Single-ascending Oral Dose Study to Investigate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of ACT-281959 / ACT-246475 in Healthy Male Subjects

Study Part I is a single-ascending dose study. Healthy male subjects to be included in the study and randomized in 6 dose groups, Groups A-F (8 subjects per group). Of the 8 subjects per group, 6 subjects receive the investigational drug and 2 subjects receive matching placebo. Study Part II is a 3-period, crossover, single dose study. Nine healthy male subjects to be enrolled in one group (Group G). Each subject to receive 2 different formulations of the prodrug and one formulation of the active drug in a randomized sequence.