Gene therapy – timing matters

DNA double helix. Image by Jerome Walker and Dennis Myts via Wikimedia Commons
DNA double helix. Image by Jerome Walker and Dennis Myts via Wikimedia Commons

The earlier a disease is diagnosed and treatment is started, the more likely the treatment will be successful. This is the case with all the treatment options currently available like antibiotics for bacterial infections or chemotherapy for cancer. However it hasn’t been clear whether this is true for the futuristic treatment option of gene therapy. 

Gene therapy aims to work out the underlying genetic causes of a disease, such as a mutation, and then edit out the mutation so the gene can work normally. This approach has had some major advances in the last year thanks to the new CRISPR technology. CRISPR has been used to successfully treat many different diseases in animals including muscular dystrophy, liver disease and cataracts. However, more studies need to be done before we know that it is safe enough to use in humans.

During my PhD I studied mice that had a mutation that caused heart disease. A similar mutation causes the same sort of heart disease in humans. I tried turning the mutation off in the mice at various ages to see whether their heart disease could be prevented or reversed. I found that I could only prevent heart disease in the mice if I turned off the mutation before they were six weeks old. Mice only live to be about two years old, so a six week old mouse is like a six to ten year old human. This means that if we want to use gene therapy to treat humans with the same heart disease, we might have to start that treatment while they are children.

The problem with this is that many people consider it unethical to genetically test children because they can’t give their consent. Also many parents who might be carriers of genetic diseases choose not to have themselves or their children tested because finding out that you have passed on a disease to your child causes a lot of guilt. Also it may mean that the child is told that they are sick, and treated differently, for many years before they have any symptoms. A genetic test may also cause problems with health insurance covering the cost of treatment for the disease as it could be labelled a pre-existing condition.

I think that my study shows that health insurance rules need to change so that having genetic testing doesn’t jeopardise your chance of having medical costs covered by insurance. I also think that it’s important for doctors and genetic counsellors to talk to families that might have genetic diseases to explain the potential benefits of an early diagnosis in children. The main benefit is that treatment, either current treatment options, or in the future gene therapy, could be implemented as soon as a diagnosis is made. If the diagnosis is made too late, gene therapy may be less likely to work.

My Scientific Paper (I’m very sorry to say that it is not open access, being a lowly PhD student at the time I had no say in the matter):

Cannon et al. Irreversible triggers for hypertrophic cardiomyopathy are established in the early postnatal period. JACC. 2015.

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