The purpose of the study is to evaluate the safety and tolerability of multiple ascending oral doses (MAD) of GLPG0555 given to healthy subjects for 13 days compared to placebo, and to evaluate the relative bioavailability and pharmacokinetics (PK) of two different aqueous suspensions of GLPG0555 administered for 3 days. Finally, it is aimed to characterize PK and pharmacodynamics (PD) of GLPG0555 after multiple oral administrations.