A research study is a scientific way to improve or develop new methods of health care. Studies are designed to answer specific questions on how to prevent, diagnose, or treat diseases and disorders. Many types of research studies exist. For example, the purpose of this research study is to assess an investigational medication called ralinepag (also referred to as the “investigational study drug”) in the treatment of pulmonary arterial hypertension (PAH). Ralinepag has not been approved by any regulatory authorities, including the US Food and Drug Administration (FDA); therefore, it is not available by prescription.