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Novartis says it has received reports of tumors in nine patients treated with Zolgensma, its gene therapy for spinal muscular atrophy. Two cases showed evidence of the therapy’s vector DNA integrating into patients’ DNA; the company says both patients received treatment and remain under monitoring.
Novartis said it has received nine reports of tumors in patients previously treated with Zolgensma, its gene therapy for spinal muscular atrophy (SMA), and that two cases showed evidence of the therapy’s vector DNA integrating into patients’ DNA. The company said both patients underwent treatment and continue to be monitored; the reports are being reviewed by health authorities.
A Novartis spokesperson told MedPage Today on Thursday that the reports had been received since Zolgensma’s first approval in 2019. The two cases with evidence of integration are the only ones for which the company specified that finding. Novartis did not provide details about the tumors or the timing of the other seven reports.
Zolgensma, whose generic name is onasemnogene abeparvovec, uses an adeno-associated virus (AAV) vector to deliver a working copy of the SMN1 gene. It is approved for pediatric patients under age 2 with SMA and mutations in both copies of SMN1. Novartis said it had notified health authorities and would continue working with them on next steps.
The company said more than 6,000 patients have received Zolgensma through clinical trials, managed access programs and commercial treatment. That figure is the number treated, not a rate of tumor occurrence; the company’s disclosure does not provide the information needed to calculate the frequency or assess comparative risk.
Safety Review Could Affect Zolgensma Care
The reports matter to families and clinicians because Zolgensma is a gene therapy given to young children with SMA, a serious inherited condition. The disclosure raises questions about how the reported tumors relate to treatment and whether any changes to safety monitoring or clinical guidance may be needed. Two integration findings are a safety signal for review, but they do not by themselves establish that the therapy caused those tumors.
Regulators and medical experts will need case details to assess the significance of the reports, including tumor type, timing, clinical histories and laboratory evidence. Until those details are available, patients and families should not treat the count as proof either of a causal link across the cases or of a known level of risk. Any decisions about an individual’s care should be discussed with the treating clinical team.
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A Known Theoretical Risk, Now Under Review
SMA results from insufficient survival motor neuron (SMN) protein, usually because of deletions or mutations in the SMN1 gene. The similar SMN2 gene produces only low amounts of functional protein. Zolgensma is designed to provide a working SMN1 gene using an AAV vector.
The therapy’s prescribing information already describes a theoretical tumor risk from integration of AAV vector DNA into the genome. Novartis said that potential risk is included in the prescribing information. The new disclosure is distinct from proof of causation: it identifies reports and integration evidence in two cases, while the company’s statement does not conclude that the therapy caused the tumors.
Earlier reports offer relevant but not definitive context. A 2023 case report described a spinal cord epithelioid neoplasm in a child diagnosed 14 months after treatment; the finding was considered inconclusive. A 2025 case report of a pilocytic astrocytoma said molecular analysis suggested the tumor’s development was causally independent of the therapy. Separately, researchers reported AAV-vector integration in a brain tumor in a child treated with a different AAV gene therapy. Those cases do not resolve the causes of the nine reports now disclosed.
“We understand that the relevant regulatory authorities are actively involved and are currently assessing the available evidence and determining what further steps may be needed.”
— SMA Europe
Tumor Details and Causation Remain Unknown
The public disclosure does not identify the types of tumors in the nine reports, when they arose, or when they were reported. Novartis provided evidence of vector DNA integration in two cases but did not say whether that evidence establishes a causal role in either tumor. Information on the other seven cases is also limited.
The Muscular Dystrophy Association said it was seeking more information, reviewing available scientific and safety data with clinical and research experts, and had contacted Novartis. It said the nature and timing of the events, and whether additional monitoring of treated patients may be appropriate, remained unclear. The company’s statement does not give a tumor rate or explain how the reports compare with expected risks in the broader treated population.
Regulators to Weigh Further Safety Steps
Novartis said it had notified health authorities and would continue working with them. SMA Europe said regulators were assessing the available evidence and considering whether further steps were needed. No specific regulatory action or timetable was included in the source material.
The next developments may include more information about the cases, the regulators’ assessment and any updated guidance for clinicians or patients. The Muscular Dystrophy Association said it was continuing its review and seeking details from the company. Until those reviews produce further findings, the relationship between Zolgensma and the reported tumors remains under assessment.
Key Questions
How many tumor reports did Novartis disclose?
Novartis reported nine tumors in patients previously treated with Zolgensma. The company said two cases showed evidence of vector DNA integration into patients’ DNA.
Does the disclosure prove Zolgensma caused the tumors?
No. The company disclosed reports and an integration finding in two cases, but the information provided does not establish causation. Regulators are assessing the available evidence.
What is Zolgensma used for?
Zolgensma is an AAV-vector gene therapy approved for pediatric patients under age 2 with spinal muscular atrophy and mutations in both copies of the SMN1 gene.
What information is still missing?
Public details do not specify the tumor types, timing for most cases, or the full clinical and molecular findings. The company also did not provide a comparison that would establish how frequently tumors occurred among treated patients.
Source: medpagetoday.com
