This study will look at how centanafadine works when taken together with stimulant medicines in healthy adults, and whether combining them affects how the body responds.

This is a single dose crossover study. Participants in each arm will receive 3 treatments in a 3 -sequence, 3-period, crossover design. In each arm, participants will be randomized to 1 of 3 treatment sequences: Sequence 1: ABC, Sequence 2: BCA, or Sequence 3: CAB.

Here's what each treatment incudes:

• Treatment A - centanafadine alone in both Arms 1 and 2.
• Treatment B - methylphenidate alone in Arm 1 and lisdexamfetamine alone in Arm 2.
• Treatment C - centanafadine combined with methylphenidate in Arm 1, and centanafadine combined with lisdexamfetamine in Arm 2.

The duration of trial participation for each participant will be approximately 44 days, and the overall trial duration is expected to be approximately 3 months.

Inclusion Criteria:

• Body mass index (BMI) between 18.0 to 32.0 kilogram per square meter (kg/m2).

• Must be in good health, based on:

  • Medical history
  • Physical examination
  • Heart test (Electrocardiogram [ECG])
  • Lab tests (blood, urine and other routine checks)

• Willing to stay in the clinic for the required time and agree to a follow-up phone call for safety.

• Able to sign informed consent and, in the investigator's opinion, follow all trial requirements.

Exclusion Criteria:

• History of drug and/or alcohol abuse in past 2 years.
• History of or current hepatitis or acquired immune deficiency syndrome (AIDS) or carriers of hepatitis B surface antigen (HBsAg) and/or anti-hepatitis C virus (HCV), or human immunodeficiency virus (HIV) antibodies.
• Known drug allergy or hypersensitivity.
• Any history of significant bleeding problems.
• Difficulty donating blood in the past.
• Use of tobacco or exposure to second-hand smoke in the past 2 months, or high cotinine levels in blood/urine.
• Uncontrolled high blood pressure (BP) (systolic blood pressure [SBP] > 140 millimeters of mercury (mmHg) or diastolic blood pressure [DBP] > 90 mmHg) or symptomatic low blood pressure, or orthostatic hypotension (large BP drop when standing).
• History of unexplained fainting (syncope).
• Serious mental health disorders that could interfere with participation.

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.

Data will be available after marketing approval in global markets or beginning 1-3 years following article publication. There is no end date to the availability of the data.

Otsuka will share data on the Vivli data sharing platform which can be found here: https://vivli.org/ourmember/Otsuka/