The BBC are reporting [1] a brain "'wonder-drug'", well two, actually:
- trazodone, already used for depression;
- DBM, a cancer drug.

Based on worm and mouse models, and in vitro human studies, these drugs appear to slow down the progression of a number of neurodegenerative diseases, including Parkinson's.

I'm very aware that I've recently contributed to a thread that warns of the danger of "hype". So, although we can really hope that these drugs will substantially slow the progression of PD on humans, I think the chances are low.

Reference

[1] Experts excited by brain 'wonder-drug' - BBC News

John