Zolgensma (onasemnogene abeparvovec-xioi)

Reviewed by: HU Medical Review Board | Last reviewed: April 2023

In 2019, the US Food and Drug Administration (FDA) approved Zolgensma® (onasemnogene abeparvovec-xioi) to treat children under 2 years old with spinal muscular atrophy (SMA). Zolgensma is a gene therapy. This means it delivers genes (pieces of DNA).1

In clinical trials, children treated with Zolgensma show large improvements in motor function and life expectancy. Ongoing clinical trials are looking at results of Zolgensma used to treat infants with SMA before they develop symptoms and long-term results in children.2-6

What are the ingredients in Zolgensma?

The active ingredient is Zolgensma is onasemnogene abeparvovec.1

How does Zolgensma work?

Zolgensma is a gene therapy. This means it uses genetic material to correct a genetic mutation. Zolgensma delivers a working copy of the SMN1 gene to make up for the altered SMN1 genes in SMA.1

In Zolgensma, the SMN1 gene is packaged inside a safe virus called adeno-associated virus 9 (AAV9). This helps it enter spinal motor neurons and reach the nucleus. It then gets processed to allow motor neurons to produce the “survival of motor neurons” (SMN) protein. Zolgensma also contains genetic instructions for cells to continuously produce the SMN protein.1,7

One way to imagine this is that the SMN1 gene is a recipe for your cells to make the SMN protein. But it has an error in it that makes the recipe unreadable. A new recipe would help your cells make the protein. Zolgensma gives your cells a more accurate recipe, packaged in a box that sends it directly to your kitchen (the nucleus of the cell). It even re-words the recipe to make it easier for your cells to use.

What are the possible side effects of Zolgensma?

The most common side effects of Zolgensma include:1

  • Vomiting
  • High levels of enzymes (a sign of liver damage)

Zolgensma may also cause brief decreases in platelet count (thrombocytopenia). Platelets are blood cells that react to bleeding by starting a blood clot. Doctors will check platelet counts before giving Zolgensma. Then, they will closely monitor platelet counts for at least 3 months afterward.1

Zolgensma may also cause brief increases in troponin-I levels in the heart. Troponin-I is a protein that helps regulate heart contractions. High troponin-I levels in the blood are usually a sign of heart problems. Doctors will monitor troponin-I levels before giving Zolgensma and for at least 3 months afterward.1

Zolgensma has a boxed warning, the strictest warning from the FDA. It has this warning because it can cause liver damage. People with pre-existing liver problems may be at higher risk. Before taking Zolgensma, your doctor will check your liver function with routine blood tests. To help prevent liver damage, your doctor will give you steroids before and after Zolgensma. After giving Zolgensma, doctors will monitor your liver function for at least 3 months.1

These are not all the possible side effects of Zolgensma. Talk to your doctor about what to expect when taking Zolgensma. You should also call your doctor if you have any changes that concern you when taking Zolgensma.

Things to know about Zolgensma

Zolgensma is given as a single-dose intravenous (into the vein) infusion over the course of an hour. Zolgensma is a one-time, life-long treatment. It can only be used once because people treated with Zolgensma develop antibodies against the virus packaging system, which lowers effectiveness and could cause serious side effects.1

Tell your child’s doctor about which vaccines your child has had before taking Zolgensma. Your doctor may adjust your child’s vaccination schedule. This is because some vaccines, such as MMR and varicella, should not be used with corticosteroids that are given before and after treatment with Zolgensma.1

Talk to your doctor if you notice signs of a respiratory infection before or after taking Zolgensma. This includes coughing, wheezing, sneezing, sore throat, and fever. This can lead to more serious complications.1

The estimated cost of 1 dose of Zolgensma is more than $2 million. This makes it the most expensive one-time treatment. Novartis, the maker of Zolgensma, allows insurance companies to pay $425,000 per year for 5 years. This makes it comparable to other SMA treatments. However, families must rely on insurance coverage or payment assistance programs to afford Zolgensma. Novartis also started a lottery-type system to give 100 free doses each year to infants with SMA outside the United States.7,8

Before beginning treatment for SMA, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of Zolgensma.

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