This is an open label 26 week extension study for subjects who completed SEP360-202.

This is an open-label, flexibly-dosed, 26 week extension study in children and adolescents with ADHD who have completed 6 weeks of double-blind treatment in the core study (SEP360 202). This study will evaluate the long-term safety and tolerability of dasotraline in this population.

Inclusion Criteria:

• At least one of the subject's parent/legal guardian must give written informed consent, including privacy authorization, prior to study participation. The subject will complete an informed assent prior to study participation.
• Subject and subject's parent/legal guardian are judged by the investigator to be willing and able to comply with the study procedures and visit schedules.
• Subject has completed all required assessments for Week 6 of the core study.
• Subject has not taken any medication other than the study drug for the purpose of controlling ADHD symptoms during the core study.
• Subject, if female, must not be pregnant or breastfeeding.
• Female subject: must be unable to become pregnant (eg, premenarchal, surgically sterile, etc);

-OR-

• practice true abstinence (consistent with lifestyle) and must agree to remain abstinent from signing informed consent/assent to at least 14 days after the last dose of study drug has been taken; -OR-
• is sexually active and willing to use a medically effective method of birth control from signing informed consent/assent to at least 14 days after the last dose of study drug has been taken.
• Male subject must be willing to remain sexually abstinent (consistent with lifestyle) or use an effective method of birth control, from signing informed consent/assent to at least 14 days after the last dose of study drug has been taken.
• Any subject whose weight is less than or equal to 21 kg at the OL Baseline visit should be discussed with the medical monitor prior to enrollment.
• Subject and subject's parent/legal guardian must be able to fully comprehend the informed consent/assent form (as applicable), understand all study procedures, and be able to communicate satisfactorily with the Investigator and study coordinator.

Exclusion Criteria:

• -Subject is considered by the investigator to be at imminent risk of suicide, injury to self or to others, or damage to property.
• Subject answers "yes" to "Suicidal Ideation" item 4 (active suicidal ideation with some intent to act, without specific plan) or item 5 (active suicidal ideation with specific plan and intent) for any lifetime history on the C SSRS Children's "Since Last Visit" assessment at OL Baseline.
• Subject has a clinically significant abnormality including physical examination, vital signs, ECG, or laboratory tests that the investigator in consultation with the medical monitor considers to be inappropriate to allow participation in the study.
• Subject has a positive urine drug screen (UDS) or breath alcohol test at OL Baseline.
• Subject or parents/legal guardian has commitments during the study that would interfere with attending study visits.
• Subject is at high risk of non-compliance in the investigator's opinion.

Open label