The trial had the support of patient-led org Cure Parkinson Trust, and they seem optimistic that in a few years this could possibly become a useful drug. The reports I read include statements from an actual participant who said it had improved things. So, like much in this field, perhaps.

In the meantime John's question about PD and diet also stands. It is a subject that has been discussed in this forum many times.

http://www.cureparkinsons.org.uk/News/exenatide