This Phase 1 study is designed to evaluate the safety and tolerability of midomafetamine in healthy adult participants. The study will also assess how the drug is processed in the body and characterize its effects following administration at two dose levels, including evaluation of cardiac safety using electrocardiographic assessments.

This is a single-center, open-label study in which participants will be enrolled into one of two cohorts receiving either a therapeutic dose or a supratherapeutic dose of midomafetamine. Participants will receive study drug in a split dose administration (an initial dose followed by an additional dose 1.5 hours later) and will undergo clinical assessments, laboratory testing, electrocardiographic monitoring, and monitoring for adverse events.

Information collected from this study will be used to support the ongoing clinical development of midomafetamine.

This Phase 1 study is a dedicated safety investigation conducted in healthy adult participants to further characterize the safety and tolerability of midomafetamine under controlled dosing conditions. Participants will receive a split dose administration of midomafetamine (an initial dose of study drug followed by an additional dose 1.5 hours later) in sequential dose cohorts intended to achieve therapeutic and supratherapeutic systemic exposure.

Safety assessments include monitoring of adverse events, clinical laboratory tests, vital signs, and electrocardiographic measurements. Electrocardiographic data, including assessment of corrected QT interval, will be collected to support evaluation of cardiac safety in relation to exposure.

Because midomafetamine produces acute psychoactive effects during the dosing period, pharmacodynamic assessments-including subjective effects-will be collected to support interpretation of safety and tolerability findings. Pharmacokinetic assessments will also be performed to characterize systemic exposure.

This study is not designed to evaluate efficacy or treatment effectiveness for any disease or condition. Information collected from this study will be used to support the ongoing clinical development of midomafetamine.

Inclusion Criteria:

• Healthy adult participants, 18 to 55 years of age
• Medically healthy as determined by medical history, physical examination, clinical laboratory testing, vital signs, and electrocardiogram
• Able and willing to comply with study procedures

Exclusion Criteria:

• History of clinically significant cardiovascular, neurological, or psychiatric disease
• Current or recent substance use disorder, or positive drug or alcohol screen at screening
• Prior exposure to midomafetamine exceeding a protocol-defined limit intended to minimize confounding of safety assessments (no more than 10% of participants may have lifetime prior exposure)
• Any condition that, in the opinion of the investigator, would make participation unsafe or interfere with interpretation of study results

Individual participant data collected in this study will not be shared. Summary level results may be reported in publications and regulatory submissions, as applicable.