The National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health has stopped a clinical trial testing a drug treatment for pulmonary hypertension in adults with sickle cell disease nearly one year early due to safety concerns. In an interim review of safety data from 33 participants who completed 16 weeks of treatment, researchers found that, compared to participants on placebo (dummy pill), participants taking sildenafil (Revatio) were significantly more likely to have serious medical problems. The most common problem was episodes of severe pain called sickle cell crises, which resulted in hospitalization. No deaths have been associated with the drug in the clinical trial.
Known as walk-PHaSST, the study was the first multicenter, randomized clinical trial to test the safety and effectiveness of sildenafil for pulmonary hypertension in patients with sickle cell disease, one of the most common genetic blood disorders in the United States. Pulmonary hypertension is a debilitating condition of high blood pressure in the arteries that carry blood to the lungs, which can lead to heart failure and death. Approximately 30 percent of sickle cell disease patients develop pulmonary hypertension, and even mild levels of pulmonary hypertension have been associated with sudden death in people with sickle cell disease.
"The increase in sickle cell medical problems is concern enough for us to stop this clinical trial to protect the safety of our participants," said NHLBI Director Elizabeth G. Nabel, M.D. "We will continue to look into the possible causes of these preliminary results. In the meantime, we encourage patients with sickle cell disease who are taking sildenafil for pulmonary hypertension to talk with their physicians about the potential risks and benefits of the medication and what actions they should consider, including whether to taper off this medication and how to best manage both sickle cell disease and pulmonary hypertension."
Because the medical problems experienced in walk-PHaSST were complications specific to sickle cell disease, "The findings of the walk-PHaSST study should not be applied to other groups of patients with pulmonary hypertension where the drug has been found to be safe and effective," Nabel added.
Researchers are conducting extensive analyses of the study results, which could contribute to recommendations for treating pulmonary hypertension in patients with sickle cell disease. They will prepare reports of their research for publication in peer-reviewed journals.
Walk PHaSST was conducted at the following locations:
- Children's Hospital, Oakland, Calif.
- University of Colorado, Denver
- Howard University Hospital, Washington, D.C.
- University of Illinois at Chicago
- Johns Hopkins Medical Institutions, Baltimore
- NIH Clinical Center, Bethesda, Md.
- Albert Einstein College of Medicine, New York City
- Columbia University, New York City
- Children's Hospital, Pittsburgh
- Imperial College London and Hammersmith Hospital, London, England
Rho Inc. of Chapel Hill, N.C., serves as the data coordinating center. Pfizer provided the treatment drug and placebo for the study.
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