BUILD 3 is a prospective, multicenter, randomized, double-blind, parallel group, placebo-controlled, event-driven, group sequential, phase III superiority study. The primary objective is to demonstrate that bosentan delays disease worsening or death in patients with Idiopathic Pulmonary Fibrosis.

Inclusion Criteria:

• Signed informed consent
• Male or female aged 18 years or older (females of child-bearing potential must have been surgically sterilized or use a reliable method of contraception.)
• Proven diagnosis of IPF according to American Thoracic Society / European Respiratory Society (ATS-ERS) statement, of <3 years, with surgical lung biopsy (SLB)

Exclusion Criteria:

• Interstitial lung disease due to conditions other than IPF.
• Presence of extensive honeycombing (HC) on baseline high-resolution computed tomography (HRCT) scan.
• Severe concomitant illness limiting life expectancy (<1 year).
• Severe restrictive lung disease.
• Obstructive lung disease.
• Diffusing capacity of the lung for carbon monoxide <30% predicted.
• Residual volume > or = 120% predicted.
• Documented sustained improvement of patient's IPF condition up to 12 months prior to randomization with or without IPF-specific therapy.
• Recent pulmonary or upper respiratory tract infection (up to 4 weeks prior to randomization).
• Acute or chronic impairment (other than dyspnea) limiting the ability to comply with study requirements.
• Chronic heart failure with New York Heart Association (NYHA) class III/IV or known left ventricular ejection fraction <25%.
• Alanine aminotransferase (ALT/SGPT) and/or aspartate aminotransferase (AST/SGOT) > 1.5 times the upper limit of the normal ranges.
• Moderate to severe hepatic impairment.
• Serum creatinine > or = 2.5 mg/dl or chronic dialysis.
• Hemoglobin concentration <75% the lower limit of the normal ranges.
• Systolic blood pressure <85 mmHg.
• Pregnancy or breast-feeding.
• Current drug or alcohol dependence.
• Chronic treatment with the following drugs prescribed for IPF (within 4 weeks of randomization):oral corticosteroids (>20 mg/day of prednisone or equivalent), immunosuppressive or cytotoxic drugs, antifibrotic drugs, chronic use of N-acetylcysteine (prescribed for IPF).
• Oral anticoagulants other than those indicated for a venous or arterial thrombotic disease.
• Treatment with glibenclamide (glyburide) and calcineurin inhibitors (cyclosporine A, tacrolimus) up to 1 week prior to randomization.
• Treatment with an endothelin receptor antagonist up to 3 months prior to randomization.
• Participation in the BUILD 1 trial.
• Treatment with another investigational drug up to 3 months prior to randomization or planned treatment.
• Known hypersensitivity to bosentan or any of the excipients.

All treatment-emergent adverse events occurring after the start of study treatment and within 24 hours after the end of study treatment

One subject who did not receive study treatment (bosentan) was excluded from the safety population. Events listed as idiopathic pulmonary fibrosis were reported as worsening of idiopathic pulmonary fibrosis.