Open-Label Extension Study
A follow-on study where participants who completed a blinded trial continue receiving the active treatment in an unblinded setting, typically for months or years. Open-label extensions provide valuable long-term safety and durability data for peptide drugs beyond the initial trial period.
Technical Context
OLE studies are offered to participants who complete the randomised phase, allowing those on placebo to cross over to active treatment and those on active treatment to continue. This design provides: long-term safety data (rare events may only emerge after years of exposure), durability of efficacy, immunogenicity data over extended periods, and real-world-like data on adherence and dose adjustments. Key limitations: no concurrent control group (making it difficult to attribute changes to the drug vs natural disease progression), selection bias (participants who tolerated and benefited from treatment are more likely to continue), and missing data from dropouts. OLE results for semaglutide showed sustained ~15% weight loss over 2 years of continued treatment.