Understand trials
Clinical Trial Phases
A new drug moves through phases in order: first safety in a few people, then whether it works, then large comparisons, then follow-up after approval. Device, behavioural and observational studies have no phase.
Early Phase 1
Exploratory first-in-human studies with very small doses and a handful of people, before a standard Phase 1.
1,541 open of 1,836 active
Phase 1
First tests in people: safety, dose range and how the body handles the treatment, usually in 20–100 participants.
8,524 open of 11,167 active
Phase 2
Does it work, and at what dose? Typically several hundred people who have the condition.
14,485 open of 19,013 active
Phase 3
Large comparative studies against standard care or placebo. Positive Phase 3 results usually support a marketing application.
5,882 open of 8,115 active
Phase 4
After approval: long-term safety and effectiveness in everyday use.
3,687 open of 4,303 active
Phase not applicable
Studies of devices, behaviours or procedures that are not drug trials, so FDA phases do not apply.
43,795 open of 51,973 active
A study that tests two phases at once (Phase 1/2 or Phase 2/3) is counted in both.