SAN DIEGO (TheStreet) --Acadia Pharmaceuticals'(ACAD) experimental drug pimavanserin failed to reduce psychosis in patients with Parkinson's disease compared to a placebo, according to results from a pivotal phase III study announced Tuesday.
Acadia shares closed Monday at $5.84, close to the stock's 52-week high, but were plunging nearly 70% in premarket trading Tuesday.
Acadia was a $1 stock in early May, bid up by hopeful health care investors seeking a repeat of the stock-ripping study results that catapulted Human Genome Sciences(HGSI) earlier this summer.
The primary goal of the phase III trial was to determine whether treatment with pimavanserin could significantly decrease psychosis -- mainly hallucinations and delusions - that often afflict Parkinson's patients.
Yet on this measure, the drug failed to produce positive results, as measured by the Scale for the Assessment of Positive Symptoms (SAPS). Treatment with pimavanserin at two different dose strengths resulted in mean reductions in SAPS scores of 5.8 points and 6.7 points, but treatment with a placebo resulted in a 5.9-point lowering of the SAPS score.
The difference was not statistically significant, primarily due to larger than expected improvement in placebo-treated patients, the company said.
Pimavanserin didn't exacerbate the motor impairment typically seen in patients with Parkinson's, a key secondary endpoint.
"While we obviously are disappointed with the results of this Phase III study, we continue to believe in the potential of pimavanserin based on our clinical experience to date,"said Uli Hacksell, Acadia's chief executive.
Acadia is conducting a second phase III study of pimavanserin. The drug is being developed in partnership with Canadian drug maker Biovail(BVF).
-- Reported by Adam Feuerstein in Boston