Alzheimer’s Vaccine Appears Safe in 1st Human Tests

WASHINGTON — Scientists and doctors fighting Alzheimer’s disease long have focused on alleviating the symptoms, fearing that the brain is so complex that it might be impossible to find a cure for the dreaded condition that is wiping out the memories of 4 million Americans.

But suddenly there is a fresh sense of optimism, a belief that promising developments--including a new study released Tuesday--offer the hope of an effective treatment and, perhaps someday, even a cure.

At the World Alzheimer’s Congress--a gathering here of more than 3,000 experts--a company reported that a vaccine to fight the disease cleared its first test in humans.

“It’s very exciting. It’s an important landmark finding,” said Dr. Zaven Khachaturian, a veteran researcher and the senior science advisor for the Alzheimer’s Assn.

The vaccine previously worked in mice by reducing the plaques characteristic of the disease, the tangles in the brain that slow down and disrupt the messages moving among brain cells.

Long Way From Vaccine for Humans

Now, researchers say, it has been tested in more than 100 people in the U.S. and Britain with no harmful effects. That’s an important step--no harm done--but still a long way from a vaccine that humans can use.

Elan Pharmaceuticals, a division of Elan Corp. of San Francisco, which produces the vaccines, hopes to run tests before the end of 2001 to see if the vaccine actually can help victims of the disease by alleviating their memory loss. And if that proves successful, the next step could be mass marketing of a vaccine, perhaps within four to seven years, for the 150,000 people who fall victim to the disease each year.

But the ultimate dream of a vaccine would be for prevention rather than treatment, just as the vaccines for polio and measles have eliminated those once-deadly scourges.

Alzheimer’s disease typically takes 20 or 30 years to develop, and it doesn’t become a virtual epidemic until after age 80. (About 47% of people over 85 have the disease.) So any successful immunization campaign would need to spread the vaccine when people are in their 50s.

The promise of a vaccine is one sign of a “dramatic shift in the thinking of the scientific community,” a rapidly developing new strategy focused on prevention, Khachaturian said.

The hopes for prevention also got a boost Tuesday from a separate study suggesting that vitamins C and E and vegetables might be promising deterrents to Alzheimer’s. The Erasmus Medical Center in Rotterdam studied the eating habits of 5,000 healthy people in the Netherlands over the age of 55. They were followed and reexamined over a 10-year period. The incidence of Alzheimer’s disease was much lower among those who had a high daily intake of vegetables and the two vitamins. The study also looked at fruit consumption but did not find any preventive benefit.

And yet another study to be unveiled today will point out that a high-fat diet raises the risks of contracting the disease for some people.

The appeal of a vaccine is significant because it deals with the underlying nature of the disease. A vaccine stimulates the body to produce antibodies to fight the disease.

This is in sharp contrast to the handful of Alzheimer’s drugs now on the market, which treat symptoms. These compounds slow mental deterioration for periods ranging from six months to three years. But inevitably the drugs stop working and patients continue their downward slide to total memory loss, helplessness and death.

The drugs stop working because the tangles in the patient’s brain worsen with time. Using the drugs is like putting gas into a car in which the gas tank has cracked and the fuel pours out. But the vaccine, if it works, would dissipate some of the tangles in the brain. It would be like fixing the hole in the fuel tank.

Memory Gains Shown in Mice

In mice, the vaccine already has been a success. Elan last year reported good results in improving memory performance in mice with Alzheimer’s by clearing plaques from the brain.

“Our first goal is to block further progression of the disease,” noted Dale Schenk, vice president of discovery research at Elan. “We are optimistic that we can attack this invader at its source and eventually help the millions of people and families worldwide who are living with this devastating disease.”

The Elan vaccine, called AN-1792, has been tried in 100 people without any safety problems. All the patients had cases of mild to moderate Alzheimer’s disease, and their families granted permission for them to participate in the study.

While encouraging, the result is not definitive; many things can go wrong in trying to transfer scientific successes from rodents to humans. “We do not want to raise false expectations that a vaccine is around the corner and will be the cure-all,” Khachaturian said. “Drug design is tortuous, and there are many ways it can fail.”