Long Term Safety and Efficacy of APD811 in Pulmonary Arterial Hypertension

Inclusion Criteria:

- Evidence of a personally signed and dated informed consent document

- Is willing and able to comply with scheduled visits, treatment plan, laboratory tests,
and other study procedures and is deemed an appropriate candidate for participation in
a long-term extension study and administration of APD811

- Fulfilled all eligibility criteria for APD811-003 and completed the study as
planned

- Patients who discontinued for clinical worsening in APD811-003 and were assigned
to placebo and completed all end of study procedures including right heart
catheterization (RHC) may participate after their data from the APD811-003 study
is cleaned and locked

Exclusion Criteria:

- Patients who enrolled in APD811-003 and were withdrawn from study drug treatment due
to any AE, SAE, or clinical worsening if assigned to APD811, or patients who did not
complete the APD811 003 study for other reasons.

- Female patients who wish to become pregnant

- Systolic BP <90 mmHg at Baseline/Day 1

- Other severe acute or chronic medical or laboratory abnormality that may increase the
risk associated with study participation or investigational product administration or
may interfere with the interpretation of study results and, in the judgment of the
investigator, would make the patient inappropriate for entry into this study