An AE is any untoward medical occurrence in a clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. Serious Adverse Event (SAE) is defined as any untoward medical occurrence that, at any dose results in death, is life-threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, is a congenital anomaly/birth defect. Refer to the general AE/SAE module for a list of AEs and SAEs. Participant's final visit in Study AMB115811 was used as the entry visit of this open-label extension study. Safety (Extension) Population: all participants who enrolled and took at least one dose of study treatment during the extension study.

Safety (Extension) Population

Hematology parameters were assessed at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and end of study. Change from study AMB115811 Baseline in basophils, eosinophils, lymphocytes, monocytes, total neutrophils (ANC), platelet count, and WBC count are summarized. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Participant's final visit in Study AMB115811 was used as the entry visit of this open-label extension study. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available.

Safety (Extension) Population

Hematology parameters were assessed at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and end of study. Change from study AMB115811 Baseline in hemoglobin and MCHC is summarized. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Participant's final visit in Study AMB115811 was used as the entry visit of this open-label extension study. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available.

Safety (Extension) Population

Hematology parameters were assessed at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and end of study. Change from study AMB115811 Baseline in hematocrit is summarized. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available.

Safety (Extension) Population

Hematology parameters were assessed at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and end of study. Change from study AMB115811 Baseline in mean corpuscle volume is summarized. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available.

Safety (Extension) Population

Hematology parameters were assessed at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and end of study. Change from study AMB115811 Baseline in red blood cell count and reticulocytes is summarized. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available.

Safety (Extension) Population

Blood samples were collected post Entry visit of the extension study and up to end of study for evaluation of the clinical chemistry parameters of alanine amino transferase (ALT), aspartate amino transferase (AST), gamma glutamyl transferase (GGT), and total bilirubin. The clinical chemistry parameters of potential clinical concern high were defined as follows: ALT, AST, GGT >=3 times upper limit of normal (ULN); total bilirubin >=2 times ULN. Participants with both normal and high values were counted once under their worst case (high). Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study.

Safety (Extension) Population

Blood samples were collected at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and end of study plus any unscheduled lab tests for creatinine. A creatinine value of potential clinical concern high was defined as >=176.8 micromoles per Liter. Participants with both normal and high values were counted once under their worst case (high). Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study.

Safety (Extension) Population

Vital signs including SBP and DBP were assessed at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and end of study. Change from study AMB115811 Baseline in SBP and DBP is summarized. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available.

Safety (Extension) Population

Vital signs including heart rate were assessed at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and end of study. Change from study AMB115811 Baseline in heart rate is summarized. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available

Safety (Extension) Population

Weight was measured at Entry visit of the extension study, Month 1, Month 3, Month 6, Month 9, Month 12, Month 15, and at end of study. Change from study AMB115811 Baseline in weight is summarized. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available.

Safety (Extension) Population

The time to change in dose of ambrisentan or other targeted PAH (pulmonary arterial hypertension) therapeutic agents (prostanoids, PDE-5 inhibitors) due to tolerability issues (e.g. adverse events). Dosing data were collected, but after the study was terminated, not all endpoints listed in the protocol were analyzed, including time to first change in dose of open-label ambrisentan. This decision was documented in the reporting and analysis plan prior to database lock.

Safety (Extension) Population

The 6-minute walk test was conducted according to the American Thoracic Society guidelines in accordance with local standard operating procedures. 6MWD was measured by a 6-minute walk test. This test measures the distance that a par. can walk in a period of 6 minutes. AMB115811 Baseline was the Week 0 value in that study. Change from study AMB115811 Baseline was calculated as the value at the indicated visit minus the Baseline value. Par.'s final visit in study AMB115811 was used as the entry visit of this extension study. For the Extension study, the visit schedule (Months 1, 3, 6, 9, 12 and 15) was mapped to the visit schedule (Months 5, 7, 10, 13, 16 and 19) for continuity with study AMB115811. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). Intent-to-treat (ITT) Population: all par. who were randomized and took at least one dose of study medication in the double-blind phase (placebo or ambrisentan).

