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Novartis says it has received reports of nine tumors in children previously treated with Zolgensma, its gene therapy for spinal muscular atrophy. The company says two cases showed evidence of the therapy’s vector DNA integrating into patients’ DNA; regulators are assessing the available evidence, and details about the cases remain limited.
Novartis said Thursday it has received reports of nine tumors in children 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 the patients’ DNA; authorities are assessing the evidence, and a causal role for the treatment has not been established for all nine reports.
Novartis told MedPage Today that the reports have been received since Zolgensma’s first approval in 2019. In the two cases with evidence of vector DNA integration, the patients underwent treatment and continue to be monitored, the company said. It did not disclose when the tumors developed or were identified in those cases, or provide equivalent details for the other seven reports.
The company said it had notified health authorities and would continue working with them on next steps. 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 development if vector DNA integrates into a patient’s genome.
Novartis said more than 6,000 patients have received the therapy in clinical trials, managed access programs and commercial treatment. That figure is a total treatment count supplied by the company, not a rate of tumors; the available information does not give a comparable follow-up period or enough detail to calculate the risk for treated patients.
Safety Questions for Zolgensma Patients
The reports have drawn attention to a known theoretical risk described in the prescribing information, while raising questions about how the newly disclosed cases should be interpreted. Evidence of vector DNA integration in two tumors is a relevant finding for safety review, but the disclosure alone does not establish that the therapy caused those tumors. The other seven reports have not been described in enough detail to assess their relationship to treatment.
Zolgensma treats SMA, a serious inherited condition associated with low levels of survival motor neuron protein. For families and clinicians, the immediate issue is whether the reports change how the therapy’s risks are understood or what monitoring may be appropriate. No change to treatment guidance or monitoring recommendations was reported in the source material.
Patient groups have sought further information. The U.S. Muscular Dystrophy Association said it was reviewing available scientific and safety data with clinical and research experts and had contacted Novartis. SMA Europe said it understood that regulators were involved in evaluating the available evidence.
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How the Tumor Reports Fit Prior Cases
Zolgensma was approved in 2019 for pediatric patients under age 2 with SMA and mutations in both copies of the SMN1 gene. SMA results from reduced SMN protein; the similar SMN2 gene produces only limited amounts of functional protein. The therapy uses an AAV vector to deliver an SMN1 gene, and its label notes a theoretical tumor risk related to vector integration.
Published case reports have described tumors in children with SMA who received the treatment, but they do not establish that Zolgensma caused the tumors. A 2023 report described a spinal-cord epithelioid neoplasm diagnosed in a boy 14 months after treatment; the finding was considered inconclusive. A 2025 report described a pilocytic astrocytoma, with molecular analysis suggesting its development was causally independent of the therapy.
Separately, researchers reported this year that vector integration was identified in a brain tumor in a child treated with a different AAV gene therapy for severe mucopolysaccharidosis type I. That case concerns another therapy and condition; it is not one of the nine Zolgensma reports described by Novartis.
“Limited information is available currently about the timing of events, nature of the tumors, and any future monitoring of treated individuals that may become appropriate.”
— Muscular Dystrophy Association
Key Details Still Missing
The disclosure does not specify when the nine tumors arose or were diagnosed, what types of tumors were reported, or how the cases were distributed among the more than 6,000 people treated. It also does not provide patient-level histories or explain whether other factors may have contributed.
For two cases, Novartis reported evidence of vector DNA integration, but the information provided does not establish that integration caused the tumors. The company has not described the findings in the other seven cases. Regulators’ conclusions and any resulting actions have not been announced in the source material.
Regulatory Review and Company Follow-Up
Novartis said it had notified health authorities and would continue working with them. Regulators are assessing the available evidence, according to SMA Europe, but no timetable or decision was provided. The next public information may clarify the tumor types, timing, molecular findings and whether authorities recommend changes to product information or patient follow-up.
The Muscular Dystrophy Association said it was seeking additional information from Novartis and reviewing the available data with experts. Until further details emerge, the disclosed total should be treated as a set of reports under review, not as proof that Zolgensma caused nine tumors or as a measure of the therapy’s tumor risk.
Key Questions
What did Novartis report about Zolgensma?
Novartis said it has received nine tumor reports involving patients previously treated with Zolgensma since the therapy was first approved in 2019. The company said two cases showed evidence of vector DNA integration.
Do the reports prove that Zolgensma caused the tumors?
No. The information released does not establish that the therapy caused all, or any, of the reported tumors. Evidence of vector integration was reported in two cases, but the company’s disclosure does not establish that integration caused those tumors.
What is vector DNA integration?
Zolgensma uses an AAV vector to deliver a working copy of the SMN1 gene. Vector DNA integration means DNA from that delivery vector is found incorporated into a patient’s DNA. The prescribing information describes tumor development from integration as a theoretical risk.
Have regulators changed Zolgensma guidance?
No change to treatment or monitoring guidance was described in the source material. Novartis said it notified health authorities, and SMA Europe said regulators were assessing the evidence. Any regulatory decision remains unreported.
What information is still unknown?
The timing and types of tumors, details of the seven cases without reported integration evidence, and how the reports compare with the number of people treated are not available. The company also has not reported a regulatory conclusion or a new monitoring recommendation.
Source: medpagetoday.com
