A Phase 2A Trial of DT402 for Autism Spectrum Disorder

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

A Phase 2A Trial of DT402 Open-Label Study in Adults with Autism Spectrum Disorder

Study Overview

• Status: Recruiting
• Conditions: Autism Spectrum Disorder; ASD
• Intervention / Treatment: Drug: DT402 (R-enantiomer of 3,4-methylenedioxymethamphetamine (MDMA))

Detailed Description

This study will enroll approximately twenty adults with Autism Spectrum Disorder (ASD) aged 18 to 65 years of age.

This is a single-center, open-label study to evaluate the effects after a single administration of DT402 to adults with ASD.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Definium Therapeutics Clinical Trials Information Requests; Phone Number: 1-332-282-0479; Email: clinicaltrials@definiumtx.com

Study Locations

• United States
  • New York
    • New York, New York, United States, 10021
      • Recruiting
      • Spectrum Neuroscience and Treatment Institute
      • Contact: Casara Ferretti; Phone Number: 1-914-315-4236; Email: cferretti@spectrumneuroscience.org

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Diagnosis of ASD per records as confirmed by standard semi-structured interview for Autism diagnosis (eg, Autism Diagnostic Observation Schedule-Second Edition)
2. Male or Female aged 18 to 65
3. Presents with clinically significant deficits in socialization and communication as determined by Social Responsiveness Scales (SRS-2) ≥66

Exclusion Criteria:

1. Has uncorrected abnormalities in eye movement, alignment, or acuity or atypical eye features that could interfere with eye tracking
2. First degree relative with or lifetime history of a psychotic disorder or bipolar disorder
3. Current diagnosis of alcohol or substance use disorder (excluding nicotine and caffeine)
4. Any clinically significant unstable illness

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: 200 mg DT402; A psychoactive substance that mediates effects mainly through a release of the monoaminergic neurotransmitters, with the greatest effect on 5-HT, followed by NE and DA	Drug: DT402 (R-enantiomer of 3,4-methylenedioxymethamphetamine (MDMA)); A psychoactive substance that mediates effects mainly through a release of the monoaminergic neurotransmitters, with the greatest effect on 5-HT, followed by NE and DA; Other Names: MDMA; R-MDMA; MM402

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change from Baseline in 11-point Numerical Rating Scale (NRS) scores	The NRS is an 11-point PRO scale used to measure the severity or intensity of effects from 0 (no effect) to 10 (high severity or intensity of effect). It consists of various items related to both positive and negative effects in the autism patient population.	Baseline, pre-dose and 2, 4, 6, 8, and 24 hours post-dose and day 15

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Subjective 5-question Drug Effects Questionnaire (DEQ) scores	The Drug Effects Questionnaire is used in studies to assess the participant's acute subjective effects after ingesting substances. It consists of 5 PRO items. The analog scale of responses ranges from "not at all" to "extremely." The score is determined by the distance between the left anchor point and the participant's mark on the line. Each item is scored separately.	1, 2, 4, 6, 8, and 24 hours post-dose
Pharmacokinetic Parameters (Cmax)	Maximum concentration (Cmax).	pre-dose and 1, 2, 4, 6, 8, and 24 hours post-dose
Pharmacokinetic Parameters (Tmax)	Time to maximum concentration (Tmax).	pre-dose and 1, 2, 4, 6, 8, and 24 hours post-dose
Pharmacokinetic Parameters (t1/2)	Time to maximum concentration half-life (t1/2).	pre-dose and 1, 2, 4, 6, 8, and 24 hours post-dose
Pharmacokinetic Parameters (AUC0-inf)	Area under the concentration curve from time 0 to infinity (AUC0-inf).	pre-dose and 1, 2, 4, 6, 8, and 24 hours post-dose
Pharmacokinetic Parameters (AUC0-24h)	Area under the concentration curve from time 0 to 24 hour (AUC0-24h).	pre-dose and 1, 2, 4, 6, 8, and 24 hours post-dose
Pharmacokinetic Plasma concentrations	Maximum Plasma Concentration [Cmax] of DT402 in the blood.	pre-dose and 1, 2, 4, 6, 8, and 24 hours post-dose

Collaborators and Investigators

• Sponsor: Definium Therapeutics US, Inc.

Study record dates

Study Major Dates

• Study Start (Actual): December 3, 2025
• Primary Completion (Estimated): August 1, 2027
• Study Completion (Estimated): August 1, 2027

Study Registration Dates

• First Submitted: December 22, 2025
• First Submitted That Met QC Criteria: December 23, 2025
• First Posted (Actual): December 26, 2025

Study Record Updates

• Last Update Posted (Actual): April 6, 2026
• Last Update Submitted That Met QC Criteria: March 31, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Mental Disorders; Neurodevelopmental Disorders; Child Development Disorders, Pervasive; Autism Spectrum Disorder; Organic Chemicals; Amines; Phenethylamines; Ethylamines; Amphetamines; N-Methyl-3,4-methylenedioxyamphetamine
• Other Study ID Numbers: MM402-105

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No