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| |  DG DISPATCH - AHA: Bosentan Increases Exercise Function In Patients With Pulmonary Hypertension By Ed Susman Special to DG News
NEW ORLEANS, LOUISIANA -- November 14, 2000 -- The investigational oral drug, bosentan, appears to increase exercise function of patients with moderate to severe pulmonary hypertension, researchers reported here at the 73rd annual scientific sessions of the American Heart Association. About 100,000 people in North America and Europe have pulmonary hypertension. Lewis Rubin, MD, professor of medicine at the University of California at San Diego, said bosentan is designed to control endothelin, a destructive molecule that causes blood vessels constriction and cell proliferation, the beginnings of the cascade of molecular events that leads to pulmonary hypertension. "Bosentan is like ‘ScotchGuard’ for the blood vessels," Dr. Rubin said. The drug blocks the ability of circulating endothelin to attach to receptors on cells where it can start the chain of events that causes inappropriate constriction of blood vessels and inappropriate cell growth. In the study, Dr. Rubin compared 21 patients who received bosentan with 11 patients who received a placebo. After 12 weeks, the bosentan patients could walk 20 percent further than the patients on placebo. At baseline, the entire group of patients could only walk about 300 yards in a standard six-minute treadmill test. A normal person can walk better than 500 yards in that time, he said. At the end of the study those in the bosentan group were able to walk 72 yards further than the placebo patients, many of whom had deteriorated in ability. Dr. Rubin said after completing the clinical trial, some patients have remained on the drug for as long as a year. "There are no clear downsides to the drug," he said. Most often patients with both bosentan and placebo reported transient headaches as the most frequent side effects. "My sense is that we have seen from these results that bosentan is an effective medication," he said. "If these treatments pan out, if would be terrific," said Dr. Rodman Starke, chief scientific officer of the American Heart Association. "Pulmonary hypertension is a very bad disease and we do not have very good treatments for it." Dr. Rubin said there are several forms of pulmonary hypertension. In some cases the cause is unknown and in others, the cause ranges from chronic lung disease to blood clots in the lungs, a complication of scleroderma. About one percent of cases are complications from HIV/AIDS infection. One of the disturbing aspects of the disease is that while blood pressure in the lungs can be four or five times the normal range and can be damaging the heart, the blood pressure measured in a person’s arm can be normal. "That can lead to misdiagnosis," Rubin said. "Typically a pulmonary hypertension patient’s disease is not diagnosed correctly until a year and a half after symptoms first appear. That is tragic, considering life expectancy is only about two years." Worse, he said, victims of the disease who are on waiting lists for organs typically have a two-and-a-half year wait. "You do the math," Dr. Rubin said, "and you see these people need help." A larger study of bosentan is underway, he said, and will provide the clinical data needed to get the drug approved by the Food and Drug Administration.
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