Safety Study of the Switch From Oral Selexipag to Intravenous Selexipag in Subjects With Stable Pulmonary Arterial Hypertension

After screening (Visit 1), each subject will participate in the following consecutive treatment periods: Period 1(treatment with oral selexipag at Visit 2/Day 1), Period 2 (treatment with intravenous selexipag at Visit 2/ Day 2 and Day 3), Period 3 (treatment with oral selexipag starting in the evening of Visit 2/Day 3 and ending 7 to 11 days later at Visit 3). Then a safety follow-up period is planned up to end of study visit (EOS), which occurs between Day 33 and Day 40.