A study where both the researchers and participants know who is getting the treatment—less rigorous than blinded trials, but still useful.In open-label studies, treatment allocation is known to investigators and participants. This design is susceptible to placebo effects, observer bias, and expectation bias. Open-label studies are appropriate for Phase I safety evaluation, dose-finding, and conditions where blinding is impractical. However, open-label efficacy data must be interpreted cautiously—particularly for subjective endpoints like pain, fatigue, or well-being. Many peptide compounds have only open-label human data, making honest assessment of evidence quality critical.