United Pharmaceuticals SAS

Eligible subjects who were previously enrolled in the UT-15C SR clinical trial protocol evaluating patients with pulmonary hypertension will continue to receive UT-15C SR. The long-term safety of UT-15C SR in these subjects will be evaluated. The effect of continued UT-15C SR treatment on exercise tolerance will be evaluated in subjects who have used UT-15C SR for more than 1 year.

1. To continue to provide UT-15C medication to eligible subjects who were previously enrolled in the UT-15C TDE-PH-310 clinical trial protocol evaluating patients with pulmonary hypertension. 2. To evaluate the long-term safety of UT-15C in subjects taking UT-15C orally. 3. To evaluate the effect of continued UT-15C treatment on exercise tolerance in subjects who have been using UT-15C for a long time.

1. To evaluate the effect of oral UT-15C on the time to first clinical deterioration and exercise endurance in PAH subjects compared with the placebo group. 2. To evaluate the change in 6-minute walk distance from baseline at week 24 in PAH subjects compared with the placebo group.