How does gene therapy work?

Gene therapy may be used to combat disease in a number of different ways. For example:

• A gene that isn't functioning properly may be deactivated (or 'knocked out') to prevent health problems.
  
  
• A mutated gene may be replaced with a healthy copy of the same gene.
  
  
• A new or modified gene may be introduced to help the patient's body fight a disease.

Delivery methods vary - scientists will sometimes engineer a retrovirus that changes the patient's genome to achieve the desired result, but in other cases, 'naked' DNA may be delivered via injection or other techniques.

What are some examples of gene therapy?

Here are some examples of gene therapy treatments that are already in use:

• Talimogene laherparepvec, better known by the brand name Imlygic, can be used to treat melanoma - a particularly deadly type of skin cancer. This gene therapy was approved by the European Medicines Agency (EMA) and the United States Food and Drug Administration (FDA) in 2015.
  
  
• Tecartus is a gene therapy that targets mantle cell lymphoma and acute lymphoblastic leukaemia. It is manufactured by Kite Pharma and received EMA and FDA approval in 2020.
  
  
• Zolgensma, manufactured by American biotech company Novartis Gene Therapies, is used to treat spinal muscular atrophy (SMA). It was used in the UK for the first time in 2021.