BACKGROUND: Recent examination of the STEADY-PD III isradipine clinical trial 
data concluded that early-stage Parkinson's disease (PD) participants who had 
longer exposure to isradipine had a significant delay in their need for 
symptomatic medication, as well as a lower medication burden at the end of the 
trial. These findings suggest that greater exposure to isradipine might slow 
disease progression.
OBJECTIVES: To test this hypothesis, the data from the STEADY-PD II isradipine 
clinical trial, in which an extended-release (ER) formulation of the drug was 
used, was re-examined.
METHODS: The re-analysis of the STEADY-PD II data was restricted to participants 
assigned placebo or tolerable isradipine treatment (10 mg isradipine/day or 
less). The effect of isradipine treatment was assessed by Unified Parkinson's 
Disease Rating Scale (UPDRS) at the end of the 52-week trial, rather than by 
last observation carried forward at the beginning of symptomatic therapy.
RESULTS: Participant cohorts were well-matched for baseline disability, initial 
disease progression, and time to initiation of symptomatic therapy. Participants 
given 10 mg/day ER isradipine had significantly smaller total and part 3 UPDRS 
scores at the end of the trial than did the placebo cohort. Post hoc adjustment 
for symptomatic therapy diminished the statistical significance of these 
differences. In those participants not taking a monoamine oxidase B inhibitor, 
the progression in UPDRS scores also was significantly reduced.
CONCLUSIONS: These results are consistent with the recent secondary analysis of 
the STEADY-PD III clinical trial-suggesting that clinically attainable brain 
exposure to isradipine may slow early-stage PD progression. © 2021 International 
Parkinson and Movement Disorder Society.