Phases of Clinical Trials
Phase refers to the stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study’s objective, the number of participants, and other characteristics. There are five phases: Early phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
ClinicalTrials.gov Glossary of Common Site Terms
U.S. Food and Drug Administration (FDA) The Drug Development Process: Step 3 Clinical Research
NCATS Toolkit for Patient-Focused Therapy Development: Clinical Trials
NCATS Toolkit for Patient-Focused Therapy Development: Educating Your Disease Community