Zolgensma: Uses, Dosage & Side Effects
A one-time gene replacement therapy for spinal muscular atrophy (SMA), delivering a functional copy of the SMN1 gene via an AAV9 viral vector to restore survival motor neuron protein production
Zolgensma (onasemnogene abeparvovec) is a groundbreaking gene replacement therapy approved for the treatment of spinal muscular atrophy (SMA), a rare and devastating inherited neuromuscular disease caused by mutations in the SMN1 gene. Zolgensma delivers a functional copy of the human SMN1 gene using an adeno-associated virus serotype 9 (AAV9) vector, enabling the body to produce the survival motor neuron (SMN) protein essential for motor neuron survival. Given as a single, one-time intravenous infusion, Zolgensma addresses the root genetic cause of SMA and has transformed outcomes for affected children. It is one of the most expensive medicines ever developed, reflecting its status as a potentially curative one-time treatment for a life-threatening condition.
Quick Facts: Zolgensma
Key Takeaways
- Zolgensma is a one-time gene therapy that delivers a functional SMN1 gene to treat spinal muscular atrophy (SMA), addressing the root genetic cause of the disease rather than just managing symptoms.
- It is given as a single intravenous infusion over approximately 60 minutes, with the dose calculated based on the patient’s body weight. No repeat doses are given.
- Patients must receive corticosteroid pre-treatment (e.g., prednisolone) starting 24 hours before infusion and continuing for at least 2 months afterward to protect against liver inflammation caused by the immune response to the viral vector.
- Serious risks include hepatotoxicity (liver damage, potentially fatal), thrombotic microangiopathy (TMA), and thrombocytopenia (low platelet count), requiring intensive monitoring with regular blood tests for at least 3 months post-treatment.
- Early treatment produces the best outcomes — children treated before symptom onset (identified through newborn screening) show the greatest motor milestone achievements, underscoring the importance of early diagnosis.
What Is Zolgensma and What Is It Used For?
Zolgensma is a type of medicine called a gene therapy. It contains the active substance onasemnogene abeparvovec, which consists of human genetic material packaged inside a modified adeno-associated virus serotype 9 (AAV9) vector. This viral vector has been engineered so that it cannot cause disease in humans but retains the ability to enter cells and deliver the therapeutic gene to where it is needed most — the motor neurons of the spinal cord and brainstem.
Spinal muscular atrophy (SMA) is a rare, serious inherited condition caused by mutations in or deletion of the SMN1 gene on chromosome 5. This gene is responsible for producing the survival motor neuron (SMN) protein, which is essential for the health and function of motor neurons — the nerve cells in the spinal cord that control voluntary muscle movement. Without sufficient SMN protein, motor neurons progressively degenerate and die, leading to muscle weakness, wasting (atrophy), and eventually the loss of the ability to move, swallow, and breathe. SMA is the most common genetic cause of infant death, with an estimated incidence of approximately 1 in 10,000 live births worldwide.
Humans carry a second, closely related gene called SMN2, which can produce small amounts of functional SMN protein. However, the SMN2 gene contains a critical nucleotide difference that causes most of its messenger RNA to be spliced incorrectly, resulting in a truncated and rapidly degraded protein. Only about 10–15% of the protein produced by SMN2 is full-length and functional. The number of SMN2 copies a patient carries influences disease severity: patients with fewer copies generally develop more severe forms of SMA, while those with more copies may have milder disease. Nevertheless, SMN2 alone cannot compensate fully for the loss of SMN1.
Zolgensma works by providing a fully functional copy of the human SMN1 gene directly to the cells that need it. The AAV9 vector has a natural ability to cross the blood-brain barrier and efficiently transduce (enter and deliver its genetic cargo to) motor neurons in the central nervous system. Once inside the cell, the therapeutic SMN1 gene remains as a stable episome — a separate piece of DNA that does not integrate into the patient’s chromosomes under normal circumstances — and directs the production of full-length, functional SMN protein. Because the transgene expression is designed to be long-lasting, a single dose of Zolgensma can provide durable, potentially lifelong SMN protein production.
