Pharmacokinetics of Tasimelteon in Subjects With Mild or Moderate Hepatic Impairment

Inclusion Criteria: All Subjects: * Ability and acceptance to provide written informed consent; * Men or women between 18 - 75 years, inclusive; * Subjects with Body Mass Index (BMI) of \>18 and \<35 kg/m2; * Women of child-bearing potential must be using an acceptable method of birth control; * Willing and able to comply with study requirements and restrictions; Subjects with mild or moderate hepatic impairment: * Stable hepatic impairment satisfying the criteria for Class A or B of the modified Child-Pugh classification documented by medical history; * Subjects with Moderate hepatic impairment must also have either liver cirrhosis or physical signs consistent with a clinical diagnosis of liver cirrhosis * Creatinine clearance greater than 50 mL/min Healthy matched controls: * Matched to subjects with hepatic impairment by gender, age, BMI, and smoking status * Good health as determined by past medical history, physical examination, electrocardiogram, laboratory tests, vital signs and urinalysis; Exclusion Criteria: * Smokers unable or unwilling to limit consumption; * Exposure to any investigational drug, including placebo, within 30 days of dosing; * Blood Donation or loss of 400 mL or more within two months prior to dosing; * Significant illness within the two weeks prior to dosing; * History of autonomic dysfunction; * History of acute or chronic bronchospastic disease, including asthma and chronic obstructive pulmonary disease, treated or not treated; * A known hypersensitivity to tasimelteon or drugs similar to tasimelteon including melatonin; * Pregnant or lactating females; * History of drug or alcohol abuse within the 12 months prior to screening * History of immunocompromise, including a positive HIV (ELISA and Western blot) test result; * Any surgical or medical condition which might significantly alter the absorption, distribution or excretion of any drug; * Clinically significant ECG abnormalities or vital sign abnormalities at screening or a history of unstable, severe, or clinically significant cardiovascular disease; Subjects with mild or moderate hepatic impairment: * Clinically significant abnormal findings, not consistent with clinical disease, upon physical examination, ECG, or laboratory evaluation; * Current symptoms or past history (within the last 6 months) of encephalopathy; * Severe ascites; * Previous surgical porto-systemic shunt including transjugular intrahepatic portosystemic shunt (TIPS); * Progressive liver disease within 4 weeks prior to screening. Healthy matched controls: * Use of any prescription medication within 1 month of dosing, and OTC medication within 14 days prior to dosing; * History or presence of liver disease or liver injury; * A positive Hepatitis B surface antigen (HBsAg) or Hepatitis C test result.