The phase 2 study will evaluate the safety, tolerability and efficacy of HLD100 at steady state (following up to 5 weeks of treatment) in children using an outpatient, single-center, open-label, flexible dose-escalation study design.

This dose-escalation study will examine HLD100 in 24 subjects.

The subjects (n=24) will be tested with HLD100 in ascending doses from 10mg up to 40mg.

This study will be divided into several phases: Screening, Active Treatment and Follow-Up. All visits have a 2 day window to allow for scheduling.

Inclusion Criteria:

• Subjects must have a diagnosis of ADHD as defined by DSM-5 criteria with confirmation using the Mini International Neuropsychiatric Interview for Children and Adolescents (MINI-KID).

• Subjects must demonstrate mild-to-moderate impairment of ADHD symptoms and function per the following at screening (V1) and/or baseline (V2):

  • ADHD-RS-IV score at or above the 90th percentile normalized for sex and age in total score and ≥24 at Baseline;
  • CGI-S score ≥4;

• Subject body weight must be ≥20 kg.

• Subject must be considered clinically appropriate for treatment with amphetamine and HLD100, including prior treatment experience with an amphetamine product, and ability to swallow treatment capsules.

Exclusion Criteria:

• History of, or current, medical condition or laboratory result which, in the opinion of the investigator, unfavorably alters the risk-benefit of study participation, may jeopardize subject safety, or may interfere with the satisfactory completion of the study and study-related procedures.
• Serious structural cardiac abnormalities, cardiomyopathy, serious heart rhythm abnormalities, or other cardiac problems that may place the subject at increased vulnerability to the sympathomimetic effects of a stimulant drug.
• History of seizure disorder (except febrile seizures prior to age 5 and with last occurrence at least 1 year prior to study participation), Tourette's disorder, or intellectual disability of minor severity or greater (DSM-5 criteria).
• History of psychosis, bipolar disorder, anorexia nervosa, bulimia, or suicide attempt. Current depression, anxiety, conduct/behavior disorder, substance use disorder, or other psychiatric condition which, in the investigator's opinion, may jeopardize subject safety or may interfere with the satisfactory completion of the study and study-related procedures.
• Active suicidal ideation as evidenced by an ideation score of 2 or greater on the C-SSRS.
• History of severe allergic reaction or intolerance to amphetamine.