Gene therapy

Gene therapy is a type of treatment that targets individual genes to treat or prevent a health condition.

  • We are made up of trillions of little units called cells. Examples of cells are our hair cells, heart cells and brain cells.  
  • Genes are the ‘instructions’ inside our cells that make proteins. Proteins are what make our bodies work.  
  • We all have variations in our DNA sequence (the code within our genes). These variations may be passed down from our biological parents, or they may occur in us by chance. Sometimes a variation in a gene can cause a health condition. Most of the time variations in genes do not cause any health problems.  

In genetic epilepsy, the overall goal of gene therapy is to correct the way the genes that cause a health condition function.  

How gene therapy works

Gene therapy works in one of several ways:

  • Adding a new or modified version of a gene 
  • Turning genes on, off or up
  • Correcting a damaged gene by changing its sequence (code).

Ways gene therapy works diagram.

In all types of gene therapy, the gene needs to be delivered to a person’s cells. This is done using a vector (vehicle), which is often a virus. The virus’s harmful effects are turned off before it is used as a vector. 

Gene therapy is specific to the particular genetic change

  • There is no ‘one size fits all’ gene therapy.
  • Gene therapies need to be developed to treat each specific genetic change.
  • The therapy is tailored to the specific gene affected and the type of change within the gene.  

Development of gene therapy for individual genetic conditions 

Gene therapy is more complicated than regular treatments.

It involves many steps:  

  1. Create working gene
  2. Build vector and add gene
  3. Test in animals with similar conditions
  4. Test in people (clinical trials)

Delivering the gene to the right part of the body, such as the brain, can be difficult.

The effect of gene therapy on seizures and other symptoms must be carefully studied in clinical trials in large numbers of people. Because of this, it will take many years for gene therapy to be ready for routine use in epilepsy.  

Some gene changes are very complex, making it difficult to develop gene therapy. Some conditions may never be suitable for gene therapy. 

Benefits of gene therapy

  • Gene therapy, if available, may reduce some children’s symptoms. It is not yet known whether gene therapy will be able to completely cure a complex condition like epileptic encephalopathy. 
  • For many genetic conditions, other types of treatments, such as targeted or ‘precision’ therapies may prove more successful than gene therapy approaches.  
  • Research is ongoing to find better treatments for children with and without a genetic diagnosis. 

Targeted or precision therapies

In genetic conditions, targeted or precision therapies are based on the specific genetic change. 

The treatment may be a special diet, vitamins or medications that target certain proteins or pathways in the body.

For more information see the Advanced Therapies Handbook. 

Gene therapy for children with a diagnosed epileptic encephalopathy

At present, gene therapy can only be considered in a child diagnosed with epileptic encephalopathy if:

  1. The gene causing the epileptic encephalopathy is known, AND
  2. Gene therapy that targets the gene is available

The gene causing the epileptic encephalopathy must be known

  • Presently, for gene therapy to work, the gene causing the condition (the ‘target gene’) must be known.  
  • Genetic testing is the only way to find a target gene. 
  • Your child may have had genetic testing but no result was found. Possible reasons for this include:
    • The cause of epilepsy is not genetic
    • The gene causing the epilepsy has not been discovered yet
    • The test was not advanced enough to detect the gene change that causes epilepsy.
  • It may be possible to look at the data again or repeat the test, to find an answer. You can contact the genetics service you visited previously to discuss your options. You may also wish to discuss this further with your treating team at your next routine appointment.  
  • If your child has not had genetic testing, you may like to discuss this with your neurologist. If your neurologist thinks that your child’s epilepsy may have a genetic cause, they can refer you to a genetics service.  

Gene therapy that targets the specific gene causing the condition must be available

There are currently no gene therapies approved or in clinical trials for any type of genetic epilepsy in Australia. However, research is ongoing, both in Australia and overseas, with the hope that one day some genetic epilepsies can be treated with gene therapy. 

What this means is:

  • At this point in time, gene therapy is not available for children with a genetic epilepsy in Australia.
  • If gene therapy does become available, a genetic diagnosis will be needed so the gene therapy can be targeted to the gene causing the epileptic encephalopathy.