Individual differences in response to medications are an important challenge in clinical practice. Drugs that work well for some patients are ineffective for others, and individuals vary markedly in their experience of adverse drug reactions. Some of this variation is associated with individual differences in the genes involved in drug uptake, distribution, metabolism, target engagement, and action. For example, individuals with the HLA-B*5701 variant have an almost 50% risk of a hypersensitivity reaction when exposed to the drug abacavir, used to treat human immunodeficiency virus infection; this adverse reaction is not seen with the use of an alternative drug in these individuals.1 The drug ivacaftor, used to treat cystic fibrosis, illustrates a different effect. This drug has genetically targeted efficacy; it binds to a defective transmembrane chloride channel protein present in a subset of patients with cystic fibrosis with a particular CFTR gene mutation (G551D), eliciting a structural change that enhances function.2 As these examples illustrate, pharmacogenetic testing offers great promise for improving the safety and efficacy of drug treatment.
Burke W, Thummel K. A Call for Accurate Pharmacogenetic LabelingTelling It Like It Is. JAMA Intern Med. 2014;174(12):1945-1946. doi:10.1001/jamainternmed.2014.3276