Acadia Pharmaceuticals has plans to combine Phase III CLARITY-2 and CLARITY-3 clinical trials of pimavanserin for the adjunctive therapy of major depressive disorder (MDD) into one study.

The announcement follows positive feedback from the US Food and Drug Administration (FDA). The combined study will involve a pre-specified statistical analysis plan.

Acadia noted that the trials will not enrol any new patients and each study will be concluded with approximately 50% enrollment. Top-line data from the combined study is expected in the third quarter of this year.

If the combined study yields positive results, along with the positive data from the previous pivotal CLARITY study, it is expected to support a supplemental new drug application for pimavanserin as the adjunctive treatment of MDD.

Pimavanserin is a selective serotonin inverse agonist and antagonist that preferentially targets 5-HT2A receptors, which are thought to be involved in psychosis, schizophrenia, depression, and other neuropsychiatric disorders.

Both CLARITY-2 and CLARITY-3 are six-week, parallel-designed, randomised, double-blind, placebo-controlled, multi-centre trials assessing the safety and efficacy of pimavanserin as adjunctive treatment for MDD.

The trials enrolled patients who have had an inadequate response to standard antidepressant therapy. Primary endpoint of the trials is the change from baseline on the 17-item Hamilton Depression Rating Scale (HAMD-17) total score.

Participants who completed the Phase III trials were eligible for an ongoing 52-week open-label extension study, which evaluates the long-term safety and tolerability of the drug in MDD patients.

Acadia said that the open-label extension study is ongoing as per the plan.

In December last year, the company reported that pimavanserin decreased the risk of psychosis relapse in dementia patients who participated in its Phase III HARMONY trial.