Introduction

Centronuclear Myopathy (CNM) is a rare, inherited muscle disorder where nuclei of cells are found in an abnormal central position in muscle fibres instead of their usual peripheral position. This disruption of muscle function leads to premature muscle weakness, delayed motor skill development, and, in the more severe forms, respiratory problems.¹ You can learn more about its diagnostic features here.²

Now, CNM treatments remain supportive—physical therapy, respiratory support, and orthopaedic care—because no disease-modifying therapies are yet available. This reality is what faces patients and families with a chronic, progressive illness and limited options.³

Antisense Oligonucleotide (ASO) Therapy is a promising therapeutic approach targeting genetic causes of neuromuscular disorders like Duchenne muscular dystrophy and spinal muscular atrophy.^4,5 This therapy can modulate gene expression with high specificity, offering a targeted and personalised treatment. Researchers are now exploring the potential of ASO therapy to treat centronuclear myopathy (CNM).⁶ This article explores: Can ASOs deliver an effective solution for the Centronuclear Myopathy? 

What are antisense oligonucleotides?

Antisense oligonucleotides (ASOs) are short, synthetic fragments of DNA or RNA that are engineered to bind particular messenger RNA (mRNA), thereby modulating gene expression. ASOs can:

• Cause degradation of mRNA via RNase H
• Block protein translation
• Modulate RNA splicing

ASOs are licensed for clinical use in a number of diseases, including:

• Duchenne muscular dystrophy (e.g., exon-skipping treatments like eteplirsen)
• Spinal muscular atrophy
• Familial hypercholesterolemia⁸

These results demonstrate that ASO-based treatments can move from bench to bedside for a broad variety of genetic disorders.⁷ 

Rationale: why target DNM2 in CNM?

In X-linked Centronuclear Myopathy, owing to mutations within MTM1, researchers have reported an overexpression of the DNM2 (Dynamin 2) protein.

The autosomal dominant form of CNM is caused by gain-of-function mutations within DNM2 itself, disrupting normal muscle fibre arrangement.⁹

Unexpectedly, reducing DNM2 levels in preclinical studies has been shown to restore muscle function in different genetic types of CNM, a cross-therapy strategy.¹⁹ This suggests that DNM2 may be a principal therapeutic target for several CNM subtypes.

Preclinical evidence supporting ASO therapy

ASO-mediated DNM2 knockdown in MTM1-linked CNM

In MTM1 knockout mice, a model for X-linked CNM, systemic administration of ASOs targeting DNM2 led to:

• Profound decrease in DNM2 protein
• Inhibition of the normal course of the disease
• Reversal of myopathy, even in drastically affected mice, by only two injections within two weeks.

In a dose-response study, treatment with ASO reduced DNM2 mRNA by 39–69%, increased muscle mass, and correspondingly improved markers of disease severity^11&15

ASO advantages in BIN1-associated CNM

In mice with the absence of muscle-specific BIN1, a gene with mutations in an alternative subtype of CNM, the injection of DNM2-targeting ASOs improved muscle strength and normalised histological defects within five weeks¹²

These findings validate the overall therapeutic potential of DNM2 reduction in Centronuclear Myopathies of various types.

Allele-specific silencing: RNA interference strategies 

In dominant DNM2 mutation-induced CNM, allele-specific silencing offers a precision approach.

Researchers engineered siRNA and shRNA sequences that uniquely silence the most common mutation, p.R465W, without touching the wild-type allele. In knock-in mouse models and patient cells, this led to restoration of muscle function.¹³

Even more encouraging, a single intramuscular injection with AAV-shRNA was linked to long-term benefit, preserving muscle integrity for at least a year and preventing age-related DNM2 accumulation.¹⁴

Clinical translation of ASO therapy

These preclinical success stories have paved the way for clinical progress.¹⁶ A company called Dynacure (non-commercial research website) is bringing DNM2-targeting ASOs to human trials. A phase 1/2 first-in-human study (UNITE-CNM) is enrolling adult patients (≥16 years) with confirmed MTM1 or DNM2 mutations. The trial is evaluating safety, tolerability, pharmacokinetics, pharmacodynamics, and early efficacy.¹⁰

This trial is a heartening milestone—one step closer to the actual treatment of CNM.