Zolgensma has been approved by the European Medicines Agency (EMA), the U.S. Food and Drug Administration (FDA), and regulatory authorities in numerous other countries. In the EU, it is indicated for the treatment of patients with 5q spinal muscular atrophy who have a bi-allelic mutation in the SMN1 gene and a clinical diagnosis of SMA Type 1, or who have up to 3 copies of the SMN2 gene. In the US, it is approved for pediatric patients less than 2 years of age with SMA, including those who are presymptomatic at diagnosis.
SMA Types and Treatment Relevance
SMA is classified into several types based on age of onset and the highest motor milestone achieved:
- SMA Type 0: The most severe form, presenting before birth with reduced fetal movement. Infants are born with severe weakness and respiratory failure. Zolgensma may offer limited benefit in this form due to extensive motor neuron loss by birth.
- SMA Type 1 (Werdnig-Hoffmann disease): The most common severe form, with onset before 6 months of age. Without treatment, affected infants never sit independently and most do not survive beyond 2 years without respiratory support. This is the primary target population for Zolgensma, and clinical trials have demonstrated remarkable improvements in survival, motor milestones, and respiratory function.
- SMA Type 2: Onset between 6 and 18 months. Children can sit but never walk independently. Zolgensma is being studied and used in some of these patients, with benefits seen particularly when treatment is given early.
- SMA Type 3 (Kugelberg-Welander disease): Onset after 18 months. Patients can walk but may lose this ability over time. Zolgensma is currently not broadly indicated for older patients with SMA Type 3.
Unlike other SMA therapies that require ongoing chronic administration (such as nusinersen, which requires repeated intrathecal injections, or risdiplam, which requires daily oral dosing for life), Zolgensma is designed as a single, one-time treatment. The AAV9 vector delivers the SMN1 gene to motor neurons, where the transgene can provide sustained SMN protein production without the need for repeat dosing. This unique characteristic makes Zolgensma fundamentally different from other SMA treatments and is central to its clinical value proposition.
Clinical trial data from the pivotal STR1VE and SPR1NT studies, as well as long-term follow-up data extending beyond 5 years, have demonstrated that Zolgensma-treated patients achieve and maintain motor milestones that would otherwise be impossible for children with SMA Type 1. Many treated patients have been able to sit independently, and some have achieved the ability to stand and walk — milestones never reached in the natural history of SMA Type 1. Event-free survival (survival without permanent ventilatory support) has been significantly prolonged compared to historical controls.
What Should You Know Before Your Child Receives Zolgensma?
Contraindications
Zolgensma must not be used if the child is allergic (hypersensitive) to onasemnogene abeparvovec or any of the other ingredients in the medicine (tromethamine, magnesium chloride, sodium chloride, poloxamer 188, hydrochloric acid, and water for injections).
Anti-AAV9 Antibody Testing
Before treatment with Zolgensma, the child’s doctor will perform a blood test to check for pre-existing antibodies against the AAV9 viral vector. If the child has high levels of anti-AAV9 antibodies, Zolgensma may not work effectively because the antibodies would neutralize the viral vector before it can deliver the therapeutic gene to the motor neurons. The decision to proceed with treatment in the presence of anti-AAV9 antibodies is made by the treating physician based on the antibody titer and clinical circumstances.
Warnings and Precautions
Zolgensma can cause serious liver damage, including liver failure and death. The child’s liver function will be tested before treatment and monitored regularly with blood tests for at least 3 months afterward. Possible signs of liver problems include vomiting, jaundice (yellowing of the skin or whites of the eyes), and decreased alertness. Contact the doctor immediately if you notice any of these symptoms. Corticosteroid treatment is given to help reduce the risk of liver inflammation.
Before and during treatment with Zolgensma, the following precautions must be observed:
- Thrombotic microangiopathy (TMA): Cases of TMA have been reported, usually within the first two weeks after Zolgensma treatment. TMA involves blood clots forming in small blood vessels and is accompanied by a decrease in red blood cells and platelets. It can affect the kidneys and may be fatal. Watch for signs including easy bruising, seizures (fits), or decreased urine output. Contact a doctor immediately if any of these signs develop.
