The investigator-administered CAARS-O:SV consists of 18 items based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). It includes a 9-item inattentive symptom subscale and a 9-item hyperactive and impulsive symptoms subscale. Each item is rated on a scale of 0 to 3 where 0=not at all, never; 1=just a little, once a while; 2=pretty much, often; and 3=very much, very frequently. The score for each subscale can range from 0 to 27. The total score is the sum of individual scores and can range from 0 to 54. Higher scores indicate worsening of symptoms. A negative change from Baseline indicates improvement.

Full Analysis Set (FAS) included all randomized participants who took at least one dose of IMP and had a Baseline and at least one post randomization evaluation for the CAARS-O:SV ADHD Symptoms total score (18-items). Number analyzed is the number of participants with data available for analysis at the given time point.

The investigator-administered CAARS-O:SV consists of 18 items based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria. It includes a 9-item inattentive symptom subscale and a 9- item hyperactive and impulsive symptoms subscale. Each item is rated on a scale of 0 to 3 where 0=not at all, never; 1=just a little, once a while; 2=pretty much, often; and 3=very much, very frequently. The score for each subscale can range from 0 to 27. The total score is the sum of individual scores and can range from 0 to 54. Higher scores indicate worsening of symptoms. A negative change from Baseline indicates improvement.

The AISRS consists of 18-items derived from DSM-IV criteria for ADHD symptoms. The AISRS total score is the sum of the 9-item inattentive symptoms subscale and 9-item hyperactive and impulsive symptoms subscale. Each item is scored as follows: 0=none, 1=mild, 2=moderate, and 3=severe. The score for each subscale can range from 0 to 27. The total score can range from 0 to 54. A negative change from Baseline indicates improvement.

The CGI-S evaluates the severity of individual symptoms and treatment response in participants with mental disorders. It is a 7-point scale that that requires the clinician to rate the severity of the participant's illness at the time of assessment as 0=not assessed, 1=normal, not at all ill, 2=borderline mentally ill, 3=mildly ill, 4=moderately ill, 5=markedly ill, 6=severely ill, 7=among the most extremely ill participants. The score 0=not assessed was set to missing. A negative change from Baseline indicates improvement.

The CGI-I is a 7-point scale that requires the clinician to assess how much the participant's illness has improved or worsened relative to a Baseline state at the beginning of the intervention and rated as: 0=not assessed, 1=very much improved, 2=much improved, 3=minimally improved, 4=no change, 5=minimally worse, 6=much worse, 7=very much worse. The score of 0 =not assessed was set to missing. Lower scores indicate improvement.

The CAARS-S:SV comprises of 30 items to measure symptoms for ADHD in adults but was limited to the 18 DSM-5 criteria relevant items for this trial. The 18-item ADHD Symptoms total score is the sum of the 9-item inattentive symptoms subscale and the 9-item hyperactive and impulsive symptoms subscale. Each item is rated on a scale of 0 to 3 where 0=not at all, never; 1=just a little, once a while; 2=pretty much, often; and 3=very much, very frequently. The score for each subscale can range from 0 to 27. Total score can range from 0 to 54. A negative change from Baseline indicates improvement.

The AAQoL is a validated, 29-item instrument for measuring the impact of ADHD symptoms on quality of life. The scale assesses 4 distinct functional domains based on the following subscales: life productivity (11 items), psychological health (6 items), life outlook (7 items), and relationships (5 items). Scores for individual items range from 1=never/not at all to 5=extremely/very often. Total and subscale scores were computed by (1) reversing scores for all items except the seven items in the Life Outlook subscale; (2) transforming all item scores to a 0-100 point scale (1=0; 2=25; 3=50; 4=75; 5=100); and (3) summing item scores and dividing by the item count to generate subscale and total scores. Higher scores indicate a greater impact.

The DEQ was used to assess the potential for abuse of OPC-64005. It is a 5-item questionnaire completed by the participant that includes the following questions: 1. Do you feel a drug effect right now? 2. Are you high right now? 3. Do you dislike any of the effects you are feeling right now? 4. Do you like any of the effects you are feeling right now? 5. would you like more of the drug you took, right now? Each item is rated on a 100-point scale of 1 (not at all) to 100 (extremely). 100 represents the highest score for that subjective state, and the higher the score, the worse the outcome.