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Novartis says it has received reports of nine tumors in patients treated with Zolgensma, its gene therapy for spinal muscular atrophy. The company says two cases showed evidence of therapy-related vector DNA integration; regulators are assessing the available evidence, and key details about the cases remain undisclosed.
Novartis said Thursday it has received reports of nine tumors in patients previously treated with Zolgensma, its gene therapy for spinal muscular atrophy (SMA). The company said two cases showed evidence that DNA from the therapy’s viral vector had integrated into patients’ DNA, a finding relevant to a tumor risk already described in the treatment’s prescribing information; the reports do not establish that the therapy caused all nine tumors.
In a statement to MedPage Today, Novartis said it had received the nine reports since Zolgensma’s first approval in 2019. In two cases, testing showed evidence of vector DNA integration. The company said both patients underwent treatment and remain under monitoring. It did not provide details about the tumor types, when the tumors developed or were identified, or the patients’ current health beyond that monitoring statement.
The drugmaker said it notified health authorities and would continue working with them on next steps. SMA Europe, an umbrella group for European SMA patient organizations, said regulators were involved and assessing the evidence. In the United States, the Muscular Dystrophy Association said it was seeking more information, reviewing available scientific and safety data with experts, and had contacted Novartis.
Novartis reported that more than 6,000 patients have received Zolgensma through clinical trials, managed access programs and commercial treatment. That figure is the company’s reported treatment total; it does not provide a rate for the tumor reports, since the available account does not give case-level details or a defined period of follow-up for all patients.
What the Tumor Reports Mean for Patients
The reports put attention on a safety risk associated with AAV vector-based gene therapies. Zolgensma uses an adeno-associated virus (AAV) vector to deliver a working copy of the SMN1 gene. Its prescribing information already describes a theoretical risk of tumor formation if vector DNA integrates into a patient’s genome. The two reports with evidence of integration are relevant to that concern, but the information released so far does not show that integration caused either tumor.
For families and clinicians, the news may prompt questions about how the reported cases will be evaluated and whether monitoring guidance will change. Regulatory review is ongoing, and neither the company’s announcement nor the statements from patient organizations specify new monitoring instructions. The nine reports are safety signals to be investigated, not by themselves proof that Zolgensma caused nine tumors or that the treatment’s benefit-risk assessment has changed.
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Zolgensma’s Known Integration Risk
SMA is a genetic disorder caused by low levels of survival motor neuron protein, usually because of changes in both copies of the SMN1 gene. The related SMN2 gene produces only a limited amount of functional protein. Zolgensma, also called onasemnogene abeparvovec, delivers a functioning SMN1 gene using an AAV vector. It was approved in 2019 for pediatric patients under age 2 with SMA and mutations in both SMN1 copies.
The product information has included a theoretical tumorigenicity risk linked to vector DNA integration. Earlier published reports describe individual tumors in children with SMA who received Zolgensma, but those reports did not establish a common cause. A 2023 case report described a spinal cord epithelioid neoplasm diagnosed 14 months after treatment and judged the finding inconclusive. A 2025 report of a pilocytic astrocytoma said molecular analysis suggested the tumor’s development was independent of the therapy.
Separately, researchers reported vector integration in a brain tumor in a child treated with a different AAV gene therapy for severe mucopolysaccharidosis type I. That case involved another disease and treatment, so it is not evidence about the nine Zolgensma reports. Zolgensma also faced a separate controversy after approval, when the FDA criticized Novartis’s AveXis unit over data manipulation affecting animal product-testing results.
“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
Key Details Still Missing
The public information does not identify the nine patients, describe the tumors in most cases, or say when they arose or were detected. Novartis has not explained whether the two cases with vector DNA integration are among previously published case reports. The company also has not stated whether those tumors were judged to be caused by treatment; evidence of integration alone does not establish that link.
It is also unclear what analyses were performed across the reports, whether the patients share relevant clinical features, and what follow-up period applies to the company’s treatment total. Regulators have not announced a conclusion or a change to the product information in the source material. The available figures therefore cannot establish how often tumors occur among treated patients or whether the reports change the therapy’s known safety profile.
Regulators to Review Safety Evidence
Novartis said it will continue to work with health authorities, which are assessing the available evidence. The company said it is evaluating new safety information and reported cases as part of its ongoing monitoring. SMA Europe said regulators would determine whether further steps are needed, while the Muscular Dystrophy Association said it was seeking additional information and reviewing the available data with clinical and research experts.
Further updates may clarify the tumor types, timing, test results and whether regulators recommend changes to monitoring or prescribing information. Until those details are released, the confirmed development is nine reported tumors, with vector DNA integration found in two cases—not a determination that Zolgensma caused all or any of them.
Key Questions
How many tumor reports has Novartis disclosed?
Novartis said it has received nine reports of tumors in patients previously treated with Zolgensma since the therapy’s first approval in 2019.
Do the reports prove that Zolgensma caused the tumors?
No. The available information does not establish that the therapy caused the tumors. Novartis said two cases showed evidence of vector DNA integration, but that finding alone does not prove the integration caused a tumor.
What has Novartis said about the two cases?
The company said both patients underwent treatment and continue to be monitored. It did not provide further details about their tumors or health status in the report.
Are regulators reviewing the reports?
SMA Europe said relevant authorities were involved and assessing the available evidence. No regulatory conclusion or new monitoring instruction was reported in the available source material.
What information has not been made public?
The available account does not give the tumor types and timing for all cases, explain whether the reports overlap with published case reports, or state whether authorities will change Zolgensma’s prescribing information or monitoring recommendations.
Source: medpagetoday.com
