Group sequential trial
A group sequential trial is a trial design that prospectively plans for one or more interim analyses of comparative data with prespecified criteria for stopping the trial. The inclusion of sequential
analyses can provide ethical and efficiency advantages by reducing the expected sample size and duration of clinical trials and by accelerating the approval of safe and effective new therapies.
Group sequential designs may include rules for stopping the trial when there is sufficient evidence of efficacy to support regulatory decision-making or when there is evidence that the trial is unlikely to demonstrate efficacy, which is often called stopping for futility.
U.S. Food and Drug Administration (FDA): Adaptive Design Clinical Trials for Drugs and Biologics Guidance for Industry
Adaptive design clinical trials: a review of the literature and ClinicalTrials.gov [2018 published article]