A Trial to Assess the Pharmacokinetics, Safety, and Tolerability of Centanafadine Capsules in Pediatric Subjects With Attention-deficit Hyperactivity Disorder

Key Inclusion Criteria: * Male or female subjects 4 to 12 years of age, inclusive, at the time of informed consent/assent. * A diagnosis of any ADHD subtype based on Diagnostic and Statistical Manual of Mental Disorders - 5th Edition (DSM-5) criteria and confirmed by the Mini International Neuropsychiatric Interview for Children and Adolescents (MINI-KID). Key Exclusion Criteria: * Subjects with a clinical presentation or history that is consistent with delirium, dementia, amnesia, or other cognitive disorders; subjects with psychiatric symptoms that are better accounted for by another general medical condition(s) or direct effect of a substance (medication, illicit drug use, etc); or subjects with a clinical presentation or history of psychotic symptoms. * Subjects with developmental disorders, such as autism spectrum disorder. * Subjects with a history of intellectual disability as determined by at least 1 of the following: intelligence quotient \< 70, or clinical evidence, or a social or school history that is suggestive of intellectual disability. * Subjects who currently have clinically significant neurological, dermatological, hepatic, renal, metabolic, hematological, immunological, cardiovascular, pulmonary, or gastrointestinal disorders such as any history of myocardial infarction, congestive heart failure, HIV seropositive status/ AIDS, or chronic hepatitis B or C. * Subjects who have history of clinically significant tachycardia or hypertension.