A Trial Evaluating the Long-term Safety and Tolerability of Centanafadine Sustained-release Tablets in Adults With Attention-Deficit/Hyperactivity Disorder

This open-label study will assess the overall safety and tolerability of 400 mg total daily
dose centanafadine sustained-release tablets in subjects, over the course of approximately 52
weeks. This study will accept rollover subjects from both the 405-201-00013 and 405-201-00014
trials. For individuals that did not participate in one of the studies mentioned above, they
will be able to enroll if they meet the inclusion criteria as outlined below.

De Novo Subjects

Inclusion Criteria:

- De novo subjects must meet the Diagnostic and Statistical Manual of Mental Disorders,
Fifth Edition (DSM-5) criteria for ADHD (including predominantly inattentive
presentation, hyperactive presentation, or combined presentation) as confirmed by the
Adult ADHD Clinical Diagnostic Scale (ACDS) Version 1.2. To confirm that ADHD is the
primary diagnosis, the Mini International Neuropsychiatric Interview (MINI) will be
used to identify and exclude other psychiatric conditions which would preclude
enrollment.

- Subjects are 18 to 55 years of age, inclusive, at the time of consent.

- Subjects have BMI of 18 to 40, inclusive

- Subjects are willing to discontinue all prohibited psychotropic medications starting
from the time of signing the informed consent and up to the 10-day safety follow-up
period.

Exclusion Criteria:

- Subject has a DSM-5 diagnosis of Other Specified or Unspecified
Attention-Deficit/Hyperactivity Disorder as confirmed by ACDS Version 1.2.

- Subject has a current comorbid psychiatric disorder that is either controlled with
medications prohibited in this trial or is uncontrolled and associated with
significant symptoms, including but not limited to: a current major depressive episode
(per DSM-5 criteria), current symptoms (past 90 days) meeting the DSM-5 criteria for a
diagnosis of generalized anxiety disorder, obsessive compulsive disorder, panic
disorder, or posttraumatic stress disorder, as established by the MINI. NOTE: Subjects
with mild mood or anxiety symptoms that do not meet criteria for diagnosis, who do not
require treatment based on the Investigator's assessment, and do not confound efficacy
or safety assessments in the opinion of the examining Investigator, may be included.

- Subjects that have a positive alcohol test (via breathalyzer or blood), a positive
drug screen for cocaine, or other illicit drugs (excluding marijuana). Subjects with a
positive drug screen for confirmed prescription medications at baseline will not be
permitted to continue participation in Trial 405-201-00015. NOTE: Subjects that tested
positive for marijuana may be permitted to be enrolled if they have no evidence of a
substance use disorder, and if they agree to refrain from use for the duration of the
trial. Allowance for subjects testing positive for marijuana at screening require
explicit approval from the medical monitor.

Rollover Subjects

Inclusion Criteria:

- Subjects who completed the double-blind treatment period and 7-day follow-up after
last dose of investigational medicinal product (IMP) in double-blind trials and who,
in the opinion of the investigator, could potentially benefit from centanafadine for
ADHD.

Exclusion Criteria:

- Subjects who, during the double-blind phase 3 trial experienced, in the opinion of the
investigator, poor tolerability to trial medication or whose safety assessments
resulted in new concerns that would suggest the subject may not be appropriate for a
52-week treatment with trial medication.

- Subjects who have re-initiated any therapy for adult ADHD during the 7-day follow-up
period after the final treatment visit of the double-blind phase 3 trial.

- Subjects that have a positive alcohol test (via breathalyzer or blood), a positive
drug screen for cocaine, or other illicit drugs (excluding marijuana). Subjects with a
positive drug screen for confirmed prescription medications at baseline will not be
permitted to continue participation in Trial 405-201-00015. NOTE: Subjects that test
positive for marijuana may not be permitted to rollover into the open label study, and
must agree to refrain from use for the duration of the open label trial. Allowance for
subjects testing positive for marijuana at time of rollover requires explicit approval
from the medical monitor.