Find could improve delivery, precision of blood-clot meds

by Meg Tirrell - Jul. 7, 2012

NEW YORK - Scientists have found a way to use the body's natural clot- producing mechanisms to deliver targeted medicine in a study that may have implications for treatments of heart attacks and stroke.

Obstructions in blood vessels lead to a force called shear stress, attracting platelets that form blood clots.

Researchers designed a drug- delivery method that activates only in those conditions, potentially enabling more targeted delivery of clot-busting medicines in lower doses that can be given before a patient gets to a hospital, they wrote in a paper published online Thursday in the journal Science.

Heart disease and stroke are some of the leading causes of death in the United States, with about 785,000 Americans a year having their first coronary attack, according to the Centers for Disease Control and Prevention.

Medicines designed to eliminate clots in those events often need to be given in a hospital and in doses that can lead to side effects, such as excessive bleeding, limiting the number of patients who can take them, said Donald Ingber, a professor of vascular biology at Harvard Medical School in Boston and an author of the study.

"People have wanted to figure out targeting, but they haven't come up with a way," Ingber, who is also director of the Wyss Institute for Biologically Inspired Engineering at Harvard, said in a telephone interview. "We knew platelets can somehow go to narrowing vessels and thought if biology can do it, somehow we can do it."

The delivery system, called shear- activated nanotherapeutics, is a bundle of tiny drug-coated particles that travel together until they reach the obstruction, when the shear stress causes them to break apart and attack clots.

The study, done in mice, used an approved clot-targeting therapy called tissue plasminogen activator, or tPA, and found that the system allowed for use of less than one-fiftieth the normal dose to dissolve clots, Ingber said.

The technique is years away from testing in humans.