Glossary of Terms
Phase I Clinical Trial
Phase 1 includes the initial introduction of an investigational new
drug into humans. These studies are closely monitored and may be conducted
in patients, but are usually conducted in healthy volunteer subjects.
These studies are designed to determine the metabolic and pharmacologic
actions of the drug in humans, the side effects associated with increasing
doses, and, if possible, to gain early evidence on effectiveness. During
Phase 1, sufficient information about the drug's pharmacokinetics and
pharmacological effects should be obtained to permit the design of well-controlled,
scientifically valid, Phase 2 studies.
Phase 1 studies also evaluate drug metabolism, structure-activity
relationships, and the mechanism of action in humans. These studies
also determine which investigational drugs are used as research tools
to explore biological phenomena or disease processes. The total number
of subjects included in Phase 1 studies varies with the drug, but is
generally in the range of twenty to eighty.
Phase II Clinical Trial
Phase 2 includes the early controlled clinical studies
conducted to obtain some preliminary data on the effectiveness of the
drug for a particular indication or indications in patients with the
disease or condition. This phase of testing also helps determine the
common short-term side effects and risks associated with the drug. Phase
2 studies are typically well controlled, closely monitored, and conducted
in a relatively small number of patients, usually involving several
hundred people.
Phase III Clinical Trial
Phase 3 studies are expanded controlled and uncontrolled
trials. They are performed after preliminary evidence suggesting effectiveness
of the drug has been obtained in Phase 2, and are intended to gather
the additional information about effectiveness and safety that is needed
to evaluate the overall benefit-risk relationship of the drug. Phase
3 studies also provide an adequate basis for extrapolating the results
to the general population and transmitting that information in the physician
labeling. Phase 3 studies usually include several hundred to several
thousand people.