- Thrombocytopenia (low platelet count): Zolgensma may decrease the number of platelets in the blood, usually within the first three weeks after infusion. Signs to watch for include abnormal bruising or unusual bleeding. The child’s platelet count will be monitored regularly through blood tests.
- Elevated troponin-I: Zolgensma may increase levels of troponin-I, a heart protein detectable through laboratory tests. The child’s doctor will monitor this as needed.
- Infections: An infection (such as a cold, flu, or bronchiolitis) before or after Zolgensma treatment can lead to more serious complications. Caregivers and close contacts should follow infection prevention practices including proper hand hygiene, coughing and sneezing into the elbow, and limiting contact with sick individuals. Notify the doctor immediately if the child develops any signs of infection before or after treatment.
- Advanced SMA: Zolgensma can rescue living motor neurons but cannot resurrect dead motor neurons. Children with less severe symptoms may have enough living motor neurons to benefit significantly. Zolgensma may not work as well in children who already have severe muscle weakness, paralysis, breathing problems, inability to swallow, or extensive malformations (such as heart defects), including patients with SMA Type 0.
- Potential risk of tumor formation: As with all gene therapies that use viral vectors, there is a theoretical possibility that the vector DNA may integrate into human cell DNA. As a consequence, Zolgensma could contribute to a risk of tumor formation. Discuss this with the child’s doctor. In the event of a tumor, the doctor may take a sample for further evaluation.
Required Monitoring
Before treatment with Zolgensma begins, the child will undergo several blood tests and assessments:
| Test | Before Treatment | After Treatment |
|---|---|---|
| Liver function (AST, ALT, bilirubin) | Baseline assessment required | Regular monitoring for at least 3 months |
| Complete blood count (including platelets) | Baseline assessment required | Regular monitoring, especially first 3 weeks |
| Troponin-I | Baseline level | As clinically indicated |
| Creatinine (kidney function) | Baseline assessment | Monitored for TMA risk |
| Anti-AAV9 antibodies | Must be tested | Not applicable |
Vaccinations
Because corticosteroids can affect the body’s immune system, the child’s doctor may decide to delay certain vaccinations while the child is receiving corticosteroid treatment. This is particularly important for live vaccines, which could potentially cause infection in an immunosuppressed child. Inactivated vaccines may be given but the immune response may be reduced. Discuss any questions about the vaccination schedule with the child’s doctor or nurse.
Hygiene Precautions After Treatment
The active substance in Zolgensma may be temporarily shed through the child’s body fluids and feces. This is called “shedding.” Parents and caregivers should observe good hand hygiene for at least 1 month after the child receives Zolgensma:
- Wear protective gloves when handling the child’s body fluids or feces
- Wash hands thoroughly with soap and warm running water or an alcohol-based hand sanitizer after contact
- Place soiled disposable diapers in double plastic bags before disposing of them in household waste
- Continue these practices for at least 1 month after treatment
Blood, Organ, Tissue and Cell Donation
After treatment with Zolgensma, the child will not be able to donate blood, organs, tissues, or cells at any point in the future. This is because Zolgensma is a gene therapy product and the modified genetic material will remain in the body permanently.
Zolgensma contains 4.6 mg sodium per mL, equivalent to 0.23% of the WHO maximum recommended daily sodium intake for adults. Each 5.5 mL vial contains 25.3 mg sodium and each 8.3 mL vial contains 38.2 mg sodium. The total sodium dose depends on the number of vials used, which is determined by the child’s body weight.
How Does Zolgensma Interact with Other Drugs?
Unlike conventional small-molecule drugs, Zolgensma is a gene therapy based on a viral vector and does not undergo metabolism through the cytochrome P450 enzyme system or other typical drug-metabolizing pathways. Therefore, traditional pharmacokinetic drug interactions are not expected. However, several important considerations apply to the overall treatment protocol:
Corticosteroid Co-Treatment
Prednisolone or another equivalent corticosteroid is given as part of the Zolgensma treatment protocol, starting 24 hours before the infusion and continuing daily for approximately 2 months or longer, depending on liver enzyme levels. The corticosteroid helps manage the immune response to the AAV9 vector and reduces the risk of hepatotoxicity. This corticosteroid treatment can interact with other medications and affect the immune system.