ITT Population

WHO FC indicates severity of pulmonary arterial hypertension (PAH) and is an adaptation of the New York Heart Association classification, assessed by the investigator. There are 4 grades for WHO FC based on severity of symptoms (Class I = none, Class IV = most severe). Grades mapped to numeric scale 1-4 (i.e. Class IV = 4). WHO FC system links symptoms with activity limitations, allowing clinicians to predict disease progression and prognosis. AMB115811 BL is the last value recorded on or prior to start of study treatment in that study. Change from AMB115811 BL was calculated as the value at the indicated visit minus the BL value (positive change = worsening). Par.'s final visit in AMB115811 was used as entry visit of this ext study. For Ext study, the visit schedule (M1,3,6,9,12 and 15) was mapped to the visit schedule (M5,7,10,13,16 and 19) for continuity with study AMB115811. Only par. available at the specified TP were analyzed (represented by n=X,X in the category title).

ITT Population

BCR10S score, a rating of perceived exertion, was collected immediately following completion of the 6-minute walk test. Scores range from 0 to 10 (0=nothing at all, 10=extremely strong). If par.'s perception or feeling was stronger than "10", that is "extremely strong", "Maximal" -a larger number could be used, for example 12 or still higher, that is "Absolute maximum"). AMB115811 BL data was calculated as average of 2 BCR10S values obtained following the 2 6MWD tests used in determining the BL 6MWD in that study. If only 1 measurement was available, it was used. Change from AMB115811 BL was calculated as the value at the indicated visit minus the BL value. Par.'s final visit in AMB115811 was used as the entry visit of ext study. For the Ext study, the visit schedule (M1,3,6,9,12 and 15) mapped to the visit schedule (M5,7,10,13,16 and 19) for continuity with AMB115811. Only those par. available at the specified time points were analyzed (represented by n=X,X in the category titles).

ITT Population

Time to clinical worsening of CTEPH was defined as the time from randomization in study AMB115811 to the first occurrence of any of the following events: death (all cause), lung transplantation, hospitalization for CTEPH deterioration, atrial septostomy, addition of parenteral prostanoids, appearance of two or more CTEPH worsening events. Worsening events included: >=20% of decrease in 6MWD; >=1 increase of WHO Functional Classes; worsening right ventricular failure; rapidly progressing cardiogenic, hepatic, or renal failure; refractory systolic hypotension (SBP <85 mmHg).

ITT Population

The SF-36 version 2 is a self-administered, health-related quality of life (QoL) metric. It is a 36-item questionnaire designed to measure 8 domains of functional health status and well-being: physical functioning, role-physical, bodily pain, general health perceptions, vitality, social functioning, role-emotional, and mental health as well as 2 summary measures (Physical Health and Mental Health). Each domain is scored from 0 (poorer health) to 100 (better health). Baseline of study AMB115811 was to be used. Change from study AMB115811 Baseline was to be calculated as the value at the indicated visit minus the Baseline value. The SF-36 data were collected, but after the study was terminated, not all endpoints listed in the protocol were analyzed, including the SF-36. This decision was documented in the reporting and analysis plan prior to database lock.

ITT Population

The ratio to Baseline in NT-proBNP was calculated as the ratio of the value at the specified time-point to the AMB115811 Baseline value and was expressed as a percent change from AMB115811 Baseline. This was done by taking the mean change on the log scale, exponentiating, subtracting 1 and multiplying by 100. Standard deviation (SD) of the logged values (log[SD]) have been presented. AMB115811 Baseline is the last value recorded on or prior to start of study treatment in that study. Participant's final visit in study AMB115811 was used as the entry visit of this open-label extension study. For the Extension study, the visit schedule (Months 1, 3, 6, 9, 12 and 15) was mapped to the visit schedule (Months 5, 7, 10, 13, 16 and 19) for continuity with study AMB115811. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles). NA indicates that data were not available.

