ACADIA Pharmaceuticals Announces Completion of Enrollment in Phase III Pimavanserin Trial in Parkinson’s Disease Psychosis

Top-Line Data Expected in November 2012

SAN DIEGO—(BUSINESS WIRE)—Sep. 5, 2012—ACADIA Pharmaceuticals Inc. (NASDAQ: ACAD), a biopharmaceutical companyfocused on innovative treatments that address unmet medical needs inneurological and related central nervous system disorders, todayannounced the completion of enrollment in its ongoing pivotal Phase IIItrial with pimavanserin in patients with Parkinson’s disease psychosis(PDP). Top-line results from this trial are expected to be announced bythe end of November 2012.

The Phase III trial, referred to as the -020 Study, is a multi-center,double-blind, placebo-controlled study designed to evaluate theefficacy, tolerability and safety of pimavanserin as a treatment forpatients with PDP. The -020 Study incorporates several designenhancements that were guided by previous data in ACADIA’s PDP program.A total of 198 patients have been enrolled in the study and wererandomized on a one-to-one basis to receive either 40 mg of pimavanserinor placebo once-daily for six weeks. The primary endpoint of the -020Study is antipsychotic efficacy as measured using nine items from thehallucinations and delusions domains of the Scale for the Assessment ofPositive Symptoms, or SAPS. An independent group of centralized ratersis used to assess the primary endpoint in the study. Motorictolerability is a key secondary endpoint in the study and is measuredusing Parts II and III of the Unified Parkinson’s Disease Rating Scale,or UPDRS.

About Pimavanserin

Pimavanserin is ACADIA’s proprietary small molecule that actsselectively as an antagonist/inverse agonist on serotonin 5-HT_2Areceptors and is in Phase III development as a potential first-in-classtreatment for Parkinson’s disease psychosis. Pimavanserin can be takenorally as a tablet once-a-day. ACADIA discovered and holds worldwiderights to pimavanserin.

About Parkinson’s Disease Psychosis

According to the National Parkinson’s Foundation, about one millionpeople in the United States and from four to six million peopleworldwide suffer from Parkinson’s disease. Parkinson’s diseasepsychosis, or PDP, is a debilitating disorder that develops in up to 60percent of patients with Parkinson’s disease. Currently, there is noFDA-approved therapy to treat PDP in the United States. PDP, commonlyconsisting of visual hallucinations and delusions, substantiallycontributes to the burden of Parkinson’s disease and deeply affects thequality of life of patients. PDP is associated with increased caregiverstress and burden, nursing home placement, and increased morbidity andmortality. There is a large unmet medical need for new therapies thatwill effectively treat PDP without compromising motor control inpatients with Parkinson’s disease.

About ACADIA Pharmaceuticals

ACADIA is a biopharmaceutical company focused on innovative treatmentsthat address unmet medical needs in neurological and related centralnervous system disorders. ACADIA has a pipeline of product candidatesled by pimavanserin, which is in Phase III development as a potentialfirst-in-class treatment for Parkinson's disease psychosis. ACADIA alsohas clinical-stage programs for chronic pain and glaucoma incollaboration with Allergan, Inc. and two preclinical programs directedat Parkinson’s disease and other neurological disorders. All of ACADIA’sproduct candidates are small molecules that emanate from discoveriesmade using its proprietary drug discovery platform. ACADIA maintains awebsite at www.acadia-pharm.comto which ACADIA regularly posts copies of its press releases as well asadditional information and through which interested parties cansubscribe to receive email alerts.

Forward-Looking Statements

Statements in this press release that are not strictly historical innature are forward-looking statements. These statements include but arenot limited to statements regarding expected timing for disclosure oftop-line results from ACADIA’s Phase III trial with pimavanserin inpatients with PDP, as well as statements related to the progress andtiming of ACADIA’s drug discovery and development programs, either aloneor with a partner, and the benefits to be derived from ACADIA’s productcandidates, in each case including pimavanserin. These statements areonly predictions based on current information and expectations andinvolve a number of risks and uncertainties. Actual events or resultsmay differ materially from those projected in any of such statements dueto various factors, including the risks and uncertainties inherent indrug discovery, development and commercialization, and collaborationswith others, and the fact that past results of clinical trials may notbe indicative of future trial results. For a discussion of these andother factors, please refer to ACADIA’s annual report on Form 10-K forthe year ended December 31, 2011 as well as ACADIA’s subsequent filingswith the Securities and Exchange Commission. You are cautioned not toplace undue reliance on these forward-looking statements, which speakonly as of the date hereof. This caution is made under the safe harborprovisions of the Private Securities Litigation Reform Act of 1995. Allforward-looking statements are qualified in their entirety by thiscautionary statement and ACADIA undertakes no obligation to revise orupdate this press release to reflect events or circumstances after thedate hereof, except as required by law.

Source: ACADIA Pharmaceuticals Inc.

ACADIA Pharmaceuticals Inc.
Thomas H. Aasen, ExecutiveVice President,
Chief Financial Officer and Chief BusinessOfficer
(858) 558-2871