Novel drug combats psychosis in Parkinson’s disease

By Eleanor McDermid, Senior medwireNews Reporter

The non-dopaminergic drug pimavanserin reduces psychotic symptoms in patients with Parkinson’s disease (PD) without worsening motor function, shows a randomized trial.

In a press statement, lead researcher Clive Ballard (King’s College London, UK) stressed that “the clinical benefits of pimavanserin were seen by patients, those caring for them, and independent blinded raters alike.”

Along with observed improvements in sleep, this suggests that tackling psychosis had “a broader effect on wellbeing of patients,” write Ballard and colleagues in The Lancet.

A total of 199 patients participated in the study, 185 of whom were included in the final analysis; all had a combined score of at least 6 on the neuropsychiatric inventory items delusions and hallucinations, or an individual score of at least 4.

The researchers tried to provoke a placebo effect ahead of the start of drug treatment by first providing all patients with 2 weeks of psychosocial therapy. Nevertheless, patients assigned to the placebo group still had a 14% reduction in psychotic symptoms on the PD-adapted Scale for Assessment of Positive Symptoms (SAPS) over the 6-week study period.

However, patients taking pimavanserin – a selective serotonin 5-HT2A inverse agonist – had a significantly larger 37% improvement.

In an accompanying commentary, Susan Fox (Toronto Western Hospital, Ontario, Canada) writes: “Overall, the study opens up a new therapeutic avenue in treatment of Parkinson's disease psychosis.”

Pimavanserin delivered significant benefits to patients on the SAPS hallucinations and delusions domains, and in terms of the proportion who achieved at least a 20% improvement, and was effective regardless of age, gender, and baseline cognitive performance.

Furthermore, patients taking the drug had significant improvements in all secondary endpoints measured, which included clinical global impression measures, the Scale for Outcomes of PD, and caregiver burden.

“The ability of a drug to show significance in all endpoints in a Parkinson’s disease trial is unusual, and might reflect the relatively short period of the study (6 weeks) and the fluctuating nature of psychosis,” notes Fox. “Long-term benefits of pimavanserin will be important to ascertain.”

In contrast with other antipsychotics, the improvements in psychosis were not achieved at the expense of motor function; indeed, both groups had small nonsignificant improvements in Unified PD Rating Scale scores during the study.

No safety concerns emerged, although the researchers concede that they followed up patients for just 6 weeks, so longer-term data are needed. But they add: “In view of the distressing nature of symptoms of Parkinson’s disease psychosis, treatment benefit needs to be conferred within this timeframe and maintenance of patients in a placebo-controlled trial for longer would be complex.”

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