Novartis has confirmed a number of new cases of tumors that developed in children treated with its gene therapy Zolgensma after a series of notices from spinal muscular atrophy advocacy groups this week.
The discovery, which in most cases has not established a potential causal link between the SMA therapy and the tumors, will add to the safety scrutiny that has periodically dogged Zolgensma since its approval some seven years ago.
It has also placed SMA patients, as well as their families, caregivers and those who advocate for them in a tricky position, with groups like SMA Europe this week acknowledging the concern the news may cause for the SMA community, while at the same time appealing to Novartis for further information so that families are not “left to piece together a potential safety concern from social media, rumors or incomplete reports.”
“Since first approval in 2019, Novartis has received 9 reports of tumors in patients previously treated with Zolgensma,” the company confirmed to Fierce. “Of those, two cases to date have shown evidence of vector DNA integration into the DNA of the patients. In both cases, the patients underwent treatment and continue to be monitored.”
Presence of DNA from Zolgensma in a patient’s tumor could suggest that the gene therapy was linked to the abnormal growth.
But to that point, Novartis stressed that the potential risk of tumors due to vector integration is already part of the Zolgensma prescribing information.
“Patient safety is our priority,” the company’s statement continued. “In each case, we timely and appropriately notified health authorities and will continue to work with them on next steps.”
In its own statement Thursday, advocacy group SMA Europe suggested that “relevant regulatory authorities” are actively reviewing the Zolgensma safety evidence as they work to determine if any next steps are needed.
“We have strongly urged the company to provide clear information on what is currently known, what remains uncertain, what this may mean for people who have already received treatment, and whether any additional monitoring or action is recommended,” the organization added in its communique.
That sentiment was echoed across the pond by U.S.-based advocacy groups too, such as the Muscular Dystrophy Association, which pointed to lingering uncertainties around the timing of the events, nature of the tumors and any monitoring of Zolgensma patients that may be needed going forward.
In its statement, Novartis noted that more than 6,000 patients have been treated with Zolgensma in clinical trials, managed access programs and via commercial channels.
“As part of Novartis' ongoing commitment to monitoring the safety of our medicines, we continually evaluate new safety information and assess all reported cases,” the company said.
AAV gene therapy Zolgensma won a landmark approval to treat patients with SMA back in 2019, representing a major advance in the neuromuscular disorder that leads to weakness and wasting of certain muscles in children. Patients who do not receive treatment can go on to experience respiratory failure.
Other approved therapies for SMA exist, like Biogen’s Spinraza and Roche’s Evrysdi, though these lack the allure of a one-time treatment that Zolgensma offers.
Still, the treatment hasn’t been without its safety blemishes, with researchers previously documenting two cases of tumors developing in kids treated with Zolgensma in 2023 and 2025, Stat noted in reporting the newly unveiled tumor cases this week. In turn, seven of the tumor cases Novartis spoke to constitute new information.
Meanwhile, earlier in the decade, the drug’s liver safety was put under a microscope when Novartis confirmed in 2022 that two children in Russia and Kazakhstan had died around five to six weeks after receiving Zolgensma. In those cases, both patients passed away following acute liver failure, which is a known side effect of the gene therapy and listed as a warning on its label.
Such safety concerns aren’t necessarily unique to Zolgensma in the broader gene therapy field and come amid a series of other safety scares for commercial and clinical players alike in recent years.
Last year, Zolgensma generated around $1.2 billion in total sales, representing a slim 1% climb over 2024.
In December, the company also received FDA go-ahead for Itvisma, a new version of the gene therapy to treat older patients with SMA, picking up for patients 2 years and older where Zolgensma’s label cuts off.
Both versions of the gene therapy deliver a functional copy of the human SMN gene via AAV vectors, although Itvisma is delivered straight to the central nervous system by way of intrathecal injection in the spinal cord area, whereas traditional Zolgensma is given intravenously.