What is gene therapy?
Given the hype around gene therapy and the recent approvals for use, everyone has heard or spoken about gene therapy in the last few years. For this post, we are using this definition of gene therapy: an experimental technique that uses genes to treat or prevent disease – but the technique remains risky and is still under study to ensure that it will be safe and effective
Gene therapies work by inserting genes into a cell by a vector – usually a virus that delivers the gene into the cell. The vector can be injected intravenously into a specific tissue where it is taken up or a sample of the patient cells can be removed and exposed to the vector in a laboratory setting then returned to the patient. Gene therapy has been shown to have some serious health risks, so is currently only being tested for diseases that have no other cures.
What are the risks?
Gene therapies remain largely experimental because of the associated risks, according to the Mayo Clinic, these are namely:
- Immune reaction to the viral vector – This can cause inflammation and in severe cases, organ failure.
- Unintentional targeting – As viruses can infect more than one cell type, it could target the wrong cells and cause healthy cells to be damaged
- Reactivation of viral vector – The virus could recover its ability to cause disease
- Off-target insertion – If the genes are inserted in the wrong place, it could lead to tumour formation
(feel free to not keep this just reworded to put the risk up front, then your explanation after each point)
Jesse Gelsinger was the first person to be identified to die in a gene therapy clinical trial to treat a rare metabolic disorder in 1999. He suffered an adverse reaction to the therapy and died of multiple organ failure, since then strict rules have been in place on the conduct of gene therapy trials.
In the US, the only way to receive gene therapy is to participate in a clinical trial and they are heavily monitored by the FDA and National Institutes of Health to ensure patient safety.
Where are we now?
The notion of gene therapy has been around much longer than the actual scientific ability to do it. 2018 saw the first FDA approval for Luxturna, a gene therapy to treat an inherited retinal disease developed by Spark Therapeutics. Following suit, in 2019 Novartis received FDA approval for a gene therapy for spinal muscular atrophy called Zolgensma.
While most people will see the concept of editing incurable genetic diseases as an incredibly positive scientific advancement, the technology can be applied in ways which, like all genetic testing, can be ethically questionable. With the development of CRISPR-Cas9, editing germline cells and human embryos are now possible. Germline gene therapy targets the reproductive cells, meaning that any changes to the cells will be passed on to the next generation, where disease-causing gene variants can be corrected before fertilisation. Currently, germline gene therapy is not legal in the UK due to the uncertainty of risks that could be very detrimental.
What are the ethics?
In February, we released an article on whether morally germline genome editing is different from IVF, and a review written last year by Theodore Friedmann, Head of the Friedmann Gene therapy lab at the University of San Diego, questioned the line between genetic therapies, human genetic enhancement and eugenics.
So, what are the ethical considerations of gene therapy?
- How can good or bad genes be distinguished?
- Who decides which traits are considered normal and which are considered a disability?
- As gene therapy is expensive, can only wealthy people benefit?
- If the use of gene therapies becomes widespread, will society become less accepting of those who have genetic differences?
- Should humans be able to use gene therapy to enhance “desirable” human traits such as height, intelligence, or athletic ability?
Current gene therapy research focuses on treating cells in the body which cannot be passed on to the next generation and only focuses on severe diseases. It will not be used to “design” humans and despite the progressing science, we are not at the stage where gene therapies will be used routinely to treat genetic diseases.
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