Re-reading this thread recently, I noticed a question from johnt (08-09-2017), which went unanswered:

"What is the relationship between alpha-synuclein and Exenatide? Given the supposed centrality of alpha-synuclein in the pathogenesis of PD, you would expect any treatment which slowed the progression of PD to involve alpha-synuclein in some way."

John probably has his answer now (from other sources), but for anyone else who may be pondering this same question, the following PNT article (about NLY01) sheds some light:

Compound Similar to Diabetic Medications Slows Parkinson's Progression in Mouse Study

And for anyone wanting to delve deeper, I recommend the following AlzForum article (mentioned in an earlier post):

Does Taming Killer Astrocytes Spare Neurons in Parkinson’s Disease? | ALZFORUM