Acadia Pharmaceuticals has reported that pimavanserin reduced the risk of psychosis relapse in dementia patients who participated in its Phase III HARMONY clinical trial.

Pimavanserin is a serotonin inverse agonist and antagonist that specifically targets 5-HT2A receptors.

The double-blind, placebo-controlled Phase III trial assessed the drug to treat delusions and hallucinations in 392 patients with dementia-related psychosis.

During the 12-week open-label stabilisation period of the trial, participants received 34mg pimavanserin once daily. The dose could be decreased to 20mg once daily depending on tolerability within the initial four weeks.

Later, 61.8% of patients were randomised into the trial’s double-blind period. These participants continued on pimavanserin or were given placebo.

The primary endpoint was time to relapse in the double-blind period, determined using the Kaplan-Meier curve and hazard ratio.

HARMONY met its primary endpoint, where the drug decreased the risk of psychosis relapse 2.8 fold. The key secondary endpoint was also met with a 2.2 fold decrease in the risk of discontinuation because of any reason.

In the open-label period, patients experienced a 63% and 75.2% improvement on the Assessment of Positive Symptoms-Hallucinations and Delusions (SAPS-H+D) score from baseline to week 8 and 12, respectively.

Over the nine-month study period, pimavanserin was found to be well-tolerated and had not led to worsening in cognition or motor symptoms.

The adverse events rates were 41% with the drug and 36.6% with placebo in the double-blind period. Adverse events-related discontinuations were 2.9% and 3.6%, respectively.

Acadia Pharmaceuticals president Serge Stankovic said: “First, in the 12-week open-label period, pimavanserin treatment showed a meaningful reduction of the symptoms and stabilisation of psychosis across all of the five clinically diagnosed subtypes evaluated.

“Second, in the 26-week double-blind period, patients on pimavanserin had a nearly three-fold reduction of risk of relapse compared to patients on placebo. And third, pimavanserin was well-tolerated by elderly patients with dementia-related psychosis.”

In the first half of next year, the company plans to discuss a supplemental new drug application (NDA) with the US Food and Drug Administration (FDA).

Last month, Acadia reported positive data from the Phase II ADVANCE trial of pimavanserin in schizophrenia patients.