Risk-Adjusted Phase II Clinical Trial — Covariate-Stratified Efficacy Design

A risk-adjusted Phase II clinical trial is an early-phase efficacy design that incorporates patient baseline risk strata — such as disease severity, prognostic score, or comorbidity burden — directly into the trial's stopping rules and sample size calculations. By conditioning response targets and futility/efficacy thresholds on risk group membership, the design avoids the bias that arises when a new therapy is evaluated in a population whose prognostic mix differs from the historical control on which the null hypothesis was based.