This is a multicenter, open-label study to evaluate the efficacy and safety of a daily single oral dose of tasimelteon in treating sleep disturbances in pediatric and adult participants with ASD.

Inclusion Criteria:

• Ability and acceptance to provide written informed consent of the participant or legal guardian (and assent as required).
• A confirmed clinical diagnosis of Autism Spectrum Disorder (ASD) and a recent history of sleep disturbances.
• The sleep disturbance must not be a result of another diagnosable disorder or medication.
• Male or female between 2 and 65 years of age, inclusive.
• Willing and able to comply with study requirements and restrictions.

Exclusion Criteria:

• Inability to dose daily with tasimelteon or previous intolerance to tasimelteon.
• Indication of impaired liver function.
• Evidence of increased risk of self-harm.
• Pregnant or lactating females.
• A positive test for drugs of abuse.
• Other diagnosable causes of sleep disorders or use of medications that may cause sedation or stimulation.