Safety and Tolerability Study of Macitentan in Patients With Idiopathic Pulmonary Fibrosis

Inclusion Criteria: * Signed informed consent prior to initiation of any study-related procedure. * Patients with IPF and having completed the double-blind AC-055B201/MUSIC study as scheduled, i.e., having remained in the study until the sponsor-declared end-of-study (EOS), whether or not study treatment was prematurely discontinued. * Women of childbearing potential must have a negative pre-treatment serum pregnancy test and must use a reliable method of contraception during study treatment and for at least 28 days after study treatment termination. Exclusion Criteria: * Any major violation of protocol AC-055B201/MUSIC. * Premature discontinuation of study treatment during the AC-055B201/MUSIC study due to an adverse event (AE) assessed as related to the use of macitentan, excluding events of IPF worsening. * Pregnancy or breast-feeding. * AST and/or ALT \> 3 times the upper limit of the normal range. * Any known factor or disease that might interfere with treatment compliance, study conduct or interpretation of the results, such as drug or alcohol dependence or psychiatric disease. * Known hypersensitivity to drugs of the same class as macitentan, or any of the excipients.