Challenges and future directions

Although promising, there are some challenges that must be overcome:

1. Delivery to Muscle Tissue

ASOs must be delivered to skeletal muscle in therapeutic levels. Techniques like chemical modification and improved delivery vehicles are crucial for success.³

2. Safety Issues

ASO accumulation in the liver and kidney is a potential toxicity problem. Long-term safety profiling is required before more extensive clinical use¹⁸

3. Balancing DNM2 Levels

DNM2 is of central importance in many tissues. Therapeutic lowering must be balanced with extreme caution not to jeopardise important cell function³

4. Personalisation Versus Scalability

Allele-specific treatment involves individualised design for each mutation, a time- and resource-consuming endeavour. This could be relieved by constructing modular platforms.

5. Combination Therapies

Combination with gene editing or other molecular therapies may enhance durability and therapeutic response, especially in more complex CNM presentations.

FAQs

What is centronuclear myopathy (CNM)?

Centronuclear Myopathy (CNM) is a congenital, inherited neuromuscular disease that involves muscle weakness and an abnormal central location of nuclei in muscle fibres. It tends to result in delayed motor development and, in more severe cases, respiratory involvement.

Are there any cures for CNM available today?

At present, no cure or disease-modifying treatment for CNM has been found. Therapy is still supportive in nature, with physical therapy, respiratory support, and orthopaedic management.

What are antisense oligonucleotides (ASOs)?

Antisense Oligonucleotides (ASOs) are short, synthetic pieces of DNA or RNA intended to alter gene expression. ASOs in neuromuscular disorders can degrade defective mRNA or correct misfolded splicing, providing targeted therapeutic options.

How can ASO therapy help treat centronuclear myopathy?

ASO therapy holds potential by treating the DNM2 gene, which is mutated or overactive in most CNM subtypes. Reduction of DNM2 by ASO has been demonstrated in preclinical animal models to reverse muscle pathology and enhance function.

What is DNM2, and why is it important in CNM?

DNM2 (Dynamin 2) is a protein that is implicated in cellular structure and trafficking. Overexpression or mutations in DNM2 are associated with X-linked and autosomal dominant types of CNM and thus represent an important target for gene-based therapies.

Is ASO therapy for CNM now in clinical trials?

Yes, an early phase (first-in-human) Phase 1/2 clinical trial (UNITE-CNM) is underway, assessing DNM2-targeting ASOs in MTM1 or DNM2 mutation-confirmed patients. The trial will evaluate safety, tolerability, and early efficacy.

What are the challenges in using ASO therapy in CNM?

Major challenges are:

• Effective delivery to skeletal muscle
• Overcoming off-target effects and toxicity
• Maintaining long-term safety
• Managing DNM2 reduction with balanced normal function preservation
• Tailored strategies for prevalent mutations such as p.R465W

What is the future direction of ASO therapy in CNM?

Future directions involve combination therapies, improved delivery technologies, and allele-specific silencing. These strategies promise to render ASO therapy safer, more scalable, and clinically effective for a wider CNM population.

Summary

CNM is a catastrophic neuromuscular disease with no licensed disease-modifying therapies. However, recent breakthroughs in genetic medicine, most notably ASO therapies against DNM2, bring real promise. Preclinical models have produced rapid and significant therapeutic gains in several CNM mouse models, including pathology reversal and restored muscle strength. Allele-specific RNAi strategies have provided sustained efficacy against dominant DNM2 mutations.¹⁷

With the history of human clinical trials like UNITE-CNM, we stand at an encouraging junction of therapy and real-world investigation. In spite of ongoing optimisation of delivery, safety, and individualisation issues, the body of evidence suggests that ASO-based approaches represent one of the most encouraging future therapeutics to treat CNM.