A Study to Evaluate GSK1325760A - a Long-Term Extension Study

Study AMB107818, Clinical Evaluation of GSK1325760A in the Treatment of Pulmonary Arterial Hypertension (PAH)- An Open Label Study of GSK1325760A to Evaluate the Safety and Efficacy of GSK1325760A - a Long-term Extension Study -

The primary objective of this study is to evaluate the safety of long-term administration of GSK1325760A in patients with PAH.

The secondary objectives of this study are to evaluate long-term administration of GSK1325760A on:

• Improvement in exercise capacity (six-minutes walk distance: 6MWD), change in WHO Functional Classification and time to clinical worsening of PAH
• Change in the Borg Dyspnea Index (assessed immediately following the six-minute walk test [6MWT])
• Change in plasma brain natriuretic peptide (BNP) levels
• Cardiopulmonary hemodynamics parameters (as measured by echocardiography)

Inclusion Criteria:

• Subjects who complete the 24-week administration of the Phase II/III study (Study No.AMB107816)
• Subjects who are assessed that the long-term extension administration of GSK1325760A is appropriate in the judgement of the investigator or subinvestigator
• Subjects who request the long-term extension administration of GSK1325760A, and agree to newly sign the informed consent form

Exclusion Criteria:

• Subjects who have been withdrawn from the Phase II/III study.
• Female subjects who wish to become pregnant.
• Treatment with other PAH medication is needed.
• A worsening of 2 or more levels of the WHO Functional Classification (see Appendix 2.1) comparing with the baseline of Phase II/III study (Study No.AMB107816).
• Worsening of right ventricular failure (e.g. as indicated by increased jugular venous pressure, new/worsened hepatomegaly, ascites, or peripheral edema) during Phase II/III study (Study No.AMB107816).
• Rapidly progressing cardiac, hepatic or renal failure during Phase II/III study (Study No.AMB107816).
• Participation to the long-term extension study is considered as inappropriate in the judgment of the investigator or subinvestigator.