The US Food and Drug Administration (FDA) has rejected Alkermes' filing for ALKS 5461 in major depressive disorder (MDD), asking for more clinical data.

The drugmaker said that the FDA requested more clinical data to support the efficacy of the oral selective serotonin reuptake inhibitor as an adjunctive therapy for MDD, and also indicated that it will meet with the agency to determine its next steps and clarify potential next steps for ALKS 5461.

The filing for the proprietary, investigational, once-daily oral medicine was backed by efficacy and safety data from more than 30 clinical trials, involving more than 1500 patients with MDD.

Throughout the clinical development programme, ALKS 5461 demonstrated a consistent profile of antidepressant activity, safety and tolerability in the adjunctive treatment of MDD.

ALKS 5461 is a fixed-dose combination of buprenorphine, a partial mu-opioid receptor agonist and kappa-opioid receptor antagonist, and samidorphan, a mu-opioid receptor antagonist, which first experienced setback in the US when regulatory advisors failed to back its approval in November 2018.

MDD is a condition in which patients exhibit depressive symptoms, such as a depressed mood or a loss of interest or pleasure in daily activities consistently for at least a two-week period, and demonstrate impaired social, occupational, educational or other important functioning.

An estimated 16.2 million people in the US suffered from MDD in 2016, the majority of whom may not adequately respond to initial antidepressant therapy.