Acadia Pharmaceuticals has reported top-line findings from the Phase II ADVANCE clinical trial of pimavanserin as an adjunctive treatment for the negative symptoms of schizophrenia.

The trial involved 403 patients who experienced adequate control of positive symptoms with existing antipsychotic therapy.

Pimavanserin is a serotonin inverse agonist and antagonist of 5-HT2A receptors, which are believed to be associated with neuropsychiatric disorders, including schizophrenia.

Schizophrenia is a chronic, debilitating mental disorder characterised by positive and negative symptoms. Positive symptoms include hallucinations and delusions, while negative symptoms are cognitive disturbances, loss of interest and emotional withdrawal.

ADVANCE was a randomised, double-blind, placebo-controlled, multi-centre study that evaluated the safety and efficacy of the drug in patients with predominantly negative symptoms while taking a stable background antipsychotic treatment.

Of the total patients treated with the drug, 53.8% received 34mg, 44.7% were on 20mg, and 1.5% were treated with 10mg by the end of the study.

The primary endpoint was the change in the Negative Symptom Assessment-16 (NSA-16) total score from baseline to week 26.

The Phase II trial met the primary endpoint, demonstrating a statistically significant improvement on the NSA-16 total score with Acadia’s drug, compared to placebo.

According to the results, 53.8% of patients on the 34mg dose achieved a greater improvement.

No significant difference was observed between the study groups on the secondary endpoint of the Personal and Social Performance (PSP) scale.

Pimavanserin was observed to be well-tolerated, with similar adverse event rates between the treatment and placebo arms.

Acadia Pharmaceuticals president Serge Stankovic said: “We are pleased with the positive efficacy findings in this difficult to treat patient population and identified the 34mg dose as demonstrating greater efficacy with favourable tolerability.

“We look forward to initiating a second pivotal study with the 34mg dose during the first half of 2020.”

The company reported top-line data from the Phase III ENHANCE trial of the drug in July this year.