Researchers say that a new non-dopaminergic drug called pimavanserin may be the first to offer safe and effective treatment for patients who experience psychotic symptoms associated with Parkinson’s disease. This is according to a new study published in The Lancet.

According to the research team from the US and UK, of the 10 million people worldwide who have Parkinson’s disease, more than 50% of them can experience psychosis, mainly in the form of hallucinations and delusions.

“Psychotic symptoms are common and distressing for people with Parkinson’s and those caring for them,” says Prof. Clive Ballard of King’s College London and study leader.

“Psychosis is a major driving factor for people with Parkinson’s disease being admitted to nursing homes and substantially increases the risk of dying. But no safe and effective drug therapies exist.”

At present, Parkinson’s patients who suffer with psychosis only have the choice of antipsychotic drugs – such as clozapine and quetiapine – as a form of treatment for psychosis. But Prof. Ballard says that these drugs may worsen motor symptoms of Parkinson’s, speed up cognitive decline and can be life-threatening even with short-term use.

In their phase III trial, the researchers looked to pimavanserin as a potential new drug for psychosis that does not present the negative side effects associated with current antipsychotic medication.

The drug works by blocking serotonin 5-HT2A receptors in the neocortex of the brain. The neocortex is the area of the brain responsible for sensory perceptions, conscious thought and language, and the 5-HT2A receptors are linked to visual hallucinations and delusions, the researchers say.

To test the drug, the research team recruited 199 patients with Parkinson’s disease who also experience psychosis. Patients were aged 40 years or older, and they were recruited from 54 medical centers across the US and Canada.

For a 6-week period, patients were randomly assigned to receive either 40 mg of pimavanserin orally once a day, or a placebo drug once a day.

At the baseline of the study, patients’ symptoms of psychosis were assessed using a nine-item Parkinson’s disease-adapted scale (SAPS-PD). This was also used to assess psychotic symptoms at days 15, 29 and 43.

The SAPS-PD reveals and scores the severity of any psychosis symptoms in Parkinson’s disease.

After 43 days, the researchers found that the patients who received pimavanserin demonstrated a 37% improvement in their psychotic symptoms, compared with only a 14% improvement in patients who received the placebo.

The researchers note that patients who received pimavanserin also showed improvements in their nighttime sleep, daytime wakefulness and caregiver burden.

Furthermore, the patients showed no worsening of motor improvements, and the researchers say that significant improvements in the pimavanserin patients were witnessed by the the patients’ carers and independent blinded raters.

Commenting on the drug’s effectiveness, the researchers say:

By comparison with other antipsychotics, pimavanserin’s treatment effects were not associated with exacerbation of motor disability, sedation, or other safety challenges.

As a selective 5-HT2A inverse agonist, pimavanserin is to our knowledge the first in a new class of therapeutic agents able to confer antipsychotic benefit in Parkinson’s disease psychosis without unnecessary receptor activity that compromises safety and tolerability.”

In a comment piece linked to the study, Prof. Susan Fox, of the University of Toronto in Canada, says that further studies are needed to determine the effectiveness of pimavanserin compared with current antipsychotic medication.

But she notes that the findings demonstrated in this study look positive and could even lead to treatment of psychosis in other disorders.

“The study opens up a new therapeutic avenue in treatment of Parkinson’s disease psychosis,” says Prof. Fox.

“With a potentially improved safety profile, pimavanserin might be useful for treatment of patients with Parkinson’s disease and mild symptoms of psychosis and help prevent progression to more bothersome symptoms, as well as targeting psychosis in other disorders such as Alzheimer’s disease.”

Dr. Anne Corbett of King’s College London and study author told Medical News Today that based on the strength of this study, the US Food and Drug Administration have now invited an application for the licensing of pimavanserin.

[This] is a critical step towards seeing this drug being used in clinical practice. The findings also support the urgency of a trial of pimavanserin in people with Alzheimer’s disease, and a study is now being planned to investigate this.”

Medical News Today recently reported on a study detailing the discovery of a potential link between Alzheimer’s and Parkinson’s disease.