ACADIA Pharmaceuticals Inc. (NASDAQ: ACAD), a biopharmaceutical company focused on innovative treatments that address unmet medical needs in central nervous system (CNS) disorders, today announced the initiation of CLARITY, a Phase II study to evaluate pimavanserin for adjunctive treatment in patients with major depressive disorder (MDD) who have an inadequate response to first-line therapies for clinical depression. Pimavanserin is a selective serotonin inverse agonist (SSIA) preferentially targeting 5-HT 2A receptors that may play a role in depression. "Major depressive disorder affects millions of people in the United States every year and many do not respond adequately to currently available treatments," said Professor Maurizio Fava, M.D., Executive Vice Chair, Department of Psychiatry, Massachusetts General Hospital (MGH) and Associate Dean for Clinical & Translational Research, Harvard Medical School. "With its highly selective mechanism of action, pimavanserin may provide a new approach to the adjunctive treatment of patients with major depressive disorder and may represent an opportunity to improve clinical outcomes in these patients." "We are committed to the development of pimavanserin in additional CNS disorders that are underserved by currently available therapies and represent a significant unmet medical need. Inadequate response to current antidepressants is one such condition," said Serge Stankovic, M.D., M.S.P.H., ACADIA's Executive Vice President, Head of Research and Development. "We are gratified to be able to leverage the vast knowledge and expertise of our colleagues at MGH and conduct this study in collaboration with the MGH Clinical Trials Network & Institute." About CLARITY CLARITY is a Phase II, 10-week, randomized, double-blind, placebo-controlled, multi-center study designed to examine the efficacy and safety of adjunctive use of pimavanserin in patients with major depressive disorder who have an inadequate response to standard antidepressant therapy with either a selective serotonin reuptake inhibitor (SSRI) or a serotonin norepinephrine reuptake inhibitor (SNRI). Approximately 188 patients will be randomized to receive either 34 mg of pimavanserin or placebo, orally, once daily, in addition to their ongoing antidepressant for 10 weeks. The primary endpoint of the study is the change from baseline on the Hamilton Depression Rating Scale (HAM-D) total score.