A novel design of a Phase III trial of isradipine in early Parkinson disease (STEADY-PD III)

Objective: To describe the rationale for a novel study design and baseline characteristics of a disease-modifying trial of isradipine 10 mg daily in early Parkinson disease (PD). Methods: STEADY-PDIII is a 36-month, Phase 3, parallel group, placebo-controlled study of the efficacy of isradipine 10 mg daily in 336 participants with early PD as measured by the change in the Unified Parkinson Disease Rating Scale (UPDRS) Part I-III score in the practically defined ON state. Secondary outcome measures include clinically meaningful measures of disability progression in early PD: (1) Time to initiation and utilization of dopaminergic therapy; (2) Time to onset of motor complications; (3) Change in nonmotor disability. Exploratory measures include global measures of functional disability, quality of life, change in the ambulatory capacity, cognitive function, and pharmacokinetic analysis. Rationale for the current design and alternative design approaches are discussed. Results: The entire cohort of 336 participants was enrolled at 55 Parkinson Study Group sites in North America. The percentage of male participants were 68.5% with a mean age of 61.9 years (sd 9.0), mean Hoehn and Yahr stage of 1.7 (sd 0.5), mean UPDRS total of 23.1 (sd 8.6), and MoCA of 28.1 (sd 1.4). Interpretation: STEADY-PD III has a novel and innovative design allowing for the determination of longer duration benefits on clinically relevant outcomes in a relatively small cohort on top of the benefit derived from symptomatic therapy. Baseline characteristics are similar to those in previously enrolled de novo PD trials. This study represents a unique opportunity to evaluate the potential impact of a novel therapy to slow progression of PD disability and provide clinically meaningful benefits.