ACADIA Pharmaceuticals Inc. (NASDAQ: ACAD), a biopharmaceutical company focused on innovative treatments that address unmet medical needs in central nervous system disorders, today announced the initiation of ENHANCE-1, a Phase III study to evaluate pimavanserin for adjunctive treatment of schizophrenia in patients with an inadequate response to current antipsychotic therapy. Current antipsychotics approved for schizophrenia primarily target the dopaminergic pathway. As a selective serotonin inverse agonist (SSIA), pimavanserin is a new class of antipsychotic medication with a distinct mechanism of action targeting serotonergic 5-HT 2A receptors while avoiding activity at dopamine and other receptors commonly targeted by other antipsychotics. "About 30 percent of patients with schizophrenia do not achieve an adequate response to a single antipsychotic medication, and as a result more than one in four schizophrenia patients are treated with two or more antipsychotics," said Serge Stankovic, M.D., M.S.P.H., ACADIA's Executive Vice President, Head of Research and Development. "We believe pimavanserin, through its highly selective mechanism of action, could provide an important new option for adjunctive treatment of schizophrenia and improve clinical outcomes by both augmenting the efficacy of currently used antipsychotics and lessening the undesirable side effects associated with polypharmacy." About ENHANCE-1 ENHANCE-1 is a Phase III, six-week, randomized, double-blind, placebo-controlled, multi-center, outpatient study designed to examine the efficacy and safety of adjunctive use of pimavanserin in patients with schizophrenia who have not achieved an adequate response to their current antipsychotic treatment. Approximately 380 patients will be randomized to receive pimavanserin, or placebo, orally, once daily, in addition to their ongoing antipsychotic in a flexible dosing regimen. The starting daily dose of 20 mg of pimavanserin at baseline may be adjusted to 34 mg or 10 mg during the first three weeks of treatment. The primary endpoint of the study is the change from baseline to week six on the Positive and Negative Syndrome Scale (PANSS) total score. Following participation in ENHANCE-1, patients will be eligible to enroll in a 52-week open-label extension study.