Jul 24, 2013 5:00 PM by By Dennis Thompson
WEDNESDAY, July 24 (HealthDay News) -- A new class of pulmonary hypertension drug is modestly effective in treating the disease and could provide an alternative for patients whose only option has been surgery, according to drug trial results.
Results from phase 3 trials of Riociguat, published in the July 25 issue of the New England Journal of Medicine, show that the drug can be used to treat two forms of pulmonary hypertension -- pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTPH).
Riociguat is the first in a new class of drugs known as soluble guanylate cyclase stimulators, which can help treat pulmonary hypertension by promoting the dilation of the pulmonary artery.
Pulmonary hypertension is a condition in which there's increased pressure in arteries that carry blood from the heart to the lungs. Symptoms can include shortness of breath or fainting during physical activity, fatigue, and chest pain. If left untreated, it can lead to a weakened heart and potential heart failure.
The drug has been fast-tracked by the U.S. Food and Drug Administration for its potential use in treating CTPH, which is caused by blood clotting and until now could be treated only through a complex surgical procedure called pulmonary endarterectomy.
"It's a particularly tough group of patients," said Dr. Mariell Jessup, president of the American Heart Association. "Ideally, they can undergo surgery to relieve that clot burden, but it's a very technically challenging surgery and very few hospitals are doing that type of surgery." Patients with CTPH who cannot undergo the surgery have no other treatment options.
The phase 3 trials also are testing Riociguat's effectiveness in treating PAH, a type of pulmonary hypertension that has no known cause but has been associated with genetics, drug use or conditions that affect the veins and small blood vessels of the lungs.
The trials, which involved about 700 total participants, found that both CTPH and PAH patients receiving Riociguat were able to walk farther in six minutes than people who received a placebo.
The improvement in patients on Riociguat, however, is not overwhelming, said Dr. Stephen Archer, head of the department of medicine at Queen's University in Ontario, Canada, who wrote an editorial that accompanied the drug trial results.
CTPH patients were able to walk about 150 feet farther than those on placebo, while PAH patients walked about 118 feet farther.
"People are walking not much farther on the drug than not on the drug," Archer said. "It's not like night and day. This is not a cure. It's a useful treatment."
Archer also expressed a concern shared by Jessup that some physicians might see Riociguat as an alternative to surgery for patients with CTPH. "You'd hate to have people given the easy prescription, which is not curative, but not the surgery that can be curative," Archer said.
"It's equivalent to saying you should give statins and aspirin to someone with coronary heart disease who needs coronary bypass surgery," Jessup said. "It's important to give them statins and aspirin, but first and foremost, they probably need bypass surgery."
Archer noted in his editorial that Bayer HealthCare, the maker of Riociguat, funded these drug trials and played a heavy role in the research. A Bayer employee performed the statistical analysis for both trials, and a Bayer contractor helped write the research papers.
"They did employ a statistician, and they did have an editor who contributed in unknown ways to the paper," Archer said of Bayer. "I'm not accusing them of anything, but I think the industry would be wise to avoid any apparent conflict of interest."
Although current results are modest, doctors hope that future combination trials will find that Riociguat can effectively treat pulmonary hypertension in concert with other medications, said Dr. Andrew Freeman, chairman of the American College of Cardiology's Early Career Cardiologists Council. He was not involved with the new research.
There are five types of pulmonary hypertension, and Riociguat could potentially be helpful in treating them all.
"For now, this gives us at least something that we never had before, and it opens up the door to a new class of drugs that had never been available before," said Freeman, also a cardiologist with National Jewish Health in Denver. "The treatment effect was modest, but it adds to the potential available therapies."
Visit the U.S. National Heart, Lung, and Blood Institute for more on pulmonary hypertension.