Zuranolone in Major Depressive Disorder: Results From MOUNTAIN-A Phase 3, Multicenter, Double-Blind, Randomized, Placebo-Controlled Trial.

Objective: To evaluate the efficacy and safety of zuranolone, an investigational neuroactive steroid and GABAA receptor positive allosteric modulator, in major depressive disorder (MDD).Methods: The phase 3, double-blind, randomized, placebo-controlled MOUNTAIN study enrolled adult outpatients with DSM-5-diagnosed MDD, 17-item Hamilton Depression Rating Scale total score (HDRS-17) ≥ 22, and Montgomery-Asberg Depression Rating Scale total score ≥ 32. Patients were randomized to treatment with zuranolone 20 mg, zuranolone 30 mg, or placebo for 14 days, followed by an observation period (days 15-42) and an extended follow-up (days 43-182). The primary endpoint was change from baseline (CFB) in HDRS-17 at day 15.Results: 581 patients were randomized to receive zuranolone (20 mg, n = 194; 30 mg, n = 194) or placebo (n = 193). Day 15 HDRS-17 least-squares mean (LSM) CFB was -12.5 (zuranolone 30 mg) vs -11.1 (placebo; P = .116). Improvement vs placebo was significant at days 3, 8, and 12 (all P < .05). LSM CFB (zuranolone 20 mg vs placebo) was not significant at any measured time point. Post hoc analyses of zuranolone 30 mg in patients with measurable plasma zuranolone concentration and/or severe disease (baseline HDRS-17 ≥ 24) showed significant improvement vs placebo at days 3, 8, 12, and 15 (all P < .05). Incidence of treatment-emergent adverse events was similar between zuranolone and placebo groups; the most common (≥ 5%) were fatigue, somnolence, headache, dizziness, diarrhea, sedation, and nausea.Conclusions: MOUNTAIN did not meet its primary endpoint. Significant rapid improvements in depressive symptoms were observed with zuranolone 30 mg at days 3, 8, and 12. Zuranolone was generally well tolerated in patients with MDD.Trial Registration: ClinicalTrials.gov identifier: NCT03672175.