Safety and Efficacy Study of Bosentan in Progressive Pulmonary Sarcoidosis

Inclusion Criteria: * Signed informed consent prior to any study-mandated procedure. * Male and female patients aged \> 18 and \< 70 years. * Histologically proven sarcoidosis diagnosed at least one year before screening. * Diagnosis of sarcoidosis and with evidence of pulmonary parenchymal disease on chest X-ray or CT (radiological stage II, III) with or without pulmonary hypertension. Subjects with concurrent extrapulmonary sarcoidosis are encouraged to be enrolled. * Progressive disease, defined as follows: * Deterioration in the 3-12 month period prior to screening in at least two of the following criteria: * increase in clinical symptoms (cough, shortness of breath, chest pain, fatigue or hemoptysis). * lung function: decrease of 10% in TLC, FVC or DLCO. * worsening of radiographic opacities. * Have been receiving pre-study treatment with prednisolone (or equivalent dose of corticosteroid) as a single agent (≥ 10 mg/day) or other immunosuppressants (methotrexate, azathioprine, cyclophosphamide, TNF inhibitors, etc.) within the 3-month period immediately prior to screening. Patients must be on a stable dose of these medications for \> 4 weeks before starting the study medication. * AST and ALT values within three times upper limit of normal. * Ability to communicate well with the investigator, in the local language, and to understand and comply with the requirements of the study. * Negative pregnancy test in female patients. * Adequate contraception in female patients of childbearing age. Exclusion Criteria: * Known hypersensitivity to any excipients of the drug formulation or to bosentan. * Treatment with another investigational drug within 3 months prior to screening. * Pulmonary sarcoidosis: * without disease progression as defined above * with radiological stage I * with radiological stage IV (pulmonary fibrosis with evidence of honey-combing, hilar retraction, bullae and cysts) * Other cause of pulmonary disease: * Active tuberculosis (or positive Quantiferon test), fungi infection, lymphoma. * Chronic obstructive pulmonary disease, asthma, interstitial lung disease other than sarcoid-related * Anamnesis of beryllium or asbestos exposition * Previous smoking (\> 10 PY), or active smoker * Previous administration of bosentan * Positive results from the hepatitis serology, except for vaccinated subjects, at screening. * Positive results from the HIV serology at screening. * Malignancy requiring chemotherapy or radiation * Uncontrolled other disease like * Chronic heart failure (NYHA III, IV) * Diabetes mellitus (blood glucose 2x per day \> 250 mg/dl , HbA1c \> 10 %) * Arterial hypertension (SBP \> 180 mmHg) * Concomitant treatment with cyclosporine A * Concomitant treatment with tacrolimus or sirolimus * Concomitant treatment with glibenclamide * Are pregnant, nursing, or planning pregnancy during the trial or within six month period thereafter. * Have a known substance dependency (drug or alcohol within 3 years of screening). * Presumed non-compliance. * Legal incapacity or limited legal capacity at screening.