Definium’s Single-Dose Psychedelic Therapy Shows Phase 3 Promise for Anxiety

Key Points

• Definium Therapeutics reported positive Phase 3 results for DT120, its investigational LSD-based treatment for generalized anxiety disorder, or GAD.
• A single DT120 dose reduced anxiety scores by an average of 11.6 points after 12 weeks, outperforming placebo by 5.4 points.
• The treatment showed rapid symptom improvement, with effects beginning by day two and continuing through the 12-week study period.

Definium Therapeutics has reported positive Phase 3 results for DT120, an investigational pharmaceutical-grade LSD-based therapy for generalized anxiety disorder. The study showed that one supervised dose of DT120 produced statistically significant and sustained improvements in anxiety symptoms compared with placebo.

DT120 demonstrates significant reduction in generalized anxiety symptoms

The Phase 3 trial measured anxiety symptoms using a 56-point assessment scale that evaluates emotional, cognitive, and physical effects of anxiety. After 12 weeks, participants who received DT120 experienced an average 11.6-point reduction in anxiety scores.

The treatment outperformed placebo by 5.4 points, exceeding analysts’ expectations of roughly a five-point difference. Definium said the study also met its key secondary endpoints, supporting the overall strength of the result.

Single-dose treatment produces rapid and durable effects

Definium reported that patients began to show anxiety improvement as early as two days after receiving DT120. The benefit continued through the full 12-week core study period, suggesting the potential for a durable effect after a single supervised treatment session.

This approach differs from many traditional anxiety treatments that require daily dosing and may take weeks to produce noticeable effects. DT120 remains experimental, however, and further studies will be needed to confirm its effectiveness and long-term safety.

Phase 3 safety data show no new concerns

The company said the trial did not identify new safety concerns, including no signals of suicidal thoughts or behaviors. Participants were monitored for up to eight hours after receiving the treatment to assess both physical and psychological well-being.

In the initial portion of the study, participants receiving DT120 required an average of 6.4 hours to meet the study’s end-of-session checklist. By the eight-hour monitoring cutoff, 92% of participants had completed those requirements.

Additional anxiety and depression data are expected soon

Definium expects results from a second Phase 3 generalized anxiety disorder trial in September. The company also plans to report topline results from another major depressive disorder study next year and begin a late-stage study in post-traumatic stress disorder.

The second GAD readout will be an important next step. Replicating the initial Phase 3 findings could strengthen Definium’s regulatory case for DT120 and support future development across multiple mental-health conditions.

What positive DT120 data could mean for Definium

The Phase 3 results position DT120 as a potential new treatment approach for generalized anxiety disorder, combining a single monitored dose with rapid and lasting symptom improvement. The therapy still faces important hurdles, including confirmation in another Phase 3 study, longer-term safety assessment, regulatory review, and the practical challenge of delivering an eight-hour supervised treatment session at scale.