Go-Ahead for A Wonder Drug

After months of controversy, the Food and Drug Administration last week ended its ambivalent attitude toward a genetically engineered drug that dissolves blood clots. FDA Commissioner Frank Young announced that the agency had approved the use of tissue plasminogen activator, or t-PA, as an emergency treatment for heart attacks. The drug activates an enzyme that destroys fibrin, the protein that binds clots together. Arterial clotting is thought to be a factor in most of the 1.5 million heart attacks suffered annually in the U.S., so t-PA could save thousands of lives. With an injection of the drug, said Young, "the odds of surviving a heart attack are dramatically improved."

The FDA did not always feel that way. Despite successful clinical trials of t-PA, an FDA advisory committee had unanimously voted last May not to approve it. No one disputed that t-PA could dissolve clots, but debate raged over two main points: whether the drug increased the survival rate of heart-attack victims, and whether its benefits outweighed the risks. T-PA's tendency to induce bleeding caused strokes in a number of patients. The agency then asked the drug's developer, south San Francisco-based Genentech, to provide further data.

Young established a second panel, which based its decision on two new studies showing that the heart's ability to pump blood increases after administration of t-PA. This indicates the drug can limit damage during a heart attack. However, says Harvard Cardiologist Eugene Braunwald, t-PA "has to be given within four to six hours after symptoms occur."

T-PA, which is already sold abroad, will be marketed under the brand name Activase. Genentech officials say the drug, which costs about $2,000 a treatment, could be available in two or three weeks.