Definium Clears Phase 3 Trial for its LSD-Based Depression Treatment

NEW YORK – Definium Therapeutics Inc. announced positive topline data from its Phase 3 Emerge study evaluating DT120, an orally disintegrating tablet (ODT) formulation of pharmaceutical LSD, in adults with major depressive disorder (MDD). The results highlight notable improvements in depression symptoms after a single dose, adding to the growing body of research on psychedelics in mental health treatment.

The double-blind, placebo-controlled trial enrolled 149 adults who were randomized to receive a single dose of DT120 or placebo over 12 weeks, with participants ranging from 18 to 74 years old across 20 study sites, each carrying a confirmed diagnosis of MDD.

On the trial’s main measure, the Montgomery-Åsberg Depression Rating Scale (MADRS), patients given DT120 saw their score fall by 13.3 points at six weeks, compared with a 5.2-point drop for placebo recipients. That 8.1-point gap was statistically significant at p<0.0001, and the company also reported a 7.3-point placebo-adjusted improvement at week twelve, along with an early, 14.2-point reduction recorded at week one. Response rates (at least 50% improvement) reached 35% in the treatment arm versus 7% on placebo, while remission rates (score of 12 or lower) were 24% versus 3%.

Safety data looked favorable. Most treatment-emergent adverse events were mild to moderate, transient, and occurred mainly on the dosing day. No serious adverse events tied to the drug, no signals of increased suicidality, and low discontinuation rates were reported. Participants received monitoring during the acute session but without adjunctive psychotherapy.

Definium, formerly known as MindMed, positioned DT120 as a potential new option for a condition that affects millions and carries substantial personal and economic costs. Existing antidepressants often require daily use and can take weeks to show benefit, with many patients experiencing incomplete relief or side effects.

Company executives described the data as strong relative to other treatments in the space, though cross-trial comparisons come with caveats due to differences in design and populations. A second Phase 3 study in depression, called Ascend, is underway with a low-dose arm to help maintain blinding. Additional Phase 3 trials in generalized anxiety disorder are ongoing, with more readouts expected later this year.

Wall Street took notice. Analysts said the results exceeded expectations. They called the efficacy data profound and noted the drug’s lasting effect as a clear advantage over Spravato – Johnson & Johnson’s ketamine-based nasal spray and the current standard for rapid-acting MDD treatment.

The disease burden behind the trial is sizable. MDD ranks as the second-most common mental health disorder in the U.S., affecting more than 21 million [!] adults each year, carrying a $326 billion annual economic cost, and leaving fewer than one in three patients in remission after first-line treatment. DT120 already holds Breakthrough Therapy designation from the FDA for generalized anxiety disorder (GAD), and Definium is studying the same compound for PTSD as well. The company said it now plans to push the MDD program toward an FDA submission.

The Emerge data reads as another marker in a slow-building case for federally sanctioned psychedelic medicine. Cannabis spent two decades proving a restricted substance could carry a legitimate clinical and commercial life. Psychedelic developers are now tracing a comparable route, but through the FDA’s standard approval channel rather than around it.

Definium’s numbers are strong, and the market reaction reflects that, but a single trial in 149 patients doesn’t settle questions about durability beyond twelve weeks, real-world dosing oversight, or what insurers will eventually cover. What it does provide is something the psychedelic drug sector has needed: a controlled study, large and clean enough, to hold up under regulatory review.