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Asked by anon-195412 to Reka, Tomas, Laura, Judith, Hannah, Gemma, Emma on 8 Jan 2019. This question was also asked by anon-195573.
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Reka Nagy answered on 8 Jan 2019:
That’s because while we are all humans, our DNA is not 100% identical! The small differences in our DNA make us who we are, and also influence how likely we are to respond (or not respond, or respond badly) to some treatments or medicines.
For example, one of the treatments of nonsmall cell lung cancer is the use of chemotherapy drugs gefitinib and erlotinib. These drugs target the gene EGFR (which stands for Epidermal Growth Factor Receptor), but they are only efficient in patients whose tumours have specific genetic variants within their EGFR genes.
Another example, that doesn’t relate to cancer (since cancer cell’s DNA can mutate and change), is neonatal diabetes mellitus – that is, infants who develop diabetes soon after birth. Researchers have found that these patients often have a mutation in their KCNJ11 gene which make this gene turn on when it shouldn’t. When this gene is turned on, it prevents insulin from being secreted, and without insulin, you end up with high blood sugar levels. Previously, these patients were just given insulin, but after this mutation was found, scientist realised that they could instead inhibit the activation of KCNJ11 – and drugs that do this already existed, so it was an easy switched that works really well!
The arm of genetics that is trying to figure out which subpopulations might respond better to which drugs is called precision medicine, or stratified medicine!
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Comments
Gemma commented on :
In addition to the underlying causes of diseases being different and therefore needed different drugs, we also have genetic differences in how our bodies react to medications. This area of study is called pharmacogenetics. It looks at how genetics plays a role in what the body does to the drug as well as what the drug does to the body. For example, some drugs are given as inactive pro-drugs and they are only active after the body metabolises them into an active version. Some people don’t have the enzyme required to carry out this reaction (because they have a genetic difference). If someone can’t metabolise a drug into its active form, then that drug won’t work for them and it would be better if they were treated with a different medication. Another example is that there are genetic differences in how well we can break down drugs and excrete them from our bodies. At the moment, we tend to all get given the same “average” dose of a drug but some people break it down faster than others. This means that the “fast metabolizers” may need a higher dose of drug in order to have a meaningful amount for treatment to work, whereas “slow metabolizers” are at risk of being over-dosed if given the average dose i.e. they are at risk to experience an adverse drug reaction. We are starting to understand the interplay of genetics with drug metabolism and will hopefully start tailoring drugs and dosages in a more informed way in the future i.e.personalised/precision medicine. An example of where we test people’s DNA before giving them a drug is abacavir which is a treatment for HIV. Another drug for which there is a lot of pharmacogenetic information is warfarin which is used to treat blood clots.
eerussell commented on :
I am interested to hear more about how our genetics affects how warfarin is prescribed. I know it is a reasonably common drug given to older people with heart problems, but I didn’t think they were given any genetic tests before being prescribed it. Are there some people that really shouldn’t be precribed warfarin? Or some people who might actually need higher doses?