* Safinamide shows no dyskinesia improvement at 18 months
* Newron shares fall 5.3 percent, Merck flat (Adds shares, analyst comment)
LONDON, Nov 4 (Reuters) - Newron and Merck KGaA said experimental drug safinamide missed its primary target of improving dyskinesia, or involuntary body movements, in a long-term Parkinson's disease trial.
Shares in Swiss-listed Newron fell 5.3 percent on Thursday, while German group Merck was flat in a firmer European stock market.
Despite the failure, the companies said they were encouraged by the overall data from the 18-month extension study, since the drug was shown to be safe and the latest results confirmed the effect on motor function seen at six months.
Analysts at Jefferies said the dyskinesia indication would have to wait but the miss should not stop Merck from filing safinamide for advanced Parkinson's disease.
"We believe significantly improved dyskinesia could have provided a valuable commercial differentiation for safinamide, but had not assumed this in our base case forecasts," they said.
Jefferies, which acted as sole manager for Newron's private placement last year, forecasts peak sales of $600 million for the drug and a 55 percent probability of success. (Reporting by Ben Hirschler; Editing by Erica Billingham)