Pharmacogenomics: historical perspective and current status.

Pharmacogenomics is an extension of pharmacogenetics, a science described here in terms of five stages of development: 1) some clinical observations predicted genetic alterations of drug response; 2) additional case discoveries led to the term "pharmacogenetics," a concept broadened by 3) many systemic case studies, and the realization of its wide applicability; 4) came the recognition of systematic pharmacogenetic differences between human populations. Then it became clear that 5) most human drug-response differences were multifactorial, caused by many genetic alterations plus environmental factors. The recognition of these complexities, and the advance of genetics into genomics led to the broader science of pharmacogenomics. This led to plans to create "personalized medicine," that is, making drug use more effective and safer by giving drugs that fit a person's genes. Much of the science of genetics, dealing with gene structure, was changed by the realization that gene expression and thereby gene function was variable; this leads to systematic studies of drug action on genes, reversing the traditional studies of genes affecting drug action. Finally, the realization that gene-protein variations contribute to most common diseases leads to efforts of creating new drugs that act on these variants.