- Early Phase I - Exploratory trials, involving very limited human exposure, with no therapeutic or diagnostic intent (e.g., screening studies, micro dose studies). See FDA guidance on exploratory IND studies for more information.
- I - Includes initial studies to determine the metabolism and pharmacologic actions of a medical approach in humans, the side effects associated with increasing doses or exposure, and to gain early evidence of effectiveness; may include healthy participants and/or patients.
- I/II - Includes trials that are a combination of phases I and II.
- II - Includes controlled clinical studies conducted to evaluate the effectiveness of the medical approach for a particular indication or indications in patients with the disease or condition under study and to determine the common short-term side effects and risks.
- II/III - Trials that are a combination of phases II and III.
- III - Includes expanded controlled and uncontrolled trials after preliminary evidence suggesting effectiveness of the medical approach has been obtained, and are intended to gather additional information to evaluate the overall benefit-risk relationship of the drug and provide an adequate basis for physician labeling.
- IV - Studies of FDA-approved drugs, interventions, tests or diagnostic procedures to delineate additional information including the medical approach risks, benefits, and optimal use.
- NA (Not applicable) - Trials without phases (for example, studies of devices or behavioral interventions).
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