Definium's LSD-Based Depression Drug Beats All Endpoints in Phase 3 Trial, Shares Surge More Than 50%

What the Trial Actually Found

Definium Therapeutics announced Monday, June 22 that its oral psychedelic drug DT120 met all primary and key secondary endpoints in the Phase 3 Emerge trial, according to Fierce Biotech and BioSpace. The trial enrolled 149 adults aged 18 to 74 with major depressive disorder.

The headline number: an 8.1-point placebo-adjusted reduction on the Montgomery-Åsberg Depression Rating Scale (MADRS) after six weeks. At 12 weeks, that figure held at 7.3 points, according to BioSpace. This durability finding caught Wall Street's attention.

Analysts at Stifel wrote in a Monday investor note that the results "exceeded expectations with clear and highly robust efficacy in the MDD population." Jefferies analysts called the efficacy data "profound." Before the trial read out, analysts had set a bar of 4–5 points for a strong result, according to ZeroHedge, citing Reuters. DT120 nearly doubled it.

Patients showed measurable improvement within one week after a single dose. No serious safety concerns emerged. Adverse events were mostly mild, occurring primarily on dosing day, with no increase in suicidal ideation, according to Fox4News citing Reuters.

How It Compares to Existing Treatments

Definium's own presentation, provided to Fierce Biotech ahead of the readout, placed DT120's 8.1-point reduction above every approved antidepressant measured on the same scale. The second-highest benchmark in that comparison came from Johnson & Johnson's Spravato, the ketamine-based nasal spray, at 6.8 points.

Other drugs in the comparison included Takeda's Trintellix, Axsome Therapeutics' Auvelity, and an investigational psilocybin drug from Compass Pathways. Definium's presentation labeled DT120's profile "best-in-class."

A critical caveat: Fierce Biotech noted that direct cross-trial comparisons are not scientifically valid due to differences in methodology and patient populations. Definium's own framing acknowledges this. Stifel's note made the same point while still calling DT120's durable response "a highly compelling advantage vs. Spravato," particularly because psychedelic therapies are designed for low-frequency dosing.

CEO's Assessment

Definium CEO Robert Barrow described the results as "the best data ever seen in a pivotal study of depression" in an interview with Fierce Biotech conducted before the official announcement. "It's really of a magnitude, of a rapidity, and of a durability that we've never before seen in a phase 3 study," Barrow said.

Barrow called DT120 a "potential best-in-class treatment for mental health disorders" in a statement reported by BioSpace, adding that the company is moving toward an FDA submission. A second Phase 3 trial assessing DT120 in generalized anxiety disorder is currently ongoing, according to BioSpace.

The Stock Move

Shares surged more than 50% in Monday's session, touching $37.90 intraday according to ZeroHedge. Premarket indications had the stock up more than 30% before the open, according to Fierce Biotech. As of the close of regular trading today, the magnitude of the full-session move has not been confirmed across all sources, but the intraday peak of roughly 54% is reported by ZeroHedge.

Definium was formerly known as MindMed, or Mind Medicine, before rebranding in January 2026.

The Policy Backdrop

The FDA has made psychedelics a regulatory priority under Commissioner Marty Makary and Health Secretary Robert F. Kennedy Jr., according to BioSpace. President Trump signed an executive order directing federal agencies to expand access to promising emerging therapies, and the FDA has separately unveiled measures to speed research into psychedelic treatments for depression, PTSD, and addiction, according to ZeroHedge.

That regulatory tailwind is real. But it does not equal automatic approval.

The Legitimate Skepticism

Psychedelic drugs present genuine scientific and regulatory complexity. Blinding trial participants is nearly impossible when the drug produces perceptible effects. A problem that inflates apparent placebo-adjusted scores, critics argue, occurs because patients who figure out they received the active drug may report greater improvement. This methodological challenge is a serious unresolved issue in the entire field, not just for Definium. The FDA has not yet established a clear standard for how psychedelic trial designs handle the unblinding problem.

That concern doesn't invalidate the Emerge data. But it does mean the FDA review process will scrutinize the trial design closely, and the word "potential" in Barrow's best-in-class claim carries weight.

Lykos Therapeutics' MDMA-based therapy for PTSD was rejected by the FDA in 2024 partly over trial design concerns, including the blinding issue. BioSpace noted that Compass Pathways and Definium are now leading the psychedelics approval race with "Lykos' regulatory failure now squarely in the rearview mirror."

What Comes Next

Definium said the Emerge data brings it closer to an FDA submission but has not announced a specific submission date. The open question with direct market and patient consequences is whether the FDA will require a second successful Phase 3 depression trial before approving DT120, or treat Emerge as sufficient. That determination, not CEO enthusiasm or stock price, will decide whether this drug reaches the 21 million Americans currently living with major depressive disorder.