Clinical pharmacogenomics and concept of personalized medicine / Klinička farmakogenomika i koncept personalizovane medicine

Abstract

Summary The term »personalized medicine« (PM) was coined in the late 1990s, but was not introduced to general US public until about a decade later, through Genomics and Personalized Medicine Act. According to this act, PM is defined as any clinical practice model that utilizes genomic and family history information to customize diagnostic and therapeutic interventions and improve health outcomes. One of the emerging disciplines essential for implementation of PM is clinical pharmacogenomics (PGx), where patient’s genetic information is utilized to personalize drug therapy. PGx testing includes mostly detection of small DNA variations, such single nucleotide polymorphisms (SNPs), insertions, and deletions in the genes encoding the drug transporters, receptors and metabolizing enzymes. By providing the right drug at the optimal dose to each patient, PGx promises to significantly improve drug efficacy and prevent adverse drug reactions. In the early 2000s, the US Food and Drug Administration joined scientists and laboratorians in their efforts to translate recent genetic advances into clinical practice by requiring the drug manufacturers to include genetic information on their product labels. To date several drugs including irinotecan, warfarin, abacavir and clopidogrel are labeled with the information relating different enzymatic polymorphisms with the adverse drug effects or the impaired drug efficacy. The majority of PGx testing involves SNP detection within the family of Cytochrome (CYP) P450 enzymes responsible for metabolism of most drugs, such as anti-depressants (e.g. CYP2D6) and anticoagulants (e.g. CYP2C9, 2C19) to name a few. PGx tests are still very low volume tests and it is not clear how and to what extent genotyping information is being utilized in the clinical practice, mostly due to the lack of outcome studies demonstrating the clinical utility of PGx testing. For instance, it is well known that approximately 30% of Caucasian population carries a polymorphic CYP2C9 allele that predisposes them to higher warfarin sensitivity and thus to increased bleeding risk. How - ever, there are no large, randomized outcome studies that conclusively demonstrate reduction of bleeding events or decrease in hospitalization rates in population dosed based on genotype information. The clinicians are thus reluctant to incorporate warfarin genotyping into their practice. Despite the attention PGx has received in recent years, the adoption of PGx into routine clinical testing is still far from being commonplace. The barriers to wider adoption and implementation of PGx include lack of education and understanding by prescribing physicians regarding the available tests, lack of consensus guidelines on interpretation and use of genotype results and scarcity of randomized controlled trials demonstrating the clinical utility of PGx testing. However, as ge netic testing is becoming increasingly patient driven thought di - rect-to-consumer testing, clinicians and laboratorians must continue to work toward full implementation of PGx testing into routine clinical practice.