What is gene therapy?

What does gene therapy actually mean? Here's the quick-fire science...
01 October 2019

Interview with 

Phil Sansom


A figure pulling apart strands of DNA


This week, we’re looking at the enormous medical potential now being realised by gene therapy. We’ll be hearing how these approaches can battle blindness, halt Duchenne Muscular Dystrophy, and even cure HIV... but first, what do we actually mean by “gene therapy”? Phil Sansom is here with the quick-fire science...

Phil - Most diseases that you can get have their roots in your DNA, but ever since medicine began, treating those diseases hasn't actually involve tackling those root problems. That is until 40 years ago when doctors successfully inserted new DNA into five people to help treat their melanoma. Welcome to a new type of medicine; gene therapy. So how does it work? Well a gene is a bit of DNA, and there are different ways a gene can malfunction to give you a disease. So different types of gene therapy might do different things.

One treatment might replace a harmful mutated gene with the non-mutated healthy version, or if the mutated gene isn't vital the treatment might want to stop it from working altogether. That's called knocking it out. In other cases your body might be totally missing a gene that you need. Gene therapy in this case could just add it back in. Here's the problem though; to efficiently add bits of DNA into your cells, you usually need some kind of vector.

Certain viruses are really good vectors because that's how they infect you anyway, by inserting their genes into your cells to hijack them and make more of themselves. Gene therapy can exploit that by modifying the virus, stripping out the viral genes, and replacing them with useful gene therapy ones instead. But putting foreign material like viruses into your body can be risky. It can trigger your immune system to attack, potentially leading to lethal inflammation. Plus there are other risks too. With some therapies, there's a chance that messing with your body's genetic code could cause cancer. That's why right now, doctors are moving cautiously and they usually prioritise diseases with a bad prognosis and no other cures. But for those diseases it can be a lifeline.

And as it gets safer gene therapy looks to become a pretty powerful tool.


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