A Study of First-Line Ambrisentan and Tadalafil Combination Therapy in Subjects With Pulmonary Arterial Hypertension (PAH)

Inclusion Criteria:

- Subjects must have a diagnosis of Pulmonary Arterial Hypertension (PAH) due to the
following:

a. idiopathic or heritable PAH b. PAH associated with: i. connective tissue disease
(e.g., limited scleroderma, diffuse scleroderma, mixed connective tissue disease,
systemic lupus erythematosus, or overlap syndrome) ii. drugs or toxins iii. Human
Immunodeficiency Virus (HIV) infection iv. congenital heart defects repaired greater
than 1 year prior to screening (i.e., atrial septal defects, ventricular septal
defects, and patent ductus arteriosus) NB: subjects with portopulmonary hypertension
and pulmonary veno-occlusive disease are NOT eligible for the study

- Subject must have a current diagnosis of being in World Health Organisation (WHO)
Functional Class II or III.

- Subject must meet all of the following haemodynamic criteria by means of a right
heart catheterization prior to screening:

i. mPAP of ≥25 mmHg ii. PVR ≥ 300 dynes/sec/cm5 iii. PCWP or LVEDP of ≤12 mmHg if PVR
≥300 to <500 dyne/sec/cm5 , or PCWP/LVEDP ≤ 15 mmHg if PVR ≥500 dynes/sec/cm5

- Subject must walk a distance of ≥125m and ≤500m at the screening visit

Exclusion Criteria:

- Subject received previous PAH therapy (phosphodiesterase type 5 inhibitor (PDE5i),
endothelin receptor antagonist (ERA), chronic prostanoid*) within 4 weeks prior to
the screening visit (*Chronic prostanoid use is considered >7 days of treatment)

- Subject received ERA treatment (e.g., bosentan or sitaxentan) or PDE5i treatment
(e.g. Sildenafil) at any time AND discontinued due to tolerance issues other than
those associated with liver function abnormalities

- Subjects who have previously discontinued ambrisentan or tadalafil in either another
clinical study or commercial product (Volibris/Letairis or Adcirca) for safety or
tolerability reasons.