Pimavanserin …New Drug Shows Early Promise in Treating Parkinson’s Psychosis

Pimavanserin, ACP 103

N-(4-fluorophenylmethyl)-N-(1-methylpiperidin-4-yl)-N’-(4-(2-methylpropyloxy)phenylmethyl)carbamide, 706779-91-1 ^cas

	706782-28-7 (tartrate)

THURSDAY Oct. 31, 2013 — Many people living with Parkinson’s disease suffer from hallucinations and delusions, but an experimental drug might offer some relief without debilitating side effects.

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http://www.drugs.com/news/new-shows-early-promise-treating-parkinson-s-psychosis-48630.html

The drug — pimavanserin — appears to significantly relieve these troubling symptoms, according to the results of a phase 3 trial to test its effectiveness.

Pimavanserin (ACP-103) is a drug developed by Acadia Pharmaceuticals which acts as an inverse agonist on the serotonin receptor subtype 5-HT_2A, with 40x selectivity over 5-HT_2C, and no significant affinity or activity at 5-HT_2B or dopamine receptors.^[1] As of September 3 2009, pimavanserin has not met expectations for Phase III clinical trials for the treatment of Parkinson’s disease psychosis,^[2] and is in Phase II trials for adjunctive treatment of schizophrenia alongside an antipsychotic medication.^[3] It is expected to improve the effectiveness and side effect profile of antipsychotics.^[4][5][6]

3-D MODEL OF DRUG PIMAVANSERIN, THE DEVELOPMENT OF WHICH HAS BEEN EXPEDITED BY THE FDA

1. Friedman, JH (October 2013). “Pimavanserin for the treatment of Parkinson’s disease psychosis”. Expert Opinion on Pharmacotherapy 14 (14): 1969–1975.doi:10.1517/14656566.2013.819345. PMID 24016069.
2.  ACADIA Pharmaceuticals. “Treating Parkinson’s Disease – Clinical Trial Pimavanserin – ACADIA”. Retrieved 2009-04-11.^{[dead link]}
3. “ACADIA Announces Positive Results From ACP-103 Phase II Schizophrenia Co-Therapy Trial” (Press release). ACADIA Pharmaceuticals. 2007-03-19. Retrieved 2009-04-11.
4. Gardell LR, Vanover KE, Pounds L, Johnson RW, Barido R, Anderson GT, Veinbergs I, Dyssegaard A, Brunmark P, Tabatabaei A, Davis RE, Brann MR, Hacksell U, Bonhaus DW (August 2007). “ACP-103, a 5-hydroxytryptamine 2A receptor inverse agonist, improves the antipsychotic efficacy and side-effect profile of haloperidol and risperidone in experimental models”. J Pharmacol Exp Ther 322 (2): 862–70.doi:10.1124/jpet.107.121715. PMID 17519387.
5.  Vanover KE, Betz AJ, Weber SM, Bibbiani F, Kielaite A, Weiner DM, Davis RE, Chase TN, Salamone JD (October 2008). “A 5-HT2A receptor inverse agonist, ACP-103, reduces tremor in a rat model and levodopa-induced dyskinesias in a monkey model”. Pharmacol Biochem Behav 90 (4): 540–4. doi:10.1016/j.pbb.2008.04.010. PMC 2806670.PMID 18534670.
6.  Abbas A, Roth BL (December 2008). “Pimavanserin tartrate: a 5-HT2A inverse agonist with potential for treating various neuropsychiatric disorders”. Expert Opin Pharmacother9 (18): 3251–9. doi:10.1517/14656560802532707. PMID 19040345.

Psychiatrist Herb Meltzer sadly watched the agitated woman accuse her son of trying to poison her. Although not her physician, Dr. Meltzer certainly recognized the devastating effects of his mother-in-law’s Parkinson’s disease psychosis (PDP). Occurring in up to half of all patients with Parkinson’s, symptoms of the psychotic disorder may include hallucinations and delusions. The development of PDP often leads to institutionalization and increased mortality.

“I was on the sidelines,” explains Dr. Meltzer, professor of psychiatry and physiology and director of the Translational Neuropharmacology Program at Northwestern University Feinberg School of Medicine. “I told my brother-in-law it was the disease talking, not his mother.”

Ironically, Dr. Meltzer has been far from the sidelines and right on the PDP playing field for quite a while. In fact, he may soon see a drug he helped develop become the first approved treatment for the disorder. In early April, Dr. Meltzer celebrated, along with colleagues at ACADIA Pharmaceuticals in San Diego for which he has been a clinical advisor, the stunning announcement: the Food and Drug Administration (FDA) had expedited the company’s path to filing a new drug application (NDA) for pimavanserin, a selective serotonin 5-HT_2Areceptor blocker. Typically, the FDA requires data from two successful pivotal Phase III clinical studies affirming a drug candidate’s safety and efficacy before the agency will even consider an NDA. Just as ACADIA was planning to launch another Phase III study this spring to fulfill this requirement, the FDA decided the company had amassed enough data to support an NDA filing.

HERBERT MELTZER, MD, DESIGNED ACADIA PHARMACEUTICAL’S INITIAL PROOF OF CONCEPT TRIAL OF THE DRUG PIMAVANSERIN TO TREAT PARKINSON’S DISEASE PSYCHOSIS.

“This action on the part of the FDA is extremely unusual,” says Dr. Meltzer, who designed ACADIA’s initial proof-of-concept trial of pimavanserin, a drug he had initially suggested ACADIA develop to treat schizophrenia, with PDP as a secondary indication. “The FDA staff decided that results from my small clinical study and the first successful Phase III study were sufficient to establish efficacy and safety.”

Bringing a safe and effective drug to market is a monumental achievement. Pimavanserin is not yet there but has significantly moved within striking distance with this recent nod from the regulatory agency.

24 YEARS IN THE MAKING

The neuropharmacologist’s collaboration with ACADIA began in 2000. The company wanted to develop a drug targeting the serotonin 5-HT _2A receptor, a neurotransmitter ACADIA believed played a key role in schizophrenia based upon basic research from Meltzer and their own studies. A distinguished schizophrenia investigator, then at Case Western Reserve University, he welcomed ACADIA’s offer to translate his ideas about developing safer and more effective drug treatments for psychosis. Through his provocative and groundbreaking research, Dr. Meltzer originally championed the idea that blocking the 5-HT_2A receptor would lead to better antipsychotic drugs with fewer side effects. Existing drugs often impaired motor function because they targeted the dopamine D₂ receptor. Of the 14 different types of serotonin receptors in this complex area of study, Dr. Meltzer zeroed in on the 5-HT_2A type—the same receptor that leads to hallucinogenic properties of LSD and mescaline. It was an ideal target to complement weak D₂ receptor blockade in schizophrenia and as a standalone treatment for PD psychosis.

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