DT402 · program

DT402 for Autism spectrum disorder

Phase 2RecruitingDefinium Therapeutics, Inc. (DFTX)

Phase 2a single-dose, open-label study of DT402 (200 mg) in adults with autism spectrum disorder, assessing early signals of efficacy on core socialization and communication symptoms plus pharmacodynamics and functional biomarkers (NCT07303907; n=20, ages 18-65). Initiated 4Q 2025 following a completed Phase 1 single-ascending-dose study in healthy volunteers (no dose-limiting safety issues reported at doses up to ~255 mg per company commentary). This is Definium's lead and only ASD indication for DT402.

Data current as of

Development timeline

Phase 2Dec 2025 – Dec 2026
  1. UpcomingInitial Phase 2a data for DT402 in autism spectrum disorder anticipated in 2026↗
  2. Phase 2a ASD study (NCT07303907) start date 2025-12-03; overall status RECRUITING. Company reported the trial was initiated in 4Q 2025.
Phase 1Jan 2025
  1. Single-ascending-dose Phase 1 study of DT402 in healthy adult volunteers completed; characterized safety, tolerability, PK and PD. No dose-limiting safety issues reported at doses up to ~255 mg (company commentary). Exact completion date not precisely disclosed in reviewed sources; anchored to 2025 with approximate day precision.↗

Readouts

  • 2026AnticipatedTopline dataNCT07303907

    Initial Phase 2a data for DT402 in autism spectrum disorder anticipated in 2026 ↗

Clinical trials in Autism spectrum disorder

NCT07303907Phase 2Recruitingn=20

An Open-label Study Evaluating DT402 in Adults With Autism Spectrum Disorder

Started Dec 2025· Primary completion Aug 2027· 📍 1 site across 1 country (United States)

Formulations

FormulationRouteRegimenPharmacokinetics
DT402 oral (single dose)
200 mg single dose (Phase 2a, adults with ASD)
OralSingle dose—

Mechanism of action (compound-wide)

DT402 is the R-enantiomer of MDMA, a monoamine-releasing entactogen. It acts primarily as a serotonin releaser at the serotonin transporter (SERT/SLC6A4), evoking transporter-mediated efflux of serotonin, with comparatively weak dopamine-releasing activity (~11-fold less potent at releasing dopamine than serotonin). This serotonin-biased, dopamine-sparing profile (versus the more balanced/dopaminergic S-MDMA and racemic MDMA) is the rationale for retaining pro-social effects with reduced stimulant- and dopamine-related liabilities. R-MDMA is also a weak (low-efficacy) partial agonist at the serotonin 5-HT2A receptor.

TargetActionAffinity
SERTprimarySLC6A4ReleaserEC50 340 nMⓘ
5-HT2AHTR2APartial agonistEC50 3100 nMⓘ
DATSLC6A3ReleaserEC50 3700 nMⓘ

← Full DT402 compound page (identity, identifiers, all indications)

Sources

  1. (R)-MDMA — Wikipedia
  2. A Phase 2A Trial of DT402 for Autism Spectrum Disorder (200 mg single dose) — ClinicalTrials.gov
  3. Definium Therapeutics Reports Full-Year 2025 Financial Results and Business Updates — Definium Therapeutics / BioSpace