Psychedelic · DT402
DT402
DT402 (formerly MM402; the R(-)-enantiomer of MDMA, also called R-MDMA / levomethylenedioxymethamphetamine) is an entactogen in development by Definium Therapeutics for the core social-communication symptoms of autism spectrum disorder. As a single enantiomer it is a serotonin releaser at the serotonin transporter (SERT) with substantially reduced dopaminergic stimulation relative to S-MDMA and racemic MDMA, intended to preserve pro-social effects while reducing stimulant- and dopamine-related adverse effects.
Also known as: DT402, MM402, R(-)-MDMA, R-MDMA, levomethylenedioxymethamphetamine, 81262-70-6
- Modality
- Psychedelic
- Chemical class
- Methylenedioxyphenethylamine, substituted amphetamine
- DEA schedule
- Schedule I
- Chemistry
- Single enantiomer
- Mechanism
- SERT releaser
- Highest phase
- Phase 2
- Lead indication
- Autism spectrum disorder
- Developer
- Definium Therapeutics, Inc. (DFTX)
- Trials
- 1 tracked · 1 recruiting · 1 sites
- Next catalyst
- 2026 — Topline data (Autism spectrum disorder)
Mechanism of action
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.
| Target | Action | Affinity |
|---|---|---|
| SERTprimarySLC6A4 | Releaser | EC50 340 nMⓘ |
| 5-HT2AHTR2A | Partial agonist | EC50 3100 nMⓘ |
| DATSLC6A3 | Releaser | EC50 3700 nMⓘ |
Formulations
| Formulation | Route | Regimen | Pharmacokinetics |
|---|---|---|---|
| DT402 oral (single dose) 200 mg single dose (Phase 2a, adults with ASD) | Oral | Single dose | — |
Development timeline
- Phase 2a ASD study (NCT07303907) start date 2025-12-03; overall status RECRUITING. Company reported the trial was initiated in 4Q 2025.
- 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.↗
DT402 for Autism spectrum disorder
Phase 2RecruitingAutism spectrum disorder indication →
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.
Readouts
- 2026AnticipatedTopline dataNCT07303907
Initial Phase 2a data for DT402 in autism spectrum disorder anticipated in 2026 ↗
Clinical trials
NCT07303907Phase 2Recruitingn=20
An Open-label Study Evaluating DT402 in Adults With Autism Spectrum Disorder
Identifiers
- ChEMBL CHEMBL382757
- PubChem CID 667458
- FDA UNII 3947754WXW
Sources
- (R)-MDMA — Wikipedia
- A Phase 2A Trial of DT402 for Autism Spectrum Disorder (200 mg single dose) — ClinicalTrials.gov
- Definium Therapeutics Reports Full-Year 2025 Financial Results and Business Updates — Definium Therapeutics / BioSpace