The U.S. Food and Drug Administration (FDA) has approved onasemnogene abeparvovec-brve (Itvisma) as the first gene replacement therapy for people aged 2 and up with spinal muscular atrophy (SMA) — including adults and teens. This marks the first time gene therapy has been approved for such a broad age range in SMA, offering another treatment option to people who have previously had limited options.

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The drug is approved for people with SMA who have a confirmed mutation in the SMN1 gene, which is the cause of most SMA cases.

In studies that led to its approval, the drug improved and stabilized motor function — such as movements used for sitting, standing, and other daily activities — in people with SMA. These effects were seen even in those who’d received prior SMA treatment, and the benefits lasted at least 52 weeks.

What Is Itvisma and How Does It Work?

Itvisma is a gene replacement therapy given as a single dose by intrathecal injection (injection into the fluid around the spinal cord). It’s designed to deliver a healthy copy of the SMN1 gene, the gene that’s missing or not working properly in people with SMA.

By replacing this gene, the drug helps the body make more of the survival motor neuron (SMN) protein, which is crucial for motor function. Itvisma is a one-time therapy and doesn’t require repeated dosing.

Itvisma contains the same active drug as Zolgensma, a gene therapy already approved for children under 2 with SMA. However, Itvisma is formulated at a higher concentration, allowing it to be used in older children, teens, and adults.

How Did Itvisma Perform in Clinical Trials?

The approval of Itvisma was based on clinical trial data involving children and teens living with SMA. In a phase 3 clinical trial, 126 people with SMA ages 2 to 17 years, who could sit but had never walked independently, received either Itvisma or a placebo (inactive treatment).

After 52 weeks, those who received Itvisma had an average improvement of 2.39 points on the Hammersmith Functional Motor Scale Expanded (HFMSE), which measures motor function specific to SMA. By comparison, people in the placebo group improved by an average of 0.51 points over the same period.

In a phase 3b trial, 27 people with SMA who had previously stopped other SMA treatments (such as nusinersen or risdiplam) were treated with Itvisma. These participants showed stabilization of motor function over 52 weeks, with an average HFMSE increase of 1.05 points.

As with any treatment, not everyone who received Itvisma experienced the same level of benefit, and individual results may vary.

Possible Side Effects of Itvisma

The most common side effects reported in the clinical trials were:

• Upper respiratory tract infections
• Fever
• Vomiting

There are also potential risks of liver and heart-related side effects, especially in adults with preexisting health conditions. Because of this, the FDA has included warnings and precautions, and people receiving Itvisma need to be monitored for these possible complications.

Why This Approval Matters for People With SMA

The approval of Itvisma is an important milestone for the SMA community. This is the first gene replacement therapy available to adults, teens, and children older than 2 with SMA, making it possible for more people to access a treatment that targets the genetic cause of the disease. This one-time therapy could help reduce the need for ongoing treatment and may support greater independence and physical strength for many people living with SMA.

Treatment decisions are highly personal. If you or a loved one is living with SMA, consider speaking with your healthcare provider about the latest treatment options and what might be best for your situation. They can help you understand the benefits and risks of different therapies, including gene replacement, and support you in making informed choices about your care.

Learn more about how gene therapy for SMA works.

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On mySMAteam, people share their experiences with SMA, get advice, and find support from others who understand.

Are you or a loved one considering gene therapy? Let others know in the comments below.