40 DRUG DISCOVERY & DEVELOPMENT
A personal approach to medicine
Britt Franken reveals how personalised medicine is aiding physicians in selecting the best therapeutic strategy.
P
hysicians have long been aware of the subtle differences between
patients in their responses to medications. Te recognition that a part of this variation is inherited, and therefore predictable, created the field of pharmacogenetics several years ago.
Pharmacogenetics studies the influence of genetic variation on drug response. Knowledge of gene variants causing differences in drug response among patients has the potential to allow ‘personalised’ drug therapy.
A patient’s response to a drug is often linked to common genetic variations present in their genes. One type of genetic variation is single nucleotide polymorphisms (SNPs). Knowing the types of SNPs/genetic variations present in a patient can help predict the associated drug response. Tis may not only help physicians individualise drug therapy, it can
also help improve effectiveness of the drug, decrease the chance of negative side effects and save healthcare costs.
An accurate prediction about drug response is crucial for individualised treatment. Tis is best made by combining an individual’s genetic data with clinical findings and classifying individuals into subpopulations that differ in their response to a specific drug. Using this approach, healthcare providers may be better equipped to move beyond the ‘one size fits all’ treatment strategy that defined much of patient care in the past, to care that is appropriate for specific patient subgroups.
Te discovery of genetic factors such as the cytochrome P450 (CYP) drug metabolising genes and several years of subsequent clinical research have added to our understanding of the clinically relevant genetic
variations that may help predict drug response.
Genetic variation and drug efficacy
Te extents to which patients metabolise drugs have significant impact on the effectiveness of their pharmacologic therapy. For example, individuals with genetic variation that results in ultra-high metabolism of drugs can experience therapeutic failure on the standard dose of a drug, due to rapid clearance of the drug from their system.
To a large extent, the CYP450 genotype of a patient determines the level of enzyme activity (‘phenotype’), which can be classified into four groups:
l Extensive metabolisers (EMs) have normal enzymatic activity, and carry either two wild-type alleles, or one wild-type allele and one decreased activity or null allele.
Putting the genetic variations into the clinical context.
www.scientistlive.com
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