A Open Label Study to Assess the Long-term Safety, Tolerability and Efficacy of Ambrisentan in Subjects With Inoperable Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

Inclusion Criteria:

- Have been randomized to the protocol for AMB115811 and have met one of the following:
Completed the Week 16 visit in AMB115811; Or Prematurely withdrew from AMB115811 for
whatever reason (where investigational product [IP] has been stopped due to safety or
efficacy reasons, the subject may still enter into the open label study regardless of
what treatment they are receiving [other treatments will not be supplied by the
sponsor]. The investigator will decide whether or not the subject will receive the IP

- Subject is able and willing to give written informed consent. As part of the consent,
female subjects of childbearing potential will be informed of the risk of
teratogenicity and will need to be counseled in a developmentally appropriate manner
on the importance of pregnancy prevention; and male subjects will need to be informed
of potential risk of testicular tubular atrophy and aspermia.

- Specific information regarding warnings, precautions, contraindications, adverse
events, and other pertinent information on the GSK investigational product or other
study treatment that may impact subject eligibility is provided in the Investigators
Brochure and product label for PAH indication.

- In France, a subject will be eligible for inclusion in this study only if either
affiliated to or a beneficiary of a social security category

Exclusion Criteria:

- Subject meeting any of the following criteria must not receive ambrisentan, however
may still be followed-up as part of the study and be treated according to best
clinical practice as decided by the investigator:

- Subject has a known hypersensitivity to the Investigational Products, the
metabolites, or formulation excipients

- Female subjects who are pregnant or breastfeeding or no-longer agree to comply with
using effective contraception as defined in the protocol.

- Subjects with alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST)
>= 3x Upper limit of normal (ULN)

- Subjects with bilirubin >= 2xULN (>35% direct bilirubin)

- Subjects with severe renal impairment (estimated creatinine clearance <30 millilitre
per minute (mL/min) assessed within the previous 45 days) at the point of transition
from Study AMB115811

- Subject has moderate - severe hepatic impairment (Child-Pugh class B-C with or
without cirrhosis) at the point of transition from study AMB115811

- Subject with clinically significant fluid retention in the opinion of the
investigator

- Subject with clinically significant anemia in the opinion of the investigator

- Subjects who are to enter another clinical trial or be treated with another
investigational product after exiting Study AMB115811.