Researchers often need to find answers to critical health-related questions. To find these answers, they start by doing laboratory and animal studies (known as preclinical studies). After many years of careful preclinical testing, only the studies with the most promising results are then moved on to clinical trials. A clinical trial is a type of scientific research study that is done with human participants. People who choose to participate in clinical trials may have a specific disease, or they may be healthy volunteers.
The purpose of a clinical trial is to evaluate the effects of a new intervention on human health and disease. Interventions can be in the form of a drug treatment (such as chemotherapy, immunotherapy, or targeted therapy), a treatment strategy (such as maintenance therapy or concurrent therapy), a medical device, a procedure (such as surgery or radiation therapy), or a behavioral program involving diet and exercise. A clinical trial may also be used to identify novel markers for diagnostic and prognostic predictors of outcome for a disease. Typically, a clinical trial sponsor, such as a pharmaceutical company or a private organization, will initiate and pay for the trial, while a clinical researcher known as the principal investigator has primary responsibility for carrying out and supervising the clinical trial protocol.