I think that this is a hard question; my contributions to this field have been very minor - a couple of papers about a-synuclein from a biophysical rather than clinical perspective.

I was impressed by a talk given by somebody with both a PhD and medical qualifications. He made the point that PD, like cancer, is not "one disease" - rather it, like cancer, is a multitude of conditions with some clinical signs in common.

He argued that, because of this, it will be necessary to tailor a (possibly unique) combination of treatment modalities for each individual with those clinical signs - working out how to do this will not be an easy job.