Novartis has said that two cases of tumours in children showed evidence of being linked to its gene therapy Zolgensma, a one-time treatment for spinal muscular atrophy (SMA) given to more than 6,000 children around the world.
The Swiss drugmaker said on Friday that it had received nine reports in total of tumours in patients previously treated with Zolgensma since the therapy was first approved in 2019. In two of those cases, doctors found evidence that the vector — the modified virus used to carry a working copy of a gene into the patient’s cells — had inserted its own genetic material into the patients’ DNA.
Pathology testing has so far been completed on the tumours of three of the nine children. Two were found to be specifically related to Zolgensma treatment, while the third appeared to be unrelated. Information about the remaining six cases is still limited, and further details are awaited from the regulatory authorities.
Novartis said both children in the linked cases had undergone treatment and continue to be monitored. The company said it had notified health authorities in a timely and appropriate manner in both cases, and that the potential risk of tumours caused by vector integration was already included in Zolgensma’s prescribing information.
The disclosure has raised fresh questions about the long-term safety of gene therapies, which are designed to deliver a lasting, one-time fix by altering cells. Zolgensma, known generically as onasemnogene abeparvovec, is approved in the United States for children under two with SMA and is widely used for young children elsewhere. SMA is a rare genetic condition that causes muscle weakness and wasting, and without treatment the most severe form is usually fatal in early childhood.
Patient groups urged families not to panic but to seek advice. SMA Europe said it had pressed Novartis to set out what is known, what remains uncertain and what the findings could mean for children who have already received the treatment. Muscular Dystrophy UK said it knew the reports may raise questions and concerns for its community, and that further information was awaited from the regulatory authorities.
Novartis did not say where the two linked cases occurred, and the European Medicines Agency and the US Food and Drug Administration did not immediately respond to requests for comment.
Note: the link between Zolgensma and the two tumours rests on Novartis’s own statement and the pathology findings it described; no regulator has yet published its own assessment, and the tumour types, timing and outcomes have not been disclosed.
Sources: Reuters, “Two tumour cases in children linked to SMA drug, Novartis says”, https://www.reuters.com/legal/litigation/two-tumour-cases-children-linked-sma-drug-novartis-says-2026-11-06/ ; Muscular Dystrophy UK, “Statement on recent Zolgensma safety reports”, https://www.musculardystrophyuk.org/news/zolgensma-sma-safety-reports/
