Organ transplants captured the public’s imagination when the first one was performed in the United States 50 years ago. Because of them, some people with potentially fatal kidney, liver, lung and heart disorders can now live for many years.

But though such operations may today seem routine to many Americans, doctors haven’t stopped working on making organ transplantation safer and easier. One of the biggest problems is that, for the rest of their lives, recipients must take powerful drugs to prevent their bodies from rejecting the new organs. These anti-rejection drugs can cause many serious, ultimately life-threatening side effects.

Future transplant patients may have easier recoveries. Researchers at the University of California, San Francisco are testing a new type of anti-rejection drug that appears to be far less toxic to the body. It may even train the body to accept the new organ — in this case, a kidney — without the need for a lifetime regimen of drugs.

“Our goal is, at the very least, to simplify the treatment and, second, allow patients to accept a kidney in a better way and possibly become tolerant,” says Dr. Flavio Vincenti, a professor of medicine and surgery at UC San Francisco Medical Center.

Vincenti has found that the drug, called LEA29Y, appears to be as effective as cyclosporine in preventing kidney rejection six months after transplantation. And, reporting at a meeting of the American Transplant Congress, he said that 148 patients treated with LEA29Y had fewer side effects than 73 who took cyclosporine.

The new drug prevents rejection without affecting the entire body. Current drugs suppress the entire immune function so that it doesn’t recognize the new organ as foreign. “A sizable minority of patients with liver and heart transplants develop kidney disease,” says Vincenti. “The patients who receive a kidney transplant, their kidneys are threatened by these drugs.” A recent study in the New England Journal of Medicine found that, 10 years after transplant, almost all kidneys show signs of damage from the drugs, he says.

Traditional drugs can weaken immune systems so much that patients become vulnerable to infections and have a higher risk of cancer.

However, the traditional medications work quite well to prevent rejection, and any alternative drugs must prove to be as effective.