A clinical trial is a scientific study conducted with volunteers. These studies are performed in order to evaluate a new treatment like drugs, devices, or biologics.
Before a new treatment is tried with human patients, it is carefully studied in the laboratory to show how to use the treatment safely and effectively. Laboratory research points out the new methods most likely to succeed but this early research cannot predict exactly how a new treatment will work with patients.
Studies that are usually conducted with healthy volunteers and that emphasize safety. The goal is to find out what the drug's most frequent and serious adverse events are and, often, how the drug is metabolized and excreted.
Studies that gather preliminary data on effectiveness (whether the drug works in people who have a certain disease or condition). Safety continues to be evaluated, and short-term adverse events are studied.
Studies that gather more information about safety and effectiveness by studying different populations and different dosages or by using the drug in combination with other drugs.
Studies occurring after FDA has approved a drug for marketing. These studies gather additional information about a drug's safety, efficacy, or optimal use.