This open-label, single-dose, parallel group study will assess the pharmacokinetics and safety of RO4917838 in healthy volunteers and patients with mild, moderate or severe chronic hepatic impairment. Patients and healthy volunteers will receive a single oral dose of RO4917838.

Inclusion Criteria:

General:

• Body mass index (BMI) between 18 and 32 kg/m2 inclusive

Healthy Subjects:

• Adult male or female subjects, 18-70 years of age

Hepatically impaired patients:

• Adult patients, 18-65 years of age
• Documented chronic stable mild/moderate/severe liver disease (Child-Pugh class A, B or C)
• Hepatic impairment should be primary and must not be a complication of an underlying primary disease

Exclusion Criteria:

General:

• Pregnant or lactating women
• Suspicion of drug abuse or addiction at time of screening/Day -1 or history of drug abuse in the last month (patients) or last year (healthy volunteers) prior to Day -1
• Confirmed significant allergic reactions against any drug, or multiple allergies in the judgement of the investigator
• Positive for HIV infection
• Renal insufficiency

Healthy volunteers:

• History of significant disease, or evidence of disease or condition which could interfere with the study or relapse during or immediately after the study
• Any history of depressive episodes or treatment with antidepressants
• Alcohol consumption averaging more than 2 units (16 g) of alcohol for females or 3 units (24 g) for males per day, or positive alcohol breath test at screening/Day -1
• Positive for hepatitis B and/or hepatitis C infection

Hepatically impaired patients:

• Evidence of unstable clinically significant disease other than impaired hepatic function, or condition or disease which could interfere with the study or relapse during or immediately after the study
• Episode of acute depression within the last 6 months or current or previous (within the last 6 months) antidepressant treatment
• Hepatocellular carcinoma or acute hepatic disease caused by infection or drug toxicity
• Presence of surgically created or transjugular intrahepatic portal systemic shunts
• Biliary liver cirrhosis or other causes of hepatic impairment not related to parenchyma disorder and/or disease of the liver