Feasibility of Simon Two-Stage Futility Trials in People with Early, Symptomatically Treated Parkinson's Disease.

BACKGROUND Disease-modifying treatments are a critical unmet need in Parkinson's disease (PD). Phase 2 futility trials using the Simon two-stage design offer an efficient strategy to evaluate candidate treatments in an early PD population. OBJECTIVE The aim was to assess the feasibility of Simon two-stage futility trials in early, levodopa-treated PD subjects using historical patient-level clinical trial datasets. METHODS We analyzed patient-level data from two completed trials, that is, STEADY-PD 3 (n = 336, untreated at baseline) and NET-PD LS1 (n = 1741, treated at baseline). We defined disability progression as a ≥5-point worsening on the motor (Part III) subscore of the Unified Parkinson's Disease Rating Scale at 12 and 24 months. We tested multiple scenarios, including the reanalysis of STEADY-PD 3 participant data after starting dopaminergic treatment. We assessed predictors of progression using logistic regression analysis and calculated sample size estimates. RESULTS Both trials showed similar progression rates at 12 months (~26%) and 24 months (~35%). In NET-PD LS1, older age and lower baseline motor scores were associated with worsening; no predictors were significant in STEADY-PD 3. We estimate that in futility trials that use OFF-state scores to assess motor performance, 39 early PD participants are required to detect significant disability worsening over an observation period of 12 months. CONCLUSIONS Phase 2 futility trials using the Simon two-stage methodology are feasible in early PD, including in treated and untreated patients. OFF-state scores are preferable to ON-state scores as the primary outcome measure. Futility trials offer a smaller-scale, faster, and cost-effective approach to assessing new candidate treatments in PD. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.