Shares in Acadia Pharmaceuticals have skyrocketed after the Food and Drug Administration took the unusual step of telling the US firm that existing data is sufficient to file pimavanserin to treat Parkinson's disease psychosis.

The San Diego-based company says the FDA has agreed that the data from a Phase III study, together with supportive data from other studies with pimavanserin, are sufficient to back the filing of a New Drug Application for PDP. As a result, Acadia says it will no longer conduct a second late-stage study that was planned as a confirmatory trial and was scheduled to be initiated later this month.

Acadia chief executive Uli Hacksell said "we are very pleased with the outcome of our meeting with the FDA, which we expect will reduce substantially both the time and cost of our PDP development programme". The company said it now plans to submit an NDA for pimavanserin, a non-dopaminergic once-a-day oral drug that selectively blocks serotonin 5-HT2A receptors, near the end of 2014.

About four to six million people worldwide suffer from Parkinson’s and PDP is a debilitating disorder that develops in up to 60% of patients. Currently, there is no FDA-approved therapy to treat PDP which commonly consists of visual hallucinations and delusions.

Investors are excited and Acadia shares closed up 64% to $13.10.