A Research Study To Assess The Effectiveness And Safety Of Different Doses Of Oral PF-00489791 In The Treatment Of Adult Patients With Pulmonary Arterial Hypertension

Pfizer decided to stop this trial early upon Stage 1 completion due to change in PF-00489791
development and not as a result of safety concerns for PF-00489791. Date of termination
(LSLV) occurred on July 28, 2010.

Inclusion Criteria:

- Idiopathic or familial pulmonary arterial hypertension (PAH)

- Mean PAP at least 25 mm Hg, PCWP < 15 mm Hg at rest

- For females of child-bearing potential negative pregnancy test at screening and use of
contraception during the study and 4 weeks after its completion

- Signed and dated informed consent

- Willingness to comply with the study plan and procedures

Exclusion Criteria:

- pulmonary arterial hypertension (PAH)other than idiopathic or familial

- For females, pregnancy or lactation

- Use of specific PAH treatments, potent CYP3A4 inhibitors, protease inhibitors, alpha
blockers or arginine 30 days prior tio randomization and during the study

- Change of dose or class of standard background PAH therapy, i.e. oxygen, calcium
channel blockers, digoxin, diuretics 30 days prior tio randomization and during the
study

- Large shift in altitude (defined as >5000 feet or 1524 meters) during 90 days prior to
baseline visit and/or during the study visit

- Subjects with intracardiac shunts and/or serious heart, lung or other health
conditions

- HIV positive subjects

- Subjects participating in another clinical trial with an investigational drug or
device

- Subjects with degenerative retinal disorders, history of non-arteritic anterior
ischemic optic neuropathy or untreated proliferative diabetic retinopathy

- Allergies and previous intolerance of PDE5 inhibitors

- Alcohol or drug abuse

- Blood donation during the study, or 1 month before or after the study