Long-Term Follow-Up
What is long-term follow-up?
Long-term follow-up (LTFU) is a valuable part of a clinical trial where researchers continue to monitor participants after the main study period ends.
Why is long-term follow-up important?
Extended monitoring is important for tracking the safety of gene therapies over time, as well as their efficacy (how well the therapy works) and durability (how long the benefit lasts).
Types of long-term follow-up studies
How long is extended monitoring?
This period of time can be up to 15 years and depends on the type of gene therapy.
Can patients withdraw from LTFU?
Yes. LTFU is voluntary and participants can withdraw at any time. However, gene therapies make changes to a patient’s genome, so withdrawal from the intervention in the traditional sense is not possible.


