Long-Term Follow-Up (LTFU) refers to extended participant monitoring after completion of the main treatment or observation period in a clinical trial.
LTFU is used to capture delayed safety events, durability of response, long-term outcomes, or late-emerging risks that may not appear during active treatment. It is especially important for products with prolonged biological activity, such as gene therapies, cell therapies, or long-acting modalities. LTFU requirements are typically defined in the protocol and supported by a clear plan for contact frequency, assessments, and data collection methods. Strong LTFU execution supports benefitñrisk evaluation and strengthens the evidence base for regulators and payers.