This investigator-blind, subject-blind, randomized, placebo-controlled study will evaluate the safety, pharmacokinetics and pharmacodynamics of multiple ascending doses of RO5267683 in healthy volunteers. Subjects will be randomized to receive either RO5267683 or placebo orally daily for 28 days. Follow-up will be 10 weeks after the last dose.

Inclusion Criteria:

• Healthy male and female subjects, 18 to 45 years of age,
• Body mass index (BMI) 18 to 30 kg/m2 inclusive, and a minimum weight of 50 kg at screening
• Female subjects must be surgically sterile or post-menopausal
• Male subjects must use a barrier method of contraception for the duration of the study and for 90 days after the last dose

Exclusion Criteria:

• History or evidence of any clinically significant disease or disorder
• Administration of an investigational drug or device within 3 months prior to dosing on Day 1
• Positive for hepatitis B, hepatitis C or HIV at screening
• Subjects on hormone replacement therapy who have not been receiving a stable dose for at least 2 months prior to start of dosing