Axsome Therapeutics has reported positive results from the Phase III GEMINI clinical trial of AXS-05 in patients with major depressive disorder (MDD).

AXS-05 is an investigational, oral N-methyl-D-aspartate (NMDA) receptor antagonist and sigma-1 receptor agonist being developed to treat central nervous system (CNS) disorders, including MDD.

The drug candidate consists of dextromethorphan and bupropion. It is thought to enable improved communication between brain cells and increase serotonin, noradrenaline and dopamine levels.

GEMINI is a randomised, double-blind, multi-centre, placebo-controlled study conducted to investigate a twice-daily dose of the drug candidate for six weeks in a total of 327 patients with moderate-to-severe MDD.

The primary endpoint was the change in the mean Montgomery-Åsberg Depression Rating Scale (MADRS) total score from baseline to week six, compared to placebo.

AXS-05 met the primary endpoint with a statistically significant decrease in the MADRS total score. At week six, the mean decrease from baseline was 16.6 points with AXS-05 versus 11.9 points with placebo.

In addition, the drug candidate led to improvements in depressive symptoms, demonstrating statistical significance on the MADRS total score at week one, the key secondary endpoint.

Statistically significant improvements were also observed on all secondary endpoints at week six, including remission, disease severity, functional impairment and quality of life.

At week six, remission from depression was experienced by 39.5% of patients treated with AXS-05 compared to 17.3% on placebo.

The drug candidate was found to be well-tolerated, with the most common adverse events being nausea, dizziness, headache, somnlence, diarrhoea and a dry mouth. Rates of adverse events-related discontinuation were low across the study groups.

Axsome Therapeutics CEO Herriot Tabuteau said: “With GEMINI and the previously completed ASCEND study, the efficacy of AXS-05 in major depressive disorder has now been demonstrated in two positive well-controlled trials, enabling the filing of an NDA for AXS-05, which is anticipated in the coming year.”

In March this year, the US Food and Drug Administration (FDA) awarded breakthrough therapy designation for AXS-05 to treat MDD.