Do different trial stages involve different cohorts of patients?

In a clinical trial, each phase involves different patients. Generally, one of the criteria for eligibility is that the patient has not previously taken the drug. Participants in a new phase will typically be a new subset of patients rather than a continuation from a previous one.

However, for a phase four trial, which involves repurposing an old drug, this may not always be the case.

Phase 4 studies may involve collecting data from people using the drug in their everyday lives. Some of these studies focus on using an already-approved drug for new medical conditions.

Participants from a phase 3 trial may be involved in the long-term usage phase 4 trial, where they continue taking the medication in their daily lives. This requires less effort from the participants as it aligns with their routines.

The answer is provided by Karen Faulkner,

Senior Research Physician  at Synexus Clinical Research Ltd