What does the Phase column mean?

Clinical trials run in phases, each designed to answer a specific question about a treatment:

• Phase I — Is it safe? Tests in a small group to evaluate dosage and side effects.
• Phase II — Does it work? Gathers early data on effectiveness while continuing safety evaluation.
• Phase III — Is it better? Compares the treatment against the current standard of care in a larger population. FDA approval is typically based on Phase III results.
• Phase IV — What happens long term? Studies conducted after FDA approval to monitor real-world safety and effectiveness.

Some trials — particularly those studying devices or behavioral interventions — may show “N/A” for phase.