A Clinical Study to Find Out if Macitentan is Effective and Safe in Japanese Patients With Chronic Thromboembolic Pulmonary Hypertension (CTEPH).

Inclusion Criteria:

• Written informed consent to participate in the study obtained from the subject orlegal representative a) prior to initiation of any study mandated procedure
• Japanese subjects who have been diagnosed as having CTEPH:

1. Subjects who have not undergone balloon pulmonary angioplasty (BPA) and for whomthe investigator determines not to implement pulmonary endarterectomy (PEA) atthe time of the acquisition of informed consent due to the organized thrombosislocalized in the peripheral regions, high risk (complications, old age, etc.) orfor any other reasons.
2. Subjects who have postoperative persistent or recurrent pulmonary hypertension (PH) after undergoing pulmonary endarterectomy (PEA) and/or BPA.

• PH subjects whose WHO FC is I to IV
• 6MWD measured during the screening period ranges from 150 m to 450 m
• Subjects who meet the following conditions according to the right heartcatheterization (RHC) performed during the screening period or within 8 weeks beforethe acquisition of the informed consent:

1. Resting mean pulmonary arterial pressure (mPAP) ≥ 25 mmHg
2. Pulmonary artery wedge pressure (PAWP) ≤ 15 mmHg (if PAWP cannot be measured orthe value of PAWP is not reliable, left ventricular end-diastolic pressure ≤ 13mmHg)
3. Resting PVR ≥ 400 dyn*sec/cm5

• Subjects treated with anti-coagulation agents, unfractionated heparin or low molecularweight heparin at least 90 days prior to RHC at baseline
• Women with childbearing potential with negative serum pregnancy test results and ableto follow the appropriate contraceptive methods from the date of starting the studydrug administration up to 30 days after the discontinuation or completion of the studydrug administration. Fertile male subjects able to use condom during the same period.

Exclusion Criteria:

• BPA within 90 days prior to undergoing baseline RHC
• PEA within 180 days prior to undergoing baseline RHC
• Subjects with unstable pulmonary hemodynamics who have postoperative persistent orrecurrent PH after undergoing PEA and/or BPA
• Recurrent thromboembolism undergoing treatment with oral anti-coagulation agents
• Symptomatic acute pulmonary embolism within 180 days prior to the start of study drugadministration
• Known moderate-to-severe restrictive lung disease or obstructive lung disease or knownsignificant chronic lung disease diagnosed by chest imaging (e.g., interstitial lungdisease, emphysema)
• Acute myocardial infarction during Screening period
• Severe liver impairment.
• Systolic blood pressure (SBP) < 90 mmHg at screening.
• Any known factor or disease that may interfere with treatment compliance or fullparticipation in the study