A Trial of Centanafadine Long-term Safety in Children and Adolescents with Attention-deficit/Hyperactivity Disorder (ADHD)

Rollover subjects from double-blind parent trials inclusion criteria:

• Subjects who completed the 6-week double-blind treatment period and the 7 (+2) dayfollow-up in a double-blind parent trial and who, in the opinion of theinvestigator, could potentially benefit from centanafadine QD XR for ADHD

De novo subjects inclusion criteria:

• Males and females aged 4 to 17 years (inclusive) at the time of informedconsent/assent.

• A primary diagnosis of ADHD based on DSM-5 diagnosis criteria as confirmed with theMINI KID.

• A minimum symptoms total raw score of ≥ 28 on the ADHD-RS-5 at baseline.

• A score of 4 or higher on the CGI-S-ADHD at baseline.

• Subjects aged 4 or 5 years only; has failed adequate psychotherapy or in theinvestigator's opinion, is severe enough to require pharmacotherapy in the absenceof prior psychotherapy.

Rollover subjects from double-blind parent trials exclusion criteria:

• Subjects who, during the double-blind parent trials, experienced, in the opinion ofthe investigator, poor tolerability to IMP or whose safety assessments resulted innew concerns that would suggest the subject may not be appropriate for a 52-weektreatment with IMP.

De novo subjects exclusion criteria:

• A comorbid diagnosis of: Tourette's Disorder, Generalized Anxiety Disorder that issevere enough to interfere with trial procedures, Panic Disorder, Conduct Disorder,Psychosis, Post-traumatic Stress Disorder, Bipolar Disorder, Autism SpectrumDisorder, Binge Eating Disorder (adolescents only), Anorexia (adolescents only),Bulimia (adolescents only), Oppositional Defiant Disorder that is severe enough tointerfere with trial conduct (allowed if it is not the primary focus of treatment),Obsessive-Compulsive Disorder that is severe enough to interfere with trial conduct (allowed if it is not the primary focus of treatment), MDD with current majordepressive episode, or has required treatment within the 3 months prior toscreening, or in investigator's opinion, MDD may worsen or could be expected torequire treatment during the course of this trial.

• Subjects who are breast-feeding and/or have a positive pregnancy test result priorto receiving IMP.

• A significant risk of committing suicide based on history and the investigator'sclinical judgment, or routine psychiatric status examination, current suicidalbehavior, Imminent risk of injury to self, active suicidal ideation, history ofsuicidal behavior (over the last 6 months).

• Body weight < 13 kg

• BMI ≥ 40 kg/m2

• Has initiated, changed, or discontinued receiving psychological interventions forADHD within the 30 days before the screening visit, or are anticipated to start newtreatment during the trial.