Important Interactions to Consider
| Interacting Factor | Effect | Clinical Significance |
|---|---|---|
| Live vaccines (e.g., MMR, rotavirus, varicella) | Risk of vaccine-strain infection due to corticosteroid-induced immunosuppression | Delay live vaccines until corticosteroid treatment is completed |
| Inactivated vaccines | Reduced immune response during corticosteroid treatment | May be given but response may be suboptimal; discuss timing with doctor |
| Hepatotoxic medications | Additive risk of liver damage | Avoid or use with extreme caution; monitor liver function closely |
| Anticoagulants and antiplatelet agents | Increased bleeding risk due to potential thrombocytopenia from Zolgensma | Monitor platelet counts; adjust anticoagulation as needed |
| NSAIDs (e.g., ibuprofen) | Combined risk of GI effects with corticosteroids; potential platelet effects | Use with caution during corticosteroid treatment period |
Always inform the child’s doctor about all medications, supplements, and herbal products the child is currently taking or has recently taken. Although Zolgensma itself has a limited interaction profile, the combined treatment protocol (gene therapy plus corticosteroids) requires careful coordination of all concurrent medications.
What Is the Correct Dosage of Zolgensma?
Zolgensma is administered by a doctor or nurse who is trained and experienced in the treatment of spinal muscular atrophy. The dose is calculated individually based on the child’s body weight at the time of treatment. The medicine is given intravenously (into a vein) as a single infusion over approximately 60 minutes using an infusion pump.
Dosing
Standard Dose (All Eligible Patients)
Dose: 1.1 × 1014 vector genomes per kilogram of body weight
Route: Intravenous infusion over approximately 60 minutes
Frequency: Given only ONCE in the patient’s lifetime
Preparation: The number of vials required is calculated based on the child’s weight and the concentration of vector genomes per mL (2 × 1013 vg/mL)
Corticosteroid Protocol
Prednisolone (or Equivalent Corticosteroid)
Timing: Started 24 hours before the Zolgensma infusion
Dose: Calculated based on body weight (typically 1 mg/kg/day oral prednisolone equivalent)
Duration: Daily for approximately 2 months after Zolgensma, or until liver enzymes decrease to an acceptable level
Tapering: The doctor will gradually reduce the corticosteroid dose before stopping completely
How Zolgensma Is Given
The Zolgensma infusion follows a carefully planned protocol in a specialized hospital setting:
- Pre-treatment assessment: Anti-AAV9 antibody testing, liver function tests, complete blood count, troponin-I, and creatinine levels are checked before treatment.
- Corticosteroid pre-treatment: Prednisolone (or equivalent) is started 24 hours before infusion.
- Thawing and preparation: Frozen vials are thawed in the refrigerator (12–16 hours depending on pack size) or at room temperature (4–6 hours). The medicine must not be shaken — only gently swirled.
- IV access: The required dose volume is drawn into syringes. A primary IV catheter is inserted, and a back-up catheter is recommended in case of blockage.
- Infusion: Zolgensma is administered slowly over approximately 60 minutes using a syringe pump. It must not be given as a rapid IV push or bolus injection.
- Post-infusion: The IV line is flushed with sodium chloride 0.9% solution. The child is monitored for infusion-related reactions.
- Follow-up: Regular blood tests and clinical assessments are scheduled for at least 3 months after treatment.
Zolgensma is given only ONCE in a patient’s lifetime. After the first dose, the body develops antibodies against the AAV9 vector that would neutralize any subsequent doses. Re-administration is not possible and has not been studied. The dose volume drawn into the syringe must be administered within 8 hours of preparation.
Special Populations
Zolgensma is specifically intended for pediatric patients. There is no dosing information for adults, as the indication is limited to young children with SMA. The child’s doctor will carefully evaluate eligibility based on genetic testing, clinical presentation, anti-AAV9 antibody status, liver function, and overall health before proceeding with treatment.
