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Personalised medicine and genetics
What is meant by the term ‘personalised medicine’?
The way genes interact with each other can sometimes predispose us to developing particular diseases. Research scientists have identified specific links between genes and some diseases as well as genes and the efficacy of various medicines.
‘Personalised medicine’ uses this knowledge of genetics to predict disease development and influence decisions about lifestyle choices or to tailor medical practice to an individual.
The result is better disease prevention, more accurate diagnosis of disease and more effective treatment of disease by understanding the way specific genes work with medicines.
What impact does ‘personalised medicine’ have on disease diagnosis?
In the past, disease diagnosis was based on symptoms that might be indicative of several diseases. Nowadays, diagnosis of some diseases has become more accurate because we are able to test for genes known to be associated with the disease. This method not only clearly identifies the presence of a particular disease, it can also precisely determine which subtype of a disease a person has.
For example, specific subtypes of acute promyelocytic leukaemia can be identified by testing the DNA of the leukaemia cell. Identification of the acute promyelocytic leukaemia subtype allows doctors to prescribe a drug therapy that will specifically target the subtype. Knowing the subtype of a disease can also help determine an accurate outcome for the patient.
How can genetic information be used in disease prevention?
Individual variations that may be present in our genes could increase our risk of developing a particular disease or determine how our bodies are likely to be affected by a disease. For example, a person’s genetic makeup could indicate an increased risk of developing diabetes or heart disease.
Early identification of these variations and calculation of the risks associated with them are important in disease prevention. This knowledge could influence lifestyle choices and decisions about interventions that may prevent the disease from developing, delay disease onset or reduce the impact of the disease.
There are currently a limited number of genetic tests available for this purpose. However, the field of personalised medicine is certain to expand rapidly in the near future.
What is pharmacogenetics?
Pharmacogenetics describes the science that explores relationships between the ways certain medicines interact with gene products. A process known as gene expression profiling identifies the active genes in a patient and can tell the doctor how a medicine may be broken down by the body and whether or not it will be effective.
Another word that is used to describe personalised medicine is pharmacogenomics. While the two are subtly different, they can be used interchangeably for the purpose of this topic.
How can pharmacogenetics improve the effectiveness of drug treatment?
At present, doctors use a ‘one size fits all’ approach to prescribe medicines for most diseases. Patients are first given a medicine at an average dose. The doctor then makes adjustments to the treatment according to the patient’s response.
Applying pharmacogenetics ensures patients are prescribed the most effective drug from the start. Pharmacogenetics also minimises the number of adverse reactions to medicines as it can show whether a patient is likely to have a toxic response.
As scientists gain a better understanding of genetic variations, new subtypes of diseases could be identified and more specific medicines that target the new subtypes may be manufactured.
When will personalised medicine be a reality?
Although the science is still in its infancy, pharmacogenetics is already being used to treat some diseases such as breast cancer. Before being prescribed the drug Herceptin®, breast cancer patients are tested to examine whether a particular gene, human epidermal growth factor receptor 2 (HER2), is present in the cancer cells.
Herceptin® is only effective when cancer cells have extra copies of the HER2 gene. Knowing about the HER2 genes in the cancer cell allows doctors to predict the patient’s response to a particular medicine, enabling a more appropriate medicine to be prescribed immediately, if required.