Placebo-corrected change in 6MWD from Baseline to Week 16, correlates with the current clinical standard for assessing patient functional status in the treatment of PAH and is considered an objective measure of patient functional status by the American Thoracic Society (ATS).

The 6MWD was to be assessed between 3 and 6 hours after the morning dose of study drug and background therapy(ies).

Intention to treat analysis

Definition of clinical worsening included patients who met at least one of the following criteria during the 16 weeks of study:

1. Death (all causes excluding accident)
2. Transplantation
3. Atrial septostomy
4. Hospitalization as a result of right heart failure
5. Greater than or equal to a 20% decrease in 6MWD from Baseline (or too ill to walk) AND addition of an inhaled prostacyclin analogue, ERA, or PDE-5i
6. Initiation of parenteral prostacyclin therapy (i.e., epoprostenol, iloprost, or treprostinil) for the treatment of PAH

Intention to treat analysis

The Borg dyspnea score is a 10-point scale rating the maximum level of dyspnea experienced during the six-minute walk test (6MWT). The Borg dyspnea score was assessed immediately following the 6MWT. Scores ranged from 0 (for no shortness of breath) to 10 (for the greatest shortness of breath ever experienced).

All subjects with a Baseline Borg Score were included in the analysis. One subject in the placebo group did not have a Baseline Borg Score recorded.

Class I: No limitation of physical activity. Class II: Slight limitation of physical activity. Class III: Marked limitation of physical activity. Class IV: Inability to carry out any physical activity without symptoms.

Subjects with a WHO functional class assessment at Week 16

Symptoms of PAH including fatigue, dyspnea, edema, dizziness, syncope, chest pain and orthopnea were assessed by the physician at Baseline and Week 16. Severity grade values (i.e., 0, 1, 2 or 3) for each symptom were provided each subject. A severity of 0 indicated no symptoms, the maximum severity was 3, indicating severe symptoms. Mean change in symptom severity from Baseline to Week 16 is described.

Subjects without Baseline assessments of PAH symptoms were not included in the analysis.

The dyspnea-fatigue index was assessed at Baseline and Week 16. Each of the three components of the dyspnea-fatigue index were rated on a scale 0 to 4, with 0 being the worst condition and 4 being the best condition for each component. The dyspnea-fatigue index is computed by summing the three component scores.

Subjects without a Dyspnea Fatigue Index score at Baseline were not included in the analysis.

Serum N-terminal pro-BNP concentration was assessed at Baseline and Week 16.

Subjects who were missing Week 16 samples were not included in the analysis.

Change in CAMPHOR Scores from Baseline to Week 16. The CAMPHOR is a health related quality of life instrument validated for pulmonary hypertension that assesses impairment (symptoms), disability (activities) and quality of life. The questionnaire is divided into three sections; Symptoms (Scores 0-25; high scores indicate more symptoms), Activity (Score 0-30; low score indicates good functioning)and Quality of Life (0-25; high scores indicate poor QoL). The sum of these scores equates to the Total score (0-80). In the CAMPHOR scores, lower scores indicate improvements.

Subjects in countries where the CAMPHOR has not been validated in the local language were not included in these analyses. Additionally, only subjects with completed questionnaires at Baseline and Week 16 were analyzed.

Covariate analysis of change in 6MWD by PAH etiology, specifically idiopathic or heritable PAH

Subjects with IPAH/HPAH

Subjects receiving only a PDE-5i at Baseline

Subjects who were only receiving an ERA at Baseline

Subjects receiving both an ERA and a PDE-5i at Baseline.

Subjects who have been diagnosed with PAH between 0 to 0.9 years prior to Baseline.

Subjects who had been diagnosed with PAH between 0.9 and 1.74 years prior to Baseline.

Subjects who were diagnosed with PAH between 1.8 and 3.5 years prior to Baseline.

Subjects who had been diagnosed with PAH for 3.6 to 26.4 years prior to Baseline.