Open label is a term used to describe the situation when both the researcher and the participant in a research study know the treatment the participant is receiving. Open-label is the opposite of double-blind when neither the researcher nor the participant knows what treatment the participant is receiving.
Pilot study means a smaller version of a larger study that is conducted to prepare for that (larger) study. Pilot studies are used in clinical trials, in order to test different doses, routes of administration, dosing schedules and possible barriers to adherence before a large-scale multicenter drug study is launched. Pilot studies are also used as feasibility studies, to ensure that the ideas or methods behind a research idea are sound, as well as to “work out the kinks” in a study protocol before launching a larger study.