Biomarkers to diagnose endotypes

Different types of biomarkers have been defined (1) and demonstrated to have a significant impact on personalized medicine and drug development (2). Precise diagnostic is the basis for successful medical treatment. As many diseases have subtypes with clearly different prognoses/progression and/or responses to a medical intervention, diagnostic biomarkers are used to detect or confirm presence of a disease or condition of interest or to identify individuals with a subtype of the disease. The likelihood of a future clinical event, disease recurrence or progression in an already identified group of patients is described by prognostic biomarkers and typically measured at the beginning of a medical intervention. Predictive biomarkers are used to identify patients who are more likely to respond to specific treatment and/or for participation in a controlled clinical trial. Response/pharmacodynamic biomarker indicate that an individual patient reacted to a pharmaceutical treatment or medical intervention. An endotype is a disease subtype, which is defined by a distinct pathophysiological mechanism (3). The identification of a disease endotype is closely related to the mechanism that is a cause of the disease. The use of biomarkers significantly increases the probability of success in different phases of a drug in development. The highest level of clinical validation of a diagnostic test is reached by approval as companion diagnostic (4). A companion diagnostic device has been demonstrated to be essential for the safe and effective use of a corresponding therapeutic product.