All-comers versus enrichment design strategy in phase II trials

Designs for biomarker validation have been proposed and used in the phase III oncology clinical trial setting. Broadly, these designs follow either an enrichment (i.e., targeted) strategy or an all-comers (i.e., unselected) strategy. An enrichment design screens patients for the presence or absence of a marker or a panel of markers and then only includes patients who either have or do not have a certain marker characteristic or profile. In contrast, all patients meeting the eligibility criteria (regardless of a particular biomarker status) are entered into an all-comers design. The strength of the preliminary evidence, the prevalence of the marker, the reproducibility and validity of the assay, and the feasibility of real-time marker assessment play a major role in the choice of the design. In this report, we discuss the parameters under which the enrichment or an all-comers design strategy would be appropriate for phase II trials.