There is solid scientific rational and preclinical data supporting a clinical trial of isradipine CR as a potential disease modifying agent in early PD. Human pharmacokinetic data demonstrate that it is feasible to achieve the serum concentrations in humans that were neuroprotective in preclinical models with the FDA approved dosage range. Pilot data demonstrate acceptable tolerability of isradipine CR in the PD population. Tolerability is inversely proportional to the dosage dependent. Considering that tolerability of isradipine CR is inversely proportional to the dosage exposure, it is essential to proceed with the dose selection tolerability study in preparation for the future efficacy trials.