CAMBRIDGE, Mass.—As noted by the Massachusetts Institute of Technology (MIT), the past few decades have seen scientists develop many devicesthat can reopen clogged arteries, including angioplasty balloons andmetallic stents. While generally effective, each of these treatments hasdrawbacks, including the risk of side effects. A new studyfrom MIT, however, analyzes the potential usefulness of a new treatment thatcombines the benefits of angioplasty balloons and drug-releasing stents,but may pose fewer risks.
With this new approach, a balloon is inflatedin the artery for only a brief period, during which it releases a drugthat prevents cells from accumulating and clogging the arteries overtime. While approved for limited use in Europe, thesedrug-coated balloons are still in development in the United States andhave not received U.S. Food and Drug Administration (FDA) approval. The MIT study, which models the behaviorof the balloons will, it is hoped, help scientists optimize their performance andaid regulators in evaluating their effectiveness and safety.
"Until now, people who evaluate such technology could not distinguishhype from promise," said Elazer Edelman, the Thomas D. and Virginia W.Cabot Professor of Health Sciences and Technology at MIT and senior author ofthe paper describing the study, which appeared online recently in thejournal Circulation. The lead author of the paper is VijayaKolachalama, a former MIT postdoc who is now a principal member of thetechnical staff at the Charles Stark Draper Laboratory.
In 2003, the FDA approved the first drug-eluting stent for use in theUnited States, which releases drugs that prevent cells from clumping inthe arteries. Drug-eluting stents are now the primary choice fortreating blocked arteries, but they also have side effects: The drugscan cause blood to clot over time, which has led to death in somepatients. Patients who receive these stents now need to take othermedications, such as aspirin and Plavix, to counteract blood clotting.
Edelman's lab is investigating a possible alternative to the currenttreatments: drug-coated balloons. "We're trying to understand how andwhen this therapy could work and identify the conditions in which it maynot," Kolachalama said. "It has its merits; it has some disadvantages."
The drug-coated balloons are delivered by a catheter and inflated atthe narrowed artery for about 30 seconds, sometimes longer. During thattime, the balloon coating, containing a drug such as Zotarolimus, isreleased from the balloon. The properties of the coating allow the drugto be absorbed in the body's tissues. Once the drug is released, theballoon is removed.
In their new study, Kolachalama, Edelmanand colleagues set out to rigorously characterize the properties of thedrug-coated balloons. After performing experiments in tissue grown inthe lab and in pigs, they developed a computer model that explains thedynamics of drug release and distribution. They found that factors suchas the size of the balloon, the duration of delivery time, and thecomposition of the drug coating all influence how long the drug stays atthe injury site and how effectively it clears the arteries.
One significant finding is that when the drug is released, some of itsticks to the lining of the blood vessels. Over time, that drug isslowly released back into the tissue, which explains why the drug'seffects last much longer than the initial 30-second release period.
"This is the first time we can explain the reasons why drug-coatedballoons can work," Kolachalama noted. "The study also offers areas wherepeople can consider thinking about optimizing drug transfer anddelivery."
In future studies, Edelman, Kolachalama andcolleagues plan to further examine how blood flow affects drug delivery.They also plan to study a variety of different drugs and drug coatingcompositions, as well as how the balloons behave in different types ofarteries.
The U.S. National Insitutes of Health and Abbott Vascular funded the research.
SOURCE: MIT News Office
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