This randomized, double-blind, placebo-controlled, cross-over study will assess the safety, pharmacokinetics and pharmacodynamics of RO5508887 in healthy volunteers. In Part 1, subjects will be randomized to receive single ascending doses of either RO5508887 or placebo. In Part 2, subjects will receive a single dose of RO5508887 on two occasions, with or without food. Anticipated time on study is up to 12 weeks.