Idiopathic pulmonary fibrosis (IPF) is a long-term lung disease that affects an individual's ability to breathe. In this randomized, double-blind, placebo-controlled trial, we assigned patients with idiopathic pulmonary fibrosis who had mild-to-moderate lung-function impairment to one of three groups - receiving a combination of prednisone, azathioprine, and NAC (combination therapy), NAC alone, or placebo - in a 1:1:1 ratio.

IPF is a disease with widespread and permanent scarring of lung tissue which eventually results in death. Individuals with IPF may experience breathing difficulties, cough, chest pain, and a decreased exercise capacity. Although the cause of IPF is unknown, it may be a result of an inflammatory response to an unknown substance. NAC, an antioxidant that is effective at loosening up mucus that forms in the lungs, may improve lung function. The purpose of this study is to evaluate the effectiveness of NAC at preventing the loss of lung function in people with IPF.

In the initial double-blind, placebo-controlled trial, subjects who have idiopathic pulmonary fibrosis with mild-to-moderate impairment in pulmonary function are randomly assigned to receive a three-drug regimen of prednisone, azathioprine, and acetylcysteine; acetylcysteine alone; or placebo.

After safety concerns were identified by the data and safety monitoring board, the three-drug regimen was stopped by the National Heart, Lung, and Blood Institute (NHLBI) on October 14, 2011, and a clinical alert was issued. After a brief period of interruption for modification of the protocol and approval by the institutional review boards, patients continued to be recruited for the acetylcysteine group and the placebo group and were followed for the pre-specified duration of 60 weeks.

Study visits will occur at baseline and Weeks 4, 15, 30, 45, and 60. At all study visits, a physical exam and blood collection will occur. At selected visits, the following study procedures will occur: lung function testing; urine collection; a 6-minute walk test, and questionnaires to assess health status, breathing, and quality of life. Participants will record medication usage and symptoms in a daily diary.

Inclusion Criteria:

• Forced vital capacity (FVC) greater than or equal to 50% of predicted value
• Diffusion capacity (DLCO) greater than or equal to 30% of predicted value
• Diagnosis of IPF by modified American Thoracic Society (ATS) criteria in the 48 months before study entry

Exclusion Criteria:

• History of clinically significant environmental exposure known to cause pulmonary fibrosis

• Diagnosis of connective tissue disease as the likely cause of the interstitial disease

• Extent of emphysema greater than the extent of fibrotic change (i.e., honeycombing, reticular changes) on high resolution computed tomography (HRCT) scan

• Forced expiratory volume in 1 second (FEV1)/FVC ratio less than 0.65 at the time of screening (post-bronchodilator)

• Partial pressure of arterial oxygen (PaO2) less than 55 mm Hg (less than 50 mm Hg at Denver study site)

• Residual volume greater than 120% predicted at the time of screening (post-bronchodilator)

• Evidence of active infection

• Significant bronchodilator response on screening spirometry, defined as change in FEV1 greater than or equal to 12% and absolute change greater than 200 mL OR change in FVC greater than or equal to 12% and absolute change greater than 200 mL

• Screening and baseline FVC measurements (in liters, post-bronchodilator) differing by 11%

• Listed for lung transplantation

• History of unstable or deteriorating cardiac disease

• Heart attack, coronary artery bypass, or angioplasty in the 6 months before study entry

• Unstable angina pectoris or congestive heart failure requiring hospitalization in the 6 months before study entry

• Uncontrolled arrhythmia

• Severe uncontrolled high blood pressure

• Known HIV or hepatitis C

• Known cirrhosis and chronic active hepatitis

• Active substance and/or alcohol abuse

• Pregnant or breastfeeding

• Women of childbearing potential who are not using a medically approved means of contraception

• Any clinically relevant lab abnormalities, including the following:

  1. Creatinine greater than twice the upper limit of normal (ULN)

  2. Hematology outside of specified limits

     1. White blood cells less than 3,500/mm3
     2. Hematocrit less than 25% or greater than 59%
     3. Platelets less than 100,000 mm3 at the time of screening

  3. Any of the following liver function test criteria above specified limits

     1. Total bilirubin greater than twice the ULN
     2. Aspartate (AST) or alanine aminotransferases (ALT) greater than 1.5 the ULN
     3. Alkaline phosphatase greater than three times the ULN
     4. Albumin less than 3.0 mg/dL at the time of screening

• Known hypersensitivity to study medication

• Any condition other than IPF that, in the opinion of the site PI, is likely to result in death in the 1 year after study entry

• Any condition that, in the judgment of the PI, might cause participation in this study to be detrimental or makes the person a poor candidate for the study