This article explains progress being made on a drug to treat psychosis in Parkinson's:
[The url is an org type so I think it is allowed, but if it is removed and you are interested, search for the drug's name, pimavanserin.]
This would be the first drug specifically approved for treating psychosis in a neurological condition.
I remember one (of many) conversations I had with Coy's insurance company, explaining that yes, I knew the drug was being used off-label, but that there were NO drugs tested and approved for use with his disease! The drug improved his quality of life. Until better alternatives are developed, please approve this one!!.
So finally having a drug to address behaviors like delusions that works specifically for PD, and doesn't carry the risk level of current drugs is miraculous. (Since PD and LBD both involve the presence of similar bodies of protein in the brain, there is already speculation and hope that the new drug will prove useful there, too.)
If you watched the recent NOVA episode regarding drug research for dementia, you will appreciate how far along the process this drug is. It is not on the market yet, but it is very hopeful news.