This is a multi-centre, multinational, open-label, single-dose acute hemodynamic study followed by a randomized, double-blind, parallel-group, placebo controlled study. Eligible subjects will undergo screening followed by randomized allocation to treatment group for the double-blind study, followed in turn by immediate enrollment in an open-label, single-dose acute hemodynamic study with ACT-293987 (NS-304) and 21 weeks of double-blind treatment during which subjects will receive either ACT-293987 (NS-304)or placebo twice daily (b.i.d.). Subjects who have completed the double-blind study can enter the open extension study and receive administration of ACT-293987 (NS-304) (separate protocol)if the subject wishes and the investigator considers it appropriate.~Unblinding will occur on a subject-by-subject basis when the Week 17 data for the subject have been fixed.~Approximately 44 subjects are to be randomized in a ratio of 3:1 to the two treatment groups, ACT-293987 (NS-304) and placebo (33 subjects to ACT-293987 (NS-304) and 11 subjects to placebo).~Subjects will be randomized to the study following screening.
This is a multi-centre, multinational, open-label, single-dose acute hemodynamic study followed by randomized, double-blind, parallel-group, placebo controlled study. Eligible subjects will undergo an open-label, single-dose acute hemodynamic study with ACT-293987(NS-304) and 21 weeks of double-blind treatment during which subjects will receive either ACT-293987 (NS-304) or placebo b.i.d. Subjects who have completed the double-blind study can enter the open extension study (separate protocol) and receive administration of ACT-293987 (NS-304) if the subject wishes and the Investigator considers it appropriate.