Issue of
April 7, 1999

Light-activated drug shrinks plaque buildup in arteries

BY MITCH LESLIE

A light-activated drug can partially dissolve the fatty deposits that clog arteries, say Stanford scientists who have successfully applied the treatment to several patients, using an optical fiber to "pipe" light directly to obstructed leg arteries.

Atherosclerosis, the buildup of fat-laden plaque inside arteries, is a major cause of heart attack, stroke and inadequate circulation to the extremities. To battle this problem, the Stanford research team of assistant professor of radiology Mahmood Razavi, MD, and assistant professor of medicine Stanley Rockson, MD, in collaboration with scientists from Pharmacyclics, Inc., borrowed a drug used in cancer therapy.

The drug, known as lutetium texaphyrin, is extremely specific. It kills cells that have absorbed it, but only when they are exposed to high-intensity red light. Only a few kinds of cells absorb the drug, including cancer cells and a specific type of cell that plays a role in plaque formation, said Razavi.

Rockson and Razavi gave injections of lutetium texaphyrin to 16 patients with obstructed leg arteries. A day later, after cells in the plaque had plenty of time to absorb the drug, the researchers exposed the narrowed arteries to bright red light for 15 minutes. They delivered the light to the interior of the vessels through a tiny fiber-optic filament, as thin as a paper clip, that was inserted through a small slit in the artery and maneuvered to the blockage.

Four weeks after the treatment, angiograms (arterial x-rays) showed that plaque deposits had shrunk in 12 of the 16 patients. The reductions ranged from 10 percent to 74 percent.

Razavi presented the team's results March 23 at the Society of Cardiovascular and Interventional Radiology's annual scientific meeting in Orlando, Fla.

These preliminary trials suggest that the treatment is safe for human use, Razavi said. This spring, the researchers plan to launch further trials to evaluate the treatment's effectiveness, he added.

Razavi noted that the light treatment was much less invasive than balloon angioplasty, the most common way to remedy severe arterial blockages. In that procedure, a balloon is inflated inside the clogged vessel, squashing the plaque and opening a channel for blood flow.

Even after balloon angioplasty, however, a patient's vessels often narrow again as scar tissue builds up. Early studies suggest that the light treatment may prevent this accumulation of scar tissue, Razavi said. The researchers will further evaluate this possibility in their next study.

Other members of the Stanford research team include John Cooke, MD, PhD, associate professor of medicine; Michael Dake, MD, associate professor of radiology; and postdoctoral fellows Andre Szuba, MD, and Steve Filardo, MD. Two scientists from Pharmacyclics, the drug's manufacturer, also contributed to the study: projects research director Dan Adelman, MD; and researcher Kathy Woodburn, PhD. SR