SAN DIEGO, Calif. ( TheStreet) -- Will Acadia Pharmaceuticals ( ACAD) be the next small drug firm to pull off a resounding clinical trial victory? Acadia is expected to release results later this quarter from a late-stage study of its drug to treat psychosis related to Parkinson's disease. Investors are hoping Acadia can duplicate the stock-ripping study results that catapulted Human Genome Sciences ( HGSI) just a couple of weeks ago. Acadia shares closed Tuesday at $4.38, off the year-high of $5.24 set intraday Monday but still double the stock price of two weeks ago. Acadia's drug is called pimavanserin, which is being studied in two phase III clinical trials for the treatment of Parkinson's disease psychosis (PDP). Canadian drugmaker Biovail ( BVF) is Acadia's marketing partner for pimavanserin. Results from the first of these late-stage studies will be released by Acadia later this quarter. To handicap the upcoming pimavanserin results, it's always helpful to look back at the data generated from previous studies. Acadia did run a phase II study of the drug and presented results in April 2008 at a neurology conference. The phase II study enrolled 60 patients with PDP who were treated for four weeks with either pimavanserin or placebo. Acadia successfully demonstrated that treatment with pimavanserin did not exacerbate the motor impairment typically seen in patients with Parkinson's. So, from a safety perspective, the drug came out okay. The secondary goal of the phase II study, however, was to determine whether treatment with pimavanserin could significantly decrease psychosis -- mainly hallucinations and delusions - that often afflict Parkinson's patients. On this measure, pimavanserin's performance was mixed.