['attention deficit disorder with hyperactivity']
['nfc-1', 'placebo']

        Inclusion Criteria:

          -  Subject has ADHD as defined by the Diagnostic and Statistical Manual of Mental
             Disorders, 5th edition (DSM-5) and Version 5 of the Attention Deficit Hyperactivity
             Disorder Rating Scale (ADHD-RS-5) ≥ 28 at Baseline with or without conventional ADHD
             therapy.

          -  Subject has an intelligence quotient (IQ) > 79, based on the Wechsler Abbreviated
             Scale of Intelligence, second edition (WASI-II).

          -  Subject has been genotyped previously and determined to have disruptive mutations in
             genes within the glutamate receptor metabotropic (GRM)-network as determined by the
             presence of copy number variations (CNVs) (GRM biomarker-positive subjects). The
             confirmation of a subject's positive status will be provided by the sponsor.

          -  Subject is judged to be in general good health, other than having ADHD, based on
             medical history, physical examination, vital signs measurements, laboratory safety
             tests, and the Columbia Suicide Severity Rating Scale (C-SSRS) performed at the
             Screening Visit and/or prior to administration of investigational product (IP).

          -  Subject has no clinically significant abnormality on electrocardiogram (ECG) performed
             at the Screening Visit and/or prior to administration of IP such as serious
             arrhythmia, bradycardia, tachycardia, cardiac conduction problems, or other
             abnormalities deemed to be a potential safety issue.

          -  Parent/legal guardian and subject understand the study procedures and agree to the
             subject's participation in the study as indicated by parental/legal guardian signature
             on the subject informed consent form and subject signature on the assent form.

        Exclusion Criteria:

          -  Subjects with prior diagnosis of comorbid major psychiatric disorders (ie, aside from
             ADHD), including major depression, bipolar disease, schizophrenia, pervasive
             development disorder, and intellectual disability.

          -  Subject is currently taking a prohibited medication and/or is unwilling to wean off
             current ADHD medication to participate in the study

          -  Subject has a history of any illness that in the opinion of the study investigator
             might confound the results of the study or poses an additional risk to the subject by
             his or her participation in the study.

          -  Subject has a known history or presence of syncope, cardiac conduction problems (eg,
             clinically significant heart block), exercise-related cardiac events including syncope
             and pre-syncope, or clinically significant bradycardia.

          -  Subject has a history of stroke, chronic seizures, or major neurological disorder
             which, in the opinion of the investigator, would interfere with the subject's ability
             to participate and/or be evaluated in the study.
      