What Are the Side Effects of Zolgensma?
Like all medicines, Zolgensma can cause side effects, although not all patients experience them. Because Zolgensma is a gene therapy using a viral vector, the side effects are largely related to the body’s immune response to the vector rather than to typical pharmacological mechanisms. The child’s medical team will monitor closely and manage any side effects that arise.
Serious Side Effects Requiring Immediate Medical Attention
Contact the doctor immediately if the child develops any of the following:
Very Common
May affect more than 1 in 10 patients
- Elevated liver enzymes (AST, ALT) detected on blood tests
Common
May affect up to 1 in 10 patients
- Vomiting
- Fever (pyrexia)
- Elevated troponin-I levels (a heart protein) detected on blood tests
- Thrombocytopenia (low platelet count) — watch for abnormal bruising or bleeding that lasts longer than usual
Uncommon
May affect up to 1 in 100 patients
- Hepatotoxicity (liver damage), including liver failure — signs include vomiting, jaundice (yellowing of the skin or eyes), and decreased alertness
- Thrombotic microangiopathy (TMA) — blood clots in small blood vessels that can affect kidneys; signs include easy bruising, seizures, and decreased urine output
- Infusion-related reactions — may include rash, pale skin, vomiting, swelling of face, lips, mouth, or throat (which may cause difficulty swallowing or breathing), and changes in heart rate or blood pressure
Rare
May affect up to 1 in 1,000 patients
- Serious allergic reactions (anaphylaxis)
Hepatotoxicity in Detail
Liver injury is one of the most significant risks associated with Zolgensma treatment. The AAV9 vector can trigger an immune-mediated inflammatory response in the liver, leading to elevated liver enzymes and, in severe cases, acute liver failure. Several cases of fatal liver failure have been reported in post-marketing surveillance. This risk is the primary reason why corticosteroid pre-treatment and ongoing corticosteroid therapy are mandatory components of the Zolgensma treatment protocol.
Liver function tests (including AST, ALT, and bilirubin) are performed before treatment and monitored regularly for at least 3 months afterward. If liver enzymes rise significantly, the corticosteroid dose may be increased or other immunosuppressive measures may be considered. Parents and caregivers should be vigilant for any signs of liver dysfunction, including:
- Persistent or unexplained vomiting
- Yellow discoloration of the skin or whites of the eyes (jaundice)
- Unusual sleepiness or decreased responsiveness
- Easy bruising or bleeding
- Dark-colored urine
Thrombotic Microangiopathy (TMA)
TMA is a serious condition in which blood clots form in small blood vessels throughout the body. It has been reported in patients receiving Zolgensma, typically within the first two weeks after treatment. TMA is characterized by a decrease in both red blood cells and platelets, and can damage organs, particularly the kidneys. TMA can be fatal. The child’s doctor will monitor blood counts, blood pressure, and kidney function to detect early signs of TMA.
Contact the child’s doctor or seek emergency care immediately if you notice any of the following after Zolgensma treatment: persistent vomiting, jaundice (yellow skin or eyes), decreased alertness, easy bruising, unusual bleeding, seizures, decreased urine output, difficulty breathing, or swelling of the face or throat.
If the child experiences any side effects, including those not listed in this article, inform the doctor or nurse. You can also report suspected side effects to your national pharmacovigilance authority (e.g., the EMA in Europe, the FDA MedWatch program in the United States, or the MHRA Yellow Card Scheme in the United Kingdom) to help monitor the ongoing benefit-risk profile of Zolgensma.
How Should Zolgensma Be Stored?
Keep this medicine out of the sight and reach of children. Do not use after the expiry date stated on the vial and carton after EXP. The expiry date refers to the last day of the stated month.
- Transport: Vials must be transported frozen at or below −60°C.
- Upon receipt: Vials must be immediately placed in a refrigerator at 2°C to 8°C and stored in the original carton.
- Treatment timeline: Treatment with Zolgensma must be initiated within 14 days of receiving the vials.
