Personalised medicine is the practice of using an individual’s genetic profile to inform decisions made about an individual’s treatment plan. It’s regularly hailed in the media as the next great medical revolution, but hasn’t it always been with us in one way or another?
Personalised medicine is not a new concept. As long as 2,000 years ago there was an understanding that we should all be treated as individuals, consistent with beliefs about medicine at that time.
Circa 400 BC Hippocrates was practicing a form of personalised medicine by assessing a person’s four humours, the blood, phlegm, yellow bile and black bile, to determine the best course of treatment for each patient. At about the same time, Chinese medicine was taking into account everything in a patient’s life including mental state, emotions, appetite, bowel movements, sleeping patterns, and even occupation before arriving at an individual diagnosis and treatment plan.
Even the historical precedents for modern personalised medicine stretch back to the beginning of the century. As early as 1902, the first connection between genetic inheritance and a person’s susceptibility to a disease was made by Sir Archibald Garrod. At about the same time, Victor McKusick pioneered the importance of taking a family history stating, “Of the many aspects of the workup that should alert physicians to genetic factors being particularly relevant to a patient’s condition, by far the most important is a thorough family history.”
The first report of a difference in the way people responded to a drug, a subject known as pharmacogenetics, was in the 1950’s, when it was found there is a variation in the way a very small number of individuals respond to the muscle relaxant suxamethonium chloride. Some patients exhibited a prolonged paralysis and slower recovery from surgery than others. it is now known this is due to the patient’s genetic make-up, which affects the speed at which their metabolism breaks down the drug in their system.
A significant number of older drugs are now known to possess a genetic component. For example, warfarin, which has been widely used since the mid-1950’s used to treat blood clots and stroke, deep vein thrombosis and pulmonary embolism, is well known to exhibit different behaviour in different patients. Despite its widespread use, the reason for the differences was only discovered in 1999 and it’s genetic. One gene deactivates warfarin. The other activates vitamin K, which is essential for blood clotting. There are now genetic tests available to predict with greater accuracy the dose an individual will need to maintain a stable level of warfarin in their blood.
Even the effect of painkillers may vary between individuals, depending on their genes. For example codeine is ineffective in approximately 10% of the population due to the lack of a particular enzyme, which means the body can’t break down the drug and absorb it.
Personalised medicine has been practiced in modern medicine for many years and includes tailoring a dose to a patient’s weight or altering a dose depending upon their health, for example their kidney or kidney function, age, other medication, and so on.
Despite this knowledge, however, it has been reported that 38% of depressed patients, 50% arthritic patients, 40% asthmatic and 43% diabetic patients do not respond to the initial treat they are prescribed. Indeed, depending upon the disease and the underlying genetics, it is claimed that only between 20-80% of patients respond to the most popular classes of drug. Giving a patient an ineffective medicine can be problematic and in some cases dangerous. It’s now believed that many bad reactions to drugs have a genetic cause.
With medicines accounting for over 12% of the total yearly NHS budget, (about £123 billion across Britain in 2011/2012), new genetic tests will help ensure that patients get the best, most effective medicine for them with as few side-effects as possible. This will not just reduce costs to the NHS, but ultimately improve the lives of individual patients and their families.