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.
1,544 open of 1,840 active
Phase 1
First tests in people: safety, dose range and how the body handles the treatment, usually in 20–100 participants.
8,522 open of 11,168 active
Phase 2
Does it work, and at what dose? Typically several hundred people who have the condition.
14,500 open of 19,027 active
Phase 3
Large comparative studies against standard care or placebo. Positive Phase 3 results usually support a marketing application.
5,891 open of 8,124 active
Phase 4
After approval: long-term safety and effectiveness in everyday use.
3,692 open of 4,309 active
Phase not applicable
Studies of devices, behaviours or procedures that are not drug trials, so FDA phases do not apply.
43,844 open of 52,039 active
A study that tests two phases at once (Phase 1/2 or Phase 2/3) is counted in both.