What do trial phases and ClinicalTrials.gov statuses mean?

Information as of 16 October 2026. Everything below comes from ClinicalTrials.gov's glossary and reporting requirements pages, and 42 CFR Part 11, linked below. If anything here is wrong, tell us at contact@oqro.io and we will correct it.

What do the phases mean?

The registry's glossary defines the phases used for drug and biologic trials, following the FDA's categories. Early Phase 1, formerly Phase 0, is an exploratory trial with very limited human exposure. Phase 1 studies are usually conducted with healthy volunteers and emphasize safety, dosing and side effects. Phase 2 gathers preliminary data on whether the drug works in people who have a certain condition, and continues to study safety. Phase 3 gathers more information about safety and effectiveness by studying different populations and dosages and by using the drug in combination with other drugs; these are the trials that usually support an application for approval. Phase 4 trials occur after the FDA has approved a drug for marketing and gather additional information about safety, efficacy or optimal use. A study can be labelled with two phases, for example Phase 1/Phase 2, and device trials and behavioural studies carry Not applicable.

What do the statuses mean?

The glossary also defines the recruitment statuses. Not yet recruiting: the study has not started recruiting participants. Recruiting: the study is currently recruiting. Enrolling by invitation: participants are selected from a predetermined population. Active, not recruiting: the study is ongoing and participants are receiving an intervention or being examined, but new participants are not being recruited. Completed: the study has ended normally and participants are no longer being examined or treated. Suspended: the study has stopped early but may start again. Terminated: the study has stopped early and will not start again; participants are no longer being examined or treated. Withdrawn: the study stopped early before enrolling its first participant. The primary completion date is the date the last participant was examined or received an intervention for the purposes of final collection of data for the primary outcome; it can be anticipated or actual.

When must a trial be registered and its results posted?

The reporting requirements page summarises the law: Section 801 of the Food and Drug Administration Amendments Act of 2007 requires the responsible party for an applicable clinical trial to register it and to submit results. The final rule at 42 CFR Part 11 sets the clocks. Registration is due not later than 21 days after enrolment of the first participant. Results information is due not later than one year after the primary completion date, with a delay allowed in defined cases, for example while the sponsor seeks initial approval of a product under study. Applicable clinical trials are, in broad terms, controlled interventional studies of FDA-regulated drugs, biologics and devices other than Phase 1 drug trials and small feasibility device studies. Many sponsors register other studies voluntarily. Each registered study gets an NCT number, the identifier that OQRO shows, and the entry records the date of its last update.

How does OQRO show trials?

The clinical trials page lists studies whose lead sponsor is a listed company, most recently updated first, with the phase, the status, the primary completion date and a link to the registry entry, and a chart of updates per month. A company page carries its own studies, and the approvals that can follow them appear on the FDA records page. Studies are matched by the lead sponsor name as the registry records it, so a study run by a subsidiary or a collaborator under another name is not shown.

What this does not tell you

A phase is a stage, not a result, and a status change to Completed says only that data collection for the primary outcome ended; the results, when posted, are a separate section of the entry. A Terminated status carries a reason in the sponsor's words, which can be enrolment, funding or the sponsor's decision as well as a safety or efficacy finding. The registry does not say whether the sponsor will file for approval or when. OQRO shows the record as published; it does not interpret it, and nothing here is investment advice.