A Trial to Test the Effects of Other Drugs on SEP-380135 in Healthy Men and Women

A Phase 1, Open-label, Single-sequence Pharmacokinetic Trial to Assess the Effect of a Single Oral Dose of SEP-380135 on the Potential for Cytochrome P4502D6 Mediated Drug-drug Interactions in Healthy Adults

The purpose of this study is to assess the effect of cytochrome P450 isoenzyme 2D6 (CYP2D6) inhibition by quinidine on the pharmacokinetic (PK) parameters of a single dose SEP-380135 in healthy adult participants.

Study Overview

• Status: Completed
• Conditions: Schizophrenia
• Intervention / Treatment: Drug: SEP-380135; Drug: Quinidine Gluconate

• Study Type: Interventional
• Enrollment (Actual): 12
• Phase: Phase 1

Contacts and Locations

Study Locations

• United States
  • Kansas
    • Overland Park, Kansas, United States, 66212
      • Dr. Vince Clinical Research

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Male or female participants between 18 and 55 years of age (inclusive) at time of consent
2. Body mass index from 18.0 to 32.0 kilograms per square meter (kg/m^2) (inclusive).

3. In good health as determined by:

   1. Medical history
   2. Physical examination
   3. Vital signs
   4. Neurological examination
   5. Electrocardiogram
   6. Serum chemistry, lipid panel, thyroid panel, coagulation panel, urinalysis, hematology, and serology tests (from screening visit).
4. Willing to stay in the clinic for the required period (i.e., to be hospitalized for 10 days) and willing to be contacted for the safety follow-up telephone call.
5. Ability to provide written, informed consent prior to initiation of any trial-related procedures, and ability, in the opinion of the Principal Investigator, to comply with all the requirements of the trial.

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 previous 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, first-, second-, or third-degree atrioventricular block, myocardial infarction, New York Heart Association Class II-IV heart failure, cardiomyopathy, pulmonary congestion, cardiac arrhythmia, 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. In the opinion of the investigator, should not participate in the trial.

Note: Other protocol-specified inclusion/exclusion criteria may apply.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Non-Randomized
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: SEP-380135 + Quinidine Gluconate; Participants receive SEP-380135 alone on Day 1, followed by administration of quinidine gluconate beginning on Day 6. On Day 7, SEP-380135 is coadministered with quinidine gluconate. Quinidine gluconate dosing continues from Day 8 to Day 10.	Drug: SEP-380135; Oral capsules.; Drug: Quinidine Gluconate; Oral extended-release (ER) tablets.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Maximum Observed Concentration (Cmax) of SEP-380135 and its Metabolites	Up to Day 11
Area Under the Curve from Time Zero to Last Measurable Concentration (AUC0-t) of SEP-380135 and its Metabolites	Up to Day 11
Area Under the Curve from Time Zero to Infinity (AUCinfinity) of SEP-380135 and its Metabolites	Up to Day 11
Time to Maximum Concentration (Tmax) of SEP-380135 and its Metabolites	Up to Day 11

Secondary Outcome Measures

Outcome Measure	Time Frame
Number of Participants With Treatment Emergent Adverse Events (TEAEs)	Up to 2 months
Number of Participants With Potentially Clinically Significant Changes in Vital Signs	Up to 2 months
Number of Participants With Potentially Clinically Significant Changes in Electrocardiogram (ECG) Parameters	Up to 2 months
Number of Participants With Potentially Clinically Significant Changes in Physical Examinations	Up to 2 months
Number of Participants With Potentially Clinically Significant Changes in Neurological Examinations	Up to 2 months
Number of Participants With Potentially Clinically Significant Changes in Clinical Laboratory Test Parameters	Up to 2 months
Number of Participants With Incidence of Suicidal Behavior, Suicidal Ideation and Suicidality Using the Columbia-Suicide Severity Rating Scale (C-SSRS)	Up to 2 months

Collaborators and Investigators

• Sponsor: Otsuka Pharmaceutical Development & Commercialization, Inc.

Study record dates

Study Major Dates

• Study Start (Actual): March 7, 2025
• Primary Completion (Actual): May 3, 2025
• Study Completion (Actual): May 3, 2025

Study Registration Dates

• First Submitted: December 12, 2025
• First Submitted That Met QC Criteria: December 12, 2025
• First Posted (Estimated): December 26, 2025

Study Record Updates

• Last Update Posted (Actual): January 15, 2026
• Last Update Submitted That Met QC Criteria: January 13, 2026
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: Schizophrenia; Mental Health Conditions
• Additional Relevant MeSH Terms: Schizophrenia Spectrum and Other Psychotic Disorders; Mental Disorders; Schizophrenia; quinidine gluconate
• Other Study ID Numbers: 384-201-00004

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: 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.

Drug and device information, study documents

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