A long-term extension study (LTE study), also known as an open-label extension (OLE), is a study that directly follows a completed primary study, usually randomized and controlled. It offers participants who have benefited from the treatment the opportunity to continue receiving the investigational medicinal product over a longer period. This is often ethically required, particularly in severe chronic diseases for which no other treatment options are available.
LTE studies are generally open-label, meaning that all participants (and investigators) know that they are receiving the active drug. The primary objective of these studies is to collect long-term safety and tolerability data. However, they can also provide valuable information on the long-term efficacy of the treatment. For CROs, conducting LTE studies requires efficient management to keep the burden on patients and study sites low while generating high-quality long-term data for regulatory authorities.