. SFEMG jitter (NMJ variability) was higher [median (range)] in the CMT patients [56 μs (35; 197 μs)] vs. HC [29 μs (19; 36 μs)], (p < 0.05). Blocking (NMJ failure) was higher in the CMT patients (13.4% (0.0; 90.9%)) vs. HC (0.0% (0.0; 4.5%)), (p < 0.05). In CMT, jitter and blocking correlated inversely with muscle strength, mobility, balance, and endurance. In CMT 1A and 2D mice, NMD670 increased both peak force and contractile endurance in vivo.

INTERPRETATION

Our study suggests that NMJ dysfunction contributes to muscle dysfunction in patients with CMT 1 and 2. Furthermore, our preclinical data provide proof-of-mechanism for recovery of muscle function with ClC-1 inhibition in CMT mouse models. Collectively, these findings suggest that targeting NMJ dysfunction with ClC-1 inhibitors could enhance muscle function in CMT patients, warranting further clinical trials.

From in vivo models to in vitro bioengineered neuromuscular junctions for the study of Charcot-Marie-Tooth disease

Peripheral neuropathies are disorders affecting the peripheral nervous system. Among them, Charcot-Marie-Tooth disease is an inherited sensorimotor neuropathy for which no effective treatment exists yet. Research on Charcot-Marie-Tooth disease has been hampered by difficulties in accessing relevant cells, such as sensory and motor neurons, Schwann cells, and myocytes, which interact at the neuromuscular junction, the specialized synapses formed between nerves and skeletal muscles. This review first outlines the various in vivo models and methods used to study neuromuscular junction deficiencies in Charcot-Marie-Tooth disease. We then explore novel in vitro techniques and models, including complex hiPSC-derived cultures, which offer promising isogenic and reproducible neuromuscular junction models. The adaptability of in vitro culture methods, including cell origin, cell-type combinations, and choice of culture format, adds complexity and excitement to this rapidly evolving field. This review aims to recapitulate available tools for studying Charcot-Marie-Tooth disease to understand its pathophysiological mechanisms and test potential therapies.

ClC-1 Inhibition as a Mechanism for Accelerating Skeletal Muscle Recovery After Neuromuscular Block in Rats

Neuromuscular blocking agents are used commonly to induce skeletal muscle relaxation during surgery. While muscle relaxation facilitates surgical procedures and tracheal intubation, adequate recovery of muscle function after surgery is required to support pulmonary function, and even mild residual neuromuscular block increases the risk of severe postoperative pulmonary complications. While recovery of muscle function after surgery involving neuromuscular blocking agents can be monitored and, in addition, be accelerated by use of current antagonists (reversal agents), there is a clear clinical need for a safe drug to antagonize all types of neuromuscular blocking agents. Here, we show that inhibition of the skeletal muscle-specific chloride ion (Cl-) channel, the ClC-1 channel, markedly accelerates recovery of both single contraction (twitch) and, important physiologically, sustained (tetanic) contractions in a rat model mimicking neuromuscular blocking agent-induced muscle block used during surgery. This suggests ClC-1 inhibition as a mechanism for fast and efficacious recovery of neuromuscular function induced by any neuromuscular blocking agents.

Congenital myasthenic syndromes: increasingly complex

PURPOSE OF REVIEW

Congenital myasthenia syndromes (CMS) are treatable, inherited disorders affecting neuromuscular transmission. We highlight that the involvement of an increasing number of proteins is making the understanding of the disease mechanisms and potential treatments progressively more complex.

RECENT FINDINGS

Although early studies identified mutations of proteins directly involved in synaptic transmission at the neuromuscular junction, recently, next-generation sequencing has facilitated the identification of many novel mutations in genes that encode proteins that have a far wider expression profile, some even ubiquitously expressed, but whose defective function leads to impaired neuromuscular transmission. Unsurprisingly, mutations in these genes often causes a wider phenotypic disease spectrum where defective neuromuscular transmission forms only one component. This has implications for the management of CMS patients.

SUMMARY

Given the widening nonneuromuscular junction phenotypes in the newly identified forms of CMS, new therapies need to include disease-modifying approaches that address not only neuromuscular weakness but also the multisystem involvement. Whilst the current treatments for CMS are highly effective for many subtypes there remains, in a proportion of CMS patients, an unmet need for more efficacious therapies.

Beyond Motor Neurons in Spinal Muscular Atrophy: A Focus on Neuromuscular Junction

5q-Spinal muscular atrophy (5q-SMA) is one of the most common neuromuscular diseases due to homozygous mutations in the SMN1 gene. This leads to a loss of function of the SMN1 gene, which in the end determines lower motor neuron degeneration. Since the generation of the first mouse models of SMA neuropathology, a complex degenerative involvement of the neuromuscular junction and peripheral axons of motor nerves, alongside lower motor neurons, has been described. The involvement of the neuromuscular junction in determining disease symptoms offers a possible parallel therapeutic target. This narrative review aims at providing an overview of the current knowledge about the pathogenesis and significance of neuromuscular junction dysfunction in SMA, circulating biomarkers, outcome measures and available or developing therapeutic approaches.