"The concept is sort of liquid Drano for the coronary arteries," said Dr. Steven Nissen, a Cleveland Clinic cardiologist who led the study, using the U.S. brand name for a drain-clearing product.
Larger and longer studies need to be done to determine if the experimental treatment will translate into fewer deaths, but the early results are promising, said Dr. Daniel Rader, director of preventive cardiology at the University of Pennsylvania School of Medicine.
The treatment used a laboratory-produced version of an unusually effective form of HDL, the good cholesterol that helps protect against heart disease by removing plaque, or fatty buildups, from the bloodstream.
"This is clearly on the level of a breakthrough that will have far-reaching implications," pointing the way toward a rapid treatment for fatty buildups, said Dr. Bryan Brewer, chief of molecular diseases at the National Heart, Lung and Blood Institute.
The surprisingly quick results, though preliminary, shatter a long-standing belief that heart disease is a slow-progressing disease that takes a long time to undo, said Rader, who wrote an editorial accompanying the study in Wednesday's Journal of the American Medical Association.
While some existing medicines target HDL, most conventional drug treatment works by reducing levels of LDL cholesterol, the bad kind that contributes to the formation of plaque that can clog arteries and lead to heart attacks.
Nissen's study is part of a burgeoning area of research that focuses on treatments that raise HDL levels or improve HDL's plaque-fighting abilities.
His findings stem from an unusual discovery about 25 years ago in the northern Italian village of Limone Sul Gardia. Italian researchers found that 40 residents there had very low HDL levels, yet paradoxically had low rates of coronary artery disease.
Lab tests revealed a likely explanation: All had a gene variation in a key protein component of HDL. The variation contributed to larger-than-normal HDL particles, which is believed to make HDL cholesterol especially efficient at removing plaque.
Scientists made a synthetic form of the protein, which was found to reduce plaque buildups rapidly in mice and rabbits.
The product was first tested and shown to be safe for use in humans. This latest round of experiments is the first time the substance has been used to actually treat narrowing of the arteries in people.
The study was funded by Esperion Therapeutics Inc. of Ann Arbor, Michigan, a small biotechnology company that makes the product.
In the study, 36 patients who had had heart attacks or severe chest pain received weekly intravenous infusions of the substance for five weeks. Eleven patients received dummy treatments.
At six weeks, imaging tests showed the patients receiving the synthetic protein had a visible 4 percent reduction in plaque buildup in their coronary arteries. There was no significant change in the placebo group.
Rader called the results "surprising to even the most optimistic supporters" of using HDL to treat narrowing of the arteries.
Nissen said he envisions the treatment being used in combination with other therapy including LDL-lowering drugs, but that commercial use is probably a few years off and will depend on the outcome of larger studies.