Deep Dive: FDA Investigates Malignancy Risk Linked to Zolgensma Gene Therapy for SMA

On 6 November 2026 the U.S. Food and Drug Administration announced it is investigating a serious risk of malignancy (cancer) in patients treated with Zolgensma (onasemnogene abeparvovec), the one-time AAV gene therapy approved in 2019 for infants and children under 2 years with spinal muscular atrophy (SMA).

Background

SMA is a rare genetic disorder caused by mutations in the SMN1 gene that leads to progressive muscle weakness. Without treatment, the most severe form (SMA Type 1) often results in death or permanent ventilation by age 2. Zolgensma uses an adeno-associated virus (AAV) vector to deliver a functional copy of the SMN1 gene. More than 6,000 patients have been treated worldwide since approval. The prescribing information has long noted a “theoretical risk of tumorigenicity due to integration of AAV vector DNA into the genome.”

A related product, Itvisma (same vector, given intrathecally), was approved in 2025 for patients 2 years and older.

What changed

Novartis confirmed nine reports of tumors in patients previously treated with Zolgensma. Two of those cases showed molecular evidence that the AAV vector DNA had integrated into the patient’s genome near the GLI1 oncogene (a gene that can drive cancer when overexpressed). A third GLI1-associated tumor is still under investigation. Tumors have been reported in the central and peripheral nervous systems, spinal/paraspinal regions, and kidney.

The FDA stated that the risk applies to both Zolgensma and Itvisma. No neoplasia cases have been reported with Itvisma to date. The agency said the overall benefits of both products continue to outweigh their potential risks for approved uses, but it is evaluating whether regulatory action is appropriate and is reviewing the adequacy of current labeling and long-term follow-up studies.

Patients and families should be monitored for signs of tumor formation. Healthcare providers are instructed to report suspected adverse reactions to Novartis or FDA MedWatch.

Competing viewpoints

• Regulatory/safety view: Confirmed vector integration near an oncogene moves the risk from theoretical to observed. Long-term monitoring and possible label updates are warranted even if absolute risk remains low.- Benefit-risk view (Novartis / many clinicians): SMA is life-threatening; the therapy has transformed outcomes for many infants. Nine reports among >6,000 treated patients is a rare signal. Existing warnings already address the theoretical risk, and patients are already in long-term follow-up.- Patient-advocate view: Families need clearer timelines, more data on the nature and timing of the tumors, and transparent communication so they can discuss monitoring with their care teams.

What to watch next

• FDA decision on whether to update the prescribing information or require additional post-marketing studies.- Results of Novartis’s ongoing long-term follow-up safety studies.- Any further cases reported with Zolgensma or the first cases with Itvisma.- Guidance from SMA patient organizations and pediatric neurologists on practical monitoring recommendations for already-treated children.

This is a news briefing, not medical advice. Families of children treated with Zolgensma or considering treatment should speak with their neuromuscular specialist.

Sources: FDA safety communication 6 Nov 2026; MedPage Today 6–9 Nov 2026; Novartis statements; BioPharma Dive / BioSpace reporting.