Acadia Pharmaceuticals has reported top-line data from the Phase III ENHANCE clinical trial of its pimavanserin drug to treat schizophrenia in adults with persistent inadequate response to current therapy.

The study assessed pimavanserin as an adjunctive treatment in a total of 396 participants.

Data showed consistent improvements in psychotic symptoms when the investigational drug was added to current antipsychotic therapy.

However, the treatment failed to reach statistical significance on the primary endpoint of Positive and Negative Syndrome Scale (PANSS) total score compared to adjunctive placebo.

Acadia also noted a positive trend on the key secondary endpoint of Clinical Global Impression-Severity (CGI-S) score.

A subgroup analysis of patients enrolled in Europe revealed consistent positive trends on the PANSS total score and the CGI-S score.

Full analysis demonstrated significant improvements on PANSS negative symptoms scale sub-score and PANSS Marder negative factor score, which are a secondary endpoint and exploratory endpoint, respectively.

Acadia Pharmaceuticals president Serge Stankovic said: “Unfortunately, we did not achieve a statistically significant reduction in the PANSS total score in this study.

“We are pleased with the improvement in negative symptoms observed in this study. We look forward to completing our ongoing ADVANCE trial evaluating pimavanserin in schizophrenia patients with predominant negative symptoms.”

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

The global, randomised, double-blind, placebo-controlled, multi-centre, outpatient ENHANCE trial assessed an oral, once-daily regimen of pimavanserin given adjunctive to an existing antipsychotic over six weeks.

Acadia’s therapeutic was well-tolerated and the adverse event rates were observed to be similar between the investigational and placebo groups.