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In this double blind multinational study, 330 patients with idiopathic pulmonary fibrosis were randomly assigned to treatment with either subcutaneous interferon gamma-1b (n = 162) or placebo (n = 168) three times daily for 48 weeks. Interferon gamma-1b had no significant effect on the primary end point (disease progression or death) compared with placebo. 10% of patients died in the active treatment group compared with 17% in the placebo group (p = 0.08). The median time to death or disease progression was 439 days in the active group and 344 days in the placebo group (p = 0.50). Active treatment was not associated with any differences in gas exchange, lung function, or conventional quality of life measures. Exploratory analysis did reveal a greater effect of the active treatment in reducing mortality in patients with milder disease (parameter > median value of the group—that is, baseline forced vital capacity (FVC) >62% predicted and carbon monoxide transfer factor >35% predicted). Active treatment was associated with more frequent influenza-like symptoms and a higher incidence of pneumonia. However, respiratory infections were of equal severity and discontinuation rates were similar in the two groups.
This study failed to show any significant effect of interferon gamma-1b on disease progression, death, gas exchange, lung function, or quality of life in idiopathic pulmonary fibrosis. Exploratory analysis suggested, but could not confirm, a survival benefit for the active treatment in patients with milder disease. Due to the limited size and duration of the trial, a smaller survival benefit cannot be excluded. Further trials are required of adequate power to answer these questions.