Trial Phase

**Semantic type:** Classification

**Definition:** Clinical trials are broken into three or four phases: Phase I tests a new drug or treatment for safety in a small group; Phase II expands the study to a larger group of people; Phase III expands the study to an even larger group of people to measure whether the treatment actually benefits patients, and whether its benefits exceed its risks; and Phase IV takes place after the drug or treatment has been licensed and marketed.

**Synonyms:** - STUDY_PHASE - TPHASE - Trial Phase Classification - Trial Phase Classification - Trial Phase Classification - phase - phase - phase (of clinical development)