Open-Label Study of SPN-812 Administered With Psychostimulants in Children and Adolescents With ADHD

Inclusion Criteria

• Is male or female, 6 to ≤17 years and 9 months of age at screening.
• Parent(s)/legal guardian(s) is able to read and understand the Informed Consent Form (ICF).
• Written informed consent obtained by parent(s)/legal guardian(s) and informed assent obtained from the subject, if applicable.
• Subject and parent(s)/legal guardian(s) are willing and able to comply with all of the procedures and requirements defined in the protocol, including parents(s)/legal guardian(s) oversight of morning and evening dosing of the SPN-812 and recording a daily medication/dosing diary for psychostimulant and/or SPN-812 during the study.
• Has lived with the same parent(s)/legal guardian(s) at same residence for at least the last 6 months prior to screening.
• Has a primary diagnosis of ADHD (inattentive, hyperactive, or combined presentation) confirmed with the Mini International Neuropsychiatric Interview for Children and Adolescents (MINI-KID) at screening.
• Is currently on a single, stable psychostimulant regimen (see Inclusion Criterion 8 for definition) for treatment of ADHD with a partial, but inadequate efficacy response to at least 2 weeks of treatment with a psychostimulant (methylphenidate or amphetamine) prior to screening. An inadequate response is defined as an investigator-rated ADHD-RS-5 Total score ≥24 and a CGI-S score ≥3 (mildly ill or worse) at Screening and Baseline. Subjects taking additional medication for ADHD (e.g., nonstimulant) are excluded.
• Is currently and expecting to continue and remain on a stable psychostimulant regimen throughout the study. A stable stimulant regimen is defined as taking dose at least 5 days per week (morning), no significant change in dose or dosing frequency at least 2 weeks prior to baseline (Visit 2), and the investigator believes the subject's psychostimulant dose is optimized.
• Is functioning at an age-appropriate level intellectually, as judged by the Investigator.
• Is a child (6-11 years of age) with a body weight of at least 20 kg at screening or is an adolescent (12-17 years of age) with a body weight of at least 35 kg at screening.
• Has a resting (sitting) blood pressure (BP) and resting pulse rate measurement within the 95th percentile for age, sex, and height.
• Is considered medically healthy by the Investigator via assessment of physical examination, medical and psychiatric histories, clinical laboratory tests, vital signs, and electrocardiogram (ECG).
• Females of childbearing potential (FOCP) must be either sexually inactive (abstinent) or, if sexually active, must agree to use/practice one of the following acceptable, highly effective contraceptive methods beginning/during the screening period prior to the first dose of SM and throughout the study:
• Simultaneous use of male condom and intra-uterine contraceptive device placed during screening period prior to first dose of SM
• Surgically sterile male partner (e.g., vasectomized partner is sole partner)
• Barrier method: condom with spermicidal foam/gel/film/cream/suppository or occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/suppository
• Established use of oral, injected, or implanted hormonal methods of contraception

With approval by the Investigator, subjects' parents or legal guardians may select abstinence as a form of birth control if deemed more appropriate. For the purposes of this study, all females are considered to be of childbearing potential unless they are confirmed by the Investigator to be premenarchal, biologically sterile, or surgically sterile (e.g., hysterectomy with bilateral oophorectomy, tubal ligation).

• Adolescent males, if sexually active, must:
• Use 2 methods of contraception in combination if his female partner is of childbearing potential; this combination of contraceptive methods must be used from the Baseline Visit to ≥ 1 month after the last dose of SM, or
• Have been surgically sterilized prior to th