A few comments in response:

The drug would not really be expected to have any symptomatic effect. It's use, according to the theory, would be to slow cell death and, hence, slow progression. So, yes, you would need to analyze the effects over years. The new study will be for three years.

You don't have to be drug free to use isradipine. It has very little interaction with other drugs so take anything else you want. You have to be drug free for the trial only so the researchers can rule out their impact on any results. It's strictly due to study design.

You don't need to be early stage to use the drug. Once again, this is strictly due to study design for two main reasons: first, as you said, it's easier to find people who aren't taking other drugs; and second, as with research on other potential neuroprotective interventions, you're more likely to find efficacy the earlier you begin treatment. There are more dopamine neurons left to save.

I have researched this drug extensively over the past two years, including speaking with the lead investigators of this trial and biologists who specialize in basil ganglia health. I am also the PD advocate for this trial for the U of Penn and the Atlantic neurological Inst in NJ.

I'm not going to give anyone any medical advice, but I would be more than happy to share what I learned with anyone interested. As someone who believes in using proper clinical trials to test hypotheses, I do hope this study gets the needed volunteers (336) so we can determine if the drugs really is neuroprtective.