Clinical Study to Assess the Efficacy, Safety and Tolerability of Macitentan in Subjects With Inoperable Chronic Thromboembolic Pulmonary Hypertension

Inclusion Criteria: * Written informed consent * Subject with CTEPH (WHO Group 4) judged as inoperable due to the localization of the obstruction being surgically inaccessible (i.e., distal disease). * Female of childbearing potential must have a negative pre-treatment serum pregnancy test, be advised on appropriate methods of contraception, and agree to use 2 reliable methods of contraception. Exclusion Criteria: * Previous pulmonary endarterectomy. * Recurrent thromboembolism despite sufficient oral anticoagulants. * Symptomatic acute pulmonary embolism in the 6-month period prior to randomization. * Known moderate-to-severe restrictive lung disease (i.e., TLC \< 60% of predicted value) or obstructive lung disease (i.e., FEV1 \< 70% of predicted, with FEV1/FVC \< 65%) or known significant chronic lung disease diagnosed by chest imaging (e.g., interstitial lung disease, emphysema). * Acute or chronic conditions (other than dyspnea) that limit the ability to comply with study requirements in the 3-month period prior to Screening visit or during the Screening period.