What is gene therapy?
Gene therapy is a type of treatment that changes the genetic material in your cells to treat or cure a disease. It doesn’t change all your cells, just some of them. For example, your T cells.
Examples of changing a gene might be:
- editing a gene that is not working in your body (a faulty gene)
- removing a faulty gene, or ‘switching it off’
- allowing a blocked gene to work more effectively
- adding a new working gene.
What is a gene?
A gene is a part of your DNA. Your DNA is your instruction book for your cells, like a blueprint for a house.
There are about 20,000 genes in your body. Each gene carries important information and instructions that make you ‘you’.
Genes are inherited from our parents and sometimes we can inherit faulty genes. This can cause a genetic condition. Not all faulty genes are inherited. It can also happen randomly if the cell is damaged, and can cause a disease or condition.
Who can have gene therapy?
Gene therapy is currently only available to a few people with blood disorders. This includes some people who have:
Gene therapies are also available for some other genetic conditions that aren’t related to blood cancer or blood disorders. If you’re interested in finding out more about genetic conditions and gene therapies, you can visit the following websites:
How does gene therapy use stem cells?
Some gene therapies now use stem cells . These stem cells are autologous, which means they are the patient’s own stem cells. We explain how this works in the example below.
Casgevy for sickle cell disorder and beta thalassaemia
Casgevy (exagamglogene autotemcel, or exa-cel) is an example of a gene therapy which uses stem cells to treat some patients with sickle cell disorder or beta thalassaemia.
This gene therapy edits a specific gene in a patient’s blood stem cells to increase production of a type of protein called foetal haemoglobin. Foetal haemoglobin can help stop red blood cells from turning into the sickle shape which causes pain crises and health complications in sickle cell disease.
How does it work?
- The patient’s blood stem cells are removed.
- A specific gene in the blood stem cells is edited in a laboratory.
- The patient will have conditioning therapy to prepare the body for the new, edited stem cells.
- The edited cells are put back into the patient’s body.
- The edited cells travel to the bone marrow where they start producing red blood cells that contain foetal haemoglobin.
How can gene therapy help someone with a blood disorder?
Gene therapy might be the best treatment option for someone with a blood disorder. If you live with one of the blood disorders mentioned above and are interested in whether gene therapy might be an option for you, please speak to your medical team. They will know your situation best and whether you’re eligible for gene therapy.
Is CAR T-cell therapy the same as gene therapy?
CAR T-cell therapy is a treatment which changes the DNA in your T cells specifically. It’s a cellular therapy which uses similar techniques to gene therapy, but is not itself a gene therapy.
What are the challenges of gene therapy?
The possibilities of gene therapy are exciting. But there are still lots of challenges, so it’s good to manage expectations:
Research is still needed
Gene therapy is a new treatment. Lots of research is still needed into its potential, and this takes time and money. We need to know how effective and safe a gene therapy is before it can be used.
We don't know long-term effects
We don’t yet know the long-term effects of gene therapies because they’re still quite new. Their effects will continue to be monitored to give us more information in years to come.
It takes time and money
Gene therapies can be expensive. It can cost a lot of money to:
- carry out research
- do all the necessary testing and clinical trials
- produce gene therapies, which often happens abroad
- provide them to patients.
All the steps above can also take a lot of time, so more gene therapies may take a while to appear.
They're currently only available for rarer diseases
Not everyone can have gene therapy. Currently, it’s only available for a small number of people with specific diseases.
It might feel frustrating to read this list of challenges. But the very existence and possibility of new treatments including stem cells is promising and exciting.
Research, testing and investment in these treatments is crucial. Anthony Nolan is actively campaigning for more research into gene therapies and, if it’s offered to you, we’ll be there every step of the way.
Information updated: 19/03/2025
Next review due: 19/03/2026