ZURICH: The US ​Food and Drug Administration said on Friday it was investigating a risk ‌of neoplasia, or tumour ​formation including malignancy, associated with Novartis' gene therapy Zolgensma.

The Swiss drugmaker earlier in the day disclosed two cases in which tumours in children showed evidence of being linked to its gene therapy drug used to treat patients less than 2 years old with spinal muscular atrophy.

Novartis said that it had received ⁠nine reports overall of tumours in patients previously treated with Zolgensma since the therapy was first approved in 2019.

The drugmaker has two separate gene therapies for treating spinal muscular atrophy.

One is Zolgensma, which is administered via intravenous infusion and ‌used for the treatment of paediatric patients less than 2 years old.

The other is Itvisma, administered via intrathecal injection, and used for the treatment of adults and paediatric patients ‌2 years of age and older.

The FDA said the overall ‌benefits of both Zolgensma and Itvisma continue to outweigh their potential risks ‌for their approved uses but that ‌it was evaluating whether regulatory action was appropriate in light of the risk.

The agency said there have been ​no reported cases of neoplasia ‌following administration of Novartis' ​Itvisma, which was approved last year to ⁠treat patients with a rare muscle disorder.

Zolgensma uses a modified virus to deliver a working copy of a gene into cells. In two of the cases, doctors ​found evidence that the ⁠carrier used in ⁠the treatment had inserted its genetic material into the patients’ own DNA, the company said.

The findings point to a possible link between tumours and a one-time therapy that ⁠Novartis confirmed had been given to more than 6,000 children. They also follow complaints from patient advocates that Novartis was slow to share information about the cases.

The Basel-based firm said it had notified health authorities in a timely and appropriate manner in both cases and that the potential risk of tumours is ‌included in Zolgensma's prescribing information.

Patient advocacy organisation SMA Europe had urged Novartis to provide information on what is ​known, uncertain and what it could mean for children who had received treatment.

Novartis did not provide details on where the two new cases were in its statement.

The EMA did not immediately respond to a Reuters' request for comment.