Not medical advice. This website is not medical advice, a diagnosis, a match to a trial, or a recommendation to join a study. Listings are plain-English rewrites of public ClinicalTrials.gov records. Whether a site is still enrolling, and whether you qualify, can only be confirmed by the study team and your clinician. Source registry: ClinicalTrials.gov. Editorial rules: methodology.
PlainTrials

Registry vocabulary

What “phase” means on a ClinicalTrials.gov record

These definitions are the standard FDA/ICH labels applied to the registry Phase field. They are not a result for a specific NCT number and not a ranking of treatments. Each hub lists recruiting studies from this snapshot.

Phase 1

Phase 1

First-in-human or early safety and dose studies. Small groups. Not designed to prove a treatment works.

Phase 2

Phase 2

Looks for a signal of benefit and continues to watch side effects, still in a limited population.

Phase 3

Phase 3

Larger comparative studies, often used in approval decisions. Not a guarantee of approval or benefit.

Phase 4

Phase 4

The product is already approved for some use. The study asks new real-world or additional-use questions.

Observational

Observational

Researchers measure what already happens. They do not assign the experimental treatment as the intervention.

Not a drug phase (N/A)

Not a drug phase (N/A)

Devices, behavioral programs, diagnostics, and some procedures do not use the drug phase ladder.

Related: observational vs interventional · glossary · methodology