Apart from the standard uses of personalised medicine incancer, recent studies have suggested the importance of genetic sequencing inpatient groups on anticoagulation therapy. The dosage of Warfarin given, variesbetween patients and is extremely difficult to predict accurately. This isshown above in Figure 3. Itillustrates that although there is a common weekly dose which ‘fits’ themajority of the patients, there are still a low number of patients that are atthe extreme ends of the scale and would need dose adjustments away from thenorm. Since the therapeutic window for Warfarin is relatively narrow, genetictesting in warfarin-treated patients will allow physicians to offer a dosewhich is safer and more effective than current national guidelines.
Without anaccurate dose and monitoring, patients may experienceeither insufficient anti-coagulation leading to thromboembolism, or excessive anti-coagulationresulting in haemorrhaging. The variability in the drug-responses are due topolymorphisms in the following 2 genes: CYP2C9 and Vitamin K epoxide reductasecomplex subunit 1 (VKORC1). CYP2C9 is responsible for the metabolism of the warfarinwhereas, warfarin inhibits VKORC1 (Future Medicine, 2017). Since the geneticsof these enzymes varies, so does the concentration in patients’. This accountsfor the differences in response. Particularly in the case of CYP2C9.
Whenanalysed in 200 patients on warfarin therapy, CYP2C9 variants, along with otherfactors had a large bearing on warfarin dosing. However, the genetic variationaccounts for 29% of the total variation, with the remaining 71% caused by thenon-genetic factors (Age, current medications etc.) (Wadelius M, 2017). This isonly possible due to the findings from the Human Genome Project. I stronglybelieve that in the future, this genetic data could be accessible via aPatient’s Medication Record (PMR) to help pharmacists’ clinically check aprescription, thus making any dose-adjustment recommendations. In Canada,hospitals with a dosing policy in place permit pharmacists to adjust warfarin doses,a similar approach could be implemented in the NHS. This would save time wastedcontacting the doctor and free up the doctors’ time allowing them to examineothers.
There are prospects in the future to allow community pharmacists toconduct pre-prescription screening prior to dispensing medications. Similar tothe warfarin example mentioned earlier, statins, although first-line for familialhypercholesterolemia, have variable effects on patients. In the primary caresetting, saliva swab tests could be conducted. A sample could be taken from thepatient’s oral mucosa and placed into a machine which scans through the patient’sgenome in a matter of minutes. The machine looks for a copy of a particularallele and since the results are obtained quickly, this is a cheap process comparedto the more complex testing required to sequence the entire genome of thepatient.
This helps to alter doses, aiding to deliver pharmacogenetic medicinesto patients. (Jamie, 2017).Likeeverything else, not everything about this concept is positive and there aremany obstacles that come along with it. The Human Genome Project has allowed us to venture out intothe relatively new world of modern personalised medicine and the prospect of providingus with a better understanding of disease mechanisms excites me greatly. Newsecure servers would have to be built to house all this data as well aswide-scale training programmes to educate professionals on how best to utilisethe information.
However, the future is looking extremelypromising, as we expect a shift in focus from treatment towards the preventionof disease. Patients will undergo tests establishing the defective genes, thushelping to identify effective and well-tolerated treatments as often diseaseshave different genetic causes. Further analysis of genetic markers can aidselection of a treatment with minimal side-effects, a trait sought-after by allpharma companies. Even though I havediscussed a few of the potential benefits and applications for the future andhow it may lead to preventative strategies, many people will still question theaccurateness of the data obtained and whether it’s worth the anxiety of knowingthey’ll develop a particular disease in the near future.