Sildenafil improves quality of life for pulmonary fibrosis patients but disappoints on walking ability

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A randomized trial of the blood vessel relaxant sildenafil in patients with pulmonary fibrosis has disappointed researchers by failing to improve patients’ ability to walk, but the drug did provide a small but statistically significant improvement in other outcomes that are related to quality of life, researchers reported Tuesday. The benefits on quality of life were strong enough to justify a broader and longer trial of the drug, the researchers reported in the New England Journal of Medicine and at a New Orleans meeting of the American Thoracic Society.

Pulmonary fibrosis is a scarring of the lungs that interferes with their ability to take in oxygen. Its cause is unknown, and there are no drugs presently approved to treat it. An estimated 200,000 Americans ages 50 to 70 have the condition, and about 50,000 are newly diagnosed each year. Most patients die within three to five years after diagnosis.

A small pilot study conducted at UCLA by Dr. David A. Zisman in 2007 found that sildenafil improved the ability of patients in a six-minute walking test. Twelve patients were given the drug for three months. At the end of the trial, 57% of the patients had improved the distance they could walk during the period by 20% or more.

Based on those findings, the National Institutes of Health organized a large trial headed by Zisman, who is now at the Sansum Clinic in Santa Barbara. The trial involved 180 patients at 14 centers. Half were given sildenafil three times daily and half a placebo. At the end of the 12-week period, nine of the 89 patients in the treatment group had a 20% increase in the distance they could walk in the six-minute trial, but so did six of the 91 in the placebo group. The patients in the treatment group, however, had less shortness of breath, better arterial oxygenation and a better quality of life. The presence of these benefits ‘creates clinical equipoise for further research,’ the team wrote.

Two deaths occurred during the study in the treatment group and four in the control group. Acute exacerbations of disease also occurred in two of the treatment group and four of the placebo group.

The authors acknowledged several limitations of the study, including the shortness of follow-up, the failure to test patients with less advanced disease and possible problems in the blinding of the groups.

Sildenafil is the active ingredient in Viagra. It is also sold by Pfizer under the brand name Revatio for treatment of high blood pressure in the pulmonary arteries, which is the form used in the study.

The study was funded by NIH, but Pfizer donated the drug.

— Thomas H. Maugh II