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Idiopathic Pulmonary Fibrosis Network (IPFNet) Sildenafil Trial of Exercise Performance in Idiopathic Pulmonary Fibrosis (IPFNet-STEP-IPF-BioLINCC)

Data Access NOTE: Please refer to the "Authorized Access" section below for information about how access to the data from this accession differs from many other dbGaP accessions.

Objectives: The STEP-IPF study sought to evaluate whether treatment with sildenafil would improve walk distance, dyspnea, and quality of life in participants with advanced idiopathic pulmonary fibrosis (IPF).

Background: IPF is a chronic, progressive lung disease of unknown cause that is characterized by the histopathologic pattern of usual interstitial pneumonia. Progression to end-stage respiratory insufficiency and death within 5 years after the onset of symptoms is characteristic. To date, no pharmacologic therapies have definitively been shown to improve survival or quality of life in participants with this disease.

Participants with severe IPF have abnormalities of the pulmonary vasculature leading to decreased levels of resting and exercise-induced production of nitric oxide. Since nitric oxide is a potent pulmonary vasodilator, reduced levels are associated with pulmonary vasoconstriction and impaired gas exchange.

Sildenafil (Revatio, Pfizer) is a phosphodiesterase-5 inhibitor that stabilizes the second messenger of nitric oxide, cyclic guanosine monophosphate, which leads to pulmonary vasodilatation. Such vasodilatation could improve ventilation–perfusion matching and thus gas exchange in with IPF.

Design: STEP-IPF was a double-blind, randomized, placebo-controlled trial of oral sildenafil (20 mg three times daily). Participants meeting eligibility criteria were randomly assigned in a 1:1 ratio to receive sildenafil or matched placebo with the use of a permuted-block design, with stratification according to clinical center. The primary outcome was the presence or absence of an improvement of at least 20% in the 6-minute walk distance at 12 weeks, as compared with baseline. Key secondary outcomes included changes in the 6-minute walk distance, degree of dyspnea, and quality of life.

Screening procedures included the taking of a detailed history, a physical examination, spirometry, echocardiography, CT imaging, and measurements of lung volume on plethysmography, carbon monoxide diffusion capacity, and arterial blood gases. Eligible participants returned for an enrollment visit within 6 weeks after screening. All participants received an initial dose of a study drug at this visit and were monitored for 60 minutes for adverse effects. Follow-up visits were scheduled at 1, 6, and 12 weeks. After completion of the 12-week visit, all participants were started on treatment with open-label sildenafil. Visits were scheduled at 13, 18, and 24 weeks; at 28 weeks, serious adverse events and vital status were documented. Testing of the 6-minute walk distance was performed with the use of a standardized protocol at the time of screening and enrollment and at study visits at 6, 12, 18, and 24 weeks. Participants with pulse oxygen saturation below 88% received supplemental oxygen.

Conclusions: This study did not show a benefit for sildenafil for the primary outcome. The presence of some positive secondary outcomes creates clinical equipoise for further research. There were small but significant differences in arterial oxygenation, carbon monoxide diffusion capacity, degree of dyspnea, and quality of life favoring the sildenafil group.