First Patient In (FPI) is the milestone indicating the first participant has been enrolled and typically dosed in a clinical trial.
FPI confirms that study activation prerequisites are complete, including approvals, site readiness, contracts, and informed consent processes. Sponsors and CROs use FPI as a core operational benchmark for timeline reporting and portfolio tracking. It is often tied to performance metrics, vendor deliverables, and study forecasting. Accurate tracking supports transparent reporting and proactive management of study execution.