Safety, Tolerability, and Pharmacokinetics of Multiple Rising Doses of TAK-137 in Adults With Attention-Deficit/Hyperactivity Disorder.

Inclusion Criteria: 1. Is a male or female adult who is 18 to 55 years of age, inclusive. 2. Weighs at least 45 kg and has a body mass index (BMI) between 18 and 30.0 kg/m\^2, inclusive at Screening. 3. Has a documented diagnosis of attention-deficit/hyperactivity disorder (ADHD) for a minimum of 1 year. 4. Is willing to discontinue all medications to treat adult ADHD (eg, stimulants, antidepressants) and all other medications and dietary products as specified in the protocol, from Day -7 until Follow-up phone call (Day 14). Exclusion Criteria: 1. Has received any investigational compound within 30 days prior to the first dose of study medication. 2. Has uncontrolled, clinically significant neurologic (including mildly abnormal or significantly abnormal EEG at screening), cardiovascular, pulmonary, hepatic, renal, metabolic, gastrointestinal, urologic, immunologic, endocrine disease, or psychiatric disorder (other than ADHD), or other abnormality, which may impact the ability of the participant to participate or potentially confound the study results. 3. Has previously had a seizure or convulsion (lifetime), including absence seizure and febrile convulsion. 4. Has a positive urine drug result for drugs of abuse other than amphetamines or other medications to treat ADHD or positive result for alcohol at Screening or Check-in (Day -1). 5. Has taken any excluded medication, supplements, or food products listed in the Excluded Medications and Dietary Products. 6. Is pregnant or lactating or intending to become pregnant before, during, or within 12 weeks after participating in this study; or intending to donate ova during such time period. 7. Has used nicotine-containing products (including but not limited to cigarettes, pipes, cigars, chewing tobacco, nicotine patch or nicotine gum) within 28 days prior to Check-in (Day -1).