This study checks if a new inhalation powder, called Treprostinil Palmitil (TPIP), helps people with a lung condition called Pulmonary Arterial Hypertension (PAH). PAH means the blood vessels in your lungs are too narrow, making it hard for blood to flow. This study will compare TPIP with a placebo, which looks like medicine but isn't, to see if TPIP works better. Participants must be between 18 and 75 years old and have specific types of PAH, like idiopathic (no known cause) or hereditary (runs in families). They should be stable on PAH treatment for at least a month before starting the study.

• The study involves taking TPIP or placebo and checking its effect on lung blood flow.
• Participants must not change any PAH medicines 30 days before and during the study.
• You can't join if you have other types of heart diseases, certain infections, or if you're pregnant or breastfeeding.

If you have PAH and meet these criteria, this study could be an option for you. Please talk to your doctor to see if it's right for you.