- Thawing: For packages with up to 9 vials, thaw for approximately 12 hours in the refrigerator or 4 hours at room temperature (20–25°C). For packages with up to 14 vials, thaw for approximately 16 hours in the refrigerator or 6 hours at room temperature.
- Do not refreeze: Once thawed, Zolgensma must not be frozen again.
- Handling: Gently swirl after thawing. Do NOT shake.
- Inspection: Do not use if particles or discoloration are observed after thawing.
- After preparation: Once drawn into a syringe, the dose must be administered within 8 hours.
Zolgensma contains genetically modified organisms. Unused medicine or waste must be disposed of according to local guidelines for the handling of biological waste. Since this medicine is administered by a doctor, the doctor is responsible for proper disposal. These measures help protect the environment.
As a parent or caregiver, you will not need to handle the storage of Zolgensma. The entire cold chain — from transport to thawing, preparation, and administration — is managed by the hospital pharmacy and medical team following strict protocols. The medicine is prepared and administered in a controlled healthcare environment by trained professionals.
What Does Zolgensma Contain?
Active Substance
The active substance is onasemnogene abeparvovec. Each vial contains onasemnogene abeparvovec at a nominal concentration of 2 × 1013 vector genomes per mL. The product consists of a recombinant, self-complementary AAV9 vector carrying the human SMN1 gene under the control of a cytomegalovirus (CMV) enhancer/chicken β-actin hybrid promoter. This genetic construct enables robust and sustained expression of the survival motor neuron protein in transduced cells.
Inactive Ingredients (Excipients)
- Tromethamine (buffer)
- Magnesium chloride
- Sodium chloride
- Poloxamer 188 (stabilizer)
- Hydrochloric acid (for pH adjustment)
- Water for injections
Appearance and Packaging
Zolgensma is a clear to slightly opalescent, colorless to slightly whitish solution for infusion. It is supplied in glass vials with a nominal fill volume of either 5.5 mL or 8.3 mL. Each vial is for single use only. Each carton contains between 2 and 14 vials, with the number of vials needed calculated based on the child’s body weight.
Manufacturer
Zolgensma is manufactured by Novartis Pharmaceutical Manufacturing GmbH (Langkampfen, Austria) and Novartis Pharma GmbH (Nürnberg, Germany). The marketing authorization holder is Novartis Europharm Limited, Dublin, Ireland. Zolgensma was originally developed by AveXis, Inc. (now Novartis Gene Therapies) and received FDA approval in May 2019 and EMA conditional marketing authorization in May 2020.
Frequently Asked Questions About Zolgensma
Zolgensma (onasemnogene abeparvovec) is a one-time gene therapy used to treat spinal muscular atrophy (SMA), a rare and serious inherited disease caused by mutations in the SMN1 gene. SMA causes progressive loss of motor neurons, leading to muscle weakness, wasting, and potentially death. Zolgensma delivers a functional copy of the SMN1 gene to motor neurons, enabling the production of the essential survival motor neuron (SMN) protein. It is approved for patients with SMA who have bi-allelic mutations in the SMN1 gene, including those with SMA Type 1 and presymptomatic patients with up to 3 copies of the SMN2 gene.
Zolgensma is given as a single intravenous (IV) infusion over approximately 60 minutes in a specialized hospital setting. The dose is calculated based on the child’s body weight (1.1 × 1014 vector genomes per kilogram). It is administered only once in a patient’s lifetime — no repeat doses are given. Patients receive corticosteroid pre-treatment (prednisolone or equivalent) starting 24 hours before the infusion to protect the liver from the immune response to the viral vector.
The most serious risks include hepatotoxicity (liver damage), which can be severe and potentially fatal. Liver failure and death have been reported in some patients after Zolgensma treatment. Thrombotic microangiopathy (TMA), a condition involving blood clots in small blood vessels that can affect the kidneys and other organs, has also been reported and can be life-threatening. Thrombocytopenia (low platelet count) is common. Extensive pre-treatment testing, corticosteroid therapy, and regular post-treatment blood monitoring are mandatory to detect and manage these risks.
