The second phase of a clinical trial testing a new stem-cell-based therapy on injured heart muscle has been launched by researchers at The University of Texas Medical School at Houston. It is the only study site in the Texas Medical Center.
Results from Phase I of the trial are published in today's issue of the Journal of the American College of Cardiology. Researchers reported that patients were treated safely with intravenous adult human mesenchymal stem cells (Prochymal) after a heart attack. In addition, they had fewer arrhythmias, improved heart and lung function, and improvement in overall condition.
"We are able to use a stem cell product that is on the shelf without prior preparation of anything from the patient, and this product appears to be able to help the heart muscle recover after a heart attack," said Ali E. Denktas, M.D., the trial's Houston site principal investigator and assistant professor of cardiology at the UT Medical School at Houston. "This means patients have the potential to recover quicker with less risk of an immediate secondary attack."
In many cell-based therapies, doctors harvest the patient's own cells, process them and then return them to the patient. Prochymal, developed by Osiris Therapeutics, Inc., contains adult mesenchymal stem cells from healthy donors. The cells can be stored at an emergency center until needed. For purposes of the Phase II study, Prochymal must be administered within seven days of a heart attack.
Yesterday, researchers enrolled the first patient for the Phase II study at the Houston site. Heart attack patient Melvin Dyess, 49, received an intravenous infusion of either the stem cells or placebo as part of the protocol of the double-blind study. The procedure took place at the Memorial Hermann Heart & Vascular Institute-Texas Medical Center. Denktas said UT Medical School researchers will continue to enroll willing patients into the Phase II study who are admitted to Memorial Hermann-Texas Medical Center. Neither patients nor their physicians know whether they received the stem cell drug.
Affecting 1.1 million Americans every year, heart attacks are caused by disruptions to the heart's blood supply. Muscle cells can die within minutes of the blood being reduced or cut off. The body has a limited capacity to regenerate new heart muscles and repair wounds to the heart.
Denktas said while cell-based therapies including Prochymal appear to work, researchers are not sure why. Previous studies have shown that adult stem cells have a "homing device" that sends them to the point of injury in the human body.
"Studies with acute myocardial infarction (heart attack) show that if you give cells of some sort to the heart relatively quickly, five to 10 days after the heart attack, they nest themselves in the heart and the heart improves. But, why it improves is debatable," Denktas said. Adult mesenchymal stem cells appear to have anti-inflammatory, anti-fibrotic, and tissue regenerative capacities, as shown in both animal studies and human clinical trials, according to Osiris Therapeutics, Inc.
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