Fig. 1

A schematic of a typical randomised clinical trial. A typical confirmatory phase III clinical trial, followed by an open-label extension study. During a screening period, and after signing informed consent, eligibility of the patient for the trial is assessed. Eligible patients may then be randomised to one or several test and control (placebo or active control) treatments. In a double-blind study, patients, physicians and study personnel are blinded to the patient’s treatment assignment until the core experiment has been completed and all assessments have been collected. Then the database is locked, the treatment allocation unblinded and the data analysed (core analysis). Often patients who complete a core study are offered to continue in an open-label study, for instance on the newly tested treatment until the new treatment option becomes available on the market. All assessments and study procedures are defined by a study protocol. EOS represents the end of the study