Update from ACADIA Pharmaceuticals regarding its Phase III program with pimavanserin

ACADIA Pharmaceuticals Inc. (Nasdaq: ACAD), a biopharmaceutical company utilizing innovative technology to fuel drug discovery and clinical development of novel treatments for central nervous system disorders, today provided an update on its Phase III program with pimavanserin for Parkinson’s disease psychosis (PDP), which is being pursued in collaboration with Biovail Laboratories International SRL (“Biovail”), a subsidiary of Biovail Corporation. Following the announcement on September 1^st of disappointing top-line results from the first Phase III PDP trial, ACADIA and Biovail remain committed to the successful development of pimavanserin and have established a development strategy that they believe will strengthen the PDP program. The parties also intend to pursue adjunctive therapy with pimavanserin for schizophrenia as a third indication in the collaboration.

“We remain enthusiastic about pimavanserin’s prospects in a number of specialty CNS indications, including schizophrenia where existing data for the molecule as co-therapy are compelling,” said Bill Wells, Biovail’s Chief Executive Officer. “The steps we’re taking today are designed to fully exploit pimavanserin’s potential and to bring this novel therapeutic to market as quickly as possible.”

ACADIA has conducted a substantial portion of the analysis of the data from its first Phase III PDP trial with pimavanserin (-012 Study). While the -012 Study did not meet its primary endpoint of antipsychotic efficacy and had a larger than expected placebo response, signals of antipsychotic efficacy were observed in the pimavanserin 40 mg study arm. These signals were most prominent in the United States portion of the study, which comprised nearly one-half of the patients in the trial. The efficacy signals also were supported by additional secondary and exploratory measures, including efficacy measures and favorable outcomes in assessments of sleep and caregiver burden. Several findings from the -012 Study will be used in the design of future PDP studies to help mitigate the placebo response and to increase the chances of success. These findings relate to dose selection, the method and application of ratings, and other study design elements.

ACADIA and Biovail have agreed on a development strategy for PDP that involves using the findings from the -012 Study together with those from the second, ongoing Phase III trial (-014 Study), which is testing 10 mg and 20 mg doses of pimavanserin, to arrive at an enhanced study design that may be used in new Phase III trials. Accordingly, the ongoing -014 Study will be concluded at its current enrollment level (about 120 patients) to allow for the analysis of data as soon as practicable. Meanwhile, the parties will begin planning for a new Phase III PDP trial using a 40 mg dose of pimavanserin. Consistent with the terms of the original collaboration agreement, Biovail will be responsible for the cost of this third Phase III trial. This study is expected to start in the first half of 2010. ACADIA will continue its ongoing open-label safety extension studies in patients with PDP.

In addition, Biovail intends to pursue adjunctive therapy with pimavanserin for schizophrenia as a third indication in the collaboration. Alzheimer’s disease psychosis (ADP) remains the second indication provided for in the collaboration. The parties currently intend to focus their efforts on the PDP and schizophrenia programs, but also are moving forward with planning for an initial study in ADP.

“Together, ACADIA and Biovail are pursuing a development strategy that strengthens our path forward in PDP while opening up potential opportunities for pimavanserin to address unmet medical needs of patients suffering from other psychiatric and neurological disorders, including schizophrenia and ADP,” said Uli Hacksell, Ph.D., Chief Executive Officer of ACADIA.

While pursuing its development strategy for pimavanserin, ACADIA intends to implement cost-saving measures during October to further streamline its operations, reduce its internal operating expenses, and provide added financial flexibility. ACADIA currently anticipates that its cash, investment securities and payments from its collaborations before taking any cost-saving measures will be sufficient to fund its operations into the first half of 2011, and that these measures will further extend ACADIA’s cash runway.