Definium reported that its single-dose LSD-inspired therapy DT120 produced clinically meaningful improvement in a Phase 3 trial for major depressive disorder. Six weeks after dosing, patients treated with DT120 saw a 13.3-point drop on the MADRS depression scale versus 5.2 points with placebo. At 12 weeks, the antidepressant effect narrowed but remained largely sustained, with an 11.0-point drop from baseline for DT120 compared with 3.6 points for placebo. Definium said the results bring the candidate closer to potential regulatory discussions. Investors and psychiatrists will now scrutinize whether the effect profile supports differentiation versus other late-stage approaches, and how durability plays out in longer follow-up. Trial safety, functional endpoints, and comparisons across subgroups are likely to shape the next-stage narrative. The Phase 3 readout also adds momentum to the resurgence of psychedelic-assisted development strategies that target rapid symptom change.