• Male and female subjects ≥4 and ≤12 years of age at the time of informed consent/assent.

• Females of childbearing potential who are not pregnant and not nursing.

• Females of childbearing potential who agree to practice a clinically accepted method of contraception during the study and for at least 1 month prior to study dosing and 1 month following completion of the study. Acceptable contraceptive methods include abstinence, oral contraception, surgical sterilization (bilateral tubal ligation, bilateral oophorectomy, or hysterectomy), intrauterine device, or diaphragm in addition to spermicidal foam and condom on male partner, or systemic contraception (eg, levonorgestrel-releasing implant).

• Diagnosis of ADHD (any type: combined, predominately hyperactive impulsive type or predominately inattentive type) by a psychiatrist, psychologist, pediatrician, or licensed allied healthcare professional using the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and confirmed by administration of a structured diagnostic interview using the Kiddie-Schedule for Affective Disorders and Schizophrenia for School Age Children-Present and Lifetime DSM-5 version (K-SADS-PL).

• Subjects who have received, or are receiving treatment with medication (amphetamine, methylphenidate, or non-stimulant) for ADHD must be willing to undergo a washout period of a minimum of 3 days or 5 half-lives (whichever is longer) prior to study drug administration. The washout period for prohibited concomitant medications will be at least 5 half-lives or 3 days, whichever is longer.

• If subjects are currently off treatment, this must be for any reason other than noncompliance, nonresponse, or intolerance to side effects.

• Ratings on the attention deficit/hyperactivity disorder-Rating Scale, version 5 (ADHD RS-5) when the subject is not receiving treatment for ADHD must be ≥90th percentile normative value for sex and age in at least 1 of the categories: total score, inattentive subscale, or hyperactive/impulse subscale.

• Dissatisfied with his or her current pharmacological therapy for treatment of ADHD or not currently receiving pharmacological therapy for ADHD for any reason other than nonresponse, noncompliance, or tolerability issues with stimulants. Newly diagnosed and treatment naïve subjects may be included at the discretion of the investigator.

• Must be functioning at an age-appropriate level intellectually as determined by an intelligence quotient (IQ) of ≥80 on a documented IQ assessment such as the Wechsler Abbreviated Scale of Intelligence II (WASI-II) vocabulary and matrix reasoning components, or the Kaufman Brief Intelligence Test, Second Edition (KBIT-2)

• Parent(s)/legal guardian(s) must have the ability to read and understand the language in which the informed consent is written and are mentally and physically competent to provide written informed consent for their child.

• Written or verbal assent from the subject (as applicable).

• Subject and parent(s)/legal guardian/caregiver are willing and able to comply with all the protocol requirements and parent(s)/legal guardian/caregiver must be able to provide transportation for the subject to and from the clinic visits.