Definium Therapeutics Eyes FDA Filing for LSD Treatment After Three Positive Phase 3 Studies

Definium Therapeutics (NASDAQ:DFTX) plans to submit a new drug application to the U.S. Food and Drug Administration for its LSD formulation DT120 in the first half of next year, following positive results from three Phase 3 studies, Chief Medical Officer Daniel Karlin said.

The company intends to seek approval for both generalized anxiety disorder (GAD) and major depressive disorder (MDD), though the exact structure of the filings remains under discussion with the FDA, Karlin said. Two of the completed studies were in GAD and one was in MDD.

If the FDA requires another MDD study before submission, Definium will proceed with a GAD application alone, Karlin said. A second MDD study, the company’s fourth Phase 3 trial of DT120, is underway and enrolling well, he added.

DT120 Filing and Treatment Plans

DT120 is a pharmaceutically optimized version of LSD formulated as an orally dissolving tablet. Karlin said Definium has engaged with the FDA throughout development but will not publicly guide on regulatory discussions until it is certain the company and agency are aligned.

The ongoing MDD study includes a 50-microgram control arm alongside placebo and a 100-microgram DT120 arm. Karlin said the lower-dose arm is intended to make it harder for participants to identify their treatment allocation, addressing questions about whether knowing they received the drug could influence reported results.

Definium is also conducting nine-month open-label extensions of the studies, during which participants can receive up to four additional doses. Karlin said the extensions are not necessary for the primary safety and efficacy claims but provide additional information about treatment in a less constrained setting. The company also plans to start a study in post-traumatic stress disorder next year, he said.

Karlin said Definium expects patients to return for another DT120 treatment when symptoms worsen, rather than receive the drug preventively. He described treatment as a full-day intervention requiring human observers and said the company expects to make arguments to the FDA about labeling and risk-management requirements based on data collected during its studies.

Early Autism Drug Data

Definium also recently reported a positive early-signals-of-efficacy study for DT402, its second molecule in clinical development. The drug is the R enantiomer of MDMA and is being developed for autism spectrum disorder, including potential daily use.

Karlin said the early open-label study showed a consistent effect in all five participants, with effects rising and falling alongside drug exposure. The study could have enrolled up to 20 people, but the initial results gave the company confidence to continue development, he said.

He cautioned that the study was not sufficient to seek regulatory approval. The transcript did not include numerical efficacy or safety results.

The early studies have enrolled people with preserved language skills, allowing them to report their internal states, Karlin said. Definium hopes to study people with more profound impairments as development progresses and will work with regulators on how best to measure functioning in people with autism.

Asked about potential safety concerns, Karlin identified cardiac valve toxicity as a concern associated with MDMA generally, while describing the evidence linking it to the mixed form of MDMA as uncertain. He said Definium is conducting toxicology studies and expects to release further DT402 study-design concepts, without providing a timetable.

About Definium Therapeutics (NASDAQ:DFTX)

Definium Therapeutics, Inc., a clinical stage biopharmaceutical company, develops novel products to treat brain health disorders. The company’s lead product candidates include MM120, which is in phase 3 for the treatment of generalized anxiety disorder and attention deficit hyperactivity disorder; and DT402, a R-enantiomer of 3,4-methylenedioxymethamphetamine, which is in phase 2a clinical trials for the treatment of core symptoms of autism spectrum disorder. The company was formerly known as Mind Medicine (MindMed) Inc. and changed its name to Definium Therapeutics, Inc. in January 2026.