The Human Genome Project gave medical researchers access to enormous amounts of new information about the genetic underpinings of disease. By better understanding patients' genetics, physicians are able to make more informed diagnosis and treatment decisions. Personalized medicine (sometimes called genetic, genomic, precision, or targeted medicine) is a growing medical practice that uses patients' unique genetic profiles to guide the prevention, diagnosis, and treatment of disease.
Targeted Therapies, Biomarkers, and Companion Diagnostics
Targeted therapies act on specific molecular pathways in order to treat disease. These drugs can produce unprecedented clinical effect with low toxicity compared to other therapies, but rely on molecular structures that are not present in all patients. Though it is not always possible to examine these structures directly, physicians can predict whether patients are likely to respond to a targeted therapy using biomarkers, measurable characteristics which indicate a biological state or condition. Companion diagnostics are tests that look for biomarkers and are designed for use alongside specific targeted therapies in order to predict their effectiveness.
For example: trastuzumab is a targeted drug used to treat certain breast cancers. It works by acting on the receptor for a protein called "HER2/neu." Trastuzumab is only beneficial in cases where patients overexpress HER2. Physicians can avoid prescribing an ineffective drug by using a companion diagnostic to test patients for overexpression of HER2 before recommending trastuzumab.
Because they provide a new approach to treatment, targeted medicines can sometimes offer much greater benefit than existing therapies or treat conditions for which no other therapies exist. As a result, promising targeted therapies are often able to take advantage of one or more FDA Expedited Review Programs.