The FDA has launched an investigation after receiving nine postmarketing tumour reports in patients treated with Novartis' AAV9 gene therapy Zolgensma for spinal muscular atrophy, including three cases tied to the GLI1 oncogene and two with confirmed vector DNA integration into the host genome. The agency disclosed the cases in a safety communication and said the risk may also apply to Itvisma, which uses the same vector and construct.

Why It Matters To Oncology

• For oncology and drug discovery teams, the signal sharpens concern that AAV vector integration can, in rare cases, contribute to insertional oncogenesis.

• The reported tumours involved the central and peripheral nervous systems, spinal/paraspinal regions and kidney — tissues highly relevant to long-term surveillance planning.

• The FDA also pointed to similar integration-driven oncogenesis reports in other programmes: Forge Biologics' discontinued FBX-101 and REGENXBIO's RGX-111, where a child developed an intraventricular CNS tumour four years after treatment.

The Financials

• Novartis said last week that at least two paediatric tumour cases were related to Zolgensma.

• Zolgensma won FDA approval in 2019; Itvisma, the intrathecal formulation of onasemnogene abeparvovec, was cleared in the U.S. last year for adults and children age 2 and older with SMA.

• While no Itvisma-linked neoplasia cases have been reported, any label changes, monitoring requirements or class-wide scrutiny could affect AAV gene therapy development economics and regulatory timelines.

What They're Saying

• The FDA: "Importantly, three cases involved tumours associated with the GLI1 oncogene. In two of those cases, molecular analysis of tumour tissue demonstrated Zolgensma AAV vector DNA integration into the host genome."

• The agency added that the mechanism of GLI1 overexpression in the third case remains under investigation.

• The FDA said it is "closely monitoring the risk of neoplasia, including malignancy, in other similar AAV vector-based gene therapy programmes."

What's Next

• Expect closer FDA scrutiny of integration analyses, long-term follow-up protocols and tumour workups across AAV programmes, especially those targeting the CNS.

• Developers may need to strengthen vector design, biodistribution studies and insertion-site monitoring to better characterize oncogenic risk.

• For clinicians, the near-term implication is heightened vigilance for delayed neoplasia signals in treated patients and closer attention to evolving safety language for Zolgensma and Itvisma.

Reference: Novartis' Zolgensma under FDA scrutiny over tumour reports