PART B: Efficacy and Safety of AEVI-001 in Children and Adolescents With ADHD and Without mGluR Mutations

Inclusion Criteria:

1. Subject and parent/legally authorized representative (LAR) can speak English fluently
and have provided written informed consent, and assent (as applicable) for this study.

2. Subject is 6 to 17 years of age (inclusive) at the time of consent/assent. The date of
signature of the informed consent/assent is defined as the beginning of the Screening
Period. This inclusion criterion will only be assessed at the Screening Visit (Visit
1).

3. Subject is male or non-pregnant, non-lactating female, who if of childbearing
potential agrees to comply with any applicable contraceptive requirements prior to
administration of investigational product (IP).

4. Subject meets Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition
(DSM-5) criteria for a primary diagnosis of ADHD based upon DSM 5 criteria.

5. Subject has a minimum score of ≥28 on the ADHD-RS-5 at the Baseline Visit (Visit 2).

6. Subject has been genotyped previously and has their identity confirmed (if required).

Exclusion Criteria:

1. Subject or parent/LAR is, in the opinion of the investigator, mentally or legally
incapacitated, has significant emotional problems at the time of the Screening Visit
(Visit 1) which could interfere with the conduct of study evaluations.

2. Subject has a current, controlled or uncontrolled, co-morbid major psychiatric
diagnosis (aside from ADHD), including an anxiety disorder, major depression, bipolar
disease, schizophrenia (or any psychotic disorder), and moderate or severe
intellectual disability. Mild anxiety and/or depressive symptoms that do not meet
diagnostic criteria for an anxiety disorder or major depression and/or do not require
treatment are not exclusionary.

3. Subject has autism spectrum disorder to include a DSM-IV diagnosis of autistic
disorder, Asperger's disorder, or pervasive developmental disorder.

4. Subject is currently taking any medication that might confound the results of safety
assessments conducted in the study.

5. Subject has a known history of cardiovascular disease, advanced arteriosclerosis,
structural cardiac abnormality, cardiomyopathy, serious heart rhythm abnormalities,
coronary artery disease, cardiac conduction problems, exercise-related cardiac events
including syncope and pre-syncope, or other serious cardiac problems.

6. Subject has any clinically significant abnormality on 12-lead ECG performed at the
Screening Visit (Visit 1) and/or the Baseline Visit (Visit 2) such as serious
arrhythmia, cardiac conduction problems, or other abnormalities deemed to be a
potential safety issue.