This open-label, two period crossover study will evaluate the effect of multiple doses of activated charcoal on the pharmacokinetics of a single oral dose of RO4995819 in healthy volunteers. Each enrolled subject will receive two single oral doses of RO4995819 separated by a wash-out period of up to 9 weeks. In period 1, subjects will receive concomitantly with the single dose of RO4995819 multiple oral doses of activated charcoal until Day 7. In period 2, only a single dose of RO4995819 but no activated charcoal will be administered.

Inclusion Criteria:

• Healthy male subjects, 18 to 65 years of age, inclusive
• Body mass index (BMI) 18 to 30 kg/m2 inclusive
• All subjects must agree to use a barrier method (e.g. condom) throughout the study and for up to 5 months after the last dose of study drug
• Significant past or present disorders of the central nervous system, psychiatric disorders or behavioral disturbances.

Exclusion Criteria:

• Any suspicion or history of alcohol abuse and/or consumption of other drugs of abuse
• Positive for hepatitis B, hepatitis C, or HIV 1 or HIV 2
• Participation in an investigational drug or device study within 3 months prior to first administration of the study drug
• Any confirmed allergic reaction against any drug or multiple allergies
• Dietary restrictions that would prohibit the consumption of standardized meals
• Positive cotinine test and/or any use of nicotine containing products
• Clinically relevant history of constipation or bowel disorder
• Known intolerability to activated charcoal