---

---

ACADIA Pharmaceuticals Inc.
(Exact name of registrant as specified in its charter.)

On December 20, 2016, ACADIA Pharmaceuticals Inc. announced positive top-line results from its Phase II exploratory study of pimavanserin in patients with Alzheimer's disease psychosis, or AD Psychosis. In this Phase II exploratory study, referred to as the -019 study, pimavanserin met the primary endpoint showing a statistically significant reduction in psychosis versus placebo as measured by the Neuropsychiatric Inventory-Nursing Home (NPI-NH) Psychosis score at week six of dosing (p=0.0451). A copy of ACADIA's press release related to the top-line results is attached as Exhibit 99.1.

Trial Design and Top-line Results

The Phase II -019 study was a double-blind, placebo-controlled exploratory trial designed to evaluate the efficacy and safety of pimavanserin as a treatment for patients with AD Psychosis. A total of 181 patients were enrolled in the study in the United Kingdom and randomized on a one-to-one basis to receive either 34 mg of pimavanserin or placebo once daily. The primary endpoint of the study was antipsychotic efficacy as measured by the mean change in the NPI-NH Psychosis score (combined hallucinations and delusions domains) from baseline to week six of dosing. Patients continued dosing through week 12 to gather information on secondary endpoints, including changes in cognition.

Pimavanserin demonstrated efficacy on the primary endpoint of the -019 study with a 3.76 point improvement in psychosis at week 6 compared to a 1.93 point improvement for placebo, representing a statistically significant treatment improvement in the NPI-NH Psychosis score (p=0.0451). Baseline mean scores for the pimavanserin and placebo treated groups were 9.52 and 10.00, respectively. In the -019 study, over the course of 12 weeks of treatment, pimavanserin did not impair cognition as measured by the Mini Mental State Examination (MMSE) score and was similar to placebo. On the secondary endpoint of mean change in NPI-NH Psychosis score at week 12, pimavanserin maintained the improvement on psychosis observed at the week six primary endpoint, but did not statistically separate from placebo.

Safety and Tolerability

In the -019 study, pimavanserin was generally well tolerated and the safety profile was consistent with what has been observed in previous studies. Based on a preliminary analysis of safety data, the most common adverse events reported in the -019 study were falls, urinary tract infection and agitation. The mortality rate in the -019 study was the same in the pimavanserin and placebo treatment groups. The mean age of patients in the study was 86 years.

(d) The following exhibit is furnished herewith:

99.1 Press release dated December 20, 2016.