[The concept and history of biomarker]

Biomarker is a characteristic objectively measured and an indicator of biological process. This term indicates not only biological substance, for example protein, ribonucleic acid but also imaging assays. Disease biomarkers have been applied to a wide variety of clinical areas, including oncology, metabolic disorders, neurological disease and immune dysregulation. In recent years because of the progress of analysis technology, new biomarkers continue to be devised and used as diagnostic, predictive, prognostic, and toxic marker. In drug development area, biomarkers are used as surrogate endpoint to substitute for a clinical endpoint and needed for rational drug development. Here, we summarize the concept and history of biomarker.