The purpose of the present trial is to obtain information on the absorption, distribution, metabolism, excretion and pharmacokinetics (PK) of 14C-SEP-380135 and its metabolites following a single oral dose.

Inclusion Criteria:

1. Body mass index (BMI) between 18.0 and 32.0 kilograms per square meter (kg/m²).

2. In good overall health, based on:

   1. Medical history
   2. Physical examination
   3. Neurological examination
   4. Vital signs
   5. Electrocardiogram (ECG)
   6. Blood and urine tests (serum chemistry, hematology, urinalysis, serology)

3. Regular daily bowel movements (at least one per day) for 30 days before Day -2.

4. Ability to provide written informed consent and follow all study instructions.

5. Has a stable living situation at screening and agrees to return to a similar living arrangement after the in-clinic stay.

Exclusion Criteria:

1. Have taken an investigational drug within 30 days or 5 half-lives, if known, (whichever is longer) prior to screening.
2. Have had prior exposure to SEP-380135.
3. Are currently participating in another clinical trial.
4. Attempted suicide within 12 months prior to screening.
5. A history of sick sinus syndrome, any degree of atrioventricular block, Heart attack (myocardial infarction), heart failure (NYHA Class II-IV), cardiomyopathy, pulmonary congestion, cardiac arrhythmias, prolonged QT interval, congenital long QT syndrome, family history of long QT, or moderate to severe hypokalemia. A participant with non-clinically significant ECG abnormalities at screening and check-in requires approval from the medical monitor and the sponsor's physician.
6. Are predicted poor metabolizer CYP2D6 phenotypes. Note: Other protocol-specified inclusion/exclusion criteria may apply.

Anonymized individual participant data (IPD) that underlie the results of this study will be shared with researchers to achieve aims pre-specified in a methodologically sound research proposal. Small studies with less than 25 participants are excluded from data sharing.