Zolgensma has a list price of approximately $2.125 million USD, making it one of the most expensive medicines ever developed. This price reflects several factors: the complexity and cost of manufacturing a gene therapy product using viral vectors, the very small patient population (SMA is a rare disease), the extensive research and development investment, and the fact that it is a one-time curative treatment rather than a chronic therapy. When compared to the lifetime costs of alternative SMA treatments (such as nusinersen at approximately $750,000 per year indefinitely), the manufacturer argues that the one-time cost represents value. Many national health systems and insurance programs cover the cost for eligible patients, and outcomes-based payment arrangements are available in some countries.
The approved indications for Zolgensma vary by region but are generally limited to young children. In the US, it is approved for pediatric patients under 2 years of age with SMA. In the EU, it is approved for patients with SMA Type 1 or those with up to 3 copies of the SMN2 gene, without a strict age or weight limit but with considerations about clinical benefit. In general, earlier treatment is associated with better outcomes because more motor neurons are still alive. In patients with advanced SMA where significant motor neuron loss has already occurred, the potential for benefit is limited. The use of Zolgensma in older children and adults is being investigated in clinical trials but is not currently part of the standard approved indications.
No, Zolgensma is designed as a single, one-time treatment. After the first infusion, the body develops antibodies against the AAV9 viral vector used to deliver the gene. These antibodies would neutralize any subsequent doses, making re-administration ineffective. This is also why patients are tested for pre-existing anti-AAV9 antibodies before treatment — if antibody levels are already high (from prior natural exposure to AAV9), the initial treatment may be less effective or not possible.
References
- European Medicines Agency (EMA). Zolgensma — Summary of Product Characteristics. EMA/EPAR. Last updated 2025.
- U.S. Food and Drug Administration (FDA). Zolgensma (onasemnogene abeparvovec-xioi) — Prescribing Information. Approved May 2019, revised 2024.
- Mendell JR, Al-Zaidy S, Shell R, et al. Single-dose gene-replacement therapy for spinal muscular atrophy. N Engl J Med. 2017;377(18):1713-1722. doi:10.1056/NEJMoa1706198
- Day JW, Finkel RS, Chiriboga CA, et al. Onasemnogene abeparvovec gene therapy for symptomatic infantile-onset spinal muscular atrophy in patients with two copies of SMN2 (STR1VE): an open-label, single-arm, multicentre, phase 3 trial. Lancet Neurol. 2021;20(4):284-293. doi:10.1016/S1474-4422(21)00001-6
- Strauss KA, Farrar MA, Muntoni F, et al. Onasemnogene abeparvovec for presymptomatic infants with three copies of SMN2 at risk for spinal muscular atrophy: the Phase III SPR1NT trial. Nat Med. 2022;28(7):1390-1397. doi:10.1038/s41591-022-01867-3
- Mercuri E, Finkel RS, Muntoni F, et al. Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis, rehabilitation, orthopedic and nutritional care. Neuromuscul Disord. 2018;28(2):103-115. doi:10.1016/j.nmd.2017.11.005
- Finkel RS, Mercuri E, Darras BT, et al. Nusinersen versus sham control in infantile-onset spinal muscular atrophy. N Engl J Med. 2017;377(18):1723-1732. doi:10.1056/NEJMoa1702752
- World Health Organization (WHO). WHO Model List of Essential Medicines for Children. 9th List, 2023.
Editorial Team
Medical Content
iMedic Medical Editorial Team — Specialists in Neurology, Pediatrics, and Gene Therapy
Medical Review
iMedic Medical Review Board — Independent expert panel reviewing content according to EMA, FDA, and WHO guidelines
Evidence Standard
Level 1A — Based on systematic reviews, randomized controlled trials, and regulatory authority assessments (GRADE framework)
Declaration
No conflicts of interest. No pharmaceutical company funding. Independent medical editorial content.
This article was last medically reviewed on . All information is based on the most current product labeling, peer-reviewed research, and international treatment guidelines available at the time of review. For the latest prescribing information, consult the official product labeling from the EMA or FDA.