Withdrawal of Prostacyclin Pathway Therapy in Patients With Pulmonary Arterial Hypertension Receiving Sotatercept (WATERLOO)

Pulmonary arterial hypertension (PAH) is a rare lung disease that leads to elevated blood pressure in the lungs and strain on the right side of the heart. For many years, treatments for PAH have included drugs that target the prostacyclin pathway using intravenous, subcutaneous, oral, and inhaled drugs. These drugs help widen the blood vessels in the lungs so the heart does not have to work as hard. However, these medicines can cause side effects such as jaw pain, flushing, diarrhea, and nausea, and the pump therapy can be very hard to manage day-to-day. A newer medicine called sotatercept works in a different way. It helps fix some of the root causes of PAH. Early reports suggest that some people do very well on sotatercept and may not need to keep taking their prostacyclin therapy. However, investigators do not yet know if it is safe to stop prostacyclin therapies or how to do so. This study, called WATERLOO, is designed to find out whether slowly stopping prostacyclin therapy while the participant is doing well on sotatercept is safe. Investigators will compare people who stop their prostacyclin therapy to people who keep taking it. This study is being done at PAH expert centres in Canada and Europe.

NCT Number	NCT07700303
Lead Sponsor	University of Alberta
Conditions	Pulmonary Arterial Hypertension
Enrollment	78 participants
Start Date	2026-09-30
Primary Completion	2028-03-30 (estimated)
Study Completion	2030-03-30 (estimated)
Updated on ClinicalTrials.gov	2026-07-15