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n. An experimental drug being developed to treat Parkinson's disease psychosis and schizophrenia.


Pimavanserin ( INN), or pimavanserin tartate ( USAN), marketed under the trade name Nuplazid, is a non- dopaminergic atypical antipsychotic developed by Acadia Pharmaceuticals for the treatment of Parkinson's disease psychosis and schizophrenia. Pimavanserin has a unique mechanism of action relative to other antipsychotics, behaving as a selective inverse agonist of the serotonin 5-HT receptor, with 40-fold selectivity for this site over the 5-HT receptor and no significant affinity or activity at the 5-HT receptor or dopamine receptors. The drug has met expectations for a Phase III clinical trial for the treatment of Parkinson's disease psychosis, and has completed Phase II trials for adjunctive treatment of schizophrenia alongside an antipsychotic medication.

Pimavanserin is expected to improve the effectiveness and side effect profile of antipsychotics. The results of a clinical trial examining the efficacy, tolerability and safety of adjunctive pimavanserin to risperidone and haloperidol were published in November 2012, and the results showed that pimavanserin potentiated the antipsychotic effects of subtherapeutic doses of risperidone and improved the tolerability of haloperidol treatment by reducing the incidence of extrapyramidal symptoms.

On September 2, 2014, the United States Food and Drug Administration granted Breakthrough Therapy status to Acadia's New Drug Application for pimavanserin. It was approved by the FDA to treat hallucinations and delusions associated with psychosis experienced by some people with Parkinson's disease on April 29, 2016.