The US Food and Drug Administration (FDA) said on 6 November 2026 that it is investigating a serious risk of tumour formation linked to Zolgensma, the one-time gene therapy for spinal muscular atrophy (SMA). The agency received postmarketing reports of malignancies in patients treated with the therapy, including confirmed cases in which the treatment's viral vector DNA had integrated into a patient's own genome near a gene that can drive cancer.
What the FDA Found
Three of the reported cases involved tumours associated with the GLI1 gene, which can cause cancer when it is switched on or overexpressed. In two of those cases, molecular analysis of tumour tissue showed that DNA from Zolgensma's adeno-associated virus (AAV) vector had integrated into the host genome, with the promoter region of the treatment's genetic construct inserted upstream of or within GLI1. The mechanism behind the third GLI1 case is still under investigation.
The reported tumours appeared in the central and peripheral nervous systems, in the spinal and paraspinal regions, and in the kidney. Novartis, which makes Zolgensma, said it had received nine reports of tumours in patients previously treated with the therapy since it was first approved in the United States in May 2019, and that the treatment had been given to more than 6,000 children.
Zolgensma and Itvisma
Zolgensma is given as a single intravenous infusion to children under two years of age with SMA, a rare genetic disorder that causes progressive muscle weakness. The FDA said the risk also applies to Itvisma, a second Novartis product that uses the same vector and construct, given by injection into the spinal fluid to patients aged two and older. Itvisma was approved in November 2025, and no cases of tumour formation have been reported after its use so far.
The agency also noted two published reports of AAV vector integration driving cancer in other gene therapy programmes, one involving GLI1 and one involving a different gene, PLAG1. The FDA said it is closely monitoring the risk in other similar AAV vector-based gene therapy programmes.
What Happens Next
The current prescribing information for both products describes the risk of tumour formation from vector integration as theoretical, and says a causal relationship with Zolgensma has not been established. The FDA said it is now evaluating, on an expedited basis, whether that labelling and the long-term follow-up studies Novartis is running are adequate to investigate and mitigate the risk, and whether regulatory action is appropriate. No specific regulatory action has been announced.
The FDA said the overall benefits of Zolgensma and Itvisma continue to outweigh their potential risks for their approved uses. Patients and clinical trial participants receiving either treatment should be monitored for tumour formation, and clinicians who see a tumour develop in a treated patient should report it to Novartis Gene Therapies at 1-833-828-3947 or to the FDA through MedWatch at 1-800-FDA-1088.
Why This Matters for Healthcare Organizations
For clinics and hospitals, the immediate point is vigilance rather than a change in treatment. Zolgensma remains available, and the FDA has not restricted its use. But the finding changes how the risk should be described to families, because what the label still calls theoretical now has confirmed cases behind it. Any practice that refers children for gene therapy, or follows them afterwards, should make sure tumour monitoring is part of the long-term follow-up plan and that staff know how to report a suspected case.
The investigation also matters beyond SMA. AAV vectors are the delivery mechanism for a growing number of approved and experimental gene therapies, and the FDA has said it is watching the same risk across similar programmes. The outcome of this review, including any labelling change, will shape how the whole field talks about insertional oncogenesis.
Analysis: A Known Theoretical Risk With New Evidence Behind It
The striking part of this safety communication is the gap it exposes between the label and the evidence. The prescribing information still describes tumour formation from vector integration as a theoretical risk, yet the FDA now has molecular proof that the vector inserted itself next to a cancer-driving gene in two children. That does not establish that the therapy caused every reported tumour, and the FDA has been careful to say the investigation is ongoing. But the confirmed integration cases move the risk from a possibility the field had long discussed to something documented in patients.
The other question is speed. Zolgensma has been in use since 2019, and the nine reported tumours accumulated over years. Long-term follow-up studies were already running, which is how these cases surfaced, and the system worked in the sense that the signal was found. Whether the follow-up was fast enough, and whether the label should have changed sooner, is what the FDA's review will now test.
Clinics reviewing how front-desk and patient communication work can be handled can explore MedClinicX's AI patient portal, see how after-hours calls are handled on our AI medical receptionist page, or explore the demos and request a quote. For related coverage, see our earlier articles on FDA and CMS advancing personalised gene therapies and FDA finalising potency guidance for cell and gene therapies.
Sources and References
- U.S. Food and Drug Administration — FDA Investigating Serious Risk of Malignancy Linked to Zolgensma Gene Therapy, 6 November 2026: https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/fda-investigating-serious-risk-malignancy-linked-zolgensma-gene-therapy
- Reuters — FDA probes tumour risk tied to Novartis gene therapy, 6 November 2026: https://srnnews.com/two-tumour-cases-in-children-linked-to-sma-drug-novartis-says/
- Health and Me — FDA Probes Cancer Risk After Tumours Reported In Children Given Novartis's SMA Gene Therapy, 7 November 2026: https://www.healthandme.com/health-news/fda-probes-cancer-risk-after-tumours-reported-in-children-given-novartiss-sma-gene-therapy-article-156477329
Reporting based on the sources above, accessed 7 November 2026. The FDA safety communication was read directly, and the Reuters and Health and Me reports were read directly and cross-checked against it. MedClinicX did not conduct original reporting or interviews for this article. Corrections: contact us via https://medclinicx.com/contact