Fig. 1.

Platform Trials: Simultaneously, sequentially and adaptively. A simplified illustration of a platform trial over time. It starts with a control and 2 treatment arms. The blue arrows indicate the timing of pre-planned adaptive interim analyses. Interim decisions may include early stopping (either for efficacy or futility—see intervention 1) or design adaptations such as the change of allocation ratio (see intervention 2 and 3), sample size reassessment (see intervention 4) or subgroup selection (not illustrated). For example, intervention 1 is stopped after the first interim analysis and at the same time a new arm is added (intervention 3). At the second interim analysis the allocation ratio is changed, e.g., by allocating more patients to intervention 3 compared to 2. At the interim analysis for intervention 4 a sample size re-assessment is performed (the extension is indicated by the darker colour).