There remains no proven therapy to slow progression of Parkinson’s disease (PD).

To assess the efficacy of isradipine, a dihydropyridine calcium channel antagonist to slow the progression of Parkinson’s disease (PD).

STEADY-PD III is an NINDS funded Phase 3, parallel group, 36 months study evaluating the efficacy of isradipine 10mg daily versus placebo (1:1 randomization, ITT analysis) to slow progression of disability in de novo PD participants.  The study was conducted at 54 Parkinson Study Group sites in US and Canada. The primary outcome measure was the change from baseline in the Unified Parkinson Disease Rating Scale (UPDRS) Part I-III score measured in the ON state at month 36. Secondary outcomes include change in UPDRS-III in the OFF state, time to initiation and utilization of dopaminergic therapy, time to onset of motor complications, change in non-motor disability and quality of life measures.

The study enrolled 336 participants between November 2014 -November 2015, the last participant completed the study November 20, 2018. The study retention rate was 95%. Baseline demographic and disease characteristics including age 62 (SD=9), 68% male, 0.9 (SD=0.7) years from PD diagnosis, UPDRS I-III score =23.1 (SD=8.6) were well balanced between groups. Adjusted (by ANCOVA) mean UPDRS I-III medications ON changes over 36 months were 2.99 points (isradipine) and 3.26 points (placebo) with treatment effect of 0.27 points (95% CL’s -2.5, 3.0, P =0.85). Key secondary outcomes showed no effect of isradipine treatment, Statistical adjustment for usage of symptomatic therapy did not affect the comparison.  The most notable side effect of isradipine was edema.

Isradipine 10 mg daily did not slow progression of disability in early PD. Secondary analysis is underway to explore biological and clinical correlates of disease progression in the study cohort.