A Trial of Centanafadine Efficacy and Safety in Adolescents With Attention- Deficit/Hyperactivity Disorder

Inclusion Criteria: * Males and females aged 13 to 17 years (inclusive) at the time of informed consent/assent. * A primary diagnosis of ADHD based on Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) diagnosis criteria as confirmed with the Mini International Neuropsychiatric Interview for Children and Adolescents (MINI-KID). * A minimum symptoms total raw score of ≥ 28 on the Attention-Deficit/Hyperactivity Disorder Rating Scale Version 5 (ADHD-RS-5) at baseline for all participants. * A score of 4 or higher on the Clinical Global Impression - Severity - Attention Deficit/Hyperactivity Disorder (CGI-S-ADHD) at baseline. Exclusion Criteria: * A comorbid diagnosis of: Tourette's Disorder, Generalized Anxiety Disorder severe enough to interfere with trial procedures, Panic Disorder, Conduct Disorder, Psychosis, Post-traumatic Stress Disorder, Bipolar Disorder, Autism Spectrum Disorder, Binge Eating Disorder, Anorexia, Bulimia, Oppositional Defiant Disorder severe enough to interfere with trial conduct (allowed if it is not the primary focus of treatment), Obsessive-Compulsive Disorder severe enough to interfere with trial conduct (allowed if it is not the primary focus of treatment), or major depressive disorder (MDD) with current major depressive episode. * Participants who are breast-feeding and/or have a positive pregnancy test result prior to receiving investigational medicinal product (IMP). * A significant risk of committing suicide based on history and the investigator's clinical judgment, or routine psychiatric status examination, Current suicidal behavior, Imminent risk of injury to self, Active suicidal ideation. History of suicidal behavior (over the last 6 months). * Body mass index (BMI) ≥ 40 kg/m2 or ≤ 5th percentile for age and gender based on United States (US) Centers for Disease Control and Prevention (CDC) criteria. * Has initiated, changed, or discontinued receiving psychological interventions for ADHD within the 30 days before the screening visit, or is anticipated to start new treatment during the trial.