ITT Population

The 6 minute walk distance data in a previous outcome measure were also analyzed as change from start of ambrisentan treatment. As participants started to receive ambrisentan treatment in two studies, two different time points for start of ambrisentan treatment were used for this analysis. For participants who received ambrisentan treatment in Study AMB115811, the Baseline for that study was used. For participants who received placebo in Study AMB115811, entry visit of the Extension study was defined as Baseline. Change from start of ambrisentan was calculated as the value at the indicated visit minus the start of ambrisentan value. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category title).

ITT Population. Placebo arm: includes par. who received ambrisentan treatment during extension study

The WHO functional class data in a previous outcome measure were also analyzed as change from start of ambrisentan treatment. There are 4 grades for WHO FC based on severity of symptoms of pulmonary arterial hypertension (Class I = none, Class IV = most severe). Grades mapped to numeric scale 1-4 (i.e. Class IV = 4). As participants started to receive ambrisentan treatment in two studies, two different time points for start of ambrisentan treatment were used for this analysis. For participants who received ambrisentan treatment in Study AMB115811, the Baseline for that study was used. For participants who received placebo in Study AMB115811, entry visit of the Extension study was defined as Baseline. Change from start of ambrisentan was calculated as the value at the indicated visit minus the start of ambrisentan value (positive change = worsening). Only those participants available at the specified time points were analyzed (represented by n=X, X in the category titles).

ITT Population. Placebo arm: includes par. who received ambrisentan treatment during extension study

The BCR10S data in a previous outcome measure were also analyzed as change from start of ambrisentan treatment. BCR10S score, a rating of perceived exertion, ranges from 0 to 10 (0=nothing at all, 10 extremely strong). If par.'s perception or feeling was stronger than "10", a larger number could be used. As participants started to receive ambrisentan treatment in two studies, two different time points for start of ambrisentan treatment were used for this analysis. For participants who received ambrisentan treatment in Study AMB115811, the Baseline for that study was used. For participants who received placebo in Study AMB115811, entry visit of the Extension study was defined as Baseline. Change from start of ambrisentan was calculated as the value at the indicated visit minus the start of ambrisentan value. Only those participants available at the specified time points were analyzed (represented by n=X, X in the category title).

ITT Population. Placebo arm: includes par. who received ambrisentan treatment during extension study

The NT-proBNP data in a previous outcome measure were also analyzed as change from start of ambrisentan treatment. The ratio to start of ambrisentan in NT-proBNP was calculated as the ratio of the value at the specified time-point to the start of ambrisentan value and was expressed as a percent change from start of ambrisentan. This was done by taking the mean change on the log scale, exponentiating, subtracting 1 and multiplying by 100. Standard deviation (SD) of the logged values (log[SD]) have been presented. As par. started to receive ambrisentan treatment in 2 studies, 2 different time points for start of ambrisentan treatment were used for this analysis. For par. who received ambrisentan treatment in study AMB115811, the Baseline for that study was used. For par. who received placebo in Study AMB115811, entry visit of the Extension study was defined as Baseline. Only those par. available at the specified time points were analyzed (represented by n=X, X in the category title).

ITT Population. Placebo arm: includes par. who received ambrisentan treatment during extension study

The time to change in dose of ambrisentan or other targeted PAH therapeutic agents (prostanoids, PDE-5 inhibitors) due to deterioration of clinical condition. Dosing data were collected, but after the study was terminated, not all endpoints listed in the protocol were analyzed, including time to first change in dose of open-label ambrisentan. This decision was documented in the reporting and analysis plan prior to database lock.

Safety (Extension) Population

The time to addition of another targeted PAH therapeutic agents (prostanoids, PDE-5 inhibitors) due to the following reasons:

Deterioration of clinical condition; Lack of beneficial effect with previous therapy (not reaching set treatment goals). PAH therapies were collected, but after the study was terminated, not all endpoints listed in the protocol were analyzed, including time to first addition of another targeted PAH therapeutic agent. This decision was documented in the reporting and analysis plan prior to database lock.

Safety (Extension) Population.