From a PubMed search for "Wyss-Coray" all that I can find is this, which is concerned with Alzheimer's Disease not PD.
It was a feasibility study but this approach could also help with PD.
Safety, Tolerability, and Feasibility of Young Plasma Infusion in the Plasma for Alzheimer Symptom Amelioration Study: A Randomized Clinical Trial. - PubMed - NCBI