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Leukaemia

The umbrella name given to a number of cancers of the bone marrow and other organs which produce white blood cells.

Vector

An agent that carries a pathogen from one organism to another. In genetics, a vector is a virus used to transfer genetic material into a cell

Placebo

A control that is used in drug trials. It looks exactly the same as the medicine under test but it does not contain the active ingredient.

Lipid

Molecules which contain a lot of stored energy built up of fatty acids and glycerol. Lipids include oils and fats

Gene therapy – hope for the future?

There are a number of genetic diseases which we now know are caused by a defect at a single gene locus. These diseases include haemophilia A, cystic fibrosis, Duchenne muscular dystrophy, sickle cell disease, Huntington’s disease and SCID (severe combined immunodeficiency). Gene therapy offers the hope of introducing healthy genes into the cells of people affected by the diseases, enabling them to function normally and restoring the patient to health. New technologies such as CRISPR-Cas9 are making it easier for scientists to manipulate the genome accurately and safely.

One of the first diseases targeted for gene therapy was cystic fibrosis (CF). For a considerable time, success was very limited. However, from 2015, results have been more promising. Researchers are using different approaches to carry the healthy genes into the lung cells of affected patients. Some are using viruses, some are using lipid bubbles. In 2015 one group recorded lung function in a group of patients treated by gene therapy as 3.7% better than the placebo group. This isn’t much, but for patients with CF, every little bit makes a real difference. 2017 sees the start of a new round of human trials using different, and hopefully more effective, vectors to transmit healthy genes into the lungs of CF patients.

There are a number of trials showing real promise in using gene therapy to treat some of the many forms of inherited blindness. Another disease where gene therapy showed great initial promise was in the treatment of severe combined immunodeficiency (SCID). Major problems arose, with some patients developing leukaemia – but scientists and doctors persisted and now there are continuing clinical trials of versions of gene therapy for SCID which are showing promise in both infants and older children.

In 2017 scientists announced the successful treatment of a teenage boy who was severely affected by the genetic disorder sickle cell disease. Doctors removed some of his bone marrow, added new genes to the cells to code for healthy beta-globin, and then replaced the bone marrow. Fifteen months later the cells are still making healthy haemoglobin and the boy is free from symptoms.

Sickled red blood cells don’t carry oxygen effectively and block blood vessels causing pain and tissue death. Genetic modification of the blood stem cells may eventually make this disease a thing of the past.
(Eleanor Robinson)

For more information see SCID and sickle cell disease – case studies in gene editing.

Activity

There are many ethical questions about using such new and experimental techniques on patients who are already very sick. Here are two pairs of commonly expressed opinions, one in favour of treatments such as gene therapy and one against. Use the resources listed below – and any others you chose to use - to find out more about gene therapy and the progress made so far. Then from each pair of statements chose the one closest to your own viewpoint. Write one or two paragraphs expressing your opinion, putting forward the main arguments for and against the idea and justifying your position.

A:

  • Gene therapy shouldn’t be used on humans until they’re sure it works

  • It is worth trying out a new therapy which may give a person some extra healthy time if they are going to die or have a very poor quality of life without the treatment

B:

  • Manipulating the genes is wrong – it’s interfering with nature

  • Medicine only progresses by trying out new treatments, even if the early patients die. Look at what happened with heart transplants!

Emily puts forward her views on why gene therapy should be allowed

Priyanka disagrees ...

FINDING OUT ABOUT GENE THERAPY:
SCID – A case study
Muscular dystrophy – the mouse model works
Silencing the genes
Germ cell gene therapy