Novartis confirms nine tumor reports in Zolgensma patients

Novartis has confirmed nine reported cases of tumors in children treated with its gene therapy Zolgensma. Two of those cases showed direct evidence that the adeno-associated virus (AAV) delivery vector integrated into patient DNA, a known theoretical risk for such treatments.

Zolgensma, approved in 2019 for children under two years old, uses an AAV vector to deliver a functional copy of the survival motor neuron (SMN) gene. The Swiss drugmaker disclosed the information to neurologists earlier this week and publicized it on Thursday after reports circulated from patient advocacy groups. More than 6,000 patients have been treated globally across clinical and commercial settings.

Tumors occurred years after treatment with no causal link established

The nine tumor cases emerged between 18 and 60 months after a single infusion of the therapy. Novartis has notified health authorities after each case. Most have not been definitively linked to Zolgensma. The company stated that seven of the nine reports have not been causally linked, and one case appeared unrelated to the therapy.

Only three of the nine tumor cases have undergone pathological testing so far. The potential risk of tumors due to vector integration is already listed in the therapy's prescribing information. As of Thursday evening, the official FDA label for Zolgensma had not been updated. This disclosure follows a parallel case in January 2026 involving a different gene therapy, RGX-111, which established a clear mechanism of insertional mutagenesis.

Patient advocacy groups demand transparency and regulatory scrutiny

Patient groups SMA Europe and Cure SMA have called for clear and timely communication from Novartis regarding the safety concerns. Families, physicians, and advocacy groups have expressed concern over the potential safety signal. SMA Europe acknowledged the reports and stated that relevant regulatory authorities are actively involved in assessing the evidence.

Cure SMA noted the findings from the three tested cases. "We are taking these reports seriously, and we are committed to sharing clear, accurate information with our community as soon as it becomes available," the organization said. Novartis issued its statement in response to the circulating reports from these patient organizations.

The company developed Zolgensma through its acquisition of AveXis. Initial FDA approval was delayed due to data manipulation concerns, though Novartis was later cleared and received broader approval. An FDA meeting in 2021 had previously featured calls for greater monitoring of cancer risks in gene therapy. Novartis says it will continue working with health authorities as their assessment continues.