A randomised, placebo-controlled 24-week study evaluating adjunctive brexpiprazole in patients with major depressive disorder

Objective To evaluate brexpiprazole adjunctive to antidepressant therapies (ADTs) as maintenance treatment in patients with major depressive disorder with inadequate response to ADT, utilising a novel study design. Methods The study comprised an 8-week prospective treatment period with open-label ADT with double-blind placebo treatment and a 24-week randomised treatment period. Investigators and patients were blinded to treatment periods, randomisation criteria, and timing of randomisation. Patients with early response to open-label ADT were withdrawn at Week 6. Patients fulfilling criteria for inadequate response were randomised to ADT+brexpiprazole 1-3 mg/day, or ADT+placebo. The primary endpoint was full remission: Montgomery-angstrom sberg Depression Rating Scale (MADRS) total score <= 10 and >= 50% decrease from randomisation (i.e. baseline) in MADRS total score for at least 8 consecutive weeks. Results The primary efficacy analysis failed to show a statistically significant difference between the proportions of patients on ADT+brexpiprazole (21.4%) and ADT+placebo (24.9%) achieving full remission; odds ratio: 0.83; p=0.2641. The secondary endpoint of change from baseline to Week 6 in MADRS total score showed no difference between ADT+brexpiprazole and ADT+placebo (-0.4; p=0.3259). The most frequent treatment-emergent adverse event (TEAE) in patients receiving ADT+brexpiprazole was weight increased (9.5% vs. 5.0% in ADT+placebo). The incidence of TEAEs leading to withdrawal in the randomised treatment period was 6.3% in the ADT+brexpiprazole group and 3.4% in the ADT+placebo group. Conclusion Adjunctive brexpiprazole did not differentiate from ADT+placebo on the primary endpoint of full remission. A number of design elements in this previously untried study design may have contributed to the study result. Brexpiprazole was well tolerated.