A Study to Test the Effects of Centanafadine in Adults With Attention-deficit/Hyperactivity Disorder and Emotional Dysregulation

Inclusion Criteria 1. Primary diagnosis of ADHD per the Adult ADHD Clinical Diagnostic Scale (ACDS). 2. Adult ADHD Investigator Symptom Rating Scale (AISRS) total score of ≥ 28 at baseline. 3. Symptoms of ED as determined by the WRAADDS-ED subscale score ≥ 7 at baseline. 4. CGI-S-ADHD rating ≥ 4 (at least moderate severity) at baseline. Exclusion Criteria 1. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for a lifetime diagnosis of bipolar and related disorders, schizophrenia spectrum and other psychotic disorders, borderline and antisocial personality disorders, neurocognitive disorders, autism spectrum disorder, or intellectual disability. 2. DSM-5 criteria for a current diagnosis of major depressive disorder, post-traumatic stress disorder, any substance use disorder, untreated/unstable obstructive sleep apnea, eating disorders, or obsessive compulsive disorder. 3. Any other current DSM-5 comorbid psychiatric disorder identified by the Mini International Neuropsychiatric Interview (MINI) or any medical condition that, in the judgment of the investigator, could be expected to require treatment with medications prohibited in this trial that cannot be safely discontinued with completion of an appropriate washout, could confound efficacy or safety assessments, or be the primary driver of ED. 4. Presence of an unstable or uncontrolled medical condition that, in the opinion of the investigator, could pose a safety risk to the participant or could manifest with psychiatric symptoms (eg, thyroid disease). 5. In the clinical opinion of the investigator, the participant has not derived significant therapeutic benefit from 2 or more ADHD therapies of 2 different classes (eg, amphetamine and methylphenidate, or amphetamine and atomoxetine) given with an acceptable dose and duration during adulthood (aged 18 years or older). 6. Current use of prohibited psychotropic medications that cannot be discontinued within 7 to 28 days prior to enrollment. 7. Any disorder that is the primary focus of treatment other than ADHD. 8. Evidence of current substance use disorder or history in the past 12 months. 9. History of any prior exposure to centanafadine. 10. Participated in other clinical trials involving investigational drugs within 180 days prior to screening or participated in more than 2 interventional clinical trials involving investigational drugs within the past year. 11. Have an allergy to the IMP or any component of the IMP. Note: Other protocol-specified inclusion/exclusion criteria may apply.