New evidence links AAV gene therapies to tumor risk, raising safety concerns

Recent cases reported this year provide strong evidence that adeno-associated viruses (AAVs), the vectors used to deliver therapeutic genes, can trigger tumor formation. The findings settle a two‑decade scientific debate about the oncogenic potential of AAV‑based treatments.

The risk is especially salient for patients with spinal muscular atrophy, who have benefited from AAV therapies such as Zolgensma. "It will change the calculus for some patients," said neurologist Sam Mackenzie of the University of Rochester, emphasizing the need to reassess treatment decisions.

Researchers and families now must balance the life‑saving promise of gene therapy against the newly confirmed cancer risk, prompting calls for improved vector designs and closer regulatory scrutiny.