University of Vermont

College of Medicine

Office of Clinical Trials Research

Phases of Clinical Trials

If all the phases are completed and the treatment being tested proved to be more effective and/or safer than the current treatments available, the FDA will approve the treatment and the treatment then becomes standard therapy. This process takes years and hundreds of volunteers are needed.

  • Phase I trials are the first set of studies performed in humans that begin following extensive animal studies. The goals of these trials are to monitor safety and become aware of unknown risks. Phase I Trials are offered to a small group of subjects for conditions in which no treatments currently exist.
  • Phase II trials test the effectiveness or response of a treatment or intervention on a group. Phase II trials are conducted with a larger group of subjects than Phase I, but still with a small number of patients due to unknown risks. These trials provide more opportunity to discover less common side effects of a treatment.
  • Phase III trials are the final phase of trials before the treatment is approved by the Food and Drug Administration (FDA) and involve a larger number of subjects. These trials test the new treatment against the standard treatment for the disease/condition.

Last modified July 15 2013 04:14 PM