A wide range of substances is currently available for the treatment of patients with pulmonary arterial hypertension. The current recommendations for initial drug therapy are based on the patient's risk profile. For patients at high risk, an initial triple combination therapy with different substances including prostanoids is recommended. The aim of the prospective, single-arm, unblinded study was to clarify whether PAH patients on triple therapy benefit from switching from selexipag to intravenous treprostinil. The primary endpoint was the achievement of a "low-risk" status after 6 (12) months. 27 PAH patients (45 (37; 61) years, 77.8% women) were included. At study entry they were assigned to low-risk (n=1), intermediate (n=12) or high-risk status (n=14). On average, 22 patients were followed for 8 (range 5-11) months. One patient was successfully transplanted after four months, another four patients died (in one case septic complications of unknown origin; in three cases progressive right heart failure). The primary endpoint (reaching "low-risk" status) was achieved in 12/21 (57.1%) patients (one further patient remained in "low-risk" status). These data indicate (despite the small number of patients) that even with established triple therapy, clinical improvement in individual patients is possible by switching from selexipag to intravenous treprostinil.