To compare time to relapse in patients with major depressive disorder (MDD) stabilised on antidepressant treatment (ADT) + brexpiprazole who were randomised to continued adjunctive brexpiprazole or brexpiprazole withdrawal (switch to placebo).

This Phase 3, multicentre, double-blind, placebo-controlled, parallel-arm, randomised withdrawal study enrolled adults with MDD and inadequate response to 2–3 ADTs. All patients started on adjunctive brexpiprazole 2–3 mg/day (Phase A, 6–8 weeks). Patients whose symptoms stabilised (Phase B, 12 weeks) were randomised 1:1 to adjunctive brexpiprazole or adjunctive placebo (Phase C, 26 weeks). The primary endpoint was time to relapse in Phase C. Depression rating scale score changes were secondary endpoints.

1149 patients were enrolled and 489 patients were randomised (ADT + brexpiprazole n = 240; ADT + placebo n = 249). Median time to relapse was 63 days from randomisation in both treatment groups for patients who received ≥1 dose. Relapse criteria were met by 22.5% of patients (54/240) on ADT + brexpiprazole and 20.6% (51/248) on ADT + placebo (hazard ratio, 1.14; 95% confidence interval, 0.78–1.67; p = 0.51, log-rank test). Depression scale scores improved during Phases A–B and were maintained in Phase C. Mean weight increased by 2.2 kg in Phases A–B and stabilised in Phase C.

Time to relapse was similar between continued adjunctive brexpiprazole and brexpiprazole withdrawal; in both groups, ∼80% of stabilised patients remained relapse free at their last visit. Adjunctive brexpiprazole therapy was generally well tolerated over up to 46 weeks, with minimal adverse effects following brexpiprazole withdrawal.

ClinicalTrials.gov identifier: NCT03538691. Funding: Otsuka, Lundbeck.