 The AIR001-CS05 study evaluated the safety and efficacy effectiveness of AIR001 over 16 weeks in subjects who have PAH. The purpose of the AIR001-CS06 study is to evaluate the intermediate long-term safety of AIR001 in subjects who have completed the AIR001-CS05 study. Assessments to evaluate the effectiveness of the study drug will include measurements of exercise ability and evaluations of PAH disease symptoms. 