Gene therapy virus can cause tumours in some patients
The virus most commonly used to deliver genes into patients was long considered safe. A series of cases now shows it can cause cancer in certain situations.
Small viruses called adeno-associated viruses are used to deliver a working copy of a defective gene to patients. They are used in conditions like spinal muscular atrophy, a severe muscle disease. Thousands of patients worldwide have been treated with gene therapies based on these viruses.
Scientists debated for years whether AAVs could cause cancer. Researchers and clinicians who described the cases say the evidence from this year is strong enough to settle the question: yes, AAVs can cause tumours in certain cases.
How large is the risk?
How often this occurs and which factors determine the risk has not yet been established. The evidence comes from a series of reported cases, not a systematic study in a representative population. The tumour risk must be weighed against the benefit of the gene therapy itself, which is life-saving for some conditions.
A neurologist at the University of Rochester said the new findings will change the calculus for certain patients, specifically mentioning those with spinal muscular atrophy. Researchers now hope to better understand when and why AAVs can be tumourigenic, so that safer variants can be designed.
What happens next
The findings do not apply equally to all gene therapies. Which applications carry the most risk, and how it can be reduced in the design of next-generation therapies, is the subject of ongoing research. Regulatory discussions about how to weigh and communicate this risk have already begun.
Search terms to explore further: adeno-associated virus tumour risk, gene therapy cancer risk, viral vector integration cancer