Pharmacogenomics is the study of the various reactions to drugs based on genetic differences among patients. The goals of this field are to allow the pharmaceutical industry to better serve the expectations of the medical community, and therefore decrease the possibilities of adverse drug reactions(ADRs).


Through extensive genetic research, scientists hope to better understand the genetics of drug responsiveness. For example, by studying the various behaviors of drug metabolizing enzymes, researchers are able to create personalized variations of drugs for each patient. Variations in ADME* genes and drug targets (and associated genes) may result in the absence of protein or the production of protein with mutated activity. Genetic variations in the ADME genes account for a variation in plasma drug concentration after consuming a fixed dosage, yet the variation in the target genes influence the clinical outcomes of the drugs.(2)



Due to endless number of possible gene variations, genetic research is mostly exploratory; testing old hypothesis and generating new ones. The early goals are, however, to ensure the discovery of drugs that combat against the most common genetic variants. The most well known example of the application of pharmacogenomics is the development of Herceptin by Genentech. This drug targets the proliferation of tumor cells that over express the gene HER2, a condition seen in more that 25% of breast cancer patients. To be prescribed Herceptin, patients must be screened for HER2 over expression. Refer to the Testing Methods page to learn more. (4)


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* ADME is an acronym for Absorption, Distribution, Metabolism, and Excretion, and describes the disposition of a drug compound within an animal or human body.


The following video is an interesting illustration of the question: "Why Personalized Medicine...?"  (Video 1)

 The video below explains pharmacogenomics and explains the future of personalized medicine. (video 3)

More Examples:

  • Erbitux (cetuximab) is a drug that requires patients with colorectal cancer to test his or her gene expression of the epidermal growth factor receptor (EGFr) prior to treatment.  (2) 

  • One treatment for Alzheimer's disease is tacrine, but this drug responds differently to various genotypic variations of the apoliproprotein E(APOE) gene found on chromosome 19. The drug is most effective with patients who do express the APOE ε2 and APOE ε3 variation(or alleles) as opposed to those with the APOE ε4 allele.(2)

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