Safety, Pharmacokinetics and Efficacy Study of QCC374 in PAH Patients

Inclusion Criteria:

- Male and female patients 18 years of age or older with symptomatic PAH.

- Subjects with PAH belonging to one of the following subgroups of the Updated Clinical
Classification Group 1 (Nice, 2013):

- Idiopathic PAH

- familial PAH

- PAH associated with connective tissue disease, congenital heart disease (surgically
repaired at least 12 months prior to screening) or drug or toxin induced (for example,
anorexigen use).

- Subjects must have persistent symptoms due to PAH despite therapy with at least one of
the following PAH medications: an endothelin receptor antagonist, asoluble guanylate
cyclase stimulator or a phosphodiesterase inhibitor. The subjects' PAH medication
regimen, with typical medications including calcium channel blockers, endothelin
receptor antagonists, soluble guanylate cyclase stimulators and/or phosphodiesterase
inhibitors, must have been used at a stable dose and frequency for at least 12 weeks
before the screening visit and during the screening period.

- Diagnosis of PAH established according to the standard criteria before the screening
visit:

- Resting mean pulmonary arterial pressure > 25 mmHg.

- PVR > 240 dynes s/cm5.

- Pulmonary capillary wedge pressure or left ventricular end diastolic pressure < 15
mmHg

- PVR > 400 dynes s/cm5 at the time of the baseline right heart catheterization (RHC)
(if a RHC was completed within one month of the screening visit, that result may be
used for inclusion).

- 6-minute walk distance greater than 150 meters at Screening. This distance must be
confirmed by a second 6MWT prior to randomization. The value of the second 6MWD should
be within ± 15% of the value obtained at Screening.

Exclusion Criteria:

- Subjects with clinically unstable right heart failure within the last three months
(New York Heart Association (NYHA) Class IV).

- Subjects with PAH associated with portal hypertension, Human Immunodeficiency Virus
(HIV) infection or unrepaired congenital systemic to pulmonary shunts

- Subjects who have received or have been scheduled to receive long-term treatment with
epoprostenol or any prostacyclin within the three months prior to the screening visit
or during the screening period.

- Hypotensive subjects (systemic systolic blood pressure < 85 mmHg)

- Subjects with a history of left sided heart disease, chronic left sided heart failure,
congenital or acquired valvular disease and/or pulmonary venous hypertension.

- Subjects with significant obstructive (forced expiratory volume in one second
[FEV1]/forced vital capacity [FVC] < 70% predicted) or restrictive (total lung
capacity < 70% predicted) lung disease at screening.