What are clinical studies?

Clinical trials are conducted to collect data regarding the safety and efficacy of drugs, devices, treatments, or preventive measures in humans. Drugs and devices are first tested extensively in laboratories. If the laboratory research is successful, the data is sent to the Food and Drug Administration (FDA) for approval to continue research and testing in humans. Human testing of experimental drugs or devices are typically conducted in four phases. Each phase is considered a separate study. Upon completion of a phase, the Investigators are required to submit their data to the FDA for approval before continuing to the next phase.

Human Clinical Trial Phases

Phase I studies assess the safety of a drug or device. This phase will include only a small number of healthy volunteers, usually less than 100 subjects. The study is designed to evaluate the effects of the drug or device on humans including how it is absorbed, metabolized, and excreted. This phase also looks at side effects of the drug that occur at different doses.

Phase II studies assess the effectiveness of a drug or device. This phase may include several hundred participants that have the disease being targeted. Phase II studies are randomized studies where one group of patients receives the experimental drug while a second "control" group receives a standard treatment or placebo. These studies are often "blinded" meaning that neither the patient or the researchers know who has received the experiemental drug. This allows the FDA access to comparative information about the relative safety and effectiveness of the investigational drug. The FDA must give approval before the drug or device can move on to phase III studies.

Phase III studies are large randomized, blinded studies that may enroll hundreds to thousands of subjects. These studies may last from several weeks up to several years to provide the pharmaceutical company and the FDA with important information on the long term safety and effectiveness of the investigational drug. These studies also evaluate the benefit and possible adverse reactions from the drug. Approximately 70% to 90% of drugs that enter phase III studies successfully complete this phase of testing. The pharmaceutical or device company can request FDA approval for marketing after completion of the phase III studies.

Phase IV studies are conducted after a drug or device has been approved for sale. These studies may be done to compare a drug with other drugs already on the market or to monitor the drug's long-term effectiveness and impact on a patient's quality of life.