Study to Investigate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of ACT-389949 in Healthy Subjects

This is a single-center, double-blind, parallel-group, randomized, placebo-controlled, multiple-ascending oral dose study to investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of ACT-389949 in healthy subjects. Part A of the study will evaluate the safety and tolerability following once a day oral dosing of ACT-389949 for 9 days and investigate ACT-389949 pharmacokinetics and pharmacodynamics. Part B of the study will evaluate the safety and tolerability of ACT-389949 following a maximum of two different oral dosing regimens: ACT-389949 given either every 3 days for 13 days or every 2 days for 9 days (5 doses for each regimen). Part C of the study, if required, will provide additional information to that obtained from Parts A and B in terms of safety, tolerability, pharmacokinetics, and pharmacodynamics of ACT-389949.