Child reaching for DNA strand, symbolizing gene therapy for SMA

Gene Therapy Breakthrough: Can a Single Dose Correct Spinal Muscular Atrophy?

Kai Mendoza in Health & Wellness December 2025 • 4 min read.

"A groundbreaking study explores the potential of one-time intravenous gene therapy to transform the lives of infants with SMA type 1, offering hope where there was once little."

Spinal Muscular Atrophy type 1 (SMA1) is a severe genetic condition that affects infants, leading to muscle weakness and motor skill delays. It's caused by a deficiency in the SMN1 gene, crucial for producing a protein that keeps motor neurons healthy. Without enough of this protein, muscles weaken, affecting movement, breathing, and survival.

Traditionally, SMA1 has been a challenging condition to treat, often requiring ongoing support. While new treatments like Nusinersen (Spinraza) have emerged, they require repeated administration. The quest for more effective, less burdensome therapies continues, driving research into innovative solutions like gene therapy.

A recent study published in the New England Journal of Medicine explored a promising approach: a single-dose intravenous gene therapy using an adeno-associated virus (AAV9) to deliver a working copy of the SMN1 gene. This article breaks down the study's findings, explaining how this therapy works and what it could mean for infants with SMA1 and their families.

How Does Single-Dose Gene Therapy Work for SMA1?

Child reaching for DNA strand, symbolizing gene therapy for SMA

The study focused on using a modified virus (AAV9) to carry a healthy copy of the SMN1 gene directly into the patient's cells. AAV9 is effective because it can cross the blood-brain barrier, delivering the gene to motor neurons in the spinal cord and brain. This approach aims to provide a long-lasting solution with a single treatment, unlike other therapies that require frequent doses.

Researchers administered the gene therapy to 15 patients with SMA1. They used two different dose levels to assess the therapy's safety and effectiveness. The primary goal was to ensure the treatment was safe, but researchers also looked for improvements in motor function and survival compared to what is typically seen in SMA1.

Improved Survival: All patients were alive and without needing permanent ventilation at 20 months, a significant improvement compared to historical data.
Motor Function Gains: CHOP INTEND scores, which measure motor skills, increased substantially after gene therapy.
Milestone Achievement: Many children in the higher-dose group achieved motor milestones like sitting unassisted, rolling over, and even speaking – milestones rarely seen in SMA1.
Safety Considerations: Some patients experienced elevated liver enzymes, which were managed with prednisolone.

These results suggest that a single dose of gene therapy can significantly alter the course of SMA1, offering the potential for improved survival and motor function. However, it's important to note that this study is just one step, and longer-term data is needed to fully understand the therapy's safety and effectiveness.

The Future of SMA1 Treatment: What's Next?

This study offers a beacon of hope for families affected by SMA1. The potential for a single-dose gene therapy to dramatically improve outcomes is truly transformative. However, it's crucial to remember that this is an evolving field, and ongoing research is essential.

The success of this study highlights the importance of early diagnosis. Newborn screening for SMA can identify affected infants before symptoms appear, allowing for earlier intervention and potentially maximizing the benefits of gene therapy. As research continues and more data becomes available, the treatment landscape for SMA1 is likely to evolve further.

While challenges remain, the future for infants with SMA1 is brighter than ever before. Innovative therapies like gene replacement offer the promise of a better quality of life, improved motor function, and increased survival. Continued research and advocacy are crucial to ensuring that these life-changing treatments reach all those who need them.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

What exactly is Spinal Muscular Atrophy type 1 (SMA1), and how does it affect infants?

Spinal Muscular Atrophy type 1, or SMA1, is a genetic disorder primarily affecting infants. It's characterized by muscle weakness and delays in achieving motor skills. This is due to a deficiency in the SMN1 gene, which is responsible for producing a crucial protein required for the health and function of motor neurons. Without sufficient protein, the motor neurons degenerate, leading to progressive muscle weakening which impacts movement, breathing, and ultimately, survival.

How does the single-dose gene therapy work to address the underlying cause of SMA1?

The single-dose gene therapy for SMA1 utilizes a modified adeno-associated virus, specifically AAV9, as a delivery mechanism. AAV9 is engineered to carry a healthy, functional copy of the SMN1 gene directly into the patient's cells. The crucial advantage of AAV9 is its ability to cross the blood-brain barrier, allowing it to reach the motor neurons in the spinal cord and brain. By delivering a working copy of the SMN1 gene, the therapy aims to provide a long-lasting solution from a single administration, unlike other treatments that need repeated doses.

What were the key findings of the study on single-dose gene therapy for SMA1, and how significant are these results?

The study demonstrated significant improvements in infants with SMA1 who received the single-dose gene therapy. All patients were alive and did not require permanent ventilation at 20 months, a significant divergence from historical data. Motor function, measured by CHOP INTEND scores, showed substantial improvement post-therapy. Notably, many children in the higher-dose group achieved motor milestones such as sitting unassisted, rolling over, and even speaking – achievements rarely observed in untreated SMA1 cases. However, some patients experienced elevated liver enzymes, which were successfully managed with prednisolone.

How does this single-dose gene therapy compare to other treatments for SMA1, like Nusinersen (Spinraza)?

Nusinersen, also known as Spinraza, represents an alternative treatment for SMA1, but it differs significantly from single-dose gene therapy. Nusinersen requires repeated administrations to maintain its therapeutic effect. The single-dose gene therapy offers the potential for a more convenient and potentially longer-lasting solution with just one treatment. While Nusinersen has shown benefits, the burden of repeated dosing highlights the appeal of a one-time intervention like gene therapy. Further research and long-term data are needed to fully compare the efficacy and durability of these two approaches.

What are the limitations of the current study, and what future research is needed to fully realize the potential of gene therapy for SMA1?

While the single-dose gene therapy holds immense promise for SMA1, it's important to acknowledge the current limitations and future research directions. One crucial area is the need for longer-term data to fully understand the therapy's safety and durability. The study reported elevated liver enzymes in some patients, managed with prednisolone, emphasizing the importance of continued safety monitoring. Future studies should explore optimal dosing strategies, identify potential biomarkers for predicting treatment response, and investigate the therapy's effectiveness in older patients or those with more advanced SMA1. Furthermore, research into combination therapies and strategies to address any potential long-term complications will be essential to maximize the benefits of this innovative approach.