Novartis Confirms 9 Tumor Reports In Zolgensma-Treated Patients, With 2 Showing Vector Integration Evidence

Novartis has confirmed that nine tumors have been reported in patients previously treated with Zolgensma, reopening scrutiny of safety risk in adeno-associated viral gene therapy. In a statement to BioSpace, the company said that two of those cases have shown evidence of vector integration into the DNA of the patients, while seven reports have not been causally linked to the therapy.

The disclosure followed social media posts from members of the spinal muscular atrophy community. One LinkedIn post cited by BioSpace said a parent had been told Zolgensma had been linked to two tumor cases with seven more likely tied to it, and alleged Novartis was using a “tiered rollout” of information. BioSpace also cited a separate anonymous parent who wrote that they learned about the issue last week and that “the two confirmed cases seems to have happened 18-60 months after dosing.”

Novartis did not frame all nine reports as therapy-related. The company said the potential risk of tumors due to vector integration is already included in Zolgensma’s prescribing information and that both patients in the two cases with evidence of integration underwent treatment and continue to be monitored.

The Safety Signal

Zolgensma was approved in 2019 for children under two years old with spinal muscular atrophy. The treatment uses an AAV vector to deliver a transgene encoding the human survival motor neuron protein, which is essential for motor neuron function. SMA is caused by a mutation or deletion in the SMN1 gene.

The key distinction in Novartis’ statement is between reported tumors and established causality. Of the nine tumor reports, only two have shown evidence of vector integration into patient DNA. The company said seven reports have not been causally linked to the therapy. That matters because the event is not a broad confirmation that Zolgensma caused all nine tumors, but it is a confirmation that cases serious enough to examine for integration have emerged in a commercial gene therapy already used in thousands of patients.

As of Thursday, Novartis said more than 6,000 patients had been treated with Zolgensma across clinical trials, managed access programs and commercial treatment. The company added that it continually evaluates new safety information and assesses all reported cases as part of ongoing monitoring.

The Regulatory Picture

Novartis said the relevant regulatory authorities are actively involved and are currently assessing the available evidence and determining what further steps may be needed. BioSpace also reported that SMA Europe had been informed through confidential channels and had told Novartis that the SMA community now needs timely public communication.

The immediate policy issue is not a new label concept, because the product already carries a warning about the theoretical risk of tumorigenicity associated with the AAV vector. The issue is whether postmarketing evidence begins to shift that risk from theoretical to better characterized, and how regulators respond if more cases accumulate or if integration findings appear beyond the two currently cited cases.

The Road Here

This is not the first safety controversy around Zolgensma, but it is a different one. Earlier scrutiny focused on liver-related adverse events. BioSpace noted that in September 2021, two years after approval, an FDA advisory committee discussed Zolgensma and Spark Therapeutics’ Luxturna. At that time, about one-third of the 500 patients who had received Zolgensma had experienced a liver-related adverse event, including one case of serious liver failure, according to FDA documents cited by Fierce Biotech in BioSpace’s account. The meeting summary concluded that benefit-risk evaluations of AAV gene therapy products should be made on a case-by-case basis.

The signal for the field is that long-tail safety remains central to the economics and regulation of one-time gene therapies. Zolgensma still has a large treated base, and Novartis has not said all reported tumors were caused by the drug. But evidence of vector integration in two tumor cases is the type of postmarketing finding that can affect monitoring expectations, disclosure practices and future regulatory review across AAV programs